Wildguzzi.com
General Category => General Discussion => Topic started by: bad Chad on March 06, 2020, 04:00:05 PM
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I know this will seem like an incredibly basic question to most of you, but for some reason I can't seem to wrap my head around the concept.
Let's stick to only rear shocks, to keep it even more basic.
Here is what I think know. Most shocks haver a preload adjustment, and by adding preload we are compressing the spring. This in turn makes the spring more resistant to compressing more under load, because it has already been partially compressed?
So a compressed spring is stiffer because it has already used up some of its finite compressibility, and thus this might be a good thing it you are adding more weight to the motorcycle. Does increasing preload/spring compression raise the ride height too? Is the only reason to add or subtract preload to better deal with varying weight?
Wouldn't one want to run with as little preload as practical?
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Real quick-spring rate is measured in force needed to compress a given amount.
Preload does NOT change the rate, only starts the spring down the road of increased force.
So using fake, easy to understand numbers:
Spring rate 25 lbs/inch of compression
Spring with no preload will move 1" when you add 25 lbs to the unladen spring.
With 25 lbs of preload, adding 25 lbs doesn't move it-it only will move 1" if you put 50 lbs on it.
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Preload basically just changes the ride height. Not enough and you bottom out the shock. Too much and you top out the shock. Changing the ride height can also impact handling.
The amount of compression of the spring is determined by the weight being carried.
A normal spring travels X number of inches per every pound added to it. It is linear, for a NORMAL spring. But progressive wound changes that, and the linkages on like a monoshock rear suspension change that relationship.
Or that is my understanding.
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When you add preload, you are only raising the perch (the seat in which the spring sits), higher up the shock body.
Indeed if you put the bike on it’s centrestand, the spring will “top out” and will have more load prior to use, but that will only mean it “sags” less when you go to ride off.
The spring will still only have the same load when in use that it had before, your mass has not changed but your ride height will be greater because the shock compressed less to achieve equilibrium.
It is a complete fallacy and always has been, to suggest that winding on pre load “stiffens” the suspension.
(https://i.ibb.co/mt087qN/6-BD2-E396-30-AF-40-EE-970-F-431113448134.png) (https://ibb.co/mt087qN)
There is a lot of material to clarify the myth. Google “spring preload, stiffness myth” or similar and all will be revealed.
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The general rule of thumb is the static sag should be set so that suspension travel compresses about 1/3 when the rider sits on the bike.
It's much easier to do this where the bike is on a shop stand and someone is measuring the suspension when the rider sits on it. It can also be done with mounting weights on the bike to mimic the weight of the rider. There are probably other ways.
That's why when you purchase a new motorcycle, the dealer should set the sag with the rider when the dealer delivers the bike (I know you Guzzi guys won't spend for a new bike and only buy used).
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So a compressed spring is stiffer because it has already used up some of its finite compressibility, and thus this might be a good thing it you are adding more weight to the motorcycle.
I know that your intention was to add a question mark after that bit.
It’s that part of your post where the misunderstanding exists..
Once the damper has moved off it’s stops, then the pre load is irrelevant to the compressibility. The damper only moves a lesser amount by the time the spring is in equilibrium with the compressive force.
You are correct in your suggestion that you will raise (or lower) the ride height by manipulation of pre load.
Here’s one (of many) explanations.
https://youtu.be/NGGlK2MLOjc
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So increasing preload (compressing spring) with no weight on the seat will RAISE the ride height?
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When you add preload, you are only raising the perch (the seat in which the spring sits), higher up the shock body.
It is a complete fallacy and always has been, to suggest that winding on pre load “stiffens” the suspension.
(https://i.ibb.co/mt087qN/6-BD2-E396-30-AF-40-EE-970-F-431113448134.png) (https://ibb.co/mt087qN)
There is a lot of material to clarify the myth. Google “spring preload, stiffness myth” or similar and all will be revealed.
Hhmm, Please keep it in layman terms, because some of the physics can get a little complicated.
Can you explain to me why, when I first got my CalVin, when it was on the first lightest spring pre load setting,it wallowed around corners like it had a hinge in the middle of the bike, and when I adjusted the preload to the highest setting, it firmed and stiffened up the corner handling a LOT!
:popcorn:
Kelly
Was that not due to the suspension being firmer?
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Hhmm, Please keep it in layman terms, because some of the physics can get a little complicated.
Can you explain to me why, when I first got my CalVin, when it was on the first lightest spring pre load setting,it wallowed around corners like it had a hinge in the middle of the bike, and when I adjusted the preload to the highest setting, it firmed and stiffened up the corner handling a LOT!
:popcorn:
Kelly
Was that not due to the suspension being firmer?
Actually it is because most of the time suspension is only operating in the first 20% of its travel .
Dusty
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So increasing preload (compressing spring) with no weight on the seat will RAISE the ride height?
No. It just won't compress as much when the rider is on the bike. So I suppose the bike will stay a little taller with the rider but it will ride very stiff.
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Hhmm, Please keep it in layman terms, because some of the physics can get a little complicated.
Can you explain to me why, when I first got my CalVin, when it was on the first lightest spring pre load setting,it wallowed around corners like it had a hinge in the middle of the bike, and when I adjusted the preload to the highest setting, it firmed and stiffened up the corner handling a LOT!
:popcorn:
Kelly
Was that not due to the suspension being firmer?
It appears that is was set too weak for your weight. Just a guess.
The traditional way to do it, is set the static sag on the stand and then adjust the rebounding and dampening as you test ride it. Test the later in a methodical method, starting from full soft. Get a feel for each adjustment of separate rides then work them in tandem. Much easier to count the adjustment from full soft.
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Hmm, so far it’s about what I was expecting. Several meaningful attempts in various levels of complexity. I will keep on tying to make the pieces fit, thanks to you all.
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So since this thread is conveniently going right now, let me pop in and ask a question that has been on my mind for a while:
Several months ago, a friend and I were out on a ride. Going down US 400, we crossed some railroad tracks. The tracks are
paved and quite smooth, with only a couple of small bumpity bumps as you cross, but as my rear wheel went over the second bump, the bike sprung my skinny butt about 4 to 5 inches off of the seat. At the end of the ride, I told my friend about it, and he said that it sounded like I needed to increase my preload. Is this correct, and if so, can someone explain the basic physics behind it?
Also, thanks for starting this thread, Chad. I'd been thinking about asking about this for a while, but never got around to it.
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Preload allows you to set proper sag. Your dampers work best in the middle third of their stroke, so you use pre-load to pre-compress the spring so when you park your ass on the seat, the ride height settles in the upper part of that middle third. If your fork allows for it, you should set pre-load there, too. One reason your handling degrades if you leave too much sag in the rear is the steering geometry, weight transfer under throttle and braking, and suspension reaction to mid-corner bumps are all affected. So while it doesn't stiffen the spring, increasing pre-load can restore the proper geometry, and keep the shock working where it dampens best. This will "tighten up" the handling and make it feel stiffer. An inch of difference between the lowest and highest perch position may not seem like much, but if your bike has 5 inches of rear wheel travel, you have 1 2/3" of "sweet spot" damping. If your weight causes the bike to sag 3" you are at the bottom of the range. An inch restores the ride height.
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So increasing preload (compressing spring) with no weight on the seat will RAISE the ride height?
Sure will Boss... :thumb:
With the proviso that you have not hit the top stop...ie, “topping out..”
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Hhmm, Please keep it in layman terms, because some of the physics can get a little complicated.
Can you explain to me why, when I first got my CalVin, when it was on the first lightest spring pre load setting,it wallowed around corners like it had a hinge in the middle of the bike, and when I adjusted the preload to the highest setting, it firmed and stiffened up the corner handling a LOT!
:popcorn:
Kelly
Was that not due to the suspension being firmer?
Dunno..
Other than altering the rake due to higher seat position, can’t say.
But here’s the thing.
Put your preload on the lowest setting and ACCURATELY measure the height to a solid point on the bike..(not the bloody seat..)
Then wind your spring preload up to the other end of it’s range and conduct the SAME measurement.
It’ll have raised the point by however much you increased the preload distance.
As long as your damper performs the same way at each part of it’s stroke, then winding on preload has not stiffened the suspension.
Y’all really need to believe this ,or just research it..
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It still is operating in the same range with respect to the spring, it’s just the damper has been extended and is operating in a different part of it’s available stroke..
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No. It just won't compress as much when the rider is on the bike. So I suppose the bike will stay a little taller with the rider but it will ride very stiff.
One of us is going to wish you hadn’t said that.. :clock:
We may need to come back to reply #9.. :popcorn:
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No. It just won't compress as much when the rider is on the bike. So I suppose the bike will stay a little taller with the rider but it will ride very stiff.
So LR..
If winding on preload has compressed the spring, why does the top of the spring not just extend outwards to achieve the same state as before, given that the damper has not topped out...Careful now... :wink:
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Preload allows you to set proper sag. Your dampers work best in the middle third of their stroke, so you use pre-load to pre-compress the spring so when you park your ass on the seat, the ride height settles in the upper part of that middle third. If your fork allows for it, you should set pre-load there, too. One reason your handling degrades if you leave too much sag in the rear is the steering geometry, weight transfer under throttle and braking, and suspension reaction to mid-corner bumps are all affected. So while it doesn't stiffen the spring, increasing pre-load can restore the proper geometry, and keep the shock working where it dampens best. This will "tighten up" the handling and make it feel stiffer. An inch of difference between the lowest and highest perch position may not seem like much, but if your bike has 5 inches of rear wheel travel, you have 1 2/3" of "sweet spot" damping. If your weight causes the bike to sag 3" you are at the bottom of the range. An inch restores the ride height.
this is the fact .............Ryan .... preload simply means you are preloading the spring :thumb:
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It still is operating in the same range with respect to the spring, it’s just the damper has been extended and is operating in a different part of it’s available stroke..
That's what I said .
Oh , as for altering rake , do the math , and inch of rear ride height won't really change the rake numbers enough to matter .
Dusty
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There are two things going on here - actually three - spring rate (preload is a subheading), compression damping and rebound damping.
Like Ryan said - preload is the way to set sag. Why do you want to be part way into the suspension (normal is 1/3rd of the way down from the top)?
Compression damping (like when the wheel runs over a rock) forces the wheel up and compresses the shock. You want as much travel as possible to absorb that movement.
But some movement of the suspension is needed for depressions, like pot holes. That's the importance of sag. The wheel needs to be able to drop into the depression rather than taking the whole bike with it. Sag guarantees there's shock travel available for pot holes.
JC85 - What happened in your case was the first bump compressed the shock. When the second bump came soon after, the shock hadn't rebounded, so it bottomed out and transferred the force directly to the frame. One of two things happened - the sag was too great (more than a 1/3rd of the way into its travel) or the rebound is too stiff and wouldn't allow the shocks to rebound quickly enough.
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So since this thread is conveniently going right now, let me pop in and ask a question that has been on my mind for a while:
Several months ago, a friend and I were out on a ride. Going down US 400, we crossed some railroad tracks. The tracks are
paved and quite smooth, with only a couple of small bumpity bumps as you cross, but as my rear wheel went over the second bump, the bike sprung my skinny butt about 4 to 5 inches off of the seat. At the end of the ride, I told my friend about it, and he said that it sounded like I needed to increase my preload. Is this correct, and if so, can someone explain the basic physics behind it?
Also, thanks for starting this thread, Chad. I'd been thinking about asking about this for a while, but never got around to it.
I had the same problem with my stock EVT shocks over a RR track. Adding preload would only make the problem worse.
I am not a shock expert. With my EVT I believe there was not enough rebound dampening. It compressed fine, but when it came time for the spring to expand, it came "flying" back to full length rather than gradually coming back, This is why I came off the seat, I believe.
I changed to a Koni set and the problem was gone.
Tom
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Wirespokes, your reply makes sense for the RR tracks.
But, at least in my case I felt as though the shock was coming up too fast and tossing me. I felt compression, but I never felt a "ummm.. a bang" to kick me off the seat like the shock was still fully compressed. More like a spring tossed me up. Over the same track, my stock shocks on my HD never gave me the problem, neither did my Eldo with Koni.
I'm still learning suspension.
There is a suspension 101 web page (I can find the link if needed). I never fully understood it, but I understood enough to be dangerous :wink:
I can't find the page to link. Search for Suspension101eBook. pdf
Tom
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Wirespokes, your reply makes sense for the RR tracks.
But, at least in my case I felt as though the shock was coming up too fast and tossing me. I felt compression, but I never felt a "ummm.. a bang" to kick me off the seat like the shock was still fully compressed. More like a spring tossed me up. Over the same track, my stock shocks on my HD never gave me the problem, neither did my Eldo with Koni.
I'm still learning suspension.
There is a suspension 101 web page (I can find the link if needed). I never fully understood it, but I understood enough to be dangerous :wink:
Tom
That's how it seemed to me in this instance. I have Koni shocks on my Eldo, but they're adjusted at the top/least amount of preload setting. I'm going to take the advice in this thread to adjust them properly. Thanks, everyone!
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Guys.
Please just stick to the original question. The waters get muddied too easily.
An example..
If you look at a shock that is loaded with the damper at mid travel, the spring is subjected to a compressive force of say 150 kg, and the length eye to eye might be say, 300 mm.
The shock will have moved in or out and come to rest where the upward force of the spring = the downward force of the mass.
Surely that’s clear..
Now if you wind the collar upwards at the bottom (generally), you’re attempting to compress the spring, but the top is free to extend outwards so the SPRING is the same length ( the load has not changed), but the top has moved up.
All you have changed is the dimension of the shock eye to eye (ride height), but the spring is in the same condition and length so it will perform identically, it’s just moved upwards.
If you like, all you’ve done is increased the distance from the bottom of the spring perch, to the lower eye.
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Guys.
Please just stick to the original question. The waters get muddied too easily.
An example..
If you look at a shock that is loaded with the damper at mid travel, the spring is subjected to a compressive force of say 150 kg, and the length eye to eye might be say, 300 mm.
The shock will have moved in or out and come to rest where the upward force of the spring = the downward force of the mass.
Surely that’s clear..
Now if you wind the collar upwards at the bottom (generally), you’re attempting to compress the spring, but the top is free to extend outwards so the SPRING is the same length ( the load has not changed), but the top has moved up.
All you have changed is the dimension of the shock eye to eye (ride height), but the spring is in the same condition and length so it will perform identically, it’s just moved upwards.
If you like, all you’ve done is increased the distance from the bottom of the spring perch, to the lower eye.
Peter , mate , if the spring is free to move upward , then increasing preload would have zero effect .
Dusty
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So LR..
If winding on preload has compressed the spring, why does the top of the spring not just extend outwards to achieve the same state as before, given that the damper has not topped out...Careful now... :wink:
point taken but fractions vs actual ride height adjustment.
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for the rail road example, the rider is pointing to an issue with almost all bikes. most are over sprung and under damped. the maker does not know whether the buyer will weigh 90 lbs or 400+, 2 up and loaded. therefore, they select a compromise. to save expenses, they usually choose suspension with only a rear preload adjustment. if by luck, you happen to fit the size that the maker has guessed, then you might get a decent ride. however, for 98% of the riders, that wont be the case. as such, preload will only make a minor difference. it seems to me that the europeans must choose 225 lbs single rider or thereabout as their optimum. also, stock shocks tend to be on the cheaper, lower quality side.
when you order a custom shock from ohlins, you supply them with your weight, riding style and weather you travel 2 up regularly. they then choose the correct spring and set the damping for you and your style. but all of this comes with a pretty hefty price.
so, to the op, you should experiment, but don't expect perfection.
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It compressed fine, but when it came time for the spring to expand, it came "flying" back to full length rather than gradually coming back, This is why I came off the seat, I believe.
If that was the case, then why wouldn't that happen on the first bump? Why would it take two?
All the pre-load is doing is keeping the suspension above mid way in its travel. No need getting into spring formulae unless ordering new ones - if the shocks are compressed too far, add preload. Not enough, reduce preload.
This is important because the shocks, besides absorbing bumps and making a smoother ride, are keeping the tires in contact with the pavement. When the suspension isn't set up correctly, the wheels bounce around and go out of contact with the road and control is reduced.
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Peter , mate , if the spring is free to move upward , then increasing preload would have zero effect .
Dusty
That is not true Dusty and just a touch condescending..
It will lengthen the overall eye to eye distance, therefore ride height.
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Read this. It will help. https://www.cycleworld.com/sport-rider/suspension-setup-guide/
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So increasing preload (compressing spring) with no weight on the seat will RAISE the ride height?
Contrary to reply #9, yes it will raise the ride height, as long as the shock has not “topped out” with the bike on it’s wheels (which should be the case..)
Remember the load on the spring from the effects of pre load and weight are not cumulative..
Once the shock comes off it’s stops under the effect of weight, then the pre load is irrelevant from the point of view of spring “stiffness..”
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Read this. It will help. https://www.cycleworld.com/sport-rider/suspension-setup-guide/
If you just confine yourself to the OP’s question, that should help.
To muddy the waters with discussion on damping before the concept of pre load os bolted down, is counter productive.
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Well, gee. The article defines it, how to set it, and why. But hey, sorry to muddy the waters.
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Huzo , technically it is the bottom of the shock that is free to move .
Dusty
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That's why when you purchase a new motorcycle, the dealer should set the sag with the rider when the dealer delivers the bike (I know you Guzzi guys won't spend for a new bike and only buy used).
How many "dealers" out there do you think know or understand enough about suspension to do that?
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After being in this game for a while I'd say rare to none.
:-)
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Huzo , technically it is the bottom of the shock that is free to move .
Dusty
Well, if we were talking about a standard pair of shocks like on a Breva 750 as an example, that would not be true would it ?
Raising the ride height lifts the top mount and takes the top of the spring with it..
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Well, gee. The article defines it, how to set it, and why. But hey, sorry to muddy the waters.
That’s a good thing to read Ryan, but my point about the mud was..
While there are guys digesting one concept, it clouds the issue to contaminate the discussion with more information.
But your teaspoon sized dose of thinly disguised sarcasm is totally justified and understandable..
I just re read my #33 response and it had an edge to it that was not intended.
I could have phrased it better, the section on pre load was good.
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Read this. It will help. https://www.cycleworld.com/sport-rider/suspension-setup-guide/
Hey Ryan, Tks very much for posting that link, I'll take all the help I can get, especially if it's free (guzzi content).
I've downloaded a few suspension set up guides over the years, that is definitely one of the better ones :thumb:
It's filed away safely for future reference
Tks
Kelly
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How many "dealers" out there do you think know or understand enough about suspension to do that?
Sit on the bike on the shop stand. Then ask the tech to crank the preload until it's about 1/3 compressed. Put the other adjusters in the middle and make a test ride. Repeat until the sag is done. Not rocket science. The factory setup should give the approximate weight of the average rider, so it's pretty easy to know to go up or down as a start. This much easier as two man job. I think that's part of the set up fee.
Then it's up to the rider set the rebound and dampening. I think starting full soft, and then experimenting with each separately perhaps half way & go for a ride, then do the opposite for the other setting. That way the rider will feel what each adjuster does. After that, work both adjusters in tandem. It will take a few rides to dial it in.
I'm not one that adjusts for every situation but I have to soften the fork on the Greenie when I put the HB Jr bags on, sometimes the shock but not so much since I determined the fork was my issue. My other bikes are set it and forget it.
When I picked up my Duc, I asked them to set the sag for my weight (classified info). It seemed spot on, whether they did it or not. I've only taken a round of rebound off the rear for these bouncy Okla roads.
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Well, if we were talking about a standard pair of shocks like on a Breva 750 as an example, that would not be true would it ?
Raising the ride height lifts the top mount and takes the top of the spring with it..
Actually it pushes the swingarm down .
Dusty
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There are 3 distinct definitions that must be held separate to understand each.
1. Spring rate (pounds required to compress spring 1 inch)
2. Pre-load (the distance the spring is compressed while installed, at full suspension extension)
3. Sag (the distance suspension is compressed by the weight of bike and rider compared to full extension, or from static to 'with rider')
The *purpose* of 'sag', at it's core, is to allow outward travel of the suspension into depressions; everyone thinks about absorbing bumps, but rarely consider the holes. The 'perfect' sag is entirely dependent upon your riding environment and style. Where I am in South Florida, the roads are very smooth compared to most of the country. I don't require as much sag as in say, Detroit (lol) because the average roadway depression here is maybe 1/2 to 1" where in Detroit it's entirely expected to encounter 2-4" holes in the road.
Spring rate and pre-load are both considerations more of weight (and dynamic compression) than of road surface, and of riding requirements (pleasure + comfort vs. racing).
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Actually it pushes the swingarm down
The swing arm can’t go down unless the ground moves, which it doesn’t. The frame rises.
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The swing arm can’t go down unless the ground moves, which it doesn’t. The frame rises.
The frame rises because the swingarm is pushed down .
Dusty
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Normally the coordinate system when discussing things rising or falling is considered to be fixed relative to the earth, not to the motorcycle. The rear axle and swing arm do not change location relative to the ground. The frame does rise relative to the the ground. The motorcycle rises, it does not push the ground downward.
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Normally the coordinate system when discussing things rising or falling is considered to be fixed relative to the earth, not to the motorcycle. The rear axle and swing arm do not change location relative to the ground. The frame does rise relative to the the ground. The motorcycle rises, it does not push the ground downward.
Exactly , it rises because as the swingarm is pushed down the frame has to rise .
Dusty
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I’m surprised that nobody has discussed the fact that gyroscopic precession above about 35 mph typically causes a torque absess on most twin shock Guzzis that lack a non-Euclidean swingarm.
So I wear all my gear, sit on the bike, and set pre-load to achieve about 1/3 sag.
I figure that without a drawn reciprocation dingle arm, there is really no effective way to reduce the sinusoidal repleneration.
So I do 1/3 sag and call it good.
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It's true Norm , it's really true .
Dusty
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I’m surprised that nobody has discussed the fact that gyroscopic precession above about 35 mph typically causes a torque absess on most twin shock Guzzis that lack a non-Euclidean swingarm.
So I wear all my gear, sit on the bike, and set pre-load to achieve about 1/3 sag.
I figure that without a drawn reciprocation dingle arm, there is really no effective way to reduce the sinusoidal repleneration.
So I do 1/3 sag and call it good.
Finally someone explains it in simple layman terms :bow: :evil:
:popcorn:
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I’m surprised that nobody has discussed the fact that gyroscopic precession above about 35 mph typically causes a torque absess on most twin shock Guzzis that lack a non-Euclidean swingarm.
So I wear all my gear, sit on the bike, and set pre-load to achieve about 1/3 sag.
I figure that without a drawn reciprocation dingle arm, there is really no effective way to reduce the sinusoidal repleneration.
So I do 1/3 sag and call it good.
Yes , and according to the theory of relativity , gravity pushes down .
Dusty
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And here I thought gravity sucked!
I disagree with the notion the frame is what moves and not the ground.
That's definitely the case with no suspension.
The objective is to keep the frame from moving up and down - the wheels should do all of that. That's what suspension is all about!
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Actually it pushes the swingarm down .
Dusty
Closer to the road..?
I would have thought that the axle would always be the same distance from the road surface..
Does the tyre go below the level of the road..
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Exactly , it rises because as the swingarm is pushed down the frame has to rise .
Dusty
Dusty..
I think you are purposely taking the piss and you got me..
As that great philosopher John Mc Enroe said...”YOU CAN’T BE SERIOUS..”
The distance of the axle to the ground never changes.....Think mate..
If I squat down then push down with my feet to stand up, I don’t succeed in pushing my feet down because they are on the ground, the equal and opposite force pushes me up.
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Yes , and according to the theory of relativity , gravity pushes down .
Dusty
Well not actually according to the theory.
The lesser mass will be attracted to the greater mass, there is no “up” or “down..”
For Chrissakes Dusty, go back to talking sense and put this into “Thread Drift..”
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The frame rises because the swingarm is pushed down .
Dusty
The bleedin’ obvious Dusty..
So does cranking on pre load actually MOVE the axle downward or not.
A one word answer of two or three letters will suffice.
It will start with a “Y” or an “N”...
And then we’ll know which of your comments to delete.. :popcorn:
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If my understanding is correct Dusty is correct. My engineer friend informs me that this is sometimes called a paradox-in where an observed "issue" is thought to be one thing due to 'commom knowledge" but in fact is some other. While the observation may be the bike is raising-in fact it is changing due to the force exerted into the ground.
Thing of a space station in orbit. It's falling at a constant rate and, to keep it VERY simple, stayes in it's relative orbit as the earth is "falling" away at the sdame constant rate. Yes, there are other factors but this is the basic concept.
The notion of "oversprung and underdamped" is spot on. That's the defination of a cheap shock, which almost every OEM can claim.
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Effectively a spring is a lever that can apply force in two directions . Thing of the human arm which is also a lever arm like early Moto Guzzi suspension or the lever style shocks used on some British cars . What happens when you do a push up , where is the force being applied ? Now turn over on to your back and make the same arm motion involved in a push up . What happens , nothing , right ?
Dusty
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Dusty...
A lever is a beam that operates through a fulcrum or pivot, a spring is an expanding mechanism releasing stored energy.
If the bike sails across a depression in the road then yes, the axle will be pushed “downward” in the accepted sense to maintain contact with the surface. But we are talking about winding on preload with the bike static and at rest, so to suggest that this results in pushing the swing arm down, is a touch infantile and ill advised.
KOF I really do love you
(https://i.ibb.co/dBxcwxT/E38-CE06-D-36-EC-4-DD4-8-BA3-B19232-B86-F01.png) (https://ibb.co/dBxcwxT)
But mates or not, if you read Dusty’s assertion word for word..?
He’s not correct.
He SAID... “it pushes the swing arm down...” BS
He SHOULD have said...”it pushes down on the swing arm..” Yes.
Tusayan understands..(as usual..).
And KOF mate..
Analogies about falling space stations while well intended, are a bit of a flight of fancy into uncharted waters of tangential argument, full of more holes than Swiss cheese..
Sound engineering principles with correctly applied terminology will be more likely to win the day... :popcorn:
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Dusty...
You said... “it pushes the swing arm down...” BS
You SHOULD have said...”it pushes down on the swing arm..” Yes.
Tusayan understands..(as usual..).
OK , the force is applied downward to the swingarm . How does that change what is happening ?
Dusty
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OK , the force is applied downward to the swingarm . How does that change what is happening ?
Dusty
It doesn’t, but I’ll hammer away at the misconceptions one by one.
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It doesn’t, but I’ll hammer away at the misconceptions one by one.
Oh please do .
You do understand that in effect a spring is still a lever , even by your definition . In fact , the force applied won't work unless it is applied to something , in this case the ground . Lay on your back and do a push up , what happens ?
Dusty
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Oh please do .
You do understand that in effect a spring is still a lever , even by your definition . In fact , the force applied won't work unless it is applied to something , in this case the ground . Lay on your back and do a push up , what happens ?
Dusty
Not by my definition it’s not..
Where’s the pivot ?
(https://i.ibb.co/DCYHcrP/98-DCC2-B6-D292-4-A94-A352-CA91-FFF856-A0.png) (https://ibb.co/DCYHcrP)
I do understand the concept that the force won’t work unless it’s applied to the ground..
Archimedes said..
“Give me a place to set my foot and I will move the world..”
If I lay on my back to do a push up, what happens..?
I go to sleep.
This should be in “Thread drift..”
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A few of you have made some helpful comments, thanks.
But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!
My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?
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So, I have a Magni Swing arm on my Tonti frame bike. When adding preload, where is this lever action pushing? From the gear box to the upper shock frame mount? From the bell crank section to the torque arm and lower frame? Or a combination of both? Does the will base get shorter as the swing arm folds up? Does the rear wheel axle move in an arc around the front swingarm mounting point or does it move in a slope/angle?
And why does the bike squat now instead of raising the rear of the bike with a Magni swingarm?
What good is preload or sag on a shaft drive bike if the torque causes the swingarm to drive under the bike, top out the shocks and making the rear shocks useless while accelerating?
There is an awful lot going and trying to make it all work in an imperfect world is impossible. I find that sitting in the lazy boy has the best seat of the pants feel and the best handling characteristics. Warm in the winter, cool in the summer, always dry and the view changes as I move the chair around the house.
Explaining all the various functions and variable is one thing, making it all work together and make each individual rider happy all the time, never going to happen. My back is killing me this morning and I just got out of my $2,000 bed.
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Preload basically just changes the ride height.
Or that is my understanding.
This bloke seems to be universally loved..
He is correct and we should have stopped here..
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A few of you have made some helpful comments, thanks.
But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!
My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?
Heck, we did not get to stiction or how the mounting eyes with rubber bushing influence a shocks performance. Or how duel or multi rate springs really do not work because the lighter portion is preloaded out to support the bike and rider without bottoming out the shock.
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A few of you have made some helpful comments, thanks.
But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!
My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?
What happens here Chad is that in an attempt to enter the fray, all sorts of extraneous argument and irrelevant analogies, can be inserted into the debate that only serve to contaminate the facts.
Can you give me three names that helped and three names that didn’t ?
I’ll come up with two that helped..
Wayne Orwig and Tusayan.
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Heck, we did not get to stiction or how the mounting eyes with rubber bushing influence a shocks performance. Or how duel or multi rate springs really do not work because the lighter portion is preloaded out to support the bike and rider without bottoming out the shock.
Off you go then..
BTW..
It’s dual, what’s happening between some of us here is a duel..
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Ah, Huzo, that would be a to vulgar display of my power! All I can say is, "you know who you are!"
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All I can say is, "you know who you are!"
I do believe that can be the problem Chad.
Sometimes you don’t..
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I sense regret from Chad that he posted such a simple question, and we all realize now, that just like life, "suspension" is a miracle.
Discussions, arguments,& posts like this, can be like life itself, "Will the Circle be Unbroken"
Interesting comment from John in regards to the Magni swingarms, I came close to buying a former race bike once, that had a Magni rear end, so I've always been interested in the engineering.
I recently watched a VRRA racer, who is a very competent respected builder, suffer a catastrophic failure his first test race on the track,with his home built/designed Magni style swing arm on his Guzzi. The solid steel brackets and welds completely blew apart at the anchor points in the swing arm pivot area, very obviously some huge forces at play, that neither he nor I fully understood.
It has been a fruitful discussion, I will continue to crank my preload so the bike doesn't wallow going around a corner,lol,,, :laugh: but now I realize, from the article Ryan posted,that my understanding of damping was backwards; the first thing I'm going to try this spring is lighter damping settings on my rear shock on the CalVin to see if the wheel responds quicker to changes in the road surface, going around rough corners. :thumb:
Tks
Kelly
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So, I have a Magni Swing arm on my Tonti frame bike.
1. When adding preload, where is this lever action pushing? From the gear box to the upper shock frame mount? From the bell crank section to the torque arm and lower frame? Or a combination of both? Does the will base get shorter as the swing arm folds up?
2. Does the rear wheel axle move in an arc around the front swingarm mounting point or does it move in a slope/angle?
3. And why does the bike squat now instead of raising the rear of the bike with a Magni swingarm?
4. What good is preload or sag on a shaft drive bike if the torque causes the swingarm to drive under the bike, top out the shocks and making the rear shocks useless while accelerating?
There is an awful lot going and trying to make it all work in an imperfect world is impossible. I find that sitting in the lazy boy has the best seat of the pants feel and the best handling characteristics. Warm in the winter, cool in the summer, always dry and the view changes as I move the chair around the house.
Explaining all the various functions and variable is one thing, making it all work together and make each individual rider happy all the time, never going to happen. My back is killing me this morning and I just got out of my $2,000 bed.
1. 'pushing' at the front end of the arm. See #2.
2. The *axle* moves;
a. In an arc the radius of the height of the triangle created by the swingarm and reaction rod theoretical intersection, when they intersect in front of the axle;
b. In an arc the radius of the length of the swingarm and rod, when they are equal length and parallel;
c. In a reverse arc difficult to calculate when the swingarm and rod intersect theoretically behind the axle (they never do, in my experience)
3. The bike squats because with the parallelogram linkage, the shaft jacking is countered by the suspension geometry, and the weight transferred to the rear under acceleration is free to compress the suspension, as with other bikes (ignoring chain jacking)
4. Well...something is better than nothing. Sag still works until the jacking effect removes it.
For you mechanical engineers, let's not fall into the 3rd decimal place on my mathematical descriptions.
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(https://i.ibb.co/cb9Rd9x/7-FF6-BCAB-0682-45-F1-9690-D17-CE647-A065.png) (https://ibb.co/cb9Rd9x)
So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.
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Say what?
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(https://i.ibb.co/cb9Rd9x/7-FF6-BCAB-0682-45-F1-9690-D17-CE647-A065.png) (https://ibb.co/cb9Rd9x)
So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.
Thanks! I needed that.
This subject is getting way to serious. (as in way off the deep end)
:-)
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(https://i.ibb.co/cb9Rd9x/7-FF6-BCAB-0682-45-F1-9690-D17-CE647-A065.png) (https://ibb.co/cb9Rd9x)
So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.
Direct your attention to centre stage folks..
Behold one of the greatest comedians to ever tread the boards...!
The incomparable zedXmick... :bow: :thumb:
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Huzo said to Dusty: “And KOF mate.”
What does KOF mean?
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Huzo said to Dusty: “And KOF mate.”
What does KOF mean?
King of Fleece
Dusty
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Thanks! I needed that.
This subject is getting way to serious. (as in way off the deep end)
:-)
The great man Albert Einstein was once quoted as saying..
If you can’t explain something simply, you probably don’t understand it yourself..
I didn’t think I complicated it too much..
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(https://i.ibb.co/cb9Rd9x/7-FF6-BCAB-0682-45-F1-9690-D17-CE647-A065.png) (https://ibb.co/cb9Rd9x)
So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.
All so very true, until you bolt them to a bike
Then what huzo says, frame height changes
Or, what dusty says, swinging arm goes down
Either way, eye to eye distance changes
Let’s call it suspension travel
Adjust to weight
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Huzo said to Dusty: “And KOF mate.”
What does KOF mean?
I would have been more accurate if I’d put KoF...(King of Fleece)
(He gave me those lovely badges for my V85, I gave those eagle things the arse..) :thumb: :bow:
Sorta’ like the “of” in AoA...(angle of attack)
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I'm touched............ ............in the nice way!
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Thanks! I needed that.
This subject is getting way to serious. (as in way off the deep end)
:-)
Sorry, he's dead wrong.
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I’ve turned those dials every which way in every combination imaginable and can’t tell little to no different in the ability of being able to control a particular motorcycle in any particular riding conditions or road type. So there’👍
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All so very true, until you bolt them to a bike
Then what huzo says, frame height changes
Or, what dusty says, swinging arm goes down
Either way, eye to eye distance changes
Let’s call it suspension travel
Adjust to weight
Of course that goes without saying...suspension travel. Only thing you change with more preload is sag setting, you don’t change “ride height”. Now the shock below let’s you add “ride height” by adjusting Lenght adjuster.
(https://www.omniaracing.net/images/products/sospensioni/ammortizzatori/S36PLl.jpg)
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A few of you have made some helpful comments, thanks.
But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!
My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?
Regarding your question relating to correct oil for your tyres, you’ve inadvertently stumbled upon the only topic in the world that I am not an acknowledged expert on...
But I can give an educated guess if you wish..(which I’m sure will ultimately be proven to be completely correct..)
Now on the topic of sub atomic particles an Quantum/String Theory..?
That’s another matter entirely..
I’ve put the full stop on all there is to know about science.
You could say I put the “period” in “periodic table..”
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Only thing you change with more preload is sag setting, you don’t change “ride height”.
(https://www.omniaracing.net/images/products/sospensioni/ammortizzatori/S36PLl.jpg)
Well, yes you do..
You see if you had 30 mm of sag with your weight on your bike, then you wound on some pre load..
You would have less sag when you jumped back on...Yes ?
So, if you have less sag after winding on pre load (let’s say 20 mm) then it means your seat has sunk 10 mm less than before..
Now things are getting hazy here, but what do you think that would have done to your ride height ?
There is always a third possibility here and that is that you may be just winding us up..(as it were). :wink:
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I fully understand what Zed is saying especially with the example of the shocks.
I do agree with Huzo as well. If you set X amount of sag and your bike is too low, add more preload to raise the seat/lower the swingarm.
Now I do like the shocks in Zsd post. Set your sag and if your bike hits every speed bump, screw out the eye. Make your 12" shock a 12.25".
Tom
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So in this example you have both sets of shocks set to a perfect sag of 150mm now you want to change your ride height. One set of shocks you have to “compromise” your perfect sag to “fake change your seat height“ The other set of shocks you are still at your perfect sag height and now you truly change your ride height by changing the length adjuster.
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Thanks Huzo and company. I pretty much get it now. If I don’t over think it, it’s fairly easy to comprehend!
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Thanks Huzo and company. I pretty much get it now. If I don’t over think it, it’s fairly easy to comprehend!
:thumb: :thumb:
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Thanks Huzo and company. I pretty much get it now. If I don’t over think it, it’s fairly easy to comprehend!
What I find incredible, is how I have read so many articles over the years where some scribe says..
“I wound on some pre load and that firmed up the arse end...”
You could have an arse end like Serena Williams (firm), and winding on pre load’ll do nothing.
They think it was firmer because the seat didn’t drop as far when they jumped on..( the bike , not Serena...)
An idealised example, lets start with a 9” one...(wouldn’t THAT be nice.. :evil: :drool:)
A. Zero pre load +. 200 lbs load = 4” of spring compression to stabilise to a compressed length of 5”.
B. 1” of pre load + 200 lbs load = 3” of spring compression to stabilise to a compressed length of 5”.
C. 2” of pre load +200 lbs load = 2” of spring compression to stabilise to a compressed length of 5”.
And so on until you could wind on enough pre load so the spring compressed 1/4” when you dragged your carcass aboard and you’d convince yourself that the suspension was as hard as a bull’s arse but not so..
The ride height has changed but..THE COMPRESSED LENGTH OF THE SPRING IS ULTIMATELY THE SAME.
In all examples, the spring “winds up” ( :grin:) arriving at the same compressed length, but y’all will have thought examples “B” & “C” were firmer settings, ‘cos it didn’t drop as far when you clambered aboard.
Once the damper has come off the top stop (ie not topped out), the pre load you applied becomes irrelevant to the spring performance as an isolated system..
Moreover.
If the shock had no damper rod and the spring was free to expand or contract with no mechanical limitations, it can be seen more easily, that winding on pre load has zero effect on firmness...(just picture that for some time..)
So it therefore can be accepted that if the damper stays off the stops...? (No topping or bottoming out..)
The preloading has no effect other than ride height... :popcorn:
Hope that helps..
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The preloading has no effect other than ride height...
For a linear spring, yes, agreed.
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For a linear spring, yes, agreed.
I’ll need educating on that..
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A. Zero pre load +. 200 lbs load = 4” of spring compression to stabilise to a compressed length of 5”.
B. 1” of pre load + 200 lbs load = 3” of spring compression to stabilise to a compressed length of 5”.
C. 2” of pre load +200 lbs load = 2” of spring compression to stabilise to a compressed length of 5”.
In all examples, the spring “winds up” ( :grin:) arriving at the same compressed length, but y’all will have thought examples “B” & “C” were firmer settings, ‘cos it didn’t drop as far when you clambered aboard.
The preloading has no effect other than ride height... :popcorn:
I'm almost afraid to jump back into this, :evil: because as I read your post, I said to myself, finally "clarity" but as I thought about it a bit more, not so much. :undecided:
ie. I'm pushing my CalVin, the refined couch that it is, hard around a bumpy corner with your setting "A" and it seems to wallow as I use up the 4" of available spring compression before I hit the firmer 5" compressed spring.
Repeat the same thing but with your setting "C" but now I only have to use up 2" of available spring compression before I feel that secure stable firm feeling of the 5" compressed spring.
The bike to me on your setting "C" feels like it is tracking and responding much more securely and decisively, much firmer ride and much less wallowing.
Am I dreaming? I don't think so, ime setting "A" can feel unsettling, vs setting "C" feels much more stable and secure.
Seems to me, that a little bit more than just ride height is being accomplished.
fwiw ymmv
Kelly
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I mean this in all sincerity, not to be sarcastic and I’m not hiding a swipe..
I cannot explain what my point is any other way without repeating myself.
However, there is one point of which I may make mention. The example “A” with no preload present, compared to “C” with max. preload does contain one potential difference in reality.
The “A” example allows for larger stroke on the shock/s due to the fact that it won’t “top out” as readily. This of course means that there will be more pitching motion and that will amplify any geometric changes to your bike in the dynamic environment that you describe.
That however is no more than an educated guess that I would not readily hang my hat on... :popcorn:
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The “A” example allows for larger stroke on the shock/s due to the fact that it won’t “top out” as readily. This of course means that there will be more pitching motion and that will amplify any geometric changes to your bike in the dynamic environment that you describe.
^^^^^^That makes sense, especially with cheaper older shocks with loose bushings/seals etc :thumb: :bow:
fwiw I had a bargain lined up on a new set of Ikons, because Wolfgang out in British Columbia is getting out of the biz,(will still service Ikon but no new sales once stock is gone) but he didn't have my model :cry:
Tks for your insight and patience
Kelly
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@Huzo, you have this figured out fine. The only thing that may be missing is that with the static sag reduced by higher preload, and the shock (s) now being thereby longer when carrying a given rider, rear suspension linkage geometry may be different at the static sag position and the effective suspension rate at the wheel slightly changed by that geometry change.
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@Huzo, you have this figured out fine. The only thing that may be missing is that with the static sag reduced by higher preload, and the shock (s) now being thereby longer when carrying a given rider, rear suspension linkage geometry may be different at the static sag position and the effective suspension rate at the wheel slightly changed by that geometry change.
Things that make ya’ go
Hmmmm...
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I’ll need educating on that..
Take a look at a bike with a non-linear spring. The stock V85 rear spring is such an example.
You will observe that the coils are wound tighter (less space between windings) than those at the bottom. As the spring compresses, the top windings will close together, and therefore unable to compress any further. This in effect creates a spring of shorter length, which has a higher compression rate. Then it requires greater force to compress this spring further.
There's probably other forces not considered in my simple explanation, but that's how I understand it.
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Look that’s fine.
Also the tighter wind gives a less vertical aspect to the wire, which increases the bending moment yada yada...
What I REALLY wanna’ know is, how will pre load affect this arrangement ?
I’m developing my understanding
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Just because I am still a little confused and not sure who is correct on ride height...….
How about some pics with measurements to prove you theory???
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Also the tighter wind gives a less vertical aspect to the wire, which increases the bending moment yada yada...
Them's the other forces I'm talking about, but insignificant IMHO. Nothing's perfect.
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Look that’s fine.
Also the tighter wind gives a less vertical aspect to the wire, which increases the bending moment yada yada...
What I REALLY wanna’ know is, how will pre load affect this arrangement ?
I’m developing my understanding
The effect of progressive spring rates is unaffected by preload, because as long as the shock moves any amount off the limits of its travel when the bike is loaded, the spring is no more or less compressed when preload is changed.
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The effect of progressive spring rates is unaffected by preload, because as long as the shock moves any amount off the limits of its travel when the bike is loaded, the spring is no more or less compressed when preload is changed.
Agreed. That is, until the closer wound coils reach the end of their travel (hopefully not all at once). Then the spring becomes effectively shorter, and therefore provides a greater resistance to further movement.
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Agreed. That is, until the closer wound coils reach the end of their travel (hopefully not all at once). Then the spring becomes effectively shorter, and therefore provides a greater resistance to further movement.
Yes Dave, but by then the shock has moved off it’s stops and the pre load has become irrelevant.
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Yes Dave, but by then the shock has moved off it’s stops and the pre load has become irrelevant.
You would not want a situation where the shock has not moved off it's stops with the rider on board. If this situation exists, then there is too much preload wound 1n.
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You would not want a situation where the shock has not moved off it's stops with the rider on board. If this situation exists, then there is too much preload wound 1n.
Well I guess so Dave, but no one suggested otherwise.
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Four pages on preload? It must still be winter.. :evil: :smiley:
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Well I guess so Dave, but no one suggested otherwise.
What really matters is what oil you use in the shocks. Dino or synthetic?
:violent1:
And a couple of pages devoted to if preload changes the ride height. :boozing:
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I have to toot my own horn, I’ve started a lot of far too long threads over the years!
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If 20 guys were chosen at random from the membership, I’m given to wonder what % would be able to explain definitively what pre load is and a few of the basic facts surrounding it... :popcorn: