LIve axle suspension bush refresh

[Gridgway]

I've not done a full check yet of all the suspension bushes on my new to me crossflow.  I have changed the a-frame to axle bush though to get rid of the rear axle steer and resulting clonking!

Looking at the front rubber bushes they are definitely very perished.

Is there likely to be a suitable bush kit for the car from anywhere, or will it require some individual sourcing?  I'm not specifically looking to "upgrade" as I suspect the original rubber is good enough.

Cheers, Graham

[Jonathan Kay]

I'd have a chat with Redline.

Jonathan

[7 wonders of the world]

Powerflex offer kits and individual bushes.

Worth looking at your rear dampers too and have them refitted with rose joints both ends if you have not already done so since in OE form the lower mount puts a bending moment thro the shaft as its transverse - the rose joints isolate the damper form this

[Gridgway]

Powerflex only seem to have kits for DD caterhams, not live axle.

I'll try Redline, but not had much success there in recent times (maybe I'm off the Christmas card list!)

[rkeywood]

Hi, I never got on with Powerflex (which can still be bought singly in the sizes needed) and would stick with standard from Redline or caterham direct. At the end of the day a little compliance is not a bad thing, just change them regularly. I'd do all bushes annually and A frame more often if used heavily. Also get the thin plastic washers to shim them and reduce flexing in the wrong direction. If they've deteriorated to the point the rubber is going you'll most likely need bolts as well as new nylocs. You can get these with the suspension bush kit or from any bolt supplier (Kay's Fastenings and Spalding Fasteners are good).

Rose jointing is whole different and costly ballgame that wouldn't be high on my list even for a track car. I'm also not sure on the extent of the bending - on mine the dampers are splayed by 1/8" which limits what is in any case a very small movement and the tops 'float' in the top runner bobbins. I've driven several car with rose jointed rear ends in the past and chose not to do it on mine, which, whilst largely a race car, still had plenty of road use. Decent dampers do however make a big difference. 
R

[aerobod - near CYYC]

I've run the Powerflex A-frame "black" bushes for a couple of years on track and road now, I find them much better for deDion location without the issue of tearing the stock centre bush.

[7 wonders of the world]

Powerflex  remove all the parasitic stiction which permits the springs and dampers to be unhindered in their operation.

I run adjustable rose jointed radius arm on my Dedion to permit correct alignment of the rear end too.

[Gridgway]

Now just to be picky I don't think there is stiction in the rubber bushes. Stiction means something moves after enough force is applied to unstick it.

 

The rubber bushes just flex. That has the effect of slightly increasing the spring rate.

 

So I don't think it's parasitic at all!

[rayjackson1950]

I'd stick with Redline. They were very busy earlier this year, which aused delays but I have just bought some gear ad all was sorted in a few days.

[Gridgway]

Yes, Im in communication with redline to work out exactly what I need. Happy days!

[7 wonders of the world]

True, however there is a degree of stiction in the bush assembly, the main friction is within the elastic nature of the rubber in rotational shear,  providing the suspension has been installed correctly (which often it has not) there will be variable increase in spring rate in compression this is reversed in rebound - which works against the wishes of the coil which is attempting to maintain tyre to road contact, once moving beyond the horiztonal in a downward motion. 

The spring and damper need to be isolated from these which are parasitic in order to work correctly in all conditions and temperatures.

Metalasitc rubber bushes are naturally a very cheap method of reducing NVH however have a short life and fail with contact with petroleum products, during operation they suffer deformation and distortion which is detrimental to maintaining correct geometry.

There is however more stiction which can be removed by replacing the upper ball joint and TRE with spherical joints on the front.

Powerflex / Spherical joints are a significant improvement.

Never understod why CC dont offer Powerflex on the upgrades list....

[Wrightpayne]

Don't the powerflex (other brands are available) bushes simply work as a bearing? They do come with special grease to add when installing. I expect they come with their own maintenance/replacement regime and are not a fit and forget solution.

I think if you are looking to exploit the nth amount of performance out of your seven then there are many aspects of the OEM specification you can change to eek out gains. I think for many owners the OEM spec is perfect for their needs. In fact I'm aware of one owner returning to factory Bilstein dampers and Eibach springs as they are pretty good for a road biased seven.

Regards

Ian

[Ivaan]

I've found that rubbing candle wax over the surface of the rubber bushes before installation seems to make them last longer. Whether it's is a form of lubrication or a protective coat I don't know, but they seem to hold together better.