Suspension problem or tyre-sensitive handling?!
Discussion
I've had a funny handling problem over the last 18 months or so since I got my car, which for the record is an '02 BMW 330D Touring (maybe not the best forum to be discussing diesel estates but hey ho! 
)
It has felt decidedly twitchy at the front end, in the worst instances tugging the wheels noticably left or right. It's not done it to a dangerous extent yet, but that has been on my mind! Typically it goes with the camber, but not always. Rough-ish surfaces e.g. roads that have suffered many roadworks, and taking the car over the ridge down the middle of the road tend to provide the worst results.
I've had it checked out by 3 garages independently and all have them have said the car has a clean bill of health- one of those garages being BMW. The worst report back said there was a tiny bit of play but nothing untoward that would give me my symptoms.
I recently tried taking pressures down by 5psi to see if the extra compliance made a difference. It might have been a little better, but still did the same basic thing.
I then swapped wheels from front to back (and back up to normal pressures). I originally had Eagle F1s up front and Continental (I think ) Asymmetrico on the rear. All 225/45 on 17" rims (NB not standard wheels for the car, but BMW wheels all the same, and with a spec suitable for the car). So now with the Asymmetricos on the front, the problem has completely or at least almost entirely gone away.
Which has left me a bit confused over what was the problem- a suspension problem masked by one pair of tyres but magnified by the others?
Or genuine difference in handling qualities of tyres with a car tuned for one type but not another?
Any thoughts or similar experiences appreciated!
Mark
)It has felt decidedly twitchy at the front end, in the worst instances tugging the wheels noticably left or right. It's not done it to a dangerous extent yet, but that has been on my mind! Typically it goes with the camber, but not always. Rough-ish surfaces e.g. roads that have suffered many roadworks, and taking the car over the ridge down the middle of the road tend to provide the worst results.
I've had it checked out by 3 garages independently and all have them have said the car has a clean bill of health- one of those garages being BMW. The worst report back said there was a tiny bit of play but nothing untoward that would give me my symptoms.
I recently tried taking pressures down by 5psi to see if the extra compliance made a difference. It might have been a little better, but still did the same basic thing.
I then swapped wheels from front to back (and back up to normal pressures). I originally had Eagle F1s up front and Continental (I think ) Asymmetrico on the rear. All 225/45 on 17" rims (NB not standard wheels for the car, but BMW wheels all the same, and with a spec suitable for the car). So now with the Asymmetricos on the front, the problem has completely or at least almost entirely gone away.
Which has left me a bit confused over what was the problem- a suspension problem masked by one pair of tyres but magnified by the others?
Or genuine difference in handling qualities of tyres with a car tuned for one type but not another?
Any thoughts or similar experiences appreciated!
Mark
To start with I should say... I am no expert but I have read a few books on the subject.
The rubber around the wheel is a significant part of the suspension and changing specification of the wheel and tyres must have an effect on how the system works.
I'm sure that BMW spent many hundreds of thousands of pounds developing the suspension to work acceptably well for just about any road/driving condition. If you change the specification you might improve some aspects to your liking but you will almost certainly introduce some other variations. These "variations" might not be evident immediately or be significant problems but it is extremely optimistic to think that by choosing a new wheel/tyre combination based on a development budget of the cost of the wheels and tyres will be successful.
I'm not saying you shouldn't change the spec to your liking but I am saying that I'm not surprised that some strange artefacts can be introduced.
The rubber around the wheel is a significant part of the suspension and changing specification of the wheel and tyres must have an effect on how the system works.
I'm sure that BMW spent many hundreds of thousands of pounds developing the suspension to work acceptably well for just about any road/driving condition. If you change the specification you might improve some aspects to your liking but you will almost certainly introduce some other variations. These "variations" might not be evident immediately or be significant problems but it is extremely optimistic to think that by choosing a new wheel/tyre combination based on a development budget of the cost of the wheels and tyres will be successful.
I'm not saying you shouldn't change the spec to your liking but I am saying that I'm not surprised that some strange artefacts can be introduced.
Mark Wibble1 said:
I originally had Eagle F1s up front and Continental (I think ) Asymmetrico on the rear. All 225/45 on 17" rims (NB not standard wheels for the car, but BMW wheels all the same, and with a spec suitable for the car). So now with the Asymmetricos on the front, the problem has completely or at least almost entirely gone away.
My GF had F1s on the front of her MX-5 and Bridgestone ER30 at the rear when she collected it and it was all over the place with symptoms that you describe. Replaced the F1s with another pair of ER30 and the problem pretty much went away. It still follows the camber a lumps a bit but no worse than I'd expect an 45 profile tyres. 
Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff