Expert Suspension Gurus -- Assist!

[kawchkjf]

So this has been bugging me for awhile...

The rear end of the suspension appears to have been bent.

The vehicle won't go into specs, and rear won't camber less than -1.3 on the right side.

The right side appears to be alright. This goes all the way to -2.5.

Toe appears to be alright for both sides.

I went to the dealership for inspection. I'm not an entirely clueless about cars either...

Visually, nothing looks bent. Whether it can be knuckle, control arm links, guide rods...it is all a guess at this point. Because visually everything looks OK.

It's been suggested that I replace the entire subframe. Now, this seems excessive at $6000+...

What would you replace to gamble and get this back in spec?

[BzsBimmer]

Adjustable rear camber arms?

[s85e90]

Rear arms are prob bent as that's meant to give
First. Not the subframe I imagine. The oem adjusters are via eccentric bolts. Shouldn't be an expensive fix.

[M3ANMACHINE]

Wow. Full subframe replacement?! That's excessive

[kenwelch]

This is an article from I-CAR that should help you with the diagnosis and measurements needed to locate the bent parts. At the bottom of the page you can download the PDF an take it to the tech if needed.
http://www.i-car.com/html_pages/tech...8/020508.shtml

Comparing the accurate measurements of right to left sides will be helpful. The illustrations provide good view of what you are looking for.

[s85e90]

Originally Posted by kenwelch

This is an article from I-CAR that should help you with the diagnosis and measurements needed to locate the bent parts. At the bottom of the page you can download the PDF an take it to the tech if needed.
http://www.i-car.com/html_pages/tech...8/020508.shtml

Comparing the accurate measurements of right to left sides will be helpful. The illustrations provide good view of what you are looking for.

that article is good, but refers to checking the steering knuckle which is in the front and prob not bent unless the car took a good wack..

OP check the rear trailing arms.. Get under the car and look at the little arms w/ the M logo visible. One is prob bent, will be near impossible to see but that should help getting the rear aligned back to OE

[kenwelch]

Originally Posted by s85e90

that article is good, but refers to checking the steering knuckle which is in the front and prob not bent unless the car took a good wack..

OP check the rear trailing arms.. Get under the car and look at the little arms w/ the M logo visible. One is prob bent, will be near impossible to see but that should help getting the rear aligned back to OE

It will take a good wack to bend any of the rear suspension.
Sorry, I should have pointed out that the article title is about checking the steering knuckle, but the methods as stated in the article work on other types of suspension. The diagnostic methods using an LED light and looking for changes in appearance might assist in finding the problem component.
Article Quote:
"Even though we are doing this using a
strut-type suspension, the same
concepts can also be applied to solid
axle and short-arm, long-arm (SLA)
suspensions."

Also reading the section on "Visual Inspection" will help with the technique.

I have included a graphic to help because BMW does not use the term "trailing arm" to ID a component in the E92 M3 technical manual. Focus your inspection on the "wishbone" (upper smaller arm) part #5 and the "Camber Strut" part #3. If parts #2, #4, #6 are bent then the toe-in should be affected. If the "Wheel Carrier" is bent then the camber could also be affected. Compare the camber eccentric bolt and bushing on both sides of the vehicle for differences, but major differences here might also change the toe readings.

Before you spend the $6k on a sub-frame replacement locate a good BMW and I-CAR certified body shop that would be willing to complete an accurate measurement of the sub-frame on their uni-body measurement system. Take your alignment readings printout and explain the issue.

[SenorFunkyPants]

Just out of interest who did your alignment check? and do you still have it to post here?