suspension friction - Polybush?

[350Matt]

Peeps

Being as friction in suspension systems is generally a bad thing I was considering polybushing the griff throughout, now I've fitted these things before and I think they're generally a superior bush provding you fit the grade of poly-urethane thats equivalent to the orginal rubber in hardness ( no nylon here thanks).

However What I 'd like to know is from those who've fittted poly urethane throughout do they feel the suspension is more free than before?

I'd have thought ride quality should be improved and enjoy better suspension response to cross corner bump etc

Your thoughts?

[Huff]

I'd be really surprised if it made a difference - suspension response is utterly (and deliberately) dominated by the dampers. Friction at pivots is trivial in comparison.

Polybushes are good though IME

[Sam_68]

350Matt said:

Being as friction in suspension systems is generally a bad thing I was considering polybushing...I'd have thought ride quality should be improved and enjoy better suspension response to cross corner bump etc?

The opposite... polybushes (and Rose joints) actually have a rotating 'bearing' surface and so have some 'stiction' (ie. initial friction that has to be covercome before they can start to move), whereas the standard rubber bushes work by torsional flexing of the rubber itself, therefore don't have any initial 'stiction' (except at a molecular level, and of course the individual molecules don't all start moving at once).

As Huff says, though, it's pretty trivial compared to the initial 'nose' force on the dampers, so I wouldn't worry about it too much.

[GreenV8S]

Are you thinking specifically of the Powerflex glacier style poly bushes with a PTFE bearing between the inner sleeve and the mounting bolt, Matt?

I'm using the ordinary (and cheaper) superflex bushes which are just two top hats and an inner sleeve which is lightly clamped between two flanges. There's plenty of friction between the bush and the car and the main suspension movement involves sheering the bush - just like the original rubber bushes. I don't know what the shore rating is but they feel slightly softer than the original rubber bushes, so I suppose they would be 70-80 ish. I can easily move the outboard end of the wishbones up and down an inch or so under light hand pressure, and compared to the spring and damper loads I would have thought the torsional stiffness of the bush was insignificant.

[350Matt]

GreenV8S said:

Are you thinking specifically of the Powerflex glacier style poly bushes with a PTFE bearing between the inner sleeve and the mounting bolt, Matt?

Yes and going to urethane on the anti-roll bar mounts.

Whats focused my attention is my current job where I'm making nearly every joint in the racing car suspension on needle rollers, mind you the forces are somewaht higher than on a road car

[350Matt]

well I've replaced just the front ARB mounts with poly's and lashings of silicone grease.


took it out for a test drive and guess what ....


Its slightly better in initial bump and feels like a slightly softer ride

Need to look at doing the rear ARB well I think.

I did however manage to do something bad to the front wiring loom during fitting as the cooling fans now barely trickle round and also put teh side lights on.....

hmmm