What is the correct way to measure sag?

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#1
I know this is a stupid question but I dont have a clue what you guys are talking about when it comes to "race sag", "static sag" etc... Where and how do I set my 400 EXC for the best handling? Please forgive my ingorance on such a stupid question!
 

Jaybird

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#2
scottyr,
NO question is a stupid question, IMHO.
Static sag is how much sag your bike has when it has nobody on it.
Race sag is how much sag your bike has with YOU on , in the attack position.
(standing, body centered on the bike, maybe slightly forward)
Place your bike on a stand with the rear wheel not touching, measure from the axle center to a good point of reference, ie..the bolt that holds your seat on. Now take the bike off the stand and bounce it a couple times. Remeasure the same place....that is your bikes "static sag". Now get on the bike, roll forward a bit while bouncing a couple of times and get into the attack position.(You almost always need a friend to help you with this part) Have your friend measure the same place you did before. Now take that length and subtract it from the static sag you already know. That is your "race sag".
Do the above for the shock first, you should have somthing like 95-110mm of sag on the rear shock. If not, you can adjust the sag accordingly with the spring pre-load.
Once the shock is done, then you can repeat the process on the front. You should have about 35-55 mm sag on the front. Adjusting the sag on the front is harder than the rear shock. You can use fork spring pre-load spacers to do some adjusting (inside the fork).
Once you have got the sag on both ends acceptable, check out your static sag on the rear again. If you are a heavy dewd, then you may have robbed all of the rears static sag when you adjusted. THIS is when you need to look for a different rated spring.
I'm sure perfectionists may differ with my procedure a bit, as well they should, but you will get a good picture of whats happening by doing this once or twice. If you aren't real light or real heavy, then you will find that just a tweek is all you need to get in the range.
BTW....Don't ask Ricky Carmichael how to do this! :p
 

Hick

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#3
That “bounce” method may work better, but what I usually do is the push down, release and measure, and pull up, release and measure, and then average the two.

Interestingly enough the difference between the two on my buddy’s 400 EXC was very small. On my YZ it is much more significant. All that linkage, bearings etc. really creates a lot of drag.

BTW my buddy goes for around 210, and we ended up with too little static sag when we were done. I’m still trying to explain to him that he needs new springs, but he is glad that he can now make the bike turn.
 
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#4
Race sag is anything that hangs out of your kidney belt, both above and below. Static sag is everything that hangs over you belt buckle. The bounce method is very dangerous and should not be attempted by a beginner. You could very well end up with internal bleeding. Now you know the real truth. :)
 

Jaybird

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#5
I always use the bounce method.....every time I fall!
:D