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Suspension 101

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I have seen a lot of posts lately with questions on suspension. I hope to clear up any confusion by offering the basics. Keep in mind that this is ONLY the basics.

The ultimate goal of your suspension system is to maintain tire contact with the ground in order to provide traction for turning, braking, and acceleration without unsettling the chassis or the (your legs help in this last part ->) rider.

When you think spring rate you should think ride height - not harshness or anti-bottoming. If you follow the directions in your owners manual (1st - set your race sag to 100mm. 2nd - ensure your free sag is between 10 and 25mm - if your free sag is LESS than 10mm then you need a STIFFER spring. If your free sag is MORE than 25mm then you need a SOFTER spring) you will know if you have the correct shock spring rate for your weight. If using this system you have to change shock springs you should do a corresponding fork spring change (unless your trying to change the way the bike is balanced). In theory, for optimal plushness, you want to use the minimum spring rate that still maintains proper ride hight for your body weight.

Dampening and oil viscosity have a lot more to do with how harsh your suspension feels and bottoming prevention by controlling the velocity you go through your suspension travel. Too much compression dampening and your forks will feel harsh. Too little and you'll blast through your travel and bottom. Too much rebound dampening and your forks will pack (not reset before the next obstacle). Too little rebound dampening and you will "pogo."

There is air trapped in your forks. This trapped air acts as a progressive air spring. Your oil height determines how much air. Changes to oil height most greatly affect the final 4" of travel in your forks and have almost no affect on the initial travel (with the exception of extremely high oil heights which, in conjunction with rising operating temperatures [i.e. pressure], can cause harshness - kind of like preloading). The higher your oil the more important it is to release excess air pressure between motos. Higher oil height - less bottoming. Lower oil hight - more bottoming.

For optimal plushness your suspension should be set up to use its entire travel (bottom slightly) on the biggest obstacle once per lap. If it doesn't you are unnecessarily damped too harshly and are wasting suspension travel.

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Another big mistake alot of riders make is "tightening up" a too soft spring, thinking it will make the bike "stiffer". Well, it DOES, but only on small chop and makes the bike even HARDER to ride. By tightening a spring down so much, you basically increase the force required to START it moving beyond the force that it would take to make a stiffer spring move the same amount.

I agree and always have, spring rate is to set chassis attitude/ride height. While a stiffer spring will slightly help as far as bottoming, it is a relatively small part. The only thing I see is that I like to allow a rider to have up to 35mm free sag. And I think 10mm is a bit shy, I don't like to see less than 15mm. Some riders just prefer a firmer feel. Like me. I can't stand a wallowy bike, period.

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