Tapered pistons...up or down?

[c0sie]

Ive just bought some Ghea pistons (thanks Wraggy!) and after reading all the threads about them im still confused to which way around the pistons go...

I have read a thread recently that said that the taper needs to be aiming downways towards the end of the shaft....but surely that would mean that on landing a jump itll pack normally but the rebound will pop the car up quicker than with a standard piston?

Surely running the taper upwards towards the shock cap would mean that landing a jump would allow the car to absorb the jump faster but not pop up so fast on the rebound?

Any clever people fancy clearing my mind??

Thanks

[millzy]

remeber with salt you can allways add but not take away , but with a hair cut you can allways take away but never add


you should now have a clear mind my son

[c0sie]

Pmsl!

Stoopid boy!

[GRIFF55]

flat to the top chris. They work superb Make the car stay in contact with the ground loads more, very smooth

[c0sie]

Cheers Andy, ill see what they are like at Caldi tonight

[Apricot Slice]

Originally Posted by c0sie

Ive just bought some Ghea pistons (thanks Wraggy!) and after reading all the threads about them im still confused to which way around the pistons go...

I have read a thread recently that said that the taper needs to be aiming downways towards the end of the shaft....but surely that would mean that on landing a jump itll pack normally but the rebound will pop the car up quicker than with a standard piston?

Surely running the taper upwards towards the shock cap would mean that landing a jump would allow the car to absorb the jump faster but not pop up so fast on the rebound?

Any clever people fancy clearing my mind??

Thanks

this may help:-http://www.sardesonracing.com/shock_tuning.htm

[university_dave]

When Xray did tapered pistons for the original XB8 shocks I used to run them either way up depending on the track. It depends whether you want quicker compression or rebound, so for me it was dependant on the size and frequency of any bumps and whether there were any big jumps on the track.

[SlowOne]

Excuse me being thick, but why would the direction of fitment (taper up or down) make any difference at all? Surely these are being presented to the oil in exactly the same way whichever direction they run - same holes, same side clearance - so how would they affect the damping rate if fitted one way or the other? Thanks.

[discostu]

if the piston has a tapper it is more pointed and flow though the oil faster so depend ing on which way the piston sits in the oil depends which way the shock will react faster.

[SlowOne]

That would be true if the piston were in a free state in the oil, but it's not. It's bounded very closely by the cylinder on all sides, creating a small gap through which the oil flows. The piston cannot get up enough speed for the taper to have any effect, since the oil flow around the sides, and through the holes, will go turbulent long before the hydrodynamics of the piston shape come into play.

I'm not saying it doesn't make a difference, I'd just like to know why!!

[JohnM]

Having them in my Durango shocks, I can say for sure that they do make a difference, maybe part of it, is that on the tapered side, the hole appears larger to the oil, due to the way the hole is drilled straight from the flat side.

[discostu]

Originally Posted by SlowOne

That would be true if the piston were in a free state in the oil, but it's not. It's bounded very closely by the cylinder on all sides, creating a small gap through which the oil flows. The piston cannot get up enough speed for the taper to have any effect, since the oil flow around the sides, and through the holes, will go turbulent long before the hydrodynamics of the piston shape come into play.

I'm not saying it doesn't make a difference, I'd just like to know why!!

so what your saying is a taperd piston cannot work as it sit inside the cylinder and the shape wont make any difference in that theroy teflon piston shouldn't make a differnce either as the turbulance of the oil should out way the efect of the hydroynamics of the piston silky smoothness cool thats saves a lot of money.