Terrible handling – (now a lot better)

Newbers · Oct 6, 2019

The handling on my Coupe has recently become really horrible. This primarily manifests itself as:

1. A tendency to wander about when you are trying to drive straight. Not as vicious as the tyre related tramlining, more a case of constantly having the correct the steering.

2. More disconcerting, when I turn in the car will start to turn as normal but then suddenly turn a bit too much so I have to correct. This seems to be very similar on left and right turns and is more pronounced the harder I turn.

Ironically it just passed its MOT at the main stealer on Wednesday and I swear its worse now.
I took the rear wheels off today and had a really good look at all the bushes. It’s really hard to get access to see all of them but I pretty sure one has failed.
Looking at this (courtesy of RealOEM)

I believe it is part no. 9 located behind the diff. It is notable as it runs transversely across the car.
I got a couple of pictures where it doesn’t look healthy. I didn’t invest the time to work out its role – (possibly picking up the diff?) so not sure if this is the culprit.

I wonder if anyone has experienced this part failing and/or changed it?
I’m at a point now (12 years/80,000miles) where it might make sense to drop out that entire rear sub-chassis and do every bush (I think seven) + those on the suspension that have not yet been done (only a couple). This would give me some peace of mind looks like a big job. Unless they can be changed in situ?

ph001 · Oct 6, 2019

It is a lot of work to replace every bush!

The ones that typically wear are no.3 (front wishbone bushes) and no.4 (RTAB). I would go for Meyle HD as replacements. (Sorry, image has gone awol - will repost later)

A universal bush removal insertion kit from ebay is also great for jobs like this ...

ph001 · Oct 6, 2019

You can see the image in this thread...

https://z4-forum.com/forum/viewtopic.php?f=3&t=104218&hilit=Bush&start=15

brillomaster · Oct 6, 2019

I had the symptoms you describe on my e85 3.0i... was a collapsed rtab on the right side. Also got some m3 toe arms put on at the same time. Car was perfect afterwards.

Newbers · Oct 6, 2019

This pic!

I actually had all of those done in the last couple of years (the fronts were definitely end of life). so I'm looking at the next on the list!

Newbers · Oct 6, 2019

The M3 toe arms to give you a bit more castor adjustment? My car is quite low and they ran out of adjustment when they did the alignment. It's never been quite right (although I thought that was probably more to do with toe-in than castor). I take it the M3 part is a little bit longer?

brillomaster · Oct 6, 2019

If i remember correctly, the m3 arm has threaded adjustment, with a ball joint on the end, as opposed to a standard arm with limited adjustment, and a bush on the end. So defo worth asking about!

Newbers · Oct 6, 2019

I just had a look on Real OEM

It looks like the (E46) M has a very similar looking part (they call it the lower wishbone) albeit with a different part number.

From what I can see you need to go aftermarket for the ball joint and adjustment - this type of thing:
Millway Control arm camber rear (toe-link) Uniball, BMW E36 E46 Z4

Could the part on your car be from a specialist?

Newbers · Oct 6, 2019

Looks like these are the wishbones to get (to sort out the poor alignment):

Unless anyone can recommend better?

For the other bush it looks like this from Powerflex:

Or this from Meyle

Issue now is can you change just that bush without dropping the whole subframe?

Liam22 · Oct 7, 2019

The handling woes sounds like rear bump steer. The loaded rear wheel goes into toe out during compression.

The main diff mount bush is not to blame - only look at that if you get axle tramp juddering when pulling away.

The adjustable rear control arm affects camber adjustment - not toe. Nice things, but probably not the culprit either.

Rear toe is adjusted at the rear trailing arm bush (RTAB). As others have said - that is a common issue. And unlike pretty much every other rear bush, they *can* be replaced in-situ. Realoem part #4 (in the above diagram).

saj77 · Oct 7, 2019

Liam22 said:
And unlike pretty much every other rear bush, they *can* be replaced in-situ. Realoem part #4 (in the above diagram).

Liam, is replacing the RTAB possible working from a jack/axle stands?

Newbers · Oct 7, 2019

Liam22 said:
The handling woes sounds like rear bump steer. The loaded rear wheel goes into toe out during compression.

The main diff mount bush is not to blame - only look at that if you get axle tramp juddering when pulling away.

The adjustable rear control arm affects camber adjustment - not toe. Nice things, but probably not the culprit either.

Rear toe is adjusted at the rear trailing arm bush (RTAB). As others have said - that is a common issue. And unlike pretty much every other rear bush, they *can* be replaced in-situ. Realoem part #4 (in the above diagram).

Thanks Liam22 - that's most helpful. I did have the RTAB's changed for Meyle HD's + PSB limiters about two years ago. I did see that the limiters were still intact but didn't investigate more (assuming it was a bit early for them to fail) I'll have a closer look.

The car is quite low (although it never grounds). Would that be a factor?

I vaguely recall reading that bump steer could occur as the lower control arm goes beyond horizontal (diff end lower than hub end). My control arms (at rest) are slightly higher at the diff end. Assuming that the wish bone is a similar length (which is probably not a sensible assumption). The wheels could go from toe-in to toe-out back to toe-in as the suspension is progressively loaded.

I haven't liked the handling since I lowered the car but I have just fitted new rear tyres (Uniroyal RS3) I don't know if its conceivable that they are making this so noticeable all of a sudden?

MrPT · Oct 7, 2019

Is it definitely steering abnormally from the rear? If not I’d suspect front rear control arm (lollipop) bushes before anything else. Especially with a non-M - the EPAS doesn’t give you any feedback about the issue until the effects of it become quite pronounced. Knackered lollipops would be an MOT oversight though. They are easy to check compared RTABs.

If it’s RTABs then you should also be feeling some strange behaviour under power.

G600 · Oct 7, 2019

saj77 said:
Liam22 said:

And unlike pretty much every other rear bush, they *can* be replaced in-situ. Realoem part #4 (in the above diagram).

Click to expand...

Liam, is replacing the RTAB possible working from a jack/axle stands?

Yes you'll need a removal tool though.

saj77 · Oct 7, 2019

G600 said:
saj77 said:

Liam22 said:

And unlike pretty much every other rear bush, they *can* be replaced in-situ. Realoem part #4 (in the above diagram).

Click to expand...

Liam, is replacing the RTAB possible working from a jack/axle stands?

Click to expand...

Yes you'll need a removal tool though.

Thanks might give it go, over the winter while car is off the road.

Newbers · Oct 7, 2019

MrPT said:
Is it definitely steering abnormally from the rear? If not I’d suspect front rear control arm (lollipop) bushes before anything else. Especially with a non-M - the EPAS doesn’t give you any feedback about the issue until the effects of it become quite pronounced. Knackered lollipops would be an MOT oversight though. They are easy to check compared RTABs.

If it’s RTABs then you should also be feeling some strange behaviour under power.

Yes definitely the rear. it's a really obvious feeling. Everything on the front has less than 20k (mostly motorway) miles.
When I had the RTAB's done I did wonder whether the garage had set the levels (preload) properly - no reason why they shouldn't have except that they specialise in racing Ford's and often say they are not very familiar with BMW's. If they had got this wrong I wonder if it would have shagged the (Meyle HD) bushes that quickly.

I must say I haven't noticed anything out of the ordinary under power although I wouldn't want to accelerate hard out of a bend the way it is.

It's going back to Specialist Cars on Wednesday (they didn't close up the cabin filter properly when they did an oil service + MOT last week). I'll get them to take a look.

Liam22 · Oct 8, 2019

Newbers said:
When I had the RTAB's done I did wonder whether the garage had set the levels (preload) properly - no reason why they shouldn't have except that they specialise in racing Ford's and often say they are not very familiar with BMW's. If they had got this wrong I wonder if it would have shagged the (Meyle HD) bushes that quickly.

If they torqued up the RTAB with the suspension at full droop then the rubber part is under constant "twist" at normal ride height. That can certainly destroy bushes pretty quickly. Unfortunately it's not very easy to examine the bushes in situ.

The other thing is that RainSport 3 have quite a soft sidewall. So bump steer may be more pronounced as the sidewall introduces a delay between toe-out happening at the wheel and then the tyre "catching up" as the sidewalls go through deflection. Total conjecture BTW!

Newbers · Oct 8, 2019

I think you could be right that the RTAB's need closer inspection. I've driven 30 miles on the M25 in heavy traffic this morning - not an ideal test route but faster than I've been since this started. The car feels absolutely horrible. I think offside is worse (but difficult to tell with the ruts and camber on the motorway). It's a bit like the rear offside wheel is a castor, you turn, the front goes as it should while the rear carries on straight then suddenly it lunges round like its going in to oversteer. I can also hear something light knocking (almost rattling) behind me. Not a heavy clunking like I'd expect from a major bush failure but enough to want to keep the radio on!

I wonder if some of the testing they did for the MOT (shaking it about) was the last straw for whatever has given way.

Thankfully it will be back up on a ramp tomorrow.

Darkangelv2 · Oct 8, 2019

If you replace with the Powerflex (or similar) RTABs it at least means pre-tension is no longer an issue

Newbers · Oct 8, 2019

Darkangelv2 said:
If you replace with the Powerflex (or similar) RTABs it at least means pre-tension is no longer an issue

I didn't realise that. What's the verdict on them for the road? Would I be losing fillings? I've surrendered a lot of comfort with the coilovers and Powerflex ARB bushes already. If the thing was at least nice to drive I could over look some discomfort but I don't want it too much worse....

Terrible handling – (now a lot better)

Active member

Attachments

Lifer

Lifer

Senior member

Active member

Active member

Senior member

Active member

Active member

Active member

Member

Active member

Lifer

Member

Member

Active member

Active member

Active member

Senior member

Active member

Similar threads