[aymen_a22]

Just wondering if anyone has been in a similar situation and might be able to help.

The back end stepped out on my and hit a curb (rear left wheel).

The tracking was all over the place and the rear left wheel was sticking out at the front by about 15 degrees, and I have a curb mark on my wheel. I took it to a specialist that sets up 911 race cars and they checked the car over and re-tracked it for me.

1) They could not see anything bent or broken, but the wheel was obviously pointing in the wrong direction. He had a straight edge on the rear toe links and could not see anything wrong at all.

2) When he re-tracked it, the toe aligned fine, but he could not get enough camber. To get me on my way, he balanced the camber on the rear right wheel.

3) He didn't check the wheel to see if it is running true.


The car is now driving straight, currently has no knocking, rubbing or grinding, and seems absolutely fine.

I just want to know what is likely to have been damaged?

Hub
Toe link
Lower link
Bent wheel

Any ideas please.

[bigchieftaco]

I bent a rim once on my 350z hitting a curb. I didn't know it until I got the tire balance and he said it was wobbling all over the place.

My guess is wheel is bent.

[Antetokounmpo]

15 degrees? Do you mean 1.5 degrees? With 15 degrees you'd definitely be able to see what's bent.

[aymen_a22]

It was about 15mm out at the front of the tyre and 15mm in at the back of the tyre.

Im not sure what that works out as in degrees. It was noticeable by eye though.

[bigchieftaco]

Originally Posted by aymen_a22

It was about 15mm out at the front of the tyre and 15mm in at the back of the tyre.

Im not sure what that works out as in degrees. It was noticeable by eye though.

If the wheel was bent it would wobble as it spins so after 180 degrees it would stick 15mm out the rear so I'm guessing you messed up some suspension component. I'm too new here to help on that matter but my advice would be to take it to a good shop that can figure it out, too many items under there to guess at.

[Captain comic]

When you hit a curb - usually lower part of wheel takes the hit and you end up with slightly bent lower control arm and/or lower links. Given that rear control arm is a very strong piece - it's really hard to bent, so usually links are the one that suffer as they are more fragile compared to rear control arm. If your lower links are slightly bent then your camber will suffer and you won't be able to get enough negative camber (I think by default e90 has a -1.3 or something on the rear wheel)
So to sum it up - do an alignment and if all gets within specs you are good, if you see that they can't get proper camber - then you know something is bent. It's not going to be visibly bent, but ever so slightly to appear straight, but not give enough camber

[Antetokounmpo]

Originally Posted by aymen_a22

It was about 15mm out at the front of the tyre and 15mm in at the back of the tyre.

Im not sure what that works out as in degrees. It was noticeable by eye though.

So a 30mm delta with a 25in tall tire that yields an angle of about 2.3 degrees, which is much more reasonable than 15. I would guess your LCA is slightly bent.

[aymen_a22]

So, to clarify, are you saying that part number 4 on the attached drawing from realoem is most likely the offending component?

I was there when he did the tracking and he managed to get the toe sorted with the adjuster bolts. It was only the camber that wouldn't reach the target on the camber bolts.

[Captain comic]

Originally Posted by aymen_a22

So, to clarify, are you saying that part number 4 on the attached drawing from realoem is most likely the offending component?

I was there when he did the tracking and he managed to get the toe sorted with the adjuster bolts. It was only the camber that wouldn't reach the target on the camber bolts.

Yep, pretty much. If he couldn't reach camber - there's some slight bent either in control arm or links. They would appear straight visually.

I've seen rear control arm and this motherfucker is huge and strong (compared to much weaker front control arm) - that's why I said it may be a link instead of control arm, but it's hard to guess

Try going over potholes with your rear wheel - if you'll feel slight tail shake from side to side after pothole - then it's another sign your alignment is out of specs. Depending on the angle you hit the curb it could as well be #11 or 14 in your diagram

[aymen_a22]

So if I was to replace, 4 (control arm), 11 (front lower link), and 14 (toe link), then get it re-tracked again it should all be fine?

[Captain comic]

Originally Posted by aymen_a22

So if I was to replace, 4 (control arm), 11 (front lower link), and 14 (toe link), then get it re-tracked again it should all be fine?

Most probably yes. However, you may need to get new bushings - I'm not sure if they are reusable or not. It's still better to try to pinpoint which link or control arm is damaged if possible

[aymen_a22]

Right, an update.


As mentioned in my original post, the car was re-tracked and the car was unable to reach the target camber.


Since then I have been driving it as usual and have just started noticing that the rear end is a little...loose.


When accelerating on rough roads, the traction control is flashing and I can feel that it is that rear left wheel (the damaged one) that is breaking traction.

What should I do now?

I have been looking at buying a used “whole rear subframe with suspension components” and just swap the lot. Shouldn’t be a massive job (wheels, exhaust, diff, brake lines, cables, SWAP, then put it all back on and get it tracked). Even if I get it, I can compare everything to hopefully pinpoint the problem.


Is this a sensible idea? Something doesn’t feel quite right. It feels fine when driving normally but it feels like the car wants to roll over the rear left wheel when in a long sweeping right corner.

[alfazrus]

What is holding you back from taking your car to a professional shop?

[aymen_a22]

Nothing really. I seem to be reluctant because I have already taken it to two shops and they have not been able to find anything. Due to these two shops, I feel that I am going to have more luck doing it myself.

My thinking is also that by getting a whole subframe assy, if multiple bits are slightly bent on mine, it should square it all up.

[Efthreeoh]

I'd take it to a BMW dealer with a body shop and have them measure the rear subframe. But I would think one of the suspension links is bent rather than the subframe. The E90 subframe is quite a stout piece.

The subframe remove and replace is not trivial. You need to remove (just off the top of my head):

Exhaust (you need a transmission jack - its a gangly piece once free of the chassis). You'll probably ring-off the studs too, which then means drilling out the hardened studs...
Driveshaft (or leave it hanging once disconnected from the diff input flange)
Differential (you need a transmission jack - it weighs 80 pounds)
Axle shafts (halfshafts), they are not easy to push out of the hubs
Shocks (Dampers in Brit-speak)
Springs
Brakes including the rotor (to get the emergency brake shoes out, to get the brake cables out)
Emergency brakes (to get the brake cables disconnected) and that means working behind the hub (drive) flange, which is a PIA
Brake cables
Hydraulic brake lines. The hard lines attach to the subfame, then convert to hydraulic hose, then back to hardline, then back to hydraulic hose. That all means draining the brake system and refill/bleeding it.
Unclip a bunch of fuel and evap lines

Then you get to the actual subframe bolts...

I've done a lot of the above work on my car in the last few weekends. I have a lift, air tools, great set of hand tools, and a shit load of special tools, and it was still very time consuming.

[Unknown_Car]

Originally Posted by aymen_a22

So if I was to replace, 4 (control arm), 11 (front lower link), and 14 (toe link), then get it re-tracked again it should all be fine?

Yes, no need for bushings. Go with links first, they usually damage first. I seen it few times at the shop.

[RVA_MR2]

i hit a curb last year hard enough to bend my front right control arm and both right wheels. two refurbished wheels, a control arm, and she was good as new.

[aymen_a22]

That's reassuring. I would be really happy if I only had to change a few links. Less happy if I had to change a wheel, but it seems like it was only scuffed.

I might get the back end in the air and let it idle in first to check the wheel.

I think I will try and get under the car and have another look around.

[aymen_a22]

So, another update.

Had the car on the ramp and measured everything and cannot find anything wrong.

The only thing I can see is the following:

1) The toe adjustment bolt is at its maximum adjustment to get "toe in" on the damaged side, and on the non damaged side there is still a lot more adjustment.

2) The camber adjustment bolt on the damaged side is not at its maximum and can be adjusted further.

I think the place that did the tracking set the camber to the correct value, but could then not reach the correct toe in, so he relaxed the camber to get the toe correct. This must mean that the toe link is bent. I don't know.


However, to throw a spanner in the works, I have also noticed that the top of the tyre on the damaged side is much closer to the arch than the non damaged side. It looks like there is loads more camber on the non damaged side, but it cannot be because the angle of the wheels is equal.