I have run both of my E30's with poly bushings for the last 6 years or so (sub-frame, differential & RTAB's, stiffer M30 motor mounts). When I put them in, I thought that they were the greatest thing since sliced bread (I was 18 & 22 when I put them in my cars). The improvement in handling was immediately obvious, although I was wrong about why, and the obscene increase in road noise transmitted into the cabin was a novelty of sorts. I was into autoX at the time, and a late-teens / early twenties male, so it was almost like "proof" that I did something "cool" with my car to have to yell conversations with passengers on the highway.
Well, my interests have shifted a lot in the last few years, and my car is more for getting to work reliably (though I bike 99% of the time) and long road trips to go climbing. I also have a lot more fun doing things with the control system (my MAF conversion was a lot of fun). My last trip to Joshua Tree was a good 8-9 hours, and I suppose that was the last straw. The car also used M30 motor mounts, a cheap & easy upgrade from the stock M42 mounts (1/3 the price, and stiffer). A BIG reason I went with them was the fact that I was broke & in college when I got them lol. I also didn't want to mess with pressing in the stock rubber bushings when poly ones could be tapped in with a mallet.
Anyway, I ordered up stock motor mounts, stock trailing arm bushings, stock subframe mounts & a stock differential bushing. Using my lathe, I made some large cast iron pipe fittings into more or less perfect bushing presses, and I got the RTAB's & subframe mounts installed in about 20 minutes (everything). The diff bushing...I had to have it pressed in properly. Hammering it broke the ring on my diff cover. I also received my new SuperSprint cat-back that I had waited 5 months for, good timing there. Going into this, I had come to suspect that the dramatic improvement in handling I saw with the poly bushings was mostly due to the fact that the stock rubber bushings I was replacing were probably totally shot. Duhhh.
Well, after putting a couple hundred miles on the new bushings & mounts, I must say that poly ones are largely overrated. For street and casual/enthusiast autoX, I don't think they offer much at all because the soft stock rubber has only softened the handling a small touch. The drop in road noise & vibrations is IMMENSE, far greater than any drop in handling performance. In some ways, the car feels alot more forgiving in corners now (I have taken it out & "evaluated" its handling performance). If you track your car or autoX competitively, then there is nothing wrong with them and every little bit counts there. Furthermore, my plans to dump $ into the sound system have been put on hold for now. With the ride so much quieter, I can actually hear my music! Well, I also installed Damplifier & some 1/8" closed cell foam on every square inch of interior metal (still need to do the firewall, though). Considering that I yanked 30lbs of the lousy, sparingly placed, stock tar crap (new stuff won't stick to it), the 50lbs or so I installed really did nothing to the feel of the car. I will tell you this much, if you could only put sound deadening in ONE place, make it the doors. Those things seem to be where 75% of the noise comes from!
Going back to stock motor mounts also made a huge difference. Almost all of the interior rattles went away instantly, and the one that remained I fixed (window guide in the passenger side door was loose). The new "loudest" thing is my SuperSprint cat-back. I had been running a Rev A unit from 2002 (yes, I got 7 years from it, more had it not been through a crash 3 years ago) that had a resonator & muffler. This new Rev B one only has the muffler. If anyone has suggestions on a high quality stainless baffle-less resonator, please let me know. I would like to install one. The original SS one was just perforated tubing packed with steel wool, but it was a lot quieter. Baffles are a no-no as they inevitably come loose & rattle, and I don't want to hack my $500 cat-back up any more than necessary.
OK, this is long enough for one post! Anyone else here found that the discomfort of certain "performance" stuff outweighs the performance gains? Dammit, I must be getting old. My final words from experience would be this: Don't drop money on mods if you want a faster car. Spend it on professional driving school. Then go out & embarrass people like me, who thought investing in the car with lots of aftermarket stuff was the way to go faster, with your largely stock car. A properly maintained E30 with stock suspension is far more capable than it is given credit for, but most people don't have it properly maintained so they think it sucks.
Oh and a front toe alignment does wonders, too.
Topic: From Stiff/Poly Bushings, Back to Stock: My Observations (Read 4720 times)