XRAY - Model racing cars

Hi,

Ok firstly love my T4 its mint but i seem to have issues with the shocks which is getting to me a bit. Seem to be using a whole lot of oil and spending most of my time setting shocks and not running the car.

After reading through the forum i had gathered a lot of different ways of setting the shocks follow the manual etc etc even pulling the shaft out 25% stir the bladder on to the shock body using a screw driver nice and softly then attach the ball joint and cap after then 0% etc etc i have tried just about everything and still getting issues.

For instance yesterday cleaned checked and rebuilt my shocks taking my time expelling the bubbles using my pump leave them to sit for 10 minutes no bubbles i can assure you everything good bladder not damaged good to go set my shocks to 50% using my calipers although im looking for 25% kept checking through the evening but not pushing the shaft in or out all good still showing 50%, using 350 CST oil and no foam in the top cap left them over night in my Hudy car stand for around 12 hours the room temp is 30 degrees as im in Thailand, cant see how that would have an affect on the rebound anyway, checked this morning pushed the shaft in and out a few times slowly on all 4 shocks, 2 are still around 50% just under and the other 2 have dropped to 30-40% why is that? as they have sat all night??? would it be better for me to use the foam??? or is there other shocks to buy????

Is this common every time you run you get 0% rebound after and if so why is that? as this is the only issue i have ever had with my T312 and T4 and what do the pros do??? carry 20 shocks pre set with them then after every run change them??? because by the time i get mine sorted i would have missed the race...

Any help be greatfully received...

Scott

Normally when I build mine I aim for roughly 50% and by the morning they are 0% rebound, but they are even, so I use them like that.

It might well be something to do with the ambient temperature/humidity.
Are you building them trackside?

Have you tried setting 100% slow rebound and then leaving them overnight?

When you say cleaned the shocks, are you using motor spray or similar on the main o-ring?
These are silicone and can be damaged by the chemicals in motor spray, unlike the black o-rings in previous generations of car.

I also run a piece of wet'n'dry over the threaded part of the shock rod before fitting it just to ensure that the thread has no sharp edges that might cut into the O-ring.

Skiddins

P.S. I've only had to rebuild 2 shocks due to air in them since the kit came out.

Hi Skiddins,

Thanks for the reply its a pity i no longer live in the UK would have popped to see you at your local track and got a real heads up on this issue, as you know a lot.

This is all done in my living room and cleaned using just soapy water no chemicals and i vigorously check all components of the shock, got a lot of spares here also.

You said you set at 50% then run at 0% i guess you just ride the springs? am i right in saying that? kind of confused what is the point of setting the rebound? and would it be an advantage to use the foam to keep a good rebound?

This is the only thing kind of getting to me a bit as im thinking i need to have a good rebound as not to bottom out and sometimes going through lots of silicone oil through looking for that perfect rebound and as we know isn't cheap i have used 250, 300, 350, 400 all x-ray oil any more of your help would be great...

Thanks mate Scott

Thanks, but I certainly won't claim to know a lot

I generally try to run minimal or 0 rebound anyway.
I always use the foam inserts on the shock caps as well, I don't know why, I think it's out of habit.

Make sure you use a shock pump or similar to remove all the air. I do it quite a few times over 30mins or so to try and get every last bit of air out.

Skiddins

To take the topic a little further.

What different makes rebound versus no rebound?
What difference does the foam insert make?

1) Make sure that the o-rings at the bottom of the shock aren't damaged in any way

2) Use an air removal shock pump for shock rebuilding to have them completely air free

3) If the membranes aren't new, use the screwdriver on top tapping method which was described earlier, to remove any excess oil. If the shocks are set at 0 rebound they should stay that way. It is very rare that the shocks develop rebound from the inside overtime. Usually they loose some pressure over time.

Sometimes when travelling in an airplane, the cabin pressure can upset the shocks and bring air bubbles into them. But again I have not seen this happen very often, but it can be a good thing to have in mind.

So what is rebound to begin with? Rebound is a term used by R/C racers to describe the built in pressure in shocks. This can be regulated by the amount of oil inside the shock body, and can be measured in how much the shock shaft protrudes out of the shock body when the shock dampens back out. Full scale racing engineers typically defers from the use of rebound as shocks shall not come out of their own without the aid of a spring. Rebound creates too much bounce in their opinion. However, under certain conditions, more rebound or shock internal pressure, can be a nice tuning option for R/C cars. Typically it will make the car feel more direct, and may even give the car a feel of more overall traction. Rebound can be useful for high traction surfaces such as carpet racing.

The foam increases response much like rebound itself does, but usually the foam will take out too much traction so we don't use them for most conditions.