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Discussion Starter #1
First I'm novice in motorcycle only a few months experience.

and below is my question studying suspension setting to choose my suspension setting.

After seeing the article describing the car suspension, I applied the content to the bike



on the car there are some reasons to use stiff spring.
- reduce body roll/lean
- low ground clearance low suspension travel
- aero [email protected] ride height
- downforce presses car down(changing height)
(extracted from youtube 'engineering explanined')




* However, there are few items that can apply to bikes for using stiff spring

the reason I can find is to avoid bottom out.

- G-force caused by faster cornering
- rapid acceleration
- full-breaking
- bump when fast riding

The faster you ride, the bigger the impact. The impact is proportional to the speed
Therefore, it is understandable to use a harder spring to a fast-running bike.



Is there any other reason?

when acceleration and deceleration, front and rear are lift or down. It can affect trail, rake.

But I do not know whether it is good or bad to use a stiff spring to reduce body movement.



I know that grip is better when using a soft spring

so if the only reason to using stiff spring is to avoid bottoming out, is it a good idea to use the smoothest spring to the extent that it does not bottom out?


because I'm novice I do ride on corner not as fast as a racer or an youtuber. maybe some time full-breaking




Last how can I check out the bottom out?
I think I can check the forks with a cable tie. but how do I check the rear suspension? Is there any good idea check rear shock bottom out?
 

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Others will chime in with better explanations, but in a nutshell you want your suspension to be working in the middle of its travel. To accomplish this, spring rates (stiffness) are selected based on a combination of the bike and rider mass while sitting static. See articles on "Setting rider sag". Sag is a measurement of how much the suspension compresses when the weight of bike and rider are applied to the springs. OEM's select spring rates to accommodate riders' weights over a range. Typically Japanese bikes are undersprung for heavy American riders. If you are less than 170 lbs naked then your spring rates is likely fine. Other factors come into spring rates like type and skill of rider. Other means of making forks and shocks "compliant" have to do with a whole other discussion relating to the valves, pistons, shims and other parts I am not qualified to talk about. In short, I think you are making it too complicated for your current skill set...set your sag, go ride, and do some track days with coaching. It will multiply your riding skill and enjoyment exponentially.

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@2thdr covered it.

As riders progress on the track they do go slightly “firmer” ride but spring rates are about you + bike + gear = suspension in the top 1/3rd of travel. Damping (the rate at which the suspension travels up and down) is what most riders adjust, not so much spring rate once they are the right rate for the weight. Preload on a spring is just a way to fine tune the spring into this range.

Remember when the bike leans over to say 45deg (very few riders without track training go past 45 safely) the bump on the ground goes up/down but the suspension is traveling 1.4 times that (potentially). The geometry of 2 wheel cycles compared to cars is totally different. Harder springs don’t make you corner “flatter” or harder like a car. You actually need frame and suspension parts to flex to handle well (that’s why MotoGP bikes have $30-40,000 swingarms).

Get a suspension adjust for $40-60 by a pro and then ride!


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Stiff suspension is not the way to go if your roads aren't perfect. More supple springs and good damping help your tyres stay in contact over bumps.
 
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