Originally Posted by
BK24
This is a newbie question, but why or in what situations would one choose a tapered piston over a flat piston? What are the characteristics/advantages of one over the other?
That is a good question and one that led me to build a shock dyno to help me answer. Hearing a lot of different things about different types of pistons, and not finding any actual engineering data to back up those claims was enough for me to try and find the answers.
Short answer to your question: There is no difference or advantages between a flat or tapered piston. I have never seen in any of my data, not low speed, not high speed, not pack, not reversing them, not anything that suggests there is anything special about a tapered piston.
You can achieve the same results between them though choosing oil viscosity. The only difference is that given the same hole # and diameter (i.e. 5H 1.3mm) piston with the same viscosity oil, a tapered piston will move with less resistance. This is due to the thinner piston. You can achieve this same effect with lower viscosity oil with a standard flat piston.
Much talk is spread about how a tapered piston will slip through the oil faster in one direction than another (faster rebound if taper side is down), but this is again nonsense. I've flipped pistons several times, and never once seen a difference in rebound vs compression values. I think most people's opinions are based either on placebo effect, or that they are getting less overall damping due to the thinner piston, but attributing it to a "faster rebound".
Take a look at my shock dyno results. The link is in my signature.