BMW Z3 info needed

Kevin Allen · **Joined:** Thu Aug 28, 2003 6:42 pm **Posts:** 3479

Liz' dad included a few questions for me in an email to her, and since all I know about BMW's is what I've read in VK's posts, I'm hoping somebody who knows more will share some info.

Quote:

I was looking for parts for my ’01 Z3 and thought Kevin could provide some insight. Last week, I waited too long on replacing tires and developed a flat on right rear tire. It was time to replace the tires anyway, so it was just an inconvenience having to miss work. For the past two sets of tires, this wheel failed first wears on the inside edge and was down to the steel belt when it failed. Probably due to alignment being out of adjustment. Mechanic friends have suggested that I should look into replacing all the rubber bushings in all the suspension parts. Ok, car has 130K mostly highway/Interstate mileage (but I like to feel lateral ‘G’s in the ramps). Car also rolls in turns more now than it did when new. I recall that Kevin suggested Bilstein shocks for replacement, but should I also be looking at replacement springs and/or front/rear anti roll bar too? What manufacturer should I be looking at for these replacement parts? Internet is full of advice, but sometimes different sources conflict with each other. Thanks for any info you can provide

Matt McGrain · **Posted:** Sat Jul 23, 2011 11:44 am

If the Z3's suspension is anything like the E46 M3, the RTABs are notorious for short lives. My rear tires wore pretty aggressively on mine at just 65,000 miles. The IS300 just did the same thing to a set of DZ101's that had about 5-10k left. :cry:

Edit: and I meant the 'cupping' on the inside shoulder of course

RobLupella · **Posted:** Sat Jul 23, 2011 11:54 am

Kevin Allen wrote:

Liz' dad included a few questions for me in an email to her, and since all I know about BMW's is what I've read in VK's posts, I'm hoping somebody who knows more will share some info.

Quote:

I was looking for parts for my ’01 Z3 and thought Kevin could provide some insight. Last week, I waited too long on replacing tires and developed a flat on right rear tire. It was time to replace the tires anyway, so it was just an inconvenience having to miss work. For the past two sets of tires, this wheel failed first wears on the inside edge and was down to the steel belt when it failed. Probably due to alignment being out of adjustment. Mechanic friends have suggested that I should look into replacing all the rubber bushings in all the suspension parts. Ok, car has 130K mostly highway/Interstate mileage (but I like to feel lateral ‘G’s in the ramps). Car also rolls in turns more now than it did when new. I recall that Kevin suggested Bilstein shocks for replacement, but should I also be looking at replacement springs and/or front/rear anti roll bar too? What manufacturer should I be looking at for these replacement parts? Internet is full of advice, but sometimes different sources conflict with each other. Thanks for any info you can provide

He just needs to sell it and buy an STI :lol:

JohnByers · **Posted:** Sat Jul 23, 2011 12:12 pm

Yeah, what Matt said, some new LCA's up front and some H&R sport springs, bilsteins and the H&R bars and call it a day. Much fun!

Charlie Guthrie · **Joined:** Thu Aug 28, 2003 8:14 pm **Posts:** 832

Hi guys, as a recent purchaser of a 1998 Z3 I should point out that the Z3 uses the rear suspension from the venerable E30 which shouldn't be plagued by the suspension issues of the later Z cars and E46s.
If the car is rolling more in turns it could be that what he is experiencing a bit of wallow on turn in from worn shocks, I kind of doubt that the springs are shot. Alternately he could need new anti-sway bar bushings.
Of course if our preeminent expert on BMWs (Vincent) would care to chime in, I'm sure that he is more qualified to comment than any actual BMW owner :lol:

While I would never discourage anyone from adding sport springs and Bilsteines that may be overkill if all he wants to do is take the occasional on ramp at speed. What we really need are some right hand on ramps so I can wear out my other rear tire.
Charlie G

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

E30 style rear semi trailing arms = no alignment adjustment AT ALL. If the RR tire is wearing more than it used to then something is bent. Check the toe and camber. If it's within spec, live with the rear tire wear. BMW dials a lot of rear camber in and it eats tires, but it's safe. Corner weights could be out of whack also, but again, no adjustment and usually indicative of something bent.

Car isn't rolling more than when new, just rolling over faster. Shocks will help that but not affect tire wear. Swaybars are a waste on a street car IMO, just make it "feel" faster.

My suggestions is Bilsteins and non-directional high treadwear tires. Swap the rears when the RR looks low. Check alignment for something totally out of whack, and if he's reeeeeally curious get corner weights to be sure it's straight.

Oh and check tire pressure OFTEN.

Kevin Allen · **Joined:** Thu Aug 28, 2003 6:42 pm **Posts:** 3479

Thanks, everybody. I'll put all of this together and send it to him.

JamesShort · **Posted:** Sun Jul 24, 2011 8:32 pm

Mike, while I agree about the non-adjustability of the rear suspension of the car, there is still a very decent chance that the RTABs or other bushings are worn out causing some odd dynamic conditions and eating the tires.

Steven Carter · **Posted:** Sun Jul 24, 2011 9:10 pm

RTABs are known weak points on the rear suspension, as is the diff mount and trunk floor spot welds. At tht milege all suspensiom bushings are suspect. Ireland Engineering makes very good replacements. Check up on the Z section at bimmerforums.com

<--former M Roadster driver

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

JamesShort wrote:

Mike, while I agree about the non-adjustability of the rear suspension of the car, there is still a very decent chance that the RTABs or other bushings are worn out causing some odd dynamic conditions and eating the tires.

What RTABs exactly are you talking about? The E30 only has 4 small 1" or less diameter solid rubber bushings back there. These don't fall apart like the non-semi trailing arm bushings on E36 and later cars. Only reason people generally replace these on competition cars is to get toe adjustment.

JamesShort · **Posted:** Mon Jul 25, 2011 8:33 am

Yep, those 4. I know they are solid, but they are rubber and the only locating connections that the whole rear arms have with the chassis. But maybe they don't wear out like the e36+ chassis do (which have the voids in them). Anyway, I'm a fan of replacing bushings on an old car with bad tire wearing characteristics and it has served me well (however, in replacing them, sometimes I find bad ball joints or bend LCAs

).

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

JamesShort wrote:

Yep, those 4. I know they are solid, but they are rubber and the only locating connections that the whole rear arms have with the chassis. But maybe they don't wear out like the e36+ chassis do (which have the voids in them). Anyway, I'm a fan of replacing bushings on an old car with bad tire wearing characteristics and it has served me well (however, in replacing them, sometimes I find bad ball joints or bend LCAs

).

I won't say they aren't aged, but they definitely don't have voids and don't fail like E36 (or like Honda rtabs for that matter).

Kevin, if you suspect these bushings, have the guy get an alignment and have the guy sit under the car and push out on the front of the rear wheels. See how much flex/play there is adding toe. I bet it's not enough to cause a problem.

Question for you Spec E30 racers -- do most people replace these bushings on race cars?

Jason Tower · **Joined:** Wed Jun 11, 2008 3:31 pm **Posts:** 1173

MikeWhitney wrote:

Question for you Spec E30 racers -- do most people replace these bushings on race cars?

everyone does i think. some use eccentrics from akg or kmac, some go the weld-on tab route. neither is ideal.

http://spece30.com/forum/10-steering-an ... t-stay-put

Charlie Guthrie · **Joined:** Thu Aug 28, 2003 8:14 pm **Posts:** 832

Care to see how well these bushings hold up after 24 years, 250K miles and over 20 track events? Come on over. I'm guilty of allowing the rubber to age until it is rock solid. Since the car never had rear tire wear issues I let the cheapskate in me spend the car budget on tires and brakes and busted stuff. I'll confess that the rear bushings look like a likely candidate for replacement, but they just didn't produce any serious handling or tire wear issues. (Of course that alone could explain my lack of success in the time trial series; since I only won one.)
Charlie G

David Edwards · **Posted:** Sun Nov 20, 2011 2:57 pm

While RTAB bushings do wear on these cars, the biggest difference is going to be felt by replacing the large subframe bushings on the ends of the subframe. Its like night and day. It virtually eliminates the vague uneasy feeling you get in high speed driving when the weight transfers from side to side.

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BMW Z3 info needed

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