Wonky suspension

PeteW

So, after the rear of my car fell off the jack… (don't ask!). The suspension was noticeably wonky - one wheelarch was a couple inches lower than the other. I replaced the springs, and it seems better but it's still not even - one side is still an inch or so higher than the other and I can hear a knocking coming from it.

My next idea was to replace the shocks (and mounts?), but is there anything else I might be missing…? Will also check the subframe mounts to check I've not done something really bad…

The car is a 2002 (E46) BMW 330ci.

almillar

Very random thought specifc to your car. The rear subframe, or rather where it mounts to the car, I think, rusts. If yours was rusty, and your car took a drop at the back, you could have a big welding job on your hands. Have you measured the height of the top of the boot at both sides, for example, to see if they're even?

EdGasketTheSecond

Have you checked a drop-link hasn't sheared off?

Joe_Horner

Rear subframe bush collapsed? It's around the right age for them to be going anyway and a drop could well have finished one of them off.

Typical symptoms are an inch or so loss of ride height on the relevant side, clonking noises (especially over bumps) and possibly a tendency to wander more than it should.

Take a look underneath in front of the rear wheel arch, you'll see a big round bush sitting in the end of the subframe crossmember and a bolt going up through it into the floor. There should be a definite gap between the crossmember and the mount on the floor of the car, and it should be the same both sides.

If the low side has no gap, or a definitely smaller one, then the bush has failed.

The bushes are reasonably cheap changing them is a PITA.

Ectophile

Have you put the springs on the right way round? Sometimes, there are slightly different left and right springs, to allow for the weight balance of the car.


The shock absorbers should have no effect on how the car sits.

foxy-stoat

Joe_Horner wrote: »

Rear subframe bush collapsed?

You mean subframe floor collapsed? Real issue with the E46 M3's, not sure if the 330 is effected.

Nearly_Old

foxy-stoat wrote: »

You mean subframe floor collapsed? Real issue with the E46 M3's, not sure if the 330 is effected.

I wouldn't think it is a torn boot floor as that is caused by the torque from the diff mounting. The subframe bushes are a known issue on E36s and E46s. I run a 99 Z3 and it's one of the next jobs I've got to tackle on my preventative maintenance list as the bushes are showing signs of wear. The upside is that you have to drop the whole rear assembly, diff, drive shafts. etc so a lot of people get the parts cleaned and powder coated before reassembly.

Joe_Horner

Nearly_Old wrote: »

I wouldn't think it is a torn boot floor as that is caused by the torque from the diff mounting. The subframe bushes are a known issue on E36s and E46s.

It's an issue on a lot of their models, even with different subframes (E32, 43 etc) because of the horizontal bushes - the weight of the car is taken by the rubber (and bonding) in shear rather than compression which is, frankly, a bit daft!

At least on my '34 you can do them with the subframe in place