Poly rtabs versus stock?

[gearheadE30]

I have poly akg rtab bushings on my car, and I'm pretty sure that the inner bores are getting worn out, as other members here have experienced. So at this point, either I need to go with a different brand, or go back to stock. After 200k miles, the stock ones that I removed were basically fine. the car does see track and autocross time on a regular basis. otherwise I will probably go with poly bushings from powerflex/bmp design.

[kendogg]

From my experience - stick with stock rubber ones. After having the AKG adjustables, and getting an alignment at thge best racecar alignment shop in atlanta, and seeing where the rear camber and toe numbers were - stock bushings would've been right in the same ballpark range. They last longer, they're cheaper, no noise, and there's no hassle. Seems like a no-brainer to me.

[nando]

that's because adjustable *bushings* are junk.

as far as rubber vs poly - a harder poly is better for heavy duty use, but if I was comparing a softer "street" poly vs the stock rubber bushings, I'd choose stock.

[CorvallisBMW]

If you want adjustability and long life you can always pair the OEM rubber bushings with a weld-on eccentric kit such as Ireland Engineering sells.

[gearheadE30]

My car isn't slammed enough to warrant having eccentrics welded in, although maybe once I have a bit more money saved up I'll get that done.

I wouldn't be going with the harder poly that they have; I'd buy the 'street' bushings which are softer. I do a lot of highway driving (6 hour round trip to Chicago about once a month) so NVH is fairly important. I really doubt I'd see much difference on track, either. It's not a race car.

[nando]

then stick to stock. "soft" poly likely deflects more than the stock bushings anyway.

[kendogg]

And the bigger problem is when poly takes a really hard hit and deflects - it doesn't spring back like rubber does. They require more frequent replacement. Even racecar people will say poly has no place in the suspension. Subframe mounts - sure. Not a suitable material for suspension or engine mounting though. However, many people are happy with it as a product, and will continue to use it.

[CorvallisBMW]

^very interesting, I didn't know that

[jlevie]

I think it would take some pretty sophisticated instrumentation and testing to determine whether poly or OE RTAB's have the advantage. I've run both on my Spec E30 and can't tell any difference at all in the way the car handles. I think the OE bushings are better if you have weld in camber/toe adjusters since axis of rotation of each side of the trailing arm will probably wind up misaligned. The OE bushings are bit more compliant and tolerate that better.

[StereoInstaller1]

Currently I am running IE polys as a stopgap.

I want stock, but only after I make it adjustable.

My car is an aggressively driven cruiser. I want stock alignment specs, or stock plus a bit of negative camber, but only like 1.25.

I want to get 15,000 miles out of my tires so I can afford better quality rubber.

[gearheadE30]

Okay, just bought some stockers from BMP. $13 a pair, can't beat that.

what are you doing to get less than 15k miles out of tires, Luke? I put almost 30k on a set of Yokohama S.Drives with 4 HPDEs, 15 ish autocrosses, and the car lowered on GC coils... Just rotated the tires every 7k ish miles and kept an eye on tire pressures and never had a problem.

[StereoInstaller1]

I was routinely getting 8K out of a set of super cheap 215/40/17s with only aggressive driving. I went through 4 sets in 3 years, even having them rotated side to side, meaning dismounted and remounted, trying to get some life out of them.

I swapped to poly RTABs and have 10,000 miles on this set and have plenty of tread left.