New Subframe Bushing Changed Rear Alignment?? - PeachParts Mercedes-Benz Forum

Scott98 · #1 09-30-2008, 08:21 AM

I installed new rear subframe bushings the other day and now my rear driver's side tire is toed-in almost a 1/4 inch. I used to have zero toe on both tires. The only thing I've changed has been the rear subframe bushings. I never thought they would affect alignment but I guess they did. Now, how do I readjust the toe on one rear tire?

Thanks,

Scott

mobetta · #2 09-30-2008, 10:05 AM

what car?

a 123?

it may be that you did not get the bushing seated fully. you are only referring to the 2 bushings which are under the rear doors? the only reason I can think of off hand is the bushing is not fully seated. they are a bear, I guess I kept a 18" breaker bar and socket in my car for a month, tightening down the big bolt every few days until it was fully seated.

hughet · #3 09-30-2008, 10:49 AM

I did that job a couple of years ago including the differential mount and ended up with negative toe on the rear wheels.
The rear wheels are mounted on trailing arms attached to the subframe which is eliptically shaped. As a result, when the wheel goes up the toe goes out. When the mounts wear down and compress you get rear wheels that are toed out so the car wanders.
In my case, the subframe and differential mounts helped a lot but I still ended up with the rear wheels toed out. To fix the problem I installed new 19 mm rubber spring shims. (L5007-72928 $6.44 each in Fastlane).
What happens is that after 20 years the rubber gets hard and compresses just like the mounts so your alignment gets messed up. All that new rubber straightens out the alignment and cushions everything so you get an amazing new car ride.
With a spring compressor you can replace the spring shims in an hour. If that doesn't work then the only thing left is the trailing arm bushings and that's a tough job.

Scott98 · #4 09-30-2008, 11:10 AM

Quote:

Originally Posted by hughet

I did that job a couple of years ago including the differential mount and ended up with negative toe on the rear wheels.
The rear wheels are mounted on trailing arms attached to the subframe which is eliptically shaped. As a result, when the wheel goes up the toe goes out. When the mounts wear down and compress you get rear wheels that are toed out so the car wanders.
In my case, the subframe and differential mounts helped a lot but I still ended up with the rear wheels toed out. To fix the problem I installed new 19 mm rubber spring shims. (L5007-72928 $6.44 each in Fastlane).
What happens is that after 20 years the rubber gets hard and compresses just like the mounts so your alignment gets messed up. All that new rubber straightens out the alignment and cushions everything so you get an amazing new car ride.
With a spring compressor you can replace the spring shims in an hour. If that doesn't work then the only thing left is the trailing arm bushings and that's a tough job.

So you are saying you installed spring shims to bring the wheels down, in turn toeing them in. Mine is currently toed in so I have to bring the wheel up to toe it out. Shims won't work in my case unless I have a shim in there I can remove. I will check. Also I guess if the mount isn't fully seated, it could affect the position of the wheel - I don't know in which direction but I will check. I torqued them properly and they should be fully seated but I guess you never know. Any other ideas?

Thanks,

Scott

hughet · #5 09-30-2008, 11:27 AM

Did you change the differential mount too?
The subframe is suspended on the two subframe mounts and the differential mount. The only other elements in there which control rear wheel alignment are the spring tops and the control arm bushings. First be sure that your mounts are seated and that there is no damage to the control arms or the subframe.
Inspect the control arm bushings to see if they have collapsed The control arm bushing job sounds pretty tough so hopefully it is not that.
It is also possible that you have spring problems but as I said, as the wheel goes up the toe goes out.

Scott98 · #6 09-30-2008, 12:57 PM

Quote:

Originally Posted by hughet

Did you change the differential mount too?
The subframe is suspended on the two subframe mounts and the differential mount. The only other elements in there which control rear wheel alignment are the spring tops and the control arm bushings. First be sure that your mounts are seated and that there is no damage to the control arms or the subframe.
Inspect the control arm bushings to see if they have collapsed The control arm bushing job sounds pretty tough so hopefully it is not that.
It is also possible that you have spring problems but as I said, as the wheel goes up the toe goes out.

I haven't checked the differential mount. As it mounts in the center, I would think it would throw off the alignment on both wheels, not just one. Nonetheless, I will check it. Also, I don't think you could even install the subframe bushings if they weren't collapsed completely as it is tough to even get the bolt started. But I will check them again.

Thanks,

Scott

hughet · #7 09-30-2008, 01:09 PM

Maybe your spring turned and got unseated when you lowered and raised the left side of the subframe to install the mount. That would make that side of the car sit a little higher. Check your ride height on both sides of the car.

Scott98 · #8 09-30-2008, 03:16 PM

Quote:

Originally Posted by hughet

Maybe your spring turned and got unseated when you lowered and raised the left side of the subframe to install the mount. That would make that side of the car sit a little higher. Check your ride height on both sides of the car.

Good idea and likely cause. I lowered the driver's side much more than the passenger's side as it was the first one I did and I was still figuring things out.

Thanks for all the help.

Scott