Twitchy steering 35is - Update now FIXED!

[Maniac]

In fact it is so steady that I hardly feel a need to hold the steering wheel.

It's probably a good idea though!

[dhplachy]

Hey all,

Quick update and things aren't any better. Firstly a better description of the problem - basically when driving on a motorway at constant speed, car is great and tracks straight and true. However if you accelerate, it pulls right, and then when you come off the accelerator, it pulls left! Gets so bad that if you take your hands off the steering when it's running straight and accelerate, you end up in the right hand lane, then if you slow down, you pull into the left lane. Gets very unnerving especially as you are constantly trying to compensate.

Had the car at the dealer and had a KDS performed at their expense. Rear was slightly out, and they have fixed it, but it's no better. I even changed the car from run flats onto new Continentals and double checked pressures, but still not right.

At a loss now, dealer has raised a case with BMW technical, but are telling me it maybe torque steer and a possible characteristic of the car. This doesn't sound right at all to me. Any other thoughts? Could it be the power steering? Dealer reckons everything else seems normal?

Thanks for any help.

jelmok,

I am watching your post with great interest (and concern) as I have a 35is on order and the last thing I want is a $72K car that will "twitch" as it goes down the highway and then have the dealer tell me that "it's normal."

My question is whether your dealer is familiar with this vehicle? I have an E38 750iL and have to service my vehicle at a dealer in another town because my local dealer has no one with any experience or knowledge of the vehicle. Sure they can "try" to work on my car, but it is such a rare vehicle it isn't worth the risk. I'd rather take it 65 miles down the road to a dealer that has an experienced technician familiar with the V12.

[jelmok]

Hey all,

Quick update and things aren't any better. Firstly a better description of the problem - basically when driving on a motorway at constant speed, car is great and tracks straight and true. However if you accelerate, it pulls right, and then when you come off the accelerator, it pulls left! Gets so bad that if you take your hands off the steering when it's running straight and accelerate, you end up in the right hand lane, then if you slow down, you pull into the left lane. Gets very unnerving especially as you are constantly trying to compensate.

Had the car at the dealer and had a KDS performed at their expense. Rear was slightly out, and they have fixed it, but it's no better. I even changed the car from run flats onto new Continentals and double checked pressures, but still not right.

At a loss now, dealer has raised a case with BMW technical, but are telling me it maybe torque steer and a possible characteristic of the car. This doesn't sound right at all to me. Any other thoughts? Could it be the power steering? Dealer reckons everything else seems normal?

Thanks for any help.

jelmok,

I am watching your post with great interest (and concern) as I have a 35is on order and the last thing I want is a $72K car that will "twitch" as it goes down the highway and then have the dealer tell me that "it's normal."

My question is whether your dealer is familiar with this vehicle? I have an E38 750iL and have to service my vehicle at a dealer in another town because my local dealer has no one with any experience or knowledge of the vehicle. Sure they can "try" to work on my car, but it is such a rare vehicle it isn't worth the risk. I'd rather take it 65 miles down the road to a dealer that has an experienced technician familiar with the V12.

Yes - I know what you mean. I really didn't expect the car to do this at all (who would?), and didn't notice it on the test drive. Although I bought the car from a smaller dealer out of town, it is being looked at by a large main dealer in Central London, who I would have thought would have experience with this model.

I wouldn't worry too much about your order just yet - based on what others on the board are telling me (and my gut instinct) this is not normal behaviour, and there must be a fault somewhere that just hasn't been tracked down yet. At least that's what I am hoping....

[Maniac]

So OP, did you get anywhere on this?

[socketr]

Jelmok I would definitely have the techs take a look at the steering/suspension linkages as that torque steer effect should not be happening on a rwd car, some slight deviation under acceleration yes but not lane to lane action. I'm too looking to switch to non run flats as I really don't think they suit the Z, just need to find some rims.

Hope it's all sorted out soon for you.

[Nickm]

I've heard a tyre dealer I know say that once you take the run flats off, the car is all over the place, and very slippery when driven....am sure this may compound the problem if the run flats are off.

You're still welcome to try mine, drop me a PM

[socketr]

I've heard a tyre dealer I know say that once you take the run flats off, the car is all over the place, and very slippery when driven....am sure this may compound the problem if the run flats are off.

You're still welcome to try mine, drop me a PM

Strange I'd have thought a more advanced compound would help improve handling characteristics. I've also thought of de-sizing and going with 18's to get more rubber under the arches.

[Maniac]

I think the key here is that the car was designed/setup to use run flats.

Change that and the way the car was set up changes. The question as to whether better would be subjective to the owner.

As per the original topic however, OP I'd have the dealer check all the steering sensors, there are many. Also the actual steering processing unit as this applies steering torque for centring etc and if theres something wrong here the car can exhibit some very odd steering characteristics. There's a defined BMW process for the reset of this system also.

[Kryton]

OP, my old Z was a 35iS and there wasn't any twitchy steering at all

[socketr]

I think the key here is that the car was designed/setup to use run flats.

Change that and the way the car was set up changes. The question as to whether better would be subjective to the owner.

As per the original topic however, OP I'd have the dealer check all the steering sensors, there are many. Also the actual steering processing unit as this applies steering torque for centring etc and if theres something wrong here the car can exhibit some very odd steering characteristics. There's a defined BMW process for the reset of this system also.

Considering the sheer amount of drivers who have switched to non run flats across the BMW range I'd say there's a lot of proof out there that the handling characteristics are vastly improved. Be interesting to find out the differences in steering geometry BMW apply to cars fitted with run flats and those without.

[Sandygate128]

Hi there my 35i runs on 296 with run flats in the summer and i
Got a set of 18" with winter tyres as you can't get 19" winter
runflats
And have to say this car runs straight and true in all situations
On both wheels/ tyre combinations bit softer on the 18" but
Not worth changing for comfort as the improvement in ride
Is negligible ohh I've got adaptive sports suspension don't
Know if that would make a difference to a standard 35i
Without it.

[Nickm]

Hi there my 35i runs on 296 with run flats in the summer and i
Got a set of 18" with winter tyres as you can't get 19" winter
runflats
And have to say this car runs straight and true in all situations
On both wheels/ tyre combinations bit softer on the 18" but
Not worth changing for comfort as the improvement in ride
Is negligible ohh I've got adaptive sports suspension don't
Know if that would make a difference to a standard 35i
Without it.

Good to know, and evidence to back it up.

[jelmok]

So OP, did you get anywhere on this?

So, dealer did the KDS and found settings out. However the tech verified the problem is still there. Reckon everything is as it should be so they are stumped and have raised a Puma case with BMW. Based on the number of people on here and on another forum telling me this is unusual, I am hopeful and have some good evidence to go back to the dealer should they start telling me it's normal or a 'characteristic'!

I've heard a tyre dealer I know say that once you take the run flats off, the car is all over the place, and very slippery when driven....am sure this may compound the problem if the run flats are off.

I was worried about changing them on my car but did so on the advice of Birds tuning. I must say the handling is no different in the sense that this issue is no better. The car seems a bit less unsettled by mid corner bumps though. One thing I had to do was make sure I got extra load tyres - apparently very important. Ride is far improved however. I have kept the run flats though just in case it does turn out to be related!

You're still welcome to try mine, drop me a PM

Thanks! Should the dealer tell me this is normal, I'll be in touch to have your car as some evidence. In the meantime I am going to point te dealer to this thread and the one on the other forum to give some ideas of what to check.

OP, my old Z was a 35iS and there wasn't any twitchy steering at all

Beautiful car! I Really hope I get this sorted - I really love my car in every other respect and don't want to change it. Thank you for all the suggestions - will keep topic updated!

[jonnywells]

[/quote]

God i love them wheels! always keeping my eye on ebay for a set to replace my 294 style 18"

[jelmok]

Hi all,

Thought I would drop a quick update on this for anyone that is interested.  Had the car into a 3rd party BMW tuner to provide an independent report and initial analysis, and they confirmed the problem is there (so I'm not going mad)!  The owner even has a 35i himself which doesn't exhibit the same problem as my car.  They visibly checked all the obvious mechanical things and everything looked good, and confirmed that the KDS was done correctly.  So my car is now back with BMW.  Went out with one of the Master Technicians and he confirmed the problem was there, but warned it may take a while to diagnose and cure, as most of the obvious things have now been checked and even double checked!  Really hoping they can cure this problem - but at least they are taking me seriously and concur that there is something amiss.  Last I heard they were going to try disconnecting as many electronic aids as possible to see if it is some kind of erroneous interference from the adaptive dampers or the servotronic steering.  Hopefully I'll get an answer soon - don't really want to get rid of the car, but if they can't fix this, I can't keep it as it is....so fingers crossed!

Thanks for all the feedback and insights from everyone!