Twitchy steering 35is - Update now FIXED!

[Rialas]

Unlikely to be a tyre issue.

I'd guess a weak shock or spring causing the car to dip slightly and unevenly to one side hence steering itself left or right. It'll be hard to trace and would probably need to replace suspension components in pairs ie front until the culprit is found.
Good luck.

[jelmok]

Thanks for the insight. Hopefully I'll get an update tomorrow as its been in for another week. Last I heard they were replacing trailing arm bushes but I think that was less of a diagnosis and more about elimination. They warned me it was going to take some time. Hope to post an update tomorrow!

[jelmok]

Quick update - new steering rack and yet another KDS and no change BMW are now sending a proverbial 'man in white coat' to come and help as my dealer is stumped. I have given the dealer I bought the car from two weeks to work with my local dealer to fix the problem otherwise I am rejecting the car. I didn't really get much pushback!

[jelmok]

Well it's been nearly 3 months but I am happy to report my car is supposedly fixed

Got a call from the dealer yesterday, and they finally concluded it was the steering rack. They were initially stumped after changing the rack and finding the car was still not running right. On BMW's advice, they tried my car running on a donor set of wheels and tires, and the car ran fine. They then took off the new Continental tires that I had fitted and fitted back my old run flat tires onto my alloy wheels, and the problem was still gone. BMW got one of their technical managers involved, and he concluded that the original fault was caused by the steering rack, compounded by the new tires that had been fitted. After back to back testing with another 35is, they concluded that all was now well!

To be honest, I'm not that bothered that I can't use the new tires that I had paid for. In any case, BMW agreed to pay the cost of those tires, and also for the independent inspection that I had done. They are even paying for the lease payments for the period that the car has been offroad.

It's been a bumpy ride, but hopefully now I'll get to enjoy the car to the fullest. I must also say I have been impressed with the way BMW have handled this problem also.

[Nickm]

Good result mate, well done

[Gargybloke]

Yes, sounds a good result. Well done BMW

So apart from the bad steering rack, is the other conclusion that a 35is has to use run flats?

[Maniac]

Sounds good, let us know how your test drives go!

[jelmok]

So apart from the bad steering rack, is the other conclusion that a 35is has to use run flats?

That does seem to be their conclusion, but I know many others use standard tires. I don't know how the car drove after the rack was changed on the Continentals, but they certainly weren't happy with it, and according to them the car only handled right after the rack was chamged on the tires it was designed to use, whether my set or the donor set.

[Nickm]

Makes me reconsider getting rid of my run flats. A tyre place in Wembley, who sells a lot of tyres told me to keep with standard as the car will be all over the place with normal tyres....

[Z4andy]

Result with how they have looked after you there

Oddly mine has also had a new rack fitted as it was making groaning sounds.

Must be another common fault to add to the list.

[dhplachy]

Well it's been nearly 3 months but I am happy to report my car is supposedly fixed

Got a call from the dealer yesterday, and they finally concluded it was the steering rack. They were initially stumped after changing the rack and finding the car was still not running right. On BMW's advice, they tried my car running on a donor set of wheels and tires, and the car ran fine. They then took off the new Continental tires that I had fitted and fitted back my old run flat tires onto my alloy wheels, and the problem was still gone. BMW got one of their technical managers involved, and he concluded that the original fault was caused by the steering rack, compounded by the new tires that had been fitted. After back to back testing with another 35is, they concluded that all was now well!

To be honest, I'm not that bothered that I can't use the new tires that I had paid for. In any case, BMW agreed to pay the cost of those tires, and also for the independent inspection that I had done. They are even paying for the lease payments for the period that the car has been offroad.

It's been a bumpy ride, but hopefully now I'll get to enjoy the car to the fullest. I must also say I have been impressed with the way BMW have handled this problem also.

Thanks for the update. I collect my 35is on Monday, 25 Jun 12, and I was tracking this problem with great interest.

[P.eter]

So apart from the bad steering rack, is the other conclusion that a 35is has to use run flats?

That does seem to be their conclusion, but I know many others use standard tires. I don't know how the car drove after the rack was changed on the Continentals, but they certainly weren't happy with it, and according to them the car only handled right after the rack was chamged on the tires it was designed to use, whether my set or the donor set.

So a quick note from me

I had the same problem with my 3.0... It started after hitting a few big potholes a too much speed, the same symptoms: at high speed tramlining (new word for me as non English speaker and unstable after braking and cornering at high speed. For example I know a turn on my home-work I could easily take at 90km/h, this turn is after a stretch of +140. To my surprise my DCT got in action when doing it under the same conditions, this combining with that twiggy feeling I had a speed I knew there was a problem.
In the meantime I changed my worn rear tires which was planned and didn't help.

Turning to the dealer, they said it was something with the steering rack, so I made an appointment to get it fixed. All of the time I was sure it was a case of my mistake.

Last week my Z4 went in for fixing and the dealer came to the conclusion that it was not due to the potholes are other damage on my car and that the rack should be replaced under warranty (good work dealer!)

Running it for 2 days and tested it as far as possible (too wet at the moment) but the problems seem to have gone. To me it seems the steering rack is maybe a weak component? At least it was replaced under warranty.

Regarding those runflat tires, I don't think it related to non-runflat maybe more to make/model of the tire. In the winter I ride on non-runflat winter tires at the front and RF at the back without problems...

[The Admiral]

Glad you got it sorted and BMW treated you well

My std RFTs on 19s are quite good but by experience, expect it to be worse with R888s I have to fit and better when I fit skinny winters...

As above, tyres quite often need a few hundred miles wear before they feel settled on a car.

Cheers

Rog

[The Admiral]

Glad you got it sorted and BMW treated you well

My std RFTs on 19s are quite good but by experience, expect it to be worse with R888s I have to fit and better when I fit skinny winters...

As above, tyres quite often need a few hundred miles wear before they feel settled on a car.

Cheers

Rog