polys again..

[mrb27]

hey all, i was going to replace all my bushes with polys.. but there seems to be very mixed views and now im all confused.com!! i already have the rear arm bushes (will hopefully sort the camber and keep it sorted)

just read the post on the diff bush sagging so ill probly steer clear of that.. but what about rear beam bush, wishbone, drop link, roll bar bushes etc?

experienced views will be great guys, ill go by percentage votes..

so? to poly or not to ploy? thats the question ^^
2.7i cabby btw its also lowerd and sitting on 17's so the ride is already a bit hard

[Rav335uk]

POPCORN TIME!!!!

My cab is all polybushed, and no issues at all.

[mrb27]

ok, 1 vote in and counted

poly 1
standard 0

[redcar]

Poly

[VW-will]

Another question is, what do you intend on doing with the car? My e30 with STD bush's but all new has really bad judders from the rear beam when 3rd gear drifting, and on the odd accessional rolling burnout lol, will defiantly be polybushing the whole rear end, but if it's a cruiser and not going to be driven really hard I'd keep them STD imo

[Jimbob]

He said it's a cabby so I assume taking it on the track is out of the question...

[mrb27]

well any1 thinking about driving miss daisy wouldnt even consider polys would they?
its a pure road car but i do love to steer with the rear.. it does get driven hard at times i will admit

[Brianmoooore]

BMW stuck with rubber on the full race cars (those that weren't allowed full rose jointed stuff), so leave the plastic rubbish to the Nova/Corsa/Saxo brigade.

[harry_p]

Hmm, I expect that was more to do with sticking to regulations rather than for performance.

Wonder what proportion of pbmw series race cars use poly bushes / solid mounts ( assuming they're allowed to change them ) for what is pretty much the closest you'll get to a 'production' e30 race series.

[kilrone]

no serious race car uses cheap poly bushes. the solid style bushes they do use would likely shake out your fillings for street use, and while poly bushes may stiffen up your ride a bit their lifespan is not that great. for hard street use fit m3 front control arm bushes and original for the rest.

[HairyScreech]

poly ONLY works on bushes that have pure rotary motion an do not use the flex of the rubber for anything.
poly bushes also require regular maintenance and need stripping and re-lubricating otherwise the increase in friction is worse than the internal friction of the rubber.

[mrb27]

poly ONLY works on bushes that have pure rotary motion an do not use the flex of the rubber for anything.
poly bushes also require regular maintenance and need stripping and re-lubricating otherwise the increase in friction is worse than the internal friction of the rubber.

very good point, so poly roll bar/ drop link bushes would be total crap..
i have read that polys outlast standard bushes by far though
tbh the real question is the axle beam bushes.. its not a job i wish to do on a regular basis, i dont mind trial and error with all the other easy fit bushes but the axle beams are a pain in the quan!

as im replacing everything under the car while its off the road i want to make sure its tip top ofc,
hmm do i use standard or polys for the rer beam...

[Jhonno]

http://www.e30zone.net/modules.php?name ... highlight=

What about these alternative materials? Much the same? (Not looked in the the materials at all, jst popped to mind).

[HairyScreech]

hmm, how did i miss that one, (probably from being skint as feck and avoiding looking at shiny car parts atm)

i will take a look into the materials and give my take on it in a bit.

but sounds like theres some good products there.

the beam mount raisers look interesting as that is part of the proper way to lower a car.

in fact if the materials make sense i may look at some for myself.

[Jhonno]

I have put looking into them on my to-do list for when the time comes..

[redcar]

http://www.e30zone.net/modules.php?name ... highlight=

What about these alternative materials? Much the same? (Not looked in the the materials at all, jst popped to mind).

I purchased the raised nylatron beam mount and diff mount and poly trailing arm bushes from them

[HairyScreech]

ok, ertalon is a trade name for nylon and it just so happens i have a half meter bar of it down stairs atm.
it comes in many grades but judging by colour and application they are using 6 or 66 for the non self lubricating bushes and a graphite impregnated version for the others,
nylon is actually quite common for heavy duty bearings and does get used where production components are specified but bearing materials are free, its far too harsh for anything other than track use but is a better bet than phosphor bronze if you want to keep your fillings in.

nylon is naturally self lubricating and the graphite impregnated versions will be very low maintenance.

the poly bushes they are doing come in two versions, 75 duro and 90 duro, this gives a bit of choice in terms of stiffness and noise transmission.
For reference a car tyre is about 60-70a and a super tacky mountain bike tyre is 42a! with a skateboard wheel coming in at 98a.

the 75a is the softer of the two and will be a safe bet for a hard driven road car, should be a good bit stiffer than a rubber bushing without being so hare that they bugger up the compliance of the system.
could be a good bet for the modified e30s running more power and wider/stickier rubber.

the 90a is somewhere in between the two.


my personal take on it for a road car is as follows
an ertalon steering bush is pointless when compared to an aluminium one but a poly one has advantages for people that want to keep some buzz removal.

rear beam bushes are a tricky one and need to deflect to function properly, heres a place for the 75a bush

the trailing arms shouldnt really need to deflect the bush in order to function but the rubber ones are of little issue, perhaps a 90a in here if required

diff bush is a tricky one, a lot of people say leave it alone, but if uprating the beam bushes then the diff bush really should be done to match, after all its a system held by 3 points and if one of those points is significantly weaker than the others then it will transfer more load to the other two, hard call.

the arbs are an easy one, these should only ever experience rotation and a stiffer bushing means a better roll control as it allows the bar to act as its supposed to a 90a could be good or a full ertalon if you can put up with them on the road.

if it wasnt for the small amount of misalignment as the suspension is compressed then i would say the shock bush can be solid, but as it is a 75a would be a safe bet

front arb, same as the rear just make sure the ends of the bar dont chafe on the outer parts of the bushing as they do a bit on the stock ones.

front control arm, well the oem m3/e36 bush is a tried and tested win here, so it is probably the simplest, if full on track stiffness was needed then i would say jump direct to the nylon.
to be fair though the fully solid ball jointed nature of the front means that the front is held well in check anyway.

(just a little bit on the rear steer of the system, this was designed to work well for a road car with fairly crap tyres by modern standards, since the 80s tyres have come along a lot and some of the modified car on here are capable of cornering forces far in excess of the norm.
there is the posibility of the normal bushes being unable to cope with these levels of force and thus providing too much rear steer, infact this seems to be the case as the void fillers for the beam bushes go to show.
a classic case of too much rear steer is the wind up and sudden loss of traction the 306gti experiences, by all accounts poly bushes in the rear to remove a lot of the movement in the rear trailing arms helps this situation no end. )

also its worth bearing in mind that a car with poly bushes on will need different alignment settings to one with stock rubber bushes, this is due to less deflection when moving.
static toe in should be reduced in order to run parallel when moving and the rear will need less toe out to reach zero toe on acceleration.

[HairyScreech]

http://www.e30zone.net/modules.php?name ... highlight=

What about these alternative materials? Much the same? (Not looked in the the materials at all, jst popped to mind).

I purchased the raised nylatron beam mount and diff mount and poly trailing arm bushes from them

your in for quite a harsh ride then, the nylon beam bushes will be very stiff on the road, perhaps too much for the shell to take in that location with the state of our roads.

[skipunda]

So long as enough agree I think that post 2 up should be stored somewhere and easy to find for future. Needs discussion.

[Dezzy]

So long as enough agree I think that post 2 up should be stored somewhere and easy to find for future. Needs discussion.

Put me down as an agree....



I'll just pretend I understand it.

[skipunda]

You and me both, but someone will have something to say!

[Dezzy]

You and me both, but someone will have something to say!

Oh that goes without saying!

[Jhonno]

I think they must be using Ertalon 6 and 66 as you say from a quick scan.. I have asked in their trader thread. Some of the bushes are white some cream.

For a road car imo.. Rubber, other than perhaps trailing arm and ARB bushes where Poly would be an option, depending on your preference. No question.

For a track car.. You don't necessarily require the extra degree of movement in the rear beam offered by rubber, so I would be tempted to use some of the Ertalon offerings. Same with ARB's and trailing arms. Depends how good it's 'good sliding properties' actually are..

Front CAB bushes, well I'll be using Treehouse, which are Nylon inserts.

Diff bush however I would stick with solid rubber, or go twin mount e36 style. I think the mounting needs the properties of rubber to survive. However, you are then making it the 'weak' or flexible point in the beam mounting system, which could bring about it's own issues, increased wear, extra load on the other mounts.. Could almost consider it an all or nothing situation.

[e30-EVN]

Interesting topic this one. I agree with making this easier to find

[Jhonno]

http://www.abgrp.co.uk/data_sheet.asp?dsid=data_Nylon6

I think the UV etc at the end is interesting.. Possibly not that durable out in the elements? Or am I not thinking straight at this hour..

http://www.opelgt.com/forums/performanc ... ushes.html

Ertalon is a self lubricating Oil Filled Nylon , the highest specification material that can be used as a suspension bush. Its heat range and lubricant properties are unequalled by any other Nylon product.

http://www.r3vlimited.com/board/showthr ... ngs&page=7

[HairyScreech]

yes, i was looking at that from a "no compromise" but still for the road spec, too stiff for that will always be a problem.
theres very little in the way of bushes that flex on the e30, so mostly the down side is more regular maintenance and increased noise transmission.
provided the shell and mounts can cope with the increased force transmission, as i do have some worries with stress/fatigue and making the mounting sections weaker than the bush.

some great info on the relative hardness of the duro scale here:
http://autospeed.com/cms/title_Custom-B ... ticle.html

as said the 75a poly sounds like quite a good bet, its harder than rubber but not as hard as most poly bushes.
powerflex are 80A and afaik the raw material is available in 40-95a compounds.
now 75 to 80a maynot sound like a big change but if you look at the shore a durometer chart then you can see the difference is that of a rubber tyre to a leather belt, this coupled with a lack of voids produces one stiff coupling.

maybe a solid 75a beam and diff set that mimics the originals would be the best bet, harder but still functions as the original design, just with a higher force threshold (if threshold is the right term), this would require some kind of void to allow a measure of deflection while still being harder due to the stiffer material.
perhaps running a drill through some will do the job.
perhaps np-team could try this for us so we can have some truly great polys for the road.

i dont know how practical that would be, its not a field i have delved into as deeply as engine tech.
one thing i will do is get some responses from some of our lecturers as some of them have VERY impressive resumes in vehicle dynamics.
what i am sure of though is that the function of the rear beam bushes and the diff bush require careful balance of the stiffness of the bushes as they are mechanically linked together via the diff to beam mounting.

this is a very insightful piece of text on bushes in older applications, although it dosent apply to the e30 as none of the joints are the double cone type seen here it is still illustrative of some of the issue of switching materials. http://www.netbug.net/blogmichael/?p=103

I think they must be using Ertalon 6 and 66 as you say from a quick scan.. I have asked in their trader thread. Some of the bushes are white some cream.

For a road car imo.. Rubber, other than perhaps trailing arm and ARB bushes where Poly would be an option, depending on your preference. No question.

For a track car.. You don't necessarily require the extra degree of movement in the rear beam offered by rubber, so I would be tempted to use some of the Ertalon offerings. Same with ARB's and trailing arms. Depends how good it's 'good sliding properties' actually are..

Front CAB bushes, well I'll be using Treehouse, which are Nylon inserts.

Diff bush however I would stick with solid rubber, or go twin mount e36 style. I think the mounting needs the properties of rubber to survive. However, you are then making it the 'weak' or flexible point in the beam mounting system, which could bring about it's own issues, increased wear, extra load on the other mounts.. Could almost consider it an all or nothing situation.

the bearing properties of nylon are actually considerably good.
some good info here:
http://www.castnylon.com/pdf/Bearing_Data_Sheet.pdf
http://www.bearingboys.co.uk/Nylon_66_Rods-29-a

of the second link a very good point is raised about nylons hydroscopic nature and swelling, this may require the bushing to be resized after a while or prevention of moisture ingress.
it also makes me wonder about the contact faces of the surround, can the hydroscopic nature increase corrosion of these parts?

the bearings with molybdenum di-sulphide in them will be very good, this mix is designed for dry lubrication and the MOS is used in the black cv joint grease to do the lubing.
(its also the moly in moly-slip and chrome-moly steel etc)

the treehouse ones are very nice, but i do think for the price you could just get some 66 with moly and make your own, hell if these guys from Lithuania are willing to do them then go for those, i consider the treehouse ones to be a bit boutique and offer no real advantage over a nylon in a normal lollypop.
(provided your not doing it for clearance issues as thats there only benefit)

yes indeed for track use the rear steer element of the beam set up/geometry is pointless as all it will do is make life harder when it comes to finding the ideals of grip, its a benefit to stability and tyre wear on the road but neither of these are of serious consideration on track, neither is the small amount of bump compliance they offer.

as for it being all or nothing i do agree, as above really, stock function and relative stiffness regardless of the overall stiffness of the individual bushes or totally solid, as i think there is more load spreading going on there than we think.
certainly mine loosened off the diff bolts and cracked the beam tabs when the diff bush was shot and the beam bushes ok.
(has an 8mm plate welded on top now, crack that you cunt)

[redcar]

Hairyscreech can we see some pictures of that thick bit of steel you have welded there

Thanks

[HairyScreech]

its just a strip as wide and as thick as the cleaned up part seam welded across the top of where that is broken, wasnt simply a repair and not a lot of thought went into it.

you can see where it cracked at the bottom (change of colour as that bit had fallen off and the crack to the right of the top hole.

couple that with the resulting play chafing the inner holes a little oval (just visible in the picture) and there was some bad ju ju there.

i put it down to either shot bushes allowing too much movement/stress put into the beam or poor diff replacement at some point.

[redcar]

Oh that's the subframe
I thought you meant the actual diff mount on the car chassis was cracked

[HairyScreech]

no no no, that the bit i expect to be taking extra abuse if the beam bushes are uprated without the diff bush, as the diff will still be trying to move but the beam is fixed.

[Jhonno]

A point about raising the rear subframe.. The diff should be lowered a matching amount to suit and keep everything inline.

[HairyScreech]

in terms of propshaft alignment, yes it is a good idea to keep it stock by bringing the diff down.

although i wouldnt just use washers as there needs to be a far chunk of metal in contact with the beam bit to help stop the damage above.

[redcar]

I raised my beam
Dropped the diff just using washers.
There's still a far bit of bolt in the diff sO wouldn't worry

[HairyScreech]

its more the beam i would worry about, the diff has quite a large area to spread the load into that relatively thin bit of steel, the washers would half that area at best.

[redcar]

its more the beam i would worry about, the diff has quite a large area to spread the load into that relatively thin bit of steel, the washers would half that area at best.

I think your subframe might have been a one-off...i appreciate it has to spread the load the diff has on it, however.

I have a solid diff mount so that diff won't be moving at all, and also solid subframe mounts, so theres no movement.

The bolts are all nice and tight as well so i can't ever see the subframe bending or snapping.