Any one have experience with BavAuto/H&R/Eibach springs with respect to performance? Would anyone strongly recommend one over the others? How about Koni vs. Bilstein? Thanks!
You can't go wrong with H&R Sport and Bilstein Sport shocks. I've had them on my 89 since 1977. SO happy with the setup, I did the same thing on my 90 M3. I think the sit the car perfectly without looking slammed. Ride is exceptional, actually better in the 325 than the M3.
I don't have an opinion about the springs---I've installed them all and they all seem to work fine. I'm a Bilstein fan---I like the deflective disc/hi pressure gas technology, I like the product quality, and I like the lifetime warranty. I like the ease of warranty replacement if there is ever an issue. Over the years I've seen many more leaking Koni's than Bilsteins and I've installed hundreds of Bilsteins. I'd ask the Turner or VAC guys what springs they recommend.
What are your goals? Intend to track it & drive it on the street? Street only? I've had Eibach progressive-rate sport springs & Koni adjustable sports (Ground Control adjustable Koni sports in the rear), which I always liked because I could put them on the softest setting for acceptable street-ride quality, and max firm setting for the track. The sport Koni's dialed up to the firmest setting I've thought feel firmer than Bilstein sports, but I don't have comparison shock-test results to confirm my impressions. I haven't had so much leak problems with the Koni's, I think I had one Koni leak once, a long time ago. Can't argue w/ Terry's depth of experience over the years though. Koni's N. America headquarters are about 25 mins. away, so replacement under warranty wasn't much of an issue back then, I can see where time delays due to mailing etc. could be of concern. H&R & Bilsteins are a tried & true combo though - many, many, folks have gone that route. I doubt you can go wrong pairing either brand of shocks with any of those springs. Just be prepared for the compromise in street ride quality, you will be feeling bumps substantially more, particularly big ones, & you'll want to take extra effort to avoid potholes.
Yes, it really depends on you're car's main mission but Garrison's comments on ride quality need some clarification. Ride quality can be significantly compromised with H&R - if you choose their "Race" or "Cup" springs. Typically, spring rates increase as you get less and less spring (for the "slammed" look). If you're main mission is daily driving with occasional trips to the track, a set of H&R "Sport" with Bilstein Sport shocks will actually IMPROVE your ride quality from OEM. This setup provides a mild drop that looks perfect on the E30. Not really an issue over pot holes and believe me, Tucson has some of the worst roads west of the East Coast. The most obvious ride characteristic you will notice using the H&R Sport & Bilstein Sport setup is reaction time, the immediacy of responding to road imperfections. Over bumps, the cars up/down travel is much quicker but never uncomfortable or harsh as you might experience with the "Race" or "Cup" springs. When I bought my 40K mile 1990 M3 a few years ago, the OE shocks were pretty much frozen in place due to inactivity. It was bone-jarring over the pot holes and I DID feel and avoid them all before installing the same setup as the 325. I expected the same results in ride quality but the M3 didn't drop like the 325 did and it was never as comfortable around town as the 325, partly due to the 16" wheels & lower profile tires. With the same suspension in both cars, +1 wheels on both cars (15" for the 325) and a little more weight in the front for the 325, there was very little difference in handling. Ultimately chose to sell the M3 and keep the 325. It just does everything so well with this simple modification.