Thrust washer choice advice req..

[Zico]

After replacing the rear beam on the 106 Gti (trailing arms) and swopping the Bilsteins over to the new rear axle, I was shocked at the amount of friction in the suspension caused by the dampers rubber bushes rubbing against the stub as they rotate on their axis... even after Id tightened only one end of the damper on.. with the other damper end tightened that friction would probably be doubled!

Im thinking about adding some thrust washers on either side of the dampers rubber bushs (at both damper ends) to remove as much of this friction as possible.
I've looked at some ball raced thrust bearings such as these http://www.vxb.com/page/bearings/PROD/Thrust/Kit7853
and needle roller thrust bearings (which turn out to be directional in one way only.) The ball raced items would probably be the way to go but their combined width dictates that I'd need to grind aome material from the stub to maintain constant, a 90 Deg angle relative to the axle through the motion of the suspensions travel (trailing arms) and they would need regular maintenance due to their position under the car, because they are ball raced and because of the material they are made off. So Im thinking a mere conventional thrust washer could be the best choice for the Ap ?

What type of thrust washer, what thickness and what choice of material, ie, S/S, brass, zinc or composite, do you think I should use?

Also if anyone knows of where I can buy small quantities for a reasonable price I'd be extremely grateful.

Thanks,


Paul

[JamesH]

Are you saying that the rubber bushes just have a bolt hole through them - there is no steel inner sleeve?

Can you replace the rubber with Polyurethane bushes? You can usually get those to move quite well.

I like that bearing website - and they post worldwide...excellent link.

James

[GORDON STREETER]

I shouldn't be overly concerned as the "rotational" movement is very limited and just about all normal road cars have the same set up. Unless there is something radically wrong in the fittings I wouldn't bother. Most of the race shock absorbers are rose jointed. but if the car is mostly for road use I would plug for more compliance with the silent block rubber type.

[Zico]

Originally Posted by JamesH

Are you saying that the rubber bushes just have a bolt hole through them - there is no steel inner sleeve?

Can you replace the rubber with Polyurethane bushes? You can usually get those to move quite well.

Thanks..

Sorry for not making that clear. There is a sleeve, its the sides of the bush that rub against the side of the flange that the bolt goes through.

Didnt know you replace the actual dampers bushes with aftermarket poly... you know of a supplier?

[Zico]

Originally Posted by GORDON STREETER

I shouldn't be overly concerned as the "rotational" movement is very limited and just about all normal road cars have the same set up. Unless there is something radically wrong in the fittings I wouldn't bother. Most of the race shock absorbers are rose jointed. but if the car is mostly for road use I would plug for more compliance with the silent block rubber type.

The rotational movement is limited but for something thats so simple to improve I'd really prefer to do it. Im told high end damper manufacturers like proflex for example, ball/roller race their dampers to remove as much friction as possible to allow the dampers to perform to their optimum.

I think the ball raced thrust washers would have their own issues as I mentioned earlier but a few basic thrust washers would still be a big improvment, I'd just like to know what material I should choose.

S/S, brass, zinc or composite PTFE coated.. what would you choose and why?

Thanks.

[GORDON STREETER]

Zico I've already said that just about all cars on the road have the same compliance idea. Before you "think" that you have re invented the wheel the manufacturers of the said items know what they are doing.
The limited twisting movement works through the compliance of the rubber and doesn't actually turn on the axis of the mount. If you do what you say you will find it will make sod all difference and all it will do is keep clapping out the rubber inserts. Old ser 1 and 2 Land Rovers have an idea whereby you cant tighten the shock absorber mounts and were a complete failure as you have to fit new ones every 5 mins !
Go ahead because it looks like you will anyway whatever anyone tells you.
Seeing that I've only worked on cars in my job since 1962 I wouldn't know anything would I !

[JamesH]

I would agree with Gordon. The bolt is tightened up against the inner sleeve, which is therefor clamped solid. The rubber gives the required rotation of the shock by distortion, and there usually isn't very much distortion at all - a few degrees.

Once thing that is vital though, is to tighten the bolts up when the car is sitting on the ground - this fixes the central point at rest. That way there is no 'default' distortion.

If the side of the flange is gripping the rubber and preventing it rotating, a bit of grease with be more than enough to ease things up. Thrust bearings would be complete overkill for a shock mount because their range of movement is so small.

James

[Zico]

Originally Posted by GORDON STREETER

Zico I've already said that just about all cars on the road have the same compliance idea. Before you "think" that you have re invented the wheel the manufacturers of the said items know what they are doing.
The limited twisting movement works through the compliance of the rubber and doesn't actually turn on the axis of the mount. If you do what you say you will find it will make sod all difference and all it will do is keep clapping out the rubber inserts. Old ser 1 and 2 Land Rovers have an idea whereby you cant tighten the shock absorber mounts and were a complete failure as you have to fit new ones every 5 mins !
Go ahead because it looks like you will anyway whatever anyone tells you.
Seeing that I've only worked on cars in my job since 1962 I wouldn't know anything would I !

Thanks for the explanation Gordon but No.. Im not pigheaded, I bow to your experience/superior knowledge and will leave it well alone.
I dont think it would clap in the bushes because I wouldnt be putting any pressure on them.. unlike the landrover example you gave.. quite the opposite in fact.
Im probably wrong but I think I can see the reasoning behind it... the elastic compliance of the rubber tightening at both ends of the swing range could be to help reduce the impact on the dampers piston as it reaches both ends of its stroke?


And.. thanks for your input JamesH

[GORDON STREETER]

Cheers Zico Compliance bushes make life a lot easier for the comfort of the drivers and passengers and so that things don't break in normal day to day running. Most road car suspensions have built in bump stops to limit the amount of travel so the shocks shouldn't reach their limits.
With rose jointed shock absorbers + suspension joints + stiff springs and arb, my race car would be a nightmare to drive on most public undulating roads at speed, and would probably break something pretty quick (including my back) !