Wildguzzi.com
General Category => General Discussion => Topic started by: Huzo on September 20, 2021, 05:17:59 PM
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Rudy’s thread was becoming badly contaminated by extraneous off topic chatter.
So here’s the thing.
Tris noted that every time it started to gell for him, it drifted off.
Start by separating the spring from the damper.
Realise that the damper has two functions.
1.
To progressively dampen the oscillations of a given spring when deflected from rest.
2.
To give a top and bottom limit to the maximum and minimum length of the captured spring in the assembled unit.
Next..
The load is supported by the spring, not the damper....(ignore for now any pressurised shocks).
Consider a 200 mm spring at rest on the bench.
Now assemble the shock with no preload.
When you sit on the bike, you are effectively sitting on the spring. That un preloaded spring will compress until it reaches it’s compressed length for that load.
Can we call that length 150 mm....(it has compressed 50mm). Remember it has no preload yet.
The spring compressed, (sagged) 50 mm under the combined weight of rider and bike. You will perceive a certain “softness” that you associate with that spring.
Now put the bike back on the centrestand with the rear wheel off the ground...The shock is now “topped out” against it’s top stop, like it was on the bench.
Wind on 25 mm of pre load...Now your spring is 175 mm long.
Roll the bike off the stand and jump back on.
The total LOAD has not changed, so it’ll come as no surprise that the spring compresses back to....?...150 mm
The same as before the preload, but it has only compressed 25 mm under the effect of the load to get to that 150 mm
however it will perform the same as the unpreloaded example, because it has still only been compressed to the same length as the first example (150mm).
Here’s the crunch though.
Because you have only compressed the spring 25 mm in the second example, the eye to eye length will be more than the unpreloaded example and therefore the ride height will be greater...(the damper rod is 25 mm further extended).
But the spring performance will not have altered.
For Tris...
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Thanks for posting that. Took a bit of thought but I think I get "the crunch" now. Spring is compressed the same but the shock rides higher in it's travel due to preload on the spring. I got heavier springs on my trials bike and dirt bike as I am "American size". Makes a huge difference on the trials bike but not so much on the dirt bike???? I am not a fast dirt bike rider so maybe that has something to do with it......
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Rudy’s thread was becoming badly contaminated by extraneous off topic chatter.
So here’s the thing.
Tris noted that every time it started to gell for him, it drifted off.
Start by separating the spring from the damper.
Realise that the damper has two functions.
1.
To progressively dampen the oscillations of a given spring when deflected from rest.
2.
To give a top and bottom limit to the maximum and minimum length of the captured spring in the assembled unit.
Next..
The load is supported by the spring, not the damper....(ignore for now any pressurised shocks).
Consider a 200 mm spring at rest on the bench.
Now assemble the shock with no preload.
When you sit on the bike, you are effectively sitting on the spring. That un preloaded spring will compress until it reaches it’s compressed length for that load.
Can we call that length 150 mm....(it has compressed 50mm). Remember it has no preload yet.
The spring compressed, (sagged) 50 mm under the combined weight of rider and bike. You will perceive a certain “softness” that you associate with that spring.
Now put the bike back on the centrestand with the rear wheel off the ground...The shock is now “topped out” against it’s top stop, like it was on the bench.
Wind on 25 mm of pre load...Now your spring is 175 mm long.
Roll the bike off the stand and jump back on.
The total LOAD has not changed, so it’ll come as no surprise that the spring compresses back to....?...150 mm
The same as before the preload, but it has only compressed 25 mm under the effect of the load to get to that 150 mm
however it will perform the same as the unpreloaded example, because it has still only been compressed to the same length as the first example (150mm).
Here’s the crunch though.
Because you have only compressed the spring 25 mm in the second example, the eye to eye length will be more than the unpreloaded example and therefore the ride height will be greater...(the damper rod is 25 mm further extended).
But the spring performance will not have altered.
For Tris...
Like a dog on a bone, just gotta make it hard eh? :cool:
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Rudy’s thread was becoming badly contaminated by extraneous off topic chatter.
So here’s the thing.
Tris noted that every time it started to gell for him, it drifted off.
Start by separating the spring from the damper.
Realise that the damper has two functions.
1.
To progressively dampen the oscillations of a given spring when deflected from rest.
2.
To give a top and bottom limit to the maximum and minimum length of the captured spring in the assembled unit.
Next..
The load is supported by the spring, not the damper....(ignore for now any pressurised shocks).
Consider a 200 mm spring at rest on the bench.
Now assemble the shock with no preload.
When you sit on the bike, you are effectively sitting on the spring. That un preloaded spring will compress until it reaches it’s compressed length for that load.
Can we call that length 150 mm....(it has compressed 50mm). Remember it has no preload yet.
The spring compressed, (sagged) 50 mm under the combined weight of rider and bike. You will perceive a certain “softness” that you associate with that spring.
Now put the bike back on the centrestand with the rear wheel off the ground...The shock is now “topped out” against it’s top stop, like it was on the bench.
Wind on 25 mm of pre load...Now your spring is 175 mm long.
Roll the bike off the stand and jump back on.
The total LOAD has not changed, so it’ll come as no surprise that the spring compresses back to....?...150 mm
The same as before the preload, but it has only compressed 25 mm under the effect of the load to get to that 150 mm
however it will perform the same as the unpreloaded example, because it has still only been compressed to the same length as the first example (150mm).
Here’s the crunch though.
Because you have only compressed the spring 25 mm in the second example, the eye to eye length will be more than the unpreloaded example and therefore the ride height will be greater...(the damper rod is 25 mm further extended).
But the spring performance will not have altered.
For Tris...
I heard the same thing Saturday when a local rider was checking the suspension & preload on my Ducati. Nor sure I still understand it. The bike "feels" stiffer with more preload. But it does sit up higher with more preload, no question.
BTW- he was impressed that the suspension had so little stiction but the rear shock is too stiff (high speed) compression. we didn't change anything, it was close enough other than the "Stiff" rear shock.
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Like a dog on a bone, just gotta make it hard eh? :cool:
It’s not hard Bulldog.
But that was a bit prolonged because it allows people who are coming to terms with the concept, to work methodically through and identify where their misunderstanding begins.
You start with the bit that’s easy to understand and work your way through.
Caffeineo in the previous post, indicated that there was a light beginning to appear for him. My post was to help people who are on the cusp of getting it, not people such as yourself who (apparently) already do.
How would you have explained it more briefly without leaving out an important aspect ?
I could have done it in two lines to someone who already understood, but I’ve been trying to learn the stuff Beetle does and I like the way he patiently leads the beginner along.
BTW.
I don’t know what the emoji is supposed to convey, can you enlighten me ?
Please don’t make it too hard.... :popcorn:
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Thanks for posting that. Took a bit of thought but I think I get "the crunch" now. Spring is compressed the same but the shock rides higher in it's travel due to preload on the spring.
Almost mate.
The SPRING is compressed TO the same length, not compressed BY the same amount.
That would imply that in the second example, it was compressed 50 mm.
This is why an explanation has to be free of ambiguity. I know what you meant to say and you’d have been correct, but these points have to be nailed down to definitions. That’s why I’m criticised for being picky and I know it looks like that.
If we all just agree with BS it’ll be warm and fuzzy, but at the end of the day we’ll still be wrong.
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Without wishing to rain on anyone’s parade, research into these subjects may help in understanding motorcycle suspension and the effect of adjusting preload
1/ Progressive springs
2/ Rising rate linkage (n/a v85 but relevant to most monoshock Guzzis)
3/ Angle of shock absorber (very relevant to v85 and noticeable difference on 21 V7 compared to prior)
To understand the latter read up on 60’s Velocettes with adjustable top shock mount position.
Happy reading, no debate, it is what it is
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Cheers Huzo - this is good of you :bow: :bow:
Firstly
......Here’s the crunch though.
Because you have only compressed the spring 25 mm in the second example, the eye to eye length will be more than the unpreloaded example and therefore the ride height will be greater...(the damper rod is 25 mm further extended).
But the spring performance will not have altered.
For Tris...
GOT IT ... I think :grin:
In my words
If you changed the spring for a solid tube (spacer) the preload adjuster just changes the relative position between the top and bottom mounts as they slide on the damper that controls the max and minimum stroke (ignoring the damping effect)
So when I raise the preload to carry my lardy ass the prime objective is to maintain the suspension (say) midway through its travel (I know that's a simplistic position)
Is that right?
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Without wishing to rain on anyone’s parade, research into these subjects may help in understanding motorcycle suspension and the effect of adjusting preload
1/ Progressive springs
2/ Rising rate linkage (n/a v85 but relevant to most monoshock Guzzis)
3/ Angle of shock absorber (very relevant to v85 and noticeable difference on 21 V7 compared to prior)
To understand the latter read up on 60’s Velocettes with adjustable top shock mount position.
Happy reading, no debate, it is what it is
To be honest this bit I have more understanding of (I THINK) and simplistically
1) Spring gets stiffer the more it compresses
2) That's the application of different length levers
3) That's to do with force vectors
Assuming that is correct, it all falls apart if you don't get the basics which is where I am (was?) :thumb:
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Cheers Huzo - this is good of you :bow: :bow:
Firstly
GOT IT ... I think :grin:
In my words
If you changed the spring for a solid tube (spacer) the preload adjuster just changes the relative position between the top and bottom mounts as they slide on the damper that controls the max and minimum stroke (ignoring the damping effect)
So when I raise the preload to carry my lardy ass the prime objective is to maintain the suspension (say) midway through its travel (I know that's a simplistic position)
Is that right?
Well if it’s not then I’m not....(but I am).
The simplistic approach is always the best, if you have not introduced variables or inconsistencies into the mix.
Yes Tris, that is correct.
Once you solidify that into your thinking, you’ll be aghast at some of the people you’ll hear saying...
“The bike was too soft in the arse end through turn 4, so I wound on a bit of preload to stiffen it up a bit..”
They’ll do what they think is right then swear black and blue that it was a good idea..(better than the alternative). :rolleyes:
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I think the error is made in this type of scenario.
If your forks are going to bottom out, the tendency may be to apply some pre load. This will indeed reduce the tendency to bottom out, but not because the fork travel is reduced (stiffer ride), it is because you have pushed the bottom slider further away and given the staunchions more room to compress before the crash at the end.
The ride quality won’t have changed, but the whole thing is happening further away from the bottom stop and the tendency to bottom out is reduced.
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Great explanation, thanks
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Great explanation, thanks
^^^^^ :thumb:
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In between working :wink: I've been pondering this!
“The bike was too soft in the arse end through turn 4, so I wound on a bit of preload to stiffen it up a bit..”
Should he have
a) gotten some springs at a higher rate to cope with his weight
b) wound the compression damping up to slow the rate the suspension got to full travel?
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In between working :wink: I've been pondering this!
Should he have
a) gotten some springs at a higher rate to cope with his weight
b) wound the compression damping up to slow the rate the suspension got to full travel?
(a) Certainly yes
(b) I’d venture to say so
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It’s not hard Bulldog.
But that was a bit prolonged because it allows people who are coming to terms with the concept, to work methodically through and identify where their misunderstanding begins.
You start with the bit that’s easy to understand and work your way through.
Caffeineo in the previous post, indicated that there was a light beginning to appear for him. My post was to help people who are on the cusp of getting it, not people such as yourself who (apparently) already do.
How would you have explained it more briefly without leaving out an important aspect ?
I could have done it in two lines to someone who already understood, but I’ve been trying to learn the stuff Beetle does and I like the way he patiently leads the beginner along.
BTW.
I don’t know what the emoji is supposed to convey, can you enlighten me ?
Please don’t make it too hard.... :popcorn:
:popcorn: :popcorn: :popcorn: :popcorn:
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That’s an informative addition RK.
Someone may get more out of that than my example/s. Over the journey I’ve found that at times, I can struggle furiously over some concept and then along comes someone and blurts it out in a different way and suddenly...
Bingo...!
It’s a beaut subject and the only reason I laboured with it was that there were a lot of people struggling like I was.
Nice to hear from you by the way.... :bow: :thumb:
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I heard the same thing Saturday when a local rider was checking the suspension & preload on my Ducati. Nor sure I still understand it. The bike "feels" stiffer with more preload. But it does sit up higher with more preload, no question.
BTW- he was impressed that the suspension had so little stiction but the rear shock is too stiff (high speed) compression. we didn't change anything, it was close enough other than the "Stiff" rear shock.
As soon as your butt hits the seat as you climb aboard, you get a signal as to the perceived “firmness” of the suspension.
As an exercise.
Wind all the preload off your shock and jump on the bike, feet up with someone holding you level.
Have an assistant measure the length of the SPRING.
Now climb off and wind on a realistic amount of preload (say, 10mm).
Hop back on the bike with your feet up and with your scantily clad assistant holding you level, have your other assistant measure the SPRING length again.
It will be the same...(it will therefore perform the same).
Now put the tape measure away and stop looking at your scantily clad assistant..(don’t be tempted to try measuring anything else...) :wink:
I hope the preceeding may serve useful to anyone who made no sense of my earlier offering.
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I suspect that part of my confusion was the use of the word "Preload".
Am I right to say that the objective is NOT to pre load the spring it is to just shift the mounting point of the spring
If the shock wasn't there limiting movement then ride height would simply increase
However we have a shock limiting the movement so the spring is compressed, and mechanically compressing the spring by 1 inch is the same as applying a mass that compresses the spring by one inch
Physically ride height can never exceed the max travel of the shock however the spring doesn't know that so doesn't react until the travel created by the travel created by the mass exceeds the compression applied by the "pre load" adjuster (I'm assume simple static loads at this point)
Am I still on the right track?
Cheers
Tris
PS
My second-hand Roamer came with Hagon Nitros fitted and 17GKg springs IIRC
I wrote to Hagon last night to see if I have the right springs for my mass :grin:
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I suspect that part of my confusion was the use of the word "Preload".
Am I right to say that the objective is NOT to pre load the spring it is to just shift the mounting point of the spring
If the shock wasn't there limiting movement then ride height would simply increase
However we have a shock limiting the movement so the spring is compressed, and mechanically compressing the spring by 1 inch is the same as applying a mass that compresses the spring by one inch
Physically ride height can never exceed the max travel of the shock however the spring doesn't know that so doesn't react until the travel created by the travel created by the mass exceeds the compression applied by the "pre load" adjuster (I'm assume simple static loads at this point)
Am I still on the right track?
Cheers
Tris
PS
My second-hand Roamer came with Hagon Nitros fitted and 17GKg springs IIRC
I wrote to Hagon last night to see if I have the right springs for my mass :grin:
Mate I think so, preloading the shock is purely and simply to stop the spring having to squash so much before it will equalise to the load.
If your shock compressed 50 mm with your load in an unpreloaded condition, you could theoretically get off, wind on 49 mm of pre load and the spring would only have to squash another 1 mm to carry you when you jumped on.
But the first time you exited a depression, it would obviously top out.
Think of YOUR spring on YOUR bike with YOUR weight as an example and that spring will always compress to the same length (X), loaded at 1g.
Winding on preload will just move the bottom perch that the spring sits on, higher up the damper body and as long as the rod does not top out, the top of the spring is free to retreat away from the bottom perch as it winds up always maintaining that (X) length.
Here’s one..
If you stand a coil spring on a sheet of wood on the floor and you place a load on the spring, it will obviously compress.
Then if you grab the piece of wood and lift it upwards, the top of the coil will move upwards at the same rate as the bottom because there is no impediment to it’s motion.
Same with a coil over spring like we have.
Winding on pre load if you were sitting on the bike with the shock loaded, would just result in the top of the coil retreating upwards, again as long as the damper doesn’t top out.
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Thanks H!
It's all making sense now from a spring perspective. Just need to have a think some more about damping :grin:
In other news.
Hagon have come back to tell me I need 18Kg (/mm?) springs as opposed the 17Kg on the bike now
Just need to find out how to get them changed out
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When are we going to get to the "shocking" part?
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When are we going to get to the "shocking" part?
Well...?
The thread hasn’t been nuked and a fight hasn’t broken out yet. That’s a bit of a shock isn’t it ?
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Nobody has yet brought up the touchy subject of the flux capacitor's part in all this. I do know this much. I am short, at 5'8 on a good day. Cranking up the preload for me to carry a passenger has always made it harder for me to swing a leg over the bike & reach the ground. Regardless of the science involved.
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Well...?
The thread hasn’t been nuked and a fight hasn’t broken out yet. That’s a bit of a shock isn’t it ?
I have learned a lot from this thread and there is nothing wrong with a respectable debate, regardless of the differences in one’s opinion. Just wish I was smart enough to offer any reliable information 🤔
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I read somewhere that Henry Ford grabbed the first model T off the line and took it for a spin across a lumpy field. His debrief note read "Needs shock absorbers." Some say he specified hydraulic, some say he was not specific. It doesn't matter. The point is that springs and shocks are two different components of a suspension system, and they have been forever. With that said, I'd like to offer how I understand them. Maybe it will help. Keep in mind that I'm speaking in generalities.,,,,,,,,,,
Hey RK, Tks very much for adding to this topic, as always, extremely well written :bow:
ps glad to see you're doing well and back in the fold
:bike-037:
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When are we going to get to the "shocking" part?
I'll have a stab for sh*ts and giggles
Compression damping
Controls the rate at which the spring compresses when an upward force is applied to the wheel - say a bump in the road
Rebound damping
Controls the rate at which the spring expands when the wheel comes across (say) - a hole in the road
I'm happy to delete this reply in it's entirety if I have that wrong! :grin: :grin:
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I'll have a stab for sh*ts and giggles
Compression damping
Controls the rate at which the spring compresses when an upward force is applied to the wheel - say a bump in the road
Rebound damping
Controls the rate at which the spring expands when the wheel comes across (say) - a hole in the road
I'm happy to delete this reply in it's entirety if I have that wrong! :grin: :grin:
The damper will have a position where it is sitting during travel along a smooth surface, shall we say mid stroke.
When you hit a bump for example (it could have been a depression), the damper will be forced to compress somewhat until the bump is cleared, then the spring will force the wheel back down to the road surface. Note that the spring will slam the wheel back down faster than it would have fallen under it’s own weight.
But without damping, the suspension will theoretically try to oscillate to and fro, past that idealised mid point that we have in our example, due to the inertia in the mass of the suspension components.
If we leave the bike for a moment so as to not be distracted by all the stuff going on in the reality of riding.
Again if we have our 200 mm spring out on the bench disassembled from the damper.
If you were to compress that spring say 50 mm then release it suddenly, high speed photography would show you that it recoils out PAST the 200 mm point to say 210 mm then back to 180 then out to 205 ....etc
That is an idealised set of numbers and possibly they would be a lot less, but the point is, the spring would oscillate around that mid point until enough WORK had been done for it to come to rest.
It won’t take long because the spring has low mass and therefore low kinetic energy.
In the reality of our heavy suspension components, they will try to oscillate for a longer time up and down each side of our mid point until the energy is dissipated, this is why we have our damping.
It forces the spring to act against a hydraulic resistance after the bump has been cleared and you are back on smooth road, so that oscillation is quickly reduced to zero.
Imagine you had a bike cranked up clear of the floor with the damper removed from the rear shock(s).
Compress the suspension to it’s physical limit by some apparatus, the release it suddenly.
You’d see the spring fire the swingarm back out to the normal position but the energy stored would take it past until the spring was actually STRETCHING, then that oscillation around the mid point would commence.
The work required in moving fluid through the ports of a damping unit is what dissipates that kinetic energy.
To directly address your suggestion.
If you run over a six inch high speed hump for example..
The primary task of the damper is not to control the RATE that the suspension compresses, because unless the suspension can compress to ALL of that six inches in the instant that you hit the bump the shortfall will be transferred into the frame and YOU will go up by the residual amount.
Again the PRIMARY function of the damper is to dissipate the residual energy in the system by compelling the spring to do WORK in the pumping of the fluid through the restrictions in the shock body.
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As soon as your butt hits the seat as you climb aboard, you get a signal as to the perceived “firmness” of the suspension.
As an exercise.
Wind all the preload off your shock and jump on the bike, feet up with someone holding you level.
Have an assistant measure the length of the SPRING.
Now climb off and wind on a realistic amount of preload (say, 10mm).
Hop back on the bike with your feet up and with your scantily clad assistant holding you level, have your other assistant measure the SPRING length again.
It will be the same...(it will therefore perform the same).
Now put the tape measure away and stop looking at your scantily clad assistant..(don’t be tempted to try measuring anything else...) :wink:
I hope the preceeding may serve useful to anyone who made no sense of my earlier offering.
That was discussion. Although I didn't want to see Rich scantily clad. BTW- I took his word on it that you're both right.
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That was discussion. Although I didn't want to see Rich scantily clad. BTW- I took his word on it that you're both right.
Can you re word that LR ?
I don’t know Rich is.
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Again the PRIMARY function of the damper is to dissipate the residual energy in the system by compelling the spring to do WORK in the pumping of the fluid through the restrictions in the shock body.
Key phrase pop out in discussions like this and this is it for me. A far better way of phrasing it than my sorry attempt :wink:
I think I'm about there now
https://www.youtube.com/watch?v=HmkvHTNQNxE
Thanks H and every one else for your input :thumb: :thumb: :thumb:
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Well...?
The thread hasn’t been nuked and a fight hasn’t broken out yet. That’s a bit of a shock isn’t it ?
Now that you mention it, it is a bit shocking that no one has gotten upset that the word "compression" is dangerously close to the work "oppression".... and that we should not be oppressing inanimate objects..... yet!
Springs have feelings too!!!!
We live in a very sensitive zeitgeist!
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Can you re word that LR ?
I don’t know Rich is.
Rich was the guy that was checking the sag on my Ducati last weekend. Just as I described earlier, he held and measured the bike when I sat on it and picked it up. Ultimately made no adjustments (which was close enough for me). He was impressed how little stiction in the suspension but thought that heavier springs might improve the ride and that the shock had too much high speed compression (jolt -not adjustable).
His statements were square with yours but I still don't quite grasp it all. Rich was a club racer for many years and owned a company that sold motorcycle springs.
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Rich was the guy that was checking the sag on my Ducati last weekend. Just as I described earlier, he held and measured the bike when I sat on it and picked it up. Ultimately made no adjustments (which was close enough for me). He was impressed how little stiction in the suspension but thought that heavier springs might improve the ride and that the shock had too much high speed compression (jolt -not adjustable).
His statements were square with yours but I still don't quite grasp it all. Rich was a club racer for many years and owned a company that sold motorcycle springs.
Oh, ok mate.
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Kiwi Dave made a remark regarding progressive springs.
Even in the case of a progressive spring, the ride quality will not change if you alter pre load and nothing else. Again you must remain between the top and bottom limits of your travel.
We all accept that the “softer” part of the spring is the first to be compressed as you commence loading and the spring rate increases as you continue to load.
But again let’s have our 200 mm coil spring out on the bench, but this time it’s progressive.
If you apply enough load to compress that coil 50 mm, the initial compressing action will have been relatively easy, but rapidly became more difficult.
But the total amount of compression remains to be 50 mm to give a compressed length of 150 mm.
Now if you assemble your unit with NO pre load, the damper will compress 50 mm under the same load.
Unload the unit.
If you wind on 25 mm of pre load the SPRING length will be 175 mm, now apply the same load again.
The shock will not start to compress until (say half) of the load is added, then as you let the full weight onto the shock, it will again compress to stabilise to the same 150 mm SPRING length as before.
Progressive or linear, ride quality is not affected by pre load.
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<snip> ride quality is not affected by pre load.
This, for some reason is the hardest concept for me to fully grasp. I have always thought that adding preload will make the ride stiffer......becaus e you are "pre loading" the spring. I know the spring rate is still the same and it still takes the same weight/force to compress the spring a specific amount with/without preload. Maybe just hard to let go of after years of hearing about adding preload to stiffen up the spring...... Kind of reminds me of trying to understand trigonometry many,, many years ago. I just need to keep thinking about it until something clicks. Thanks for posting all this. :thumb:
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The term preload says it all . you are pre loading the spring to compensate for a given load yet to be applied to keep the desired ride height and suspension geometry within the ideal operating range. A loaded rear spring relative to it's preload setting will have measurable effects on handling especially if compensation to the front suspension is not considered. My guess is if the op cranks up the rear pre load a bit as well as the rear rebound damping he will cure the wobble issue. Also, I would be banding the front forks to monitor rider sag while actually riding to determine if front preload and damping adjustments are necessary. Anyone who has ever overloaded a pickup truck and had their front end pointing towards the moon will remember the front end all over the road. Even though the rear springs were not bottomed out to the axle, Vehicle load relative to pre load ,wheelbase/ chassis geometry may not affect spring rate but will defiantly affect handling . Speed only magnifies anomalies.
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Anyone who has ever overloaded a pickup truck and had their front end pointing towards the moon will remember the front end all over the road.
Yes Lucian.
That is primarily because of the large rearwards displacement of the centre of mass.
The rear drives on a rigid tray truck, are a fair way forward of the back end. Indeed, ANY mass applied rearwards of the drives, will remove weight from the steer wheels...(no surprises there for anyone who’s ever been on a seesaw or teeter totter).
But in any and all cases in rigid trucks, addition of mass evenly over the cargo area, will move the C of M rearwards.
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This, for some reason is the hardest concept for me to fully grasp. I have always thought that adding preload will make the ride stiffer......becaus e you are "pre loading" the spring. I know the spring rate is still the same and it still takes the same weight/force to compress the spring a specific amount with/without preload. Maybe just hard to let go of after years of hearing about adding preload to stiffen up the spring...... Kind of reminds me of trying to understand trigonometry many,, many years ago. I just need to keep thinking about it until something clicks. Thanks for posting all this. :thumb:
At the instant that the damper comes off it’s top stop, it becomes irrelevant what force it took to preload it.
It’s just that the first bit of weight you applied when you STARTED to climb aboard, is not enough to start compression.
(That’s where the seed is sown that it’s “stiffer”).
If 25 mm of pre load (as in our example), has applied 40 kg, then any load less than 40 kg will not cause further compression.
But exceeding that 40 kg with the remaining load, will then take the spring to it’s stabilised length.
It may help to think of preload in terms of mass (kg), rather than distance (mm).
If your spring is bearing 200 kg it will compress to 150 mm.
If you pre load it 40 kg, the first 40 kg that YOU supply when getting on won’t move the shock, but the remaining 160 kg will.
In each case, the spring when loaded with 200 kg and stabilised, will be 150 mm length.
So the progressive PERFORMANCE of the spring will still be evident in use, but how much it was PRELOADED is irrelevant.
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At the instant that the damper comes off it’s top stop, it becomes irrelevant what force it took to preload it.
It’s just that the first bit of weight you applied when you STARTED to climb aboard, is not enough to start compression.
(That’s where the seed is sown that it’s “stiffer”).
If 25 mm of pre load (as in our example), has applied 40 kg, then any load less than 40 kg will not cause further compression.
But exceeding that 40 kg with the remaining load, will then take the spring to it’s stabilised length.
It may help to think of preload in terms of mass (kg), rather than distance (mm).
If your spring is bearing 200 kg it will compress to 150 mm.
If you pre load it 40 kg, the first 40 kg that YOU supply when getting on won’t move the shock, but the remaining 160 kg will.
In each case, the spring when loaded with 200 kg and stabilised, will be 150 mm length.
So the progressive PERFORMANCE of the spring will still be evident in use, but how much it was PRELOADED is irrelevant.
Thanks for all the explanations and......just when I think I am getting "it" I add in the position of the dampner.... It helped me to think that if I only put say 50% of my weight on the bike the spring will "preload" then the rest of my weight will still cause the spring to compress the same amount as if I had just put all my weight on the bike. But......preload is to get the shock to ride higher in the stroke so it will be in the soft range and not ride in the higher resistance toward the end of the range of travel. I just need to let this roll around in my head but think I am making progress...... ;)
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Hagon have come back to tell me I need 18Kg (/mm?) springs as opposed the 17Kg on the bike now
Per cm I think you'll find.
I'll be VERY interested in your impressions/conclusions of the replacements.
Personally I find Hagons invariably supply intolerably hard shocks.
Do the 17Kg/cm shocks you have now feel too soft ?