Suspension Bushes - Rubber Vs Powerflex

[Sam Monoogian]

I remember reading somewhere about Powerflex Bushes. Do they offer any significant advantages over the standard bushes? Other than Demon Tweeks who sells them?

[tony isherwood]

FWIW

 

From what I can remember from previous threads, ( but could be wrong), the general opinions were that non rubber bushes were not a good idea, and transfered a lot of stress / strain into the chasssis. More than was reasonable. There were better ways to improve handling.

 

May be OK for an out and out race car, but made the ride / handling on the road to servere.

 

Calls for a Peter Carmichael reply.

 

[Peter Carmichael]

With a different slant to Tony's reply.

 

The material is superior and won't degrade in use.

 

Whether they are appropriate is questionable. The Seven isn't actually that hard on its bushes apart from the A frame bush. The new design A-Frame bush actually doesn't do much bushing. It means that the A-frame twists up under cornering loads and is less than clever. The important bushes to my mind are the ones for the ARBs and the dampers. The dampers could quite easily have one end changed to a rose joint with good effect which would halve the compliance. Most of the other bushes are thin sections meaning that they don't deform much at all - i.e. they don't act as bushes.

 

Some people have changed to rose joints without necessarily suffering chassis failure, but they aren't necessarily high mileage Seven drivers, so the failure mode might not yet have shown up.

[R2D2]

I think that there are a couple of issues about bush materials that need to be considered.

 

Basic "static" compliance doesn't really affect chassis loading as the force should be constant for a given cornering speed but it will influence geometry change for a given load. If this means that the car will corner at higher speed with a stiffer bush then the load will on the chassis may be greater but this should not really be very different to using stickier tyres. I wouldn't worry about bush compliance and pick up point loading.

 

The damping factor of the bush will,however, affect the transmission of higher frequency vibrations that could affect the fatigue life of the pick up points and surrounding areas. The damping factor of most elastomeric material is significantly affected by frequency and the only real way to compare bushes is to look at the damping vs frequency plot and do some fourier analysis. I could imagine that polyeurethane has more consistent and superior damping behaviour to rubber but as Peter says the basic geometry of the bush will have a significant effect on both compliance and damping behaviour.

 

I doubt much information about either type of bush is available but if a rose jointed chassis doesn't crack up then a bushed chassis of any type will be less prone to fatigue or impact damage. The Powerflex bush should be a good halfway house that doesn't shake out fillings. Whether they are worth the cost is another issue.

[EFA]

I've done about 6000 miles on rose jointed dampers, with no side effects to the chassis.

 

 

 

Fat Arn

See another FAT ARNIE here

See a meaty Vauxhall car here

See the Le Mans Trip Website here

See the Lotus Seven Club North Kent Website here

 

[V7 SLR]

Nice one Arn. Isn't your chassis currently being welded back together? smile.gif

[groutledge]

Just one more tuppenny worth on the bushes. I am currently running a rose joint and previously I had used the poweflex bushes and found them to be better than the rubber bushes. I had a brand new set of the rubber bushes when I had a new wheel bearing fitted. The bushes failed completely after a half a track day ( when they were still new !! ) . The effect of this is the back of the car acted like a 1/2 ton slide hammer and it wrecked my new bearing.

 

The rose jointing should not be a problem as the a frame is a caterham part and I do not believe they would sell a part that would knowingly destroy a chasis thru over loading.

 

In my experience a loose, unlocated axle wil cause more damage than different bush materials.

 

Graham

 

 

[Sam Monoogian]

Phoned up Demon Tweeks to find out the price of a full set of Powerflex bushes and was quoted £276.01!!

 

I then phoned up Caterham and was quoted £45+VAT for a full set of standard bushes.

 

No contest, especially when my car will be mainly a road car and the fact I won't be running sticky tyres.

 

Should I check prices anywhere else before ordering (for powerflex rather than standard)?

[R2D2]

I have a live axle car and use a Powerflex bush in the A frame as it is reasonably oil resistant and saves the need to change the bush routinely.

 

The A frame bushes that DT supplied were the wrong length and David Power at Powerflex has now made a bush that fits correctly. If you need on I would contact them directly.