Rear suspension frustration

[markwascher]

My 1995 525iT with 170,000 miles has severe inside wear on the rear tires after only 7,000 miles or one year. The car tracks straight down the road and corners nicely with no bumps or rattles from the front or rear over any road surface. According to the repair history the previous owner had been replacing the rear tires once a year for the last two years. I had an independant BMW specialist (“Strictly BMW”) and a Tire and Alignment shop (Les Schwab) inspect the rear suspension components. Both found no suspension damage and made no mention of damage to the frame. The BMW specialist diagnosed…

• No components are visually bent causing abnormal wear.
• Aftermarket shocks are soft causing lowered ride height that will affect alignment settings.
• Recommended replacing the rear shocks and performing an alignment for $850.00… pirates.


Les Scwhab gave no help other than stating “these cars are soooooo specialized and complicated that repairs were beyond our capabilities.” They couldn’t even give me an estimate. What is so complicated about four wheel independent suspension? This is, after all, a 13 year old car, not the space shuttle.

My personal inspection reveled what could be a worn or torqued left trailing arm mount. The right side looked OK. Curiously the left tire is more severely worn. The ride height is equal and correct, the shocks and springs are BMW stamped Boge and are visually in good condition (“Strictly BMW” lied about the soft aftermarket shocks).

The only thing I can assume to be the problem is worn trailing arm bushings affecting the camber to the point of misalignment. Negative camber and possible tow problem would account for severe inside tire wear correct? I can buy new bushings on-line for cheap but don’t own a press and so far no shop will use owner supplied parts. They would rather charge me three times the price plus labor. I really don’t want to remove the trailing arms myself as it is a pretty involved procedure beyond my confidence level.

Has anybody had a similar problem, and if so, how did you solve it? Has anybody had success with eccentric bushings? If so, how do you know when they are necessary?

Thanks for reading.

Mark

[genphreak]

Your expert Les Schwab fella either has NFI or just didn't like the idea of pulling the rear seat, pillar and deck covers just to remove the rear strut assemblies. Doing it is frustrating for the uninitiated, but yes its no Space Shuttle. It is just that they don't come straight out like they do in your average Galaxy (an ugly sedan- and a very bad pun).

Your problem MAY be made worse if the pitman arms are bad, or worse the subframe mounts, but both lead to imprecise or poor (retrospectively) handling.

Pitmans are cheap and are always obviously bad of the rubbers are cracked, else they are probably ok. It is possible that the shocks are no good, but I doubt it. If the car has 535 Bilstein (yellow) shocks they may have two ride positions, one 10mm or so lower than the other. Low ride height WILL cause this problem, ask anyone with a lowered e34; If the car has lowered springs you must expect it. The fix is to do the lowering job properly in the first place. Use a K-Mac camber kit (new subframe bushes for the rear that can be set on a wheel aligner) so the wheel camber can be corrected for the lower ride height. M5 came with fixed offset bushes that acheive the same thing but are not adjustable- some people just buy a set of M5 trailing arms as it is the easy to install. You must use these with M5 height springs- so best to use the K-Mac kit if you can to get things perfect.

Just remember, if your shocks are these kind and can have the lower spring perches adjusted, you will need to remove them first. If doing this, I would buy new springs (if at all necessary) and upper mounts (very necessary) as it is not something you want to bother with often.

:) nick

[Jeff N.]

Hi Mark,

You must be local to the Seattle area. There's a couple of us E34 types around here - maybe we can take a look at it and see what's up.

Strictly is usually pretty good. Expensive but good. They should have found any worn rear suspension parts so I'm guessing that's not it. I'd think it's a pretty good guess that you might have worn shocks and a bad alignment. The fact that you have one tire more worn than the other is telling. A torque trailing arm would be the same as an alignment problem; I'd start with the simple fix first of just getting it checked. Changing the trailing arm can be done but isn't the first thing you'd want to do.

BTW, I've done the rear shocks on a Touring and it's a PITA. You have to disassemble a load of interior parts to get to the upper shock mounts. I'm guessing that's why in part the quote was so expensive.

Drop me a PM and maybe we can get together and scout it out.

Jeff
Bellevue WA

[Ferret]

Isnt it usually the pitmans and the subframe mounts causing tyres to chew up if your ride height is correct?

[BigKriss]

Well said.


Your expert Les Schwab fella either has NFI or just didn't like the idea of pulling the rear seat, pillar and deck covers just to remove the rear strut assemblies. Doing it is frustrating for the uninitiated, but yes its no Space Shuttle. It is just that they don't come straight out like they do in your average Galaxy (an ugly sedan- and a very bad pun).

Your problem MAY be made worse if the pitman arms are bad, or worse the subframe mounts, but both lead to imprecise or poor (retrospectively) handling.

Pitmans are cheap and are always obviously bad of the rubbers are cracked, else they are probably ok. It is possible that the shocks are no good, but I doubt it. If the car has 535 Bilstein (yellow) shocks they may have two ride positions, one 10mm or so lower than the other. Low ride height WILL cause this problem, ask anyone with a lowered e34; If the car has lowered springs you must expect it. The fix is to do the lowering job properly in the first place. Use a K-Mac camber kit (new subframe bushes for the rear that can be set on a wheel aligner) so the wheel camber can be corrected for the lower ride height. M5 came with fixed offset bushes that acheive the same thing but are not adjustable- some people just buy a set of M5 trailing arms as it is the easy to install. You must use these with M5 height springs- so best to use the K-Mac kit if you can to get things perfect.

Just remember, if your shocks are these kind and can have the lower spring perches adjusted, you will need to remove them first. If doing this, I would buy new springs (if at all necessary) and upper mounts (very necessary) as it is not something you want to bother with often.

:) nick

[DanDombrowski]

No, its usually the RTABs, but Im sure the pitmans contribute.

[DanDombrowski]

http://www.bimmernut.com/forum/showthread.php?t=30883 Here's some stuff I went through when dealing with my rear toe problem. Short story is that it was mostly the RTABs causing toe-out. I may have more threads, I'll detail more after I get back from lunch.

[Tiger]

"Track fine" is very very very very very very very, need I say more?, verry subjective. Majority of time, nobody can tell if it is fine or not unless you compare it to another E34 who replaced alot of components.

This is simply tire alignment problem that is caused by worn suspension part... if not been in accident. A body shop can tell if it has been in an accident or not. These are the guy who will look at the car and tell you with good experience.

In any case, rear pitman arm does affect the chamber... as BMW paper I read said... for keeping chamber within spec under different circumstances.

[Jeff N.]

Worn rear pitmans tend to cause wandering and tracking problems. Same for bad subframes. Mark didn't describe those. Instead, he states it tracks fine.

I'm guessing this - there's some sort of alignment problem in the rear maybe caused by some sort of impact (curb, etc) to the left rear wheel. Until the car is put on an alignment rack, you'll never know. The alignment needs to be checked by a good alignment shop experianced with BMWs and 4 way alignments.

[markwascher]

I think you may be right. The car does track perfectly. My summer car is an e28 M5 with rock solid Dinan Stage I suspension. The e34 tracks just as well as the M5. Naturally the ride is much softer and come to think of it there is a slight vibration coming from the rear at 80mph (ho ho worn shocks!)

Its almost certain that the rear end has been impacted at some point. The rear bumper shocks have been replaced and the left side rear window strut is bent and useless. (replacing those little buggers is a whole nether story). After spending an hour removing all the freakin panels and various covers and parts from the cargo area yesterday I'll replace the factory Boge shocks with a set of new Sachs tomorrow then take the beast to an independant shop (Car Tender) in Seattle in a few weeks. Hopefully its just shocks but its probably more.

Thanks all for the input.

I'll let you know how it turns out.

Mark

[Triton540i]

So I'm a bit confused on this one. I was hoping somebody would post a detailed response on this one since I had my local alignment shop tell me that the front end of my car looked great, it was the rear-end that's outta wack?!

I replaced all four corners out with Koni fully adjustable shocks and struts with H&R springs. The shop said they've done work on several 7 series Bimmers with replacing bushings and such for lowering, but I have NO idea what they use to correct potential camber problems? My question is, I'm wondering what specific parts I should possibly replace myself to fix the problem, then have them inspect it, or should I just let them do the work. I was given a $500 quote to remedy the problem, is it worth it? I do all my own work on the car, including the suspension replacement... I just don't want to feel like I've been totally screwed by letting somebody else work on my car.

If I did it myself, what parts would you recommend going with? Is there a kit for the e34 for camber and toe-in/out or do I need to shop for a list of items to do the job myself? My 5er has been lowered 1.75" in the front and about 1.25 inches in the rear... the car might have settled a bit since my install about a year 1/2 ago.

Any recommendations? Thanks!

[Jeff N.]

so what's the problem Triton?

[BMW4LIFE]

So I'm a bit confused on this one. I was hoping somebody would post a detailed response on this one since I had my local alignment shop tell me that the front end of my car looked great, it was the rear-end that's outta wack?!

I replaced all four corners out with Koni fully adjustable shocks and struts with H&R springs. The shop said they've done work on several 7 series Bimmers with replacing bushings and such for lowering, but I have NO idea what they use to correct potential camber problems? My question is, I'm wondering what specific parts I should possibly replace myself to fix the problem, then have them inspect it, or should I just let them do the work. I was given a $500 quote to remedy the problem, is it worth it? I do all my own work on the car, including the suspension replacement... I just don't want to feel like I've been totally screwed by letting somebody else work on my car.

If I did it myself, what parts would you recommend going with? Is there a kit for the e34 for camber and toe-in/out or do I need to shop for a list of items to do the job myself? My 5er has been lowered 1.75" in the front and about 1.25 inches in the rear... the car might have settled a bit since my install about a year 1/2 ago.

Any recommendations? Thanks!

how was the wear on your last set of tires for the rear? if they were horrible and they only lasted a few thousand miles then take their consideration...but i would always get a second look.....

500 is kind of steep....especially because you know how to do it all yourself....

[genphreak]

The rear camber kit or M5 arms (or just bushes) like I said need to be installed to avoid the insides of the rear tyres wearing out if the car does not sit at stock height. If the rear springs have sagged or the fronts extended, this will be the case. If you have lowered springs, this is the case.

I don't see how one arm being bent wears both rear tyres, but maybe it can. I'd expect one rear to wear more or less uniformly (but more than usual) and the one on the bent arm to wear more towards the inside or outside.

Either way a simple algnment tells all.

Once the car is lowered you need to measure the alignment against M-tech specification. Without the right rear bushes or rear arms, this cannot be achieved... for obvious reasons. Then the aligner usually looks, scratches head and tells you your rear tyres will wear on the inside.

I don't know of you needing camber correction at the front ever, but you can buy it if you want it (for the track it is a definate need)

[Barney Paull-Edwards]

Look, lets start from basics. Get some string and run it round the car at wheel centre height, takes a bit of working oout but from that you can soon see if the wheels at either end are in alignment with each other, and whether the car is in alignment fore and aft. Then get a builders level and check that camber is equal side to side.Not rocket science but will give you an idea of any problems.