Spring pre load

[tris]

Huzo's OP and #12 are correct. Some of the other are correct, others are not.

Preload affects ride height, steering geometry and handling.
Too little preload can result in the suspension bottoming.
Too much preload and the suspension might top out during the rebound from a bump, causing the wheel to leave the ground (and traction).

Ride height examples - if you have a spring with a rate of 100 lbs per inch, and the shock is vertical (usually the shock is at an angle but that require trig - so we won't go there_.
With no preload, if you put a load of 150 lbs on the bike, directly above the shock, the shock will compress/shorten 1.5".
If you put a preload of 50 lbs on the shock by moving the adjuster 1/2 inch, when you put the 150 lb load on, the shock will shorten 1".
If you put a preload of 100 lbs on the shock by moving the adjuster an additional 1/2 inch, when you put the 150 lb load on, the shock will shorten 1/2 inch.

If this explanation is correct (I don't doubt you RH47 but suspension setup seems to be one of those subjects shrouded in rumour and myth) its by far the best one I've seen! 

The only thing I found on all the second hand bikes I've owned is the everyone has wound the pre-load up. Now either all the POs were fat lads or they all believed that winding the pre-load improves things.

I've always backed things off to the the factory settings and all feels OK - but maybe that's because I don't have the finesse to understand what I'm feeling.

I've just  spent 3 months trying to lay my hands on a book about suspension set up (Suspension Tuning: How to Set Up Your Bike for Handling, Stability, and Control on the Street and Track by Marc Cook) to understand that sort of thing, only to have the supplier cancel to Order 

Are there another recommended books that explain things simplistically ie "if it does this do that"

[Dilliw]

The troubleshooting page of Total Control is straightforward.

http://www.totalcontroltraining.net/Suspension101eBook.pdf

[tris]

That's good

Saved and printed for the garage

[Ncdan]

Ncdan,
The normal layout of those type of shocks will have the stepped ring and a "pin" that fit s the step.
That's the preload - you'll have three to five steps at different heights and adjust it by rotating the ring
with a "C" spanner. I'd start by setting it to the middle as a base point and go from there.
 
The adjustment at the top is most likely for Rebound Damping - too much will slow the suspensions return
to it's original position too much resulting in the suspension packing down over say a series of bumps.

Too little rebound damping can create wallowing as the spring overcomes the damping and pushes the suspension
back after a bump past it's original starting point.

Think of the spring on it's own with no damping - you hit a bump, the wheel bounces up with the impact and will
bounce higher than the actual bump and then return and also push past the starting point and then cycle back and forth
until it settles back at the starting point, like early Cars with no Shocks. The Compression Damping controls the springs action so it doesn't just bounce
up wildly and follows the bumps contour more closely. The Rebound Damping controls the springs action as the suspension
comes back to it's starting point so it doesn't overextend.

Maurie.
Thanks Maurie, that explanation makes things clearer for me. I weigh in at 165 so I probably need to have my spring a little longer from half way wouldn't you think?

[antmanbee]

Ncdan,

With you and whatever you are carrying on the bike, it should be about  1-1 1/2 inches compressed from the fully extended position of the shocks. About 1/3 of the travel of the suspension is a good ball park place to be.

[waxi]

Sorry, if this is off topic, but how can we assure that pre-load on both shocks is set identically (assuming we have two)? So one is not carrying more that the other? Is that as simple as counting threads?

[Huzo]

Sorry, if this is off topic, but how can we assure that pre-load on both shocks is set identically (assuming we have two)? So one is not carrying more that the other? Is that as simple as counting threads?

Nothing's ever off topic Waxi, take it anywhere you like. Fair question too BTW.

[waxi]

Nothing's ever off topic Waxi, take it anywhere you like. Fair question too BTW.

Just want to be nice. I am afraid of Pete, haha :)

[Huzo]

Just want to be nice. I am afraid of Pete, haha :)

Sorry mate, Pete who ?

[waxi]

Sorry mate, Pete who ?

Roper. He is very active here on WG.

[Orange Guzzi]

Take the two rear shocks off, hang your bike from the two top shock mounts to a scale.  Climb on the suspended bike and read the scale.  Divide that number by 2.  That will give you the maximum spring rate to support the bike with no preload.  If you want 1 inch of preload, reduce the spring rate by the amount required to compress the spring 1 inch.  Sounds easy.  Anything less than an actual weighing of bike and rider is all guess work.  Adding a passenger and gear will require additional preload.  Progressive springs are useless because you have to adjust the lighter rate out to get the ride height.  Same with the front.  Suspend the bike from the handle bars while sitting on it.  Take a weight reading. 

[Huzo]

Take the two rear shocks off, hang your bike from the two top shock mounts to a scale.  Climb on the suspended bike and read the scale.  Divide that number by 2.  That will give you the maximum spring rate to support the bike with no preload.  If you want 1 inch of preload, reduce the spring rate by the amount required to compress the spring 1 inch.  Sounds easy.  Anything less than an actual weighing of bike and rider is all guess work.  Adding a passenger and gear will require additional preload.  Progressive springs are useless because you have to adjust the lighter rate out to get the ride height.  Same with the front.  Suspend the bike from the handle bars while sitting on it.  Take a weight reading.

How do you get around the fact that when you hang your bike, the weight vector is vertical, but on the bike the shocks are angled forward, so the load on the shocks is more than the actual mass they're supporting, sounds like a bit of buggerising around.

[Huzo]

Roper. He is very active here on WG.

Nah, he's a shrinking violet. Scared of his own shadow...!

[Kiwi Dave]

Are there another recommended books that explain things simplistically ie "if it does this do that"

Race Tech's Motorcycle Suspension Bible has some good information.

[waxi]

Nah, he's a shrinking violet. Scared of his own shadow...!

 

[Orange Guzzi]

How do you get around the fact that when you hang your bike, the weight vector is vertical, but on the bike the shocks are angled forward, so the load on the shocks is more than the actual mass they're supporting, sounds like a bit of buggerising around.

There are some spring rate calculators that will give you the compensation factors based on the angle of the shock.  But a good starting point is needed to use the calculators formulas.  I found one that was used for front auto suspension set up.  You could put in several variables and it would give you the spring rate.  One variable is the top spring mount load. 

9405510200864318596 176

[Huzo]

There are some spring rate calculators that will give you the compensation factors based on the angle of the shock.  But a good starting point is needed to use the calculators formulas.  I found one that was used for front auto suspension set up.  You could put in several variables and it would give you the spring rate.  One variable is the top spring mount load.

Oh righto.

[Huzo]

Sorry, if this is off topic, but how can we assure that pre-load on both shocks is set identically (assuming we have two)? So one is not carrying more that the other? Is that as simple as counting threads?

How about, take one shock off and put a static load on the bike and measure the distance from the top shocker mount to the floor, then change shocks and see if the measurement is the same. Think that'll work ?

[Orange Guzzi]

Oh righto.

http://www.hypercoils.com/spring-calculator

The first factor is the "corner weight"  or the weight to be supported by the top shock mount.

[Ncdan]

After reading the explanations from you guys, which were very accurate and complete and doing a little further research from other sources, I have a conclusion on my own. As I am fairly new to the guzzi world with my calvin, I am a old salt in the ridding world. I have ridden 50 years now and owned dozens of different makes, sizes and styles of bikes. I have experienced old technicality up to the most recent, from basic suspension to air to this Calvin with the dampening and rebound settings. I humbly offered this info to only put a little weight to my findings.
I just returned from conducting an experiment with my calvin just to satisfy my own curiosity as to the effects of the adjustments on the suspension the calvin offers.
On the front forks I set the dials on both compression and rebound, all the way to the - negative setting. I proceeded to a rough curvey road about two miles long. I road the road mildly aggressively. I then set the settings all the way to the + setting and road the road the same way. My results are this. If I had had someone to set the settings without me knowing which one, both of full + them full - in all honesty I would not have been able to say which was which. There were no noticeable difference for me. I did not ride aggressively to an extreme but didn't mosey on either.
On the rear with the setting cranked all the way up or shorting the spring, it's a little harsher on the bumps than with the setting all the way lengthening the shock spring.
so I decided to simply make the adjustments half way on both ends and leave it to the heck alone. I will say I'm of the opinion that if one wants a drastic change in a bike like mine they might as well figure on spending big bucks and replacing the stock ones with aftermarket high Preformance type suspension.
Thanks for reading and responses are welcome just keep in mind my findings are just an opinion on my calvin and no one else's situation or bike.

[RANDM]

Ncdan,
Except that you went from one extreme to the other, that is
The recommended method. It's best to only change one
thing at a time though so you don't get confused as to what
caused what. Also not all shocks are made equal - the quality
of the damping and the effectiveness of adjustments is what
Your paying big bucks for with the top notch stuff. Horses for
courses - if your not an aggressive rider you won't need
Ohlins just good quality shocks with effective adjustments.

Waxi,
Might be overthinking it a bit - while Spring rates ona pair of
Shocks might not be exactly matched they'll be close and with
a twin shock bike the pre load is a stepped adjustment - put each
On the same step and your Golden. Screw thread Pre-load is
More the norm on Monoshock bikes.

Maurie.

[Ncdan]

Ncdan,
Except that you went from one extreme to the other, that is
The recommended method. It's best to only change one
thing at a time though so you don't get confused as to what
caused what. Also not all shocks are made equal - the quality
of the damping and the effectiveness of adjustments is what
Your paying big bucks for with the top notch stuff. Horses for
courses - if your not an aggressive rider you won't need
Ohlins just good quality shocks with effective adjustments.

Waxi,
Might be overthinking it a bit - while Spring rates ona pair of
Shocks might not be exactly matched they'll be close and with
a twin shock bike the pre load is a stepped adjustment - put each
On the same step and your Golden. Screw thread Pre-load is
More the norm on Monoshock bikes.

Maurie.

I did it the way I did as I figure I should be able to note a different from adjusting from complete one setting to the complete opposite. Common sense tells me if I don't detect any difference like that,  I'm not going to see any difference going up one notch at a time. Just speaking for myself I'm convinced I wouldn't know the difference if I didn't make the adjustments myself as to + or - adjustments, on MY calvin.  Thanks for the response as it is much respected.

[Ncdan]

Ncdan,

With you and whatever you are carrying on the bike, it should be about  1-1 1/2 inches compressed from the fully extended position of the shocks. About 1/3 of the travel of the suspension is a good ball park place to be.

Thanks Bee, now I can comprehend that explanation:)

[Huzo]

After reading the explanations from you guys, which were very accurate and complete and doing a little further research from other sources, I have a conclusion on my own. As I am fairly new to the guzzi world with my calvin, I am a old salt in the ridding world. I have ridden 50 years now and owned dozens of different makes, sizes and styles of bikes. I have experienced old technicality up to the most recent, from basic suspension to air to this Calvin with the dampening and rebound settings. I humbly offered this info to only put a little weight to my findings.
I just returned from conducting an experiment with my calvin just to satisfy my own curiosity as to the effects of the adjustments on the suspension the calvin offers.
On the front forks I set the dials on both compression and rebound, all the way to the - negative setting. I proceeded to a rough curvey road about two miles long. I road the road mildly aggressively. I then set the settings all the way to the + setting and road the road the same way. My results are this. If I had had someone to set the settings without me knowing which one, both of full + them full - in all honesty I would not have been able to say which was which. There were no noticeable difference for me. I did not ride aggressively to an extreme but didn't mosey on either.
On the rear with the setting cranked all the way up or shorting the spring, it's a little harsher on the bumps than with the setting all the way lengthening the shock spring.
so I decided to simply make the adjustments half way on both ends and leave it to the heck alone. I will say I'm of the opinion that if one wants a drastic change in a bike like mine they might as well figure on spending big bucks and replacing the stock ones with aftermarket high Preformance type suspension.
Thanks for reading and responses are welcome just keep in mind my findings are just an opinion on my calvin and no one else's situation or bike.

Jeez mate you don't have to offer anything humbly. We're (almost) all amateurs here. I've never buggerised around with my Norge fork settings, just like they were from the factory and I've owned it 8 years and 110,000 k , I reckon just leave well alone. They soak up bumps beautifully and the bike does not wallow or weave at all so what else do you need ?

[Ncdan]

Jeez mate you don't have to offer anything humbly. We're (almost) all amateurs here. I've never buggerised around with my Norge fork settings, just like they were from the factory and I've owned it 8 years and 110,000 k , I reckon just leave well alone. They soak up bumps beautifully and the bike does not wallow or weave at all so what else do you need ?

Thanks for the words of encouragement "mate";)  I just figured those settings were there for the ridder to fiddle with so my  curiosity got the best of me. I'm beginning to reason that unless you are ridding the pure hell out of one of these bikes and pushing them to the brink of maximum Preformance, these settings don't count for much. In all honesty I wish mine didn't even have them so I wouldn't have to think or worry about having it perfect as I am a perfectionist. Which is a curse:(

[Huzo]

Thanks for the words of encouragement "mate";)  I just figured those settings were there for the ridder to fiddle with so my  curiosity got the best of me. I'm beginning to reason that unless you are ridding the pure hell out of one of these bikes and pushing them to the brink of maximum Preformance, these settings don't count for much. In all honesty I wish mine didn't even have them so I wouldn't have to think or worry about having it perfect as I am a perfectionist. Which is a curse:(

How very true. I guess though there's nothing wrong with playing with it a bit though. ( just don't get caught !)

[redhawk47]

Take the two rear shocks off, hang your bike from the two top shock mounts to a scale.  Climb on the suspended bike and read the scale.  Divide that number by 2.  That will give you the maximum spring rate to support the bike with no preload.  If you want 1 inch of preload, reduce the spring rate by the amount required to compress the spring 1 inch.  Sounds easy.  Anything less than an actual weighing of bike and rider is all guess work.  Adding a passenger and gear will require additional preload.  Progressive springs are useless because you have to adjust the lighter rate out to get the ride height.  Same with the front.  Suspend the bike from the handle bars while sitting on it.  Take a weight reading.

Does not compute: How do you convert weight (pounds) to spring rate (pounds per inch)?

PS: Many shock/spring assemblies, particularly those with stepped preload adjusters, have some preload at the lowest preload setting.

[RANDM]

Thanks for the words of encouragement "mate";)  I just figured those settings were there for the ridder to fiddle with so my  curiosity got the best of me. I'm beginning to reason that unless you are ridding the pure hell out of one of these bikes and pushing them to the brink of maximum Preformance, these settings don't count for much. In all honesty I wish mine didn't even have them so I wouldn't have to think or worry about having it perfect as I am a perfectionist. Which is a curse:(

I think most people set their bike up to a good "median" and
then ride around conditions, you don't see many people stopped
by the side of the road adjusting their susp. because a set of good
corners is coming up!

Pre load and Rebound become more important when your Dinking
or carrying a load, I have three settings which cover my different
needs and can change them in a couple of minutes and it's very
worth it.

Cheers Maurie.

[Ncdan]

I think most people set their bike up to a good "median" and
then ride around conditions, you don't see many people stopped
by the side of the road adjusting their susp. because a set of good
corners is coming up!

Pre load and Rebound become more important when your Dinking
or carrying a load, I have three settings which cover my different
needs and can change them in a couple of minutes and it's very
worth it.

Cheers Maurie.
Sounds reasonable Rand. I'm going to set everything toward the middle of the road and make changes as I am sure the bike is weak in one situation or the other. Sooner or later I'll be satisfied with what she does in any situation. I think the key is that you know how your bike will react in any given environment or situation.

[tris]

......., you don't see many people stopped
by the side of the road adjusting their susp. because a set of good
corners is coming up! .......
[/quote]

I guess that's exactly what the modern electronic suspension systems do??