Black Sheep
04-21-2004, 02:43 PM
there are always a lot of threads about rear shocks. " do i need a stiffer spring", "do i need a rebuild" ect. so i figured it's time for a tech tip thread on rear suspension set up. if you follow this procedure you will be able to determine if you need a rebuild, stiffer spring or maybe a better shock.
the first step is to get the proper amount of sag in the shock. there are two differant types of sag. one os "free" sag which is the amount of sag the trike has under it's own weight. the other is called "race" sag. no don't confuse the term "race" to mean this is only for racing, it is not it is just termanology. so lets begin.
first you want to start with "race" sag and to do this you will need a tape measure, a stable stand (to hold your trike off the ground) and a friend. place your trike on the stand and measure the distance from the rear axel to a fixed point on the frame. (mark this spot with a black magic marker you will need to refure to this spot several times) try to keep the tape measure as straight as possible for accuracy. once you get this measurement wright it down. next place the trike on the ground and with all of your normal riding gear on sit on the trike and have your friend take a new measurment useing the same referance spots. wright this measurement down and then subtract the amount from your previous measurement. the differance should be one third of your total travel. example if you have a 86 ATC 250R that has 10" of travel you should have 3.3" of "race" sag when your on the trike. if you do not have the proper amount of sag then you will need to adjust the preload on the shock spring. example if you have too much sag say 4" then you will need to add preload by tightening down on the preload rings. if you don't have enough then you would loosen up the preload rings. do this untill you achieve your proper "race" sag.
the next step is to determine the "free" sag. this will tell you if the spring on your shock is the right rate for your weight. you can only take this measurement AFTER you do race sag as it is ONLY set up for you. to get "free" sag take a measurement like you did in the first step but with the trike on the ground under it's own weight (push the rear end up and down a few times before you do this). now take this measurement and subtract it from your first one. you should have about one tenth of your total travel (ex. 86 ATC 250R with 10" travel should have around 1" of free sag) if after doing this you have too much free sag you will need a stiffer spring rate. if you don't have enough free sag you need a lighter spring rate.
after you have set your race sag and free sag you can now have a better idea to determine if your shock needs a rebuild or replacement. if the shock seems close but is mushy or slow responding you might just need a rebuild if however your still bottoming out or not happy with its action you may want to consider a new shock with a more agressive valving.
p.s. mods i mad a mistake please move to general tech section
the first step is to get the proper amount of sag in the shock. there are two differant types of sag. one os "free" sag which is the amount of sag the trike has under it's own weight. the other is called "race" sag. no don't confuse the term "race" to mean this is only for racing, it is not it is just termanology. so lets begin.
first you want to start with "race" sag and to do this you will need a tape measure, a stable stand (to hold your trike off the ground) and a friend. place your trike on the stand and measure the distance from the rear axel to a fixed point on the frame. (mark this spot with a black magic marker you will need to refure to this spot several times) try to keep the tape measure as straight as possible for accuracy. once you get this measurement wright it down. next place the trike on the ground and with all of your normal riding gear on sit on the trike and have your friend take a new measurment useing the same referance spots. wright this measurement down and then subtract the amount from your previous measurement. the differance should be one third of your total travel. example if you have a 86 ATC 250R that has 10" of travel you should have 3.3" of "race" sag when your on the trike. if you do not have the proper amount of sag then you will need to adjust the preload on the shock spring. example if you have too much sag say 4" then you will need to add preload by tightening down on the preload rings. if you don't have enough then you would loosen up the preload rings. do this untill you achieve your proper "race" sag.
the next step is to determine the "free" sag. this will tell you if the spring on your shock is the right rate for your weight. you can only take this measurement AFTER you do race sag as it is ONLY set up for you. to get "free" sag take a measurement like you did in the first step but with the trike on the ground under it's own weight (push the rear end up and down a few times before you do this). now take this measurement and subtract it from your first one. you should have about one tenth of your total travel (ex. 86 ATC 250R with 10" travel should have around 1" of free sag) if after doing this you have too much free sag you will need a stiffer spring rate. if you don't have enough free sag you need a lighter spring rate.
after you have set your race sag and free sag you can now have a better idea to determine if your shock needs a rebuild or replacement. if the shock seems close but is mushy or slow responding you might just need a rebuild if however your still bottoming out or not happy with its action you may want to consider a new shock with a more agressive valving.
p.s. mods i mad a mistake please move to general tech section