Loose back end!
Discussion
Just bought a CSL having been in the Dark Age driving a 993 for some time.
I keep being amazed at how complete and fun the CSL is and the noise is addictive.
However, under hard acceleration in a straight line the car seems to weave at the back end. The yaw angles are not significant but you notice the movement and occasionally I have backed off because of it. This is unnerving having being use to the rear end grip of a 911.
The tyres are relatively new Continental Contact Sports and are at the correct pressure and the car has 22k on the clock. I appreciate that this may simply be the diff doing its job but I would have thought that it would lock and be much more progressive. It feels like the car is transferring power side to side between the rear wheels.
Anyone have any ideas what this may be?
Cheers
Carl
I keep being amazed at how complete and fun the CSL is and the noise is addictive.
However, under hard acceleration in a straight line the car seems to weave at the back end. The yaw angles are not significant but you notice the movement and occasionally I have backed off because of it. This is unnerving having being use to the rear end grip of a 911.
The tyres are relatively new Continental Contact Sports and are at the correct pressure and the car has 22k on the clock. I appreciate that this may simply be the diff doing its job but I would have thought that it would lock and be much more progressive. It feels like the car is transferring power side to side between the rear wheels.
Anyone have any ideas what this may be?
Cheers
Carl
I had the exact same symptoms when I got my CSL. It had a full brand new set of Michelin PS2s and initially I thought it may have just been the tyres moving about as they bedded in. After 1K miles the movement had decreased but had not gone completely. I have since had the rear trailing arm bushes (RTAB) checked and replaced (they were slightly worn but not completely knackered)and it transformed the handling. The back feels nicely planted now with no nervous squirming under power, unless you get a bit over-eager with the right foot and the back loses traction, especially at this time of year. You are running Contis which are not known for having very good grip though, so it could be tyres or RTABs. Either way it's any easily fixed problem and makes the car much nicer to drive closer to the limit.
Just been to the BMW garage and they don't have much experience of the RTAB problem. However, I work within the same motor retail group so the job should be done properly. He showed me the trailing arm and he could not generate any extra movement to suggest that the bush awas worn. However, they have agreed to do the work under warranty on the basis that it may take a lot of power to initiate the movement in the bush. Before they do the work can someone please confirm that RTAB is the bush holding the arm to the body rather than to the hub. ie the bush at the top of the arm rather than at the bottom.
Thanks
Carl
Thanks
Carl
Carl
The dealership is trying it on with you. The RTAB issue is a common problem on the E46's and the CSL suffers more than most because most have been used on track where the wear is accellarated due to higher cornering loads than are usually applied in road use. A large number of dealerships also don't know the CSL too well and that is why it's best to take the car to a specialist or a dealer which has had lots of CSL exposure. I would be surprised if minor wear to the RTABs could be displayed by trying to induce flex/movement by hand, and as they are covered, it isn't really possible to see wear very easily. I believe some have had the bushes disintegrate when removed whilst appearing almost normal to visual inspection. A small amount of wear or degradation will still show itself when driven due to the power and behaviour of the car under load. The RTABs are located on the end of the trailing arms where attached to the body (not at the hub end).
The dealership is trying it on with you. The RTAB issue is a common problem on the E46's and the CSL suffers more than most because most have been used on track where the wear is accellarated due to higher cornering loads than are usually applied in road use. A large number of dealerships also don't know the CSL too well and that is why it's best to take the car to a specialist or a dealer which has had lots of CSL exposure. I would be surprised if minor wear to the RTABs could be displayed by trying to induce flex/movement by hand, and as they are covered, it isn't really possible to see wear very easily. I believe some have had the bushes disintegrate when removed whilst appearing almost normal to visual inspection. A small amount of wear or degradation will still show itself when driven due to the power and behaviour of the car under load. The RTABs are located on the end of the trailing arms where attached to the body (not at the hub end).
The rear trailing arm bushes not only wear quickly on the csl but due to the design of the rear trailing arm even new bushes allow a lot of toe change under load.
The best solution for track is the spherical joint bushes but these can be a little harsh for road use.
We have found that by fitting new bushes along with the turner motorsport limiter kit this movement of the rear arm is significantly reduced and is a good compromise as well as being more cost effective. There are no side effects to this modification at all. A set up is required when fitting new bushes etc.
As a note BMW are well aware that these bushes are a problem as they released an upgraded bush last year which was stiffer!
Also to bear in mind is that the setup of the car is critical and we have seen lots of cars set up at dealers which were not exactly correct, this is important and can make a big difference.
If anyone requires advice on this or setup etc i would be happy to help.
www.simpsonmotorsport.com
The best solution for track is the spherical joint bushes but these can be a little harsh for road use.
We have found that by fitting new bushes along with the turner motorsport limiter kit this movement of the rear arm is significantly reduced and is a good compromise as well as being more cost effective. There are no side effects to this modification at all. A set up is required when fitting new bushes etc.
As a note BMW are well aware that these bushes are a problem as they released an upgraded bush last year which was stiffer!
Also to bear in mind is that the setup of the car is critical and we have seen lots of cars set up at dealers which were not exactly correct, this is important and can make a big difference.
If anyone requires advice on this or setup etc i would be happy to help.
www.simpsonmotorsport.com
That's very good info from Anthony above.
There's so much movement in those components you'd be amazed (even when the bushes are new as he says). It's actually a shocker if you ask me, and I'm amazed the cars drive as good as they do! A 'limiter kit' transforms things further and takes a lot of the load from the bushes.
There's so much movement in those components you'd be amazed (even when the bushes are new as he says). It's actually a shocker if you ask me, and I'm amazed the cars drive as good as they do! A 'limiter kit' transforms things further and takes a lot of the load from the bushes.
mrontheropes said:
That's very good info from Anthony above.
There's so much movement in those components you'd be amazed (even when the bushes are new as he says). It's actually a shocker if you ask me, and I'm amazed the cars drive as good as they do! A 'limiter kit' transforms things further and takes a lot of the load from the bushes.
There's so much movement in those components you'd be amazed (even when the bushes are new as he says). It's actually a shocker if you ask me, and I'm amazed the cars drive as good as they do! A 'limiter kit' transforms things further and takes a lot of the load from the bushes.
^^^^ What he said ^^^^
sounds like poor geometry settings and/or RTAB's
RTAB now replaced and the car is spot on. I can now confidently put the power down. The dealer replaced them without charging the excess as a goodwill gesture. The seat rails were also replaced at the same time.
Ironically, the car started making a rubbing/grinding noise on Friday which I initially assumed was the front wheel bearing problem. However, doing a little research on BM3W pointed to the hand brake sticking on slightly. The problem has now gone so I can only assume the latter.
Ironically, the car started making a rubbing/grinding noise on Friday which I initially assumed was the front wheel bearing problem. However, doing a little research on BM3W pointed to the hand brake sticking on slightly. The problem has now gone so I can only assume the latter.
I'm fairly sure mine are pretty much shot - first time for a while I drove it in the dry last night and it was moving around all over place. Had a look at the limiter fit and looks a useful bit of kit. How difficult is it to fit new bushes and the limiter kit ? Is it a job my local garage (non BMW) could do ?
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