Poly-Urathane VS' Rubber

[The Last Streetfighter]

I have used plenty of Rubbers (natural and synthetic) for many applications (mostly abrasion and chemical resistance) and Polyurethanes as well. Mostly mining industry stuff, not automotive. I think the guys at Uniroyal would be upset to hear you say that they can't control the properties and specs of their Urethane If you are interested in custom Urethane have a chat to Grahame White from G.W. Urethanes in Sydney.

The trick will be to combine the hardness properties you want, with tensile strength and compression set (rubber will suffer this but generally poly won't). I think this mix is where some people have had problems with hard poly bushes used on Aussie roads splitting. They would be OK for nice smooth track work, though.

Nylon is interesting but I thought might be a bit too stiff. I came across some poly-ester from a company called Rhino-Polychem that had the most amazing toughness and ability for "memory" that I have ever seen.

[Toobs]

Does anyone know what Durometer Rubber and Poly the suppliers are using. I imagine the rubber would be in the area of 60 Shore A and the Poly to be about 80 Shore A.

80 shore A is the norm for poly bushes.

[M.J.H]

**** edit: just asked what was answered


OK... so the benefit of rose jointing is a 110% eliminiation of lontitudinal movement, whilst giving a forever free rotation.... correct?

My guess is also that this would make the small bumps quite harsh??



The reason im interested is im going to be putting a boot full of power and loading behind my RA28, and it WILL be regularly 1/4mile track driven.... with the occasional wakefield day...... and will be road driven regularly.

The geometries and physics behind panhard rod 5 link live axle setups is not something i understand very well yet - but i wish to

I wouldn't use rose joints if you are using the car on the road.
My understanding is they have a 12-24 month service life and this is reduced greatly if used on the road where the dirt etc can get in and wear the joint.
But i'm sure someone here would know more about it than me,just not something i would use for a road/race car.Outright race car yeah no problem.

[Smokey228]

okay, so i picked up a set of poly ones today. and im gonna try put em in tomorrow, but i read that they need to be serviced, and librcated... so wen i put them in, wat sorta lubricant do i need to use? can i jus use grease?

[M.J.H]

okay, so i picked up a set of poly ones today. and im gonna try put em in tomorrow, but i read that they need to be serviced, and librcated... so wen i put them in, wat sorta lubricant do i need to use? can i jus use grease?

Should have the grease in the packet with the bushes.if not then you will need to buy the right stuff as you can't use any old grease on them.Not sure what the proper stuff is called sorry.

And when you fit the bushes be sure to apply lots of grease,don't be stingy with it.
Also once you have refitted the arms etc to the car DON'T do the bolts up tight until the weight of the car is on the wheels.

[wagonist]

okay, so i picked up a set of poly ones today. and im gonna try put em in tomorrow, but i read that they need to be serviced, and librcated... so wen i put them in, wat sorta lubricant do i need to use? can i jus use grease?

I've got urethane bushes in my rear swaybar mounts & need to know the answer to this question too, because its as squeaky as anything

[Smokey228]

wow, this is alot harder than i thought. im having trouble working out which bush goes where but im using google, so i should have it under control... lol

[Smokey228]

ummmm, with the sway bar mounts. do u have to put grease on them? they are the only packet of bushes that doesnt have grease in the bag...

also, wen i put it all together, obviously all the bushes amount to longer than the screw. so do i jus keep squizing down untill i can sorta fit the screw over?

[Smokey228]

hrmmm. never mind that. there is actualy no way i can physically squeeze the bushes enough...

so the question is now, how can i put the sway bar mount bushes on? lol, and if sum1 can plz show me the order of assembly on theres i really appreciate it.

[nb86]

you can use pbr rubber grease, it works wel and seems to hold grit in the non friction areas (good thing). with swaybar bushes you should just squeeze them over the bar through the split then push it into the d mount before bolting it up to the chassis. and yeah put some lube inside the bush befor assembly.

[Smokey228]

yeh i got them on, didnt fix the squeek but they seem pretty nice. i havent been for much of a drive but im goin again down to mona bp to get sum peddy and test the drive

oh, and the grease noltec recommends is called lithium 4, or sumfin similar. ill double check that for everyone.

[oldcorollas]

just to help sum up the thread a bit.

rubber has more compliance and is less harsh. in high performance applications, it may distort too much and lead to changes a good driver can notice.

polyurethane is (usually) firmer, has less compliance (giving more precise suspension component location), but is harsher on other components and will feel rougher.

the rubber in a stock suspension system is used to dampen all the little bumps that are on roads but you don't feel.
with poly, you will feel them, but at the same time, that shock you feel has to go thru the rest of the suspension components (ie balljoints and the like), and also the chassis... more vibration (NVH??) can cause cracking in the long term, esp sydney roads

i would have thought that after reading this thread, and since you know you will hardly ever use the car on the track, that you would have concluded rubber was better for your road driving experience? well there ya go

Cya, Stewart

[Smokey228]

yeh, i sorta look back now and think i prolly shoulda gone with rubber. but im happy with how they have been performing. i went for a run down mc carrs ck rd, dame it was bouncy, but it went quite nicely...

and to be honest, after i read this thread. i decided that the poly bushes woulda been the better choice, even after i weighed up my options... but its cool, im more inclined to go for a few track days now. i didnt realise how much i love driving her hard

but how serious is the vibration? thats a real concern. cause the road i know are rather crappy... how long before i notice anything real serious?

[oldcorollas]

but how serious is the vibration? thats a real concern. cause the road i know are rather crappy... how long before i notice anything real serious?

it's very hard to say.. depends on the roads and too many other factors that can't be accounted for..

just keep an ear out for anything getting loose etc.... it may be no problem at all

but in sydney, roads suck, and even rubber bushes won't save you

[Rodger]

Good sumation Stewart.

If there is concern about the extra vibration generated, try running the tyre pressures a couple of pound less all round.

Say 34-36 instead of 36-38psi. This will help absorb the smaller bumps such as cats-eyes as well as the annoying tarmac noises.

If adjustable shocks are used then soften them up a bit also.

Regards

Rodger