What do you lube your bush with?

[Croc]

 

Ok that got your attention! 😬

 

Replacing my CSR front suspension bushes with polyflex ones. I have been a good boy and searched this forum for past posts on how they work and what it may do to my handling. However, there was no clear consensus view on lubricant that should be used? I assume you should lube a poly bush? Was thinking either silicone or copper grease? I assume I need to go and re do this periodically to prevent excessive wear on the bush - how frequent?

 

Last thing - I get the impression from past searches that polly is not recommended on rear bushes? Is that still true?

 

 

 

 

 

[pug7]

Surely self lubricating would be the best??.... 😬

[Pendennis]

Hi, I use high temperature grease LM and not copper slip grease.

Your probably get away with doing this once a year but my advice is take one apart after, 6 months and see how it is and make your decision based upon that

 

If you can fit them on the rear as well I would as there is no reason why not to just remember you are inadvertently reducing your spring rate.

[6speedmanual]

A poly bush works in a completely different way from the factory supplied bushes.

Whilst the factory metal to rubber bonded bushes accommodate movement within the flexing of the material, a poly bush is basically a hinge surrounded by a stiff cushion.

 

If you are to use poly bushes a lubricant as waterproof as possible as it can/will eventually get washed out leaving bushes to wear faster or squeak (see internet searches). Powerflex supply a substance like copper grease but I have also seen in a USA sourced poly bush a black molybdenum disulphide waterproof grease (which I believe is probably better)

 

I personally prefer the way the bonded bushes work and replace bushes with original or uprated bonded rubber where possible. Rubber also has a huge advantage of having rising "spring" rate. Whilst driving along with very low stress/deflection on the rubber bushings they remain relative "soft". As soon as loaded the rising rate makes them stiffer and therefore holding the component (suspension link, engine mount, etc) in place more firmly the more it is deflected.

Also as Poly bushes are not bonded, as the load is applied to the bush it inherently compresses on the loaded side only (bonded rubber bush stretches on the unloaded side). This means only one side of the bush is working for you. It also means that water and road dirt can easily be drawn into the "hinge", promoting wear, friction and noise.

Because of this one sided working the relative stiffness of the polyurethane must be higher.

Finally rubber bushes do not require lubrication as there are no rubbibg friction surfaces.

 

No question that introduction of very hard bushings can "improve" chassis "feel" on some cars. In particular cars with very soft bushing where ride and noise isolation makes for softer handling response.

Tremendous "fan base" approval can be found on t'internet. Bear in mind that most of this reaction will be from people who have just rebushed a car, which probably had well worn/knackered standard bushings. The improvement from fitting a new set of standard bushes my have been just as great. Another "fan base" advantage of poly is that once the old bushes are burned and hacksawed out Polys can be easier to fit as they do not need the high press loads associated with fitting metal sleeves in interference fit range into suspension arms.

 

On a Caterham I am not convinced of the need/benefit of poly bushes. (Although there are supporters on here - some claiming perceived performance improvement, others with purchase self-confirmation statements and some with commercial intent to promote poly bushes) The bushes in a 7 have a very small amount of rubber so give minimal amount of compliance/slop for hide comfort concessions. And the limited thickness of rubber translates small amounts of strain very quickly into making the bushes highly stiff locators for the suspension.

 

Not sure about the final comment in Croc's post about not being advisable on rear (of CSR only or meaning all Caterhams?) or whether for CSR they are just not listed as no company has made a kit for this chassis?.

 

Peter

[6speedmanual]

Quoting Pendennis: 

...just remember you are inadvertently reducing your spring rate.

 

Good point. I was going to include this in my post as it is definitely another feature of a bonded bush but, as I have no data, I was not sure how significant it is.

 

I know that when you set up your race cars you've put a lot of effort into the suspension. Have you any data on the effect on spring rate of rubber bushes? Did you pro-actively compensate by using higher road spring rates when moving to poly?

 

Also any sticktion/friction issues with Poly? Or does your strip'n'rebuild regime ensure the lube is constantly being renewed?

 

Peter

[Pendennis]

Hi Peter I understand your comments.

 

I have been using Poly bushes on my race Caterhams since 2009 and I have always used LM grease, I must add I have never ever seen water or dirt ingress as you describe. Before Poly I used Nylon once again never saw any ingress.

 

It would be unwise for me to state that the poly perform significantly better than rubber bushes, but I am convinced they allow the suspension to travel easier and dampers to work for you more. After all, all of my cars have always handled very well.

 

Peter the biggest advantage for me is not having to release all the rubber bushes every time I make a set up change As you know you cannot make ride height or corner weight changes without releasing all the rubber bushes otherwise you would be preloading the bushes. I wonder how many people actually do that

[Croc]

Pendennis and 6speedmanual - thank you for your superb advice as always!

 

Peter - it was your posts on past threads with the detail on how the bushes differ in operation that gave me pause over the type of lubricant that should be used. To clarify my comment on rear bushes should not be poly - when you search blatchat there were a 5 posts than categorically said that poly should not be used on rear suspension bushes (of all Caterhams) but did not clarify why not. I suspect it is the change in spring rate reason but it was not clear.

 

Thank you Gentlemen

 

Mike

 

 

 

Edited by - Croc on 20 Apr 2014 18:44:46

[Pendennis]

I won't say that those comments are rubbish Croc 😬 But there is no reason why not

And my de dion rear has them

 

 

Edited by - Pendennis on 20 Apr 2014 19:28:32

[6speedmanual]

If you're gonna use 'em, see no reason not to use on rear too.

 

Interesting point about people not slacking off bush fixings when corner weighting. I suspect you are right. I certainly have done when building up set up from scratch.

 

Next time I get the chance I will "weigh" the spring rate effect of the front suspension arm bushes. Although I don't expect it to be much, on a light car these things can be a bigger % than one might think.

 

Peter

[Molecular--Bob]

Simon Rodgers quoted some figures in this thread here.

"Metalastic bushes actually apply 24kg of force when lifting the wheel to 4" of travel.

Powerflex apply less than 1kg"

 

[Pendennis]

Wow, I knew there was difference as you can feel it but that is significant if true

[Damdy-Cash]

Afaik not using them on the rear should be the a- frame one to the dedion only as there is some flex when the suspension works on one side only, can't see why the other rear bushes should give any problems. Cheers Volker

[Pendennis]

I use them on the A frame and DD.

 

I don't think Powerflex make a bush small enough to fit the trailing arm and watts linkage?