Suspension Setup, Springs and Preloads.

SSR Suspension - West Mids.
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SSR Suspension
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Suspension Setup, Springs and Preloads.

Post by SSR Suspension »

As a motorcycle suspension setup specialist we would be able to set your bike up to improve its handling based upon your intended use for the bike. It is very true that bikes come out of the factory with settings in the suspension, however bikes are mass produced and as such the manufacturing tolerances can vary with no bike being set perfectly for the person who has purchased it. This also rings true if you have purchased a used bike, has the previous owner ever changed the settings? Bikes are not inherently unrideable, ever. However they can be improved to suit you resulting in greater confidence, greater grip, stability and control with improved tyre wear.

Why? Springs and Preload
It is very simple to understand that Springs support the motorcycle and the rider, this is their sole job they do not provide any other function. Having the correct rate of spring will have a big difference to the handling of your bike. If your springs are too soft your bike will sag too much and will not have adequate suspension travel, if your springs are too stiff the bike will not sag enough and it may feel harsh with a reduction in grip and more often than not will not use adequate suspension travel.

Preload is a term of measurement. All forks and shocks have an amount of pre-installed preload on the spring, the initial amount of preload will vary depending upon certain design considerations. The function of preload is as the name suggests, to preload with the spring. The more preload that the spring has, the more load it takes to get the spring to move and vice versa. eg. On a linear 100gk/mm rate spring with 10mm preload would have a preload force of 1000kgf, to get this spring to move would take 1000kgf and then 100kgf for every further 1mm of movement, so to displace the spring 20mm would take 2000kgf. This is why more preload feels stiffer and less feels softer, but this is not the case.

Does adding preload make the spring stiffer?
NO, and removing preload does not make the spring softer. Still to do this day people turn their preload to max assuming that it will make the forks or shock stiffer, when in fact it does not! The only way to make the bike stiffer or softer is by changing springs and/or damping.
If you have adjustable preload it allows us to alter the dynamic sag of your bike, so thus affects how much it will sag when you sit on the bike. Otherwise we can change preload spacer length to adjust how much a bike sags.

Is Preload a ride height adjuster?
Yes, in a way, because you are changing the dynamic ride height of the bike thus the bikes geometry and affecting how much it will sag for a given weight.
More preload = less sag and thus the bike will sit higher, Less Preload = more sag and thus the bike will sit lower.

Can I lower my bike by changing preload?
No, if you wish to have your motorcycle lowered because it is too tall it would be incorrect to use the preloads of the fork and shock to do this.

Are springs available for my bike?
A great majority of bikes have springs available in varying rates, however there are only a couple of companies in the world that produce these springs off the shelf. If your bike does not have springs available off the shelf they would have to be custom made by a specialist company, this means that the bike would need to have its springs removed and measured and can become costly when looking at having a custom pair of fork springs made.

So how much preload should I have?
There is no simple answer to this, but a stiffer spring with less preload works better than a softer spring with more preload. The correct spring rate for you will generally be one that supports the bike and rider weight, gives appropriate sag numbers and allows you to use almost full fork stroke with a modest amount of preload.

Linear or Progressive Springs?
Linear springs provide a near constant rate thru its stroke, compare this to a progressive rate spring which actively gets stiffer the more the spring is compressed. Ideally you would want linear rate springs (there is an exception to certain off road models), they give you a better ride for one and more grip.

Progresseive rate springs are used as a band aid for many people who ride with a pillion but they are not always the best solution, the suspension is often much harsher at the lower end of the stroke with less grip. The spring is too easily compressed initially, making the bike front (or rear) go down more easily, returning back more slowly in the "top" range of shock absorber movement. As the forks or shocks compress further, they become noticeably stiffer, compressing less and rebounding back faster. Retro fitting progressive springs may in certain applications remove suspension travel inadvertantly because the coils bind up sooner than a linear rate spring.

Remember going around corners compresses your suspension, by quite a lot with modern tyres. With progressive or dual rate springs, that means the suspension is going to be stiffer than when upright. However mid corner is also where you most need good grip and would really prefer your tyres not to be bouncing off the ground.