Shock design length

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Shock design length

Post by BigJuice on Wed Oct 08, 2014 7:21 pm

Shock design length is a very misunderstood and miscalculated part of the race car. Here is a quick guide to checking if you have the right length on your set-up.



1) Set tire pressures to race spec.

2) Set ride height to desired /design height  (control arm angles, which in turn dictates design instant centers and design roll center height trumps just setting an arbritary height you think is right, or what the competition uses)

3) Measure the length from upper to lower mounting point

4) Place some blocks under chassis to keep the car at ride height. Remove shock and remove the spring. Measure piston length with shock fully extended.



5) Replace the shock (minus the spring), and measure extended length of piston shaft to mounting point.

6)  Subtract piston shaft lenght in step 5 from length in step 4.

This should be no less than 50% of step 4 length. If less than 50% you stand a good chance of bottoming out the shock, and limiting wheel travel (which takes away grip, and could manifest as a car with "snappy" reaction in corners)

If more than 50%, this could manifest as the constant picking up the inside wheel in corners



In the above picture you will see the o-ring on shock shaft ( with diff in full droop/shock fully extended..car on stands) ... if this were right after a run, you could think that he is using up a lot of his travel , but not bottoming -out the shock ( this car was faaast all weekend)
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BigJuice
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