- Shock Piston-Oil Quick Reference Chart -

Tuning your shock piston / oil combo is an important setup tool in offroad racing, but when changing pistons to adjust pack it can take some trial and error to find the oil which matches the static damping you are looking for. To help I have put together a chart using an excel model based on real world hydraulic orifice measurements to make it easier to compare settings and save a little trial and error.

How to use the chart:

  • Look for the piston you are using. Follow along that line to the shock oil weight you are using. That point shows the static damping (x axis) and pack (y axis).
  • If for example you want to have less pack but similar static damping, move directly down from that point to the piston you want to use, and the number will indicate which shock oil to start with.
Note the chart does not include tapered pistons - they are generally less pack but I haven't been able to find test data. The values here are for 12mm shock pistons. I cant guarantee them to be perfect but ive found when changing pistons it is good to within 2.5wt as a starting point to compare.

Theory reminder:
  • Shock absorber (also called a damper) gives a resistance force relative to the speed that the shaft is moved.
  • A large piston hole / thick oil combination will feel similar to a small hole/ thin oil combination at low shaft speed (ie handling) but for very fast shock shaft speed (such as landing off a jump or hitting a very sharp edged bump) the small hole piston will give a much higher force (often called 'pack').
  • Generally for smooth tracks / big jumps you want more pack to improve jump landing, for rough / low traction tracks you want less pack so the tyres can ride over bumps more easily
I hope this can help take out a little guesswork in your setup and make your racing more fun!! As always, make sure you check your car is in good working order and your shocks are built and bled correctly before you make setup changes.

Source:

R. Munday