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      02-14-2013, 02:23 AM   #6
Evo Junkie

Drives: E91 325D M-Sport, Evo 6
Join Date: Dec 2009
Location: Bedford, UK

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Originally Posted by CJ421 View Post
The compression stroke is where the piston is going into the damper body, and rebound the opposite.

Damping is reducing the energy of motion to acceptable levels over a certain suspension travel distance, so that the forces acting on the car don't disturb handling or put excessive vertical loads on the car and driver.

Compression damping controls the unsprung weight of the car (wheels/tires/brakes/half the suspension). The suspension will travel more than necessary if there's not enough of it, resulting in bad handling. Getting compression damping right is over and above more important than rebound for good handling.

There needs to be just enough rebound damping to not convert more energy than necessary. Translated - too much rebound means the spring cannot extend itself quickly enough; the tire will not be in firm contact with the road. A tell for too much rebound damping is a rough ride where it feels as if you are being launched out of your seat going over a bump. On the track, too much rebound will result in the car feeling unstable under braking or entering corners, and a tendency to oversteer out of the corner.

When adjusting a damper with more than one setting, make ONE adjustment at a time. I would start with both rebound and compression on full soft, and increase compression first. Go up a few clicks at a time, ride around the block, and keep doing that until you reach a point where the car feels good (each driver has a different preference, regarding suspension stiffness). Then adjust rebound and stop when you have a smooth ride. I imagine you won't go more than 1/4 - 1/2 the way towards stiff with rebound.
My preference is to keep the rear suspension settings a few clicks softer than the front; there is some benefit to rear body roll (especially if you do not have an LSD).
All good info, but rebound adjustment has far more effect on handling than compression, and is more critical to get in the sweet spot. This is the reason that 1 way damper adjustments change mainly rebound, with slight compression change.

I normally adjust compression to the softest I can get away with in respect to travel and bump absorbance. I personally think in some applications, too much bump damping is used to compensate for too soft spring rates or anti-roll bars.