XRAY - Model racing cars

Hello,

I m using the aluminum shocks with drilled hole and large (old) membranes. I pull the rod 75% out fill the body with oil, use a ride air remover and then I assemble the cap with the membrane and put it on the body. I first attach it a little angled prevent air from accumulating below the membrane. When I m tightening the cap oil is leaking from the hole and I tighten it till the oil stops leaking. On three of my four shocks I then have a rebound of around 2mm, but on one I just dont get any rebound. I re assembled it several times and also changed the membrane with the same results, any ideas what might causing this?

Can you also let me know whats the difference between the old large membranes and the new flat ones? Are they better with drilled holes in the cap? How do you set a higher rebound with drilled hole and the alu shocks?

How much rebound is usually good on carpet and what causes more or less rebound on carpet?

Thanks in advance for any advice!

Pull the rod down 100% then fill with oil. If you want 100% rebound then just fitting the cap should give you that - you will see oil seeping out as you fit the cap. If you want less then 100%, then push the rod in a percentage before fitting the cap - you will need to experiment with that. If you do not get the rebound you want, ie it is still too much then loosen the cap a turn and slowly push the rod in until you see a bit of oil seep from the hole - stop and tighten the cap and check the rebound. If still too much then repeat

Most people in our club run zero rebound on carpet. I imagine rebound is useful on bumpy outdoor tracks, because it helps the wheel return to the track surface faster after a bump (you can't generate any grip if the wheel is in the air )

I have found the new, flat membranes easier to bleed, and have also tried the Tamiya membranes which are stiffer than the XRay ones - couldn't spot any difference to be honest...(maybe my driving ability or style ) A lot of people say the Tamiya ones are "better".

I think the bladder affects the very first part of the damping action as you turn in - the softer, larger membrane will stretch and expand into the air space under the cap, so there is less damping action initially. The low profile, stiffer membranes force the oil through the piston holes earlier, so the damping action is stiffer on turn in. Thus the turn-in will be more aggressive. Obviously shock oil and holes in the piston affect all of this too.

HTH

If the rebound isn't adjustable on just one of the dampers then maybe its O-ring is damaged since you already checked its membrane.

I made a small 'tool' for always having the same rebound. It's pretty much a bottom-closed cylinder with big open sides (for grapping the shock body) with the same inner diameter the shock springs spot. To set the rebound I first set a certain distance on the shock body by turning the pre-load nut, then push the open shock in that 'tool' until it sits in the pre-load nut (shock shaft was fully pulled down before) and finally close the shock (very slow in case you have the deep membranes). I use this cylinder because the shock rod position always alters a little when applying the shock cap. Not so with the cylinder.

Lots of rebound probably leads to too much side-bite on carpet, never tried it though.