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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > Suspension | Chassis | Brakes > Need some advice: a bit wobbly when pulling straight
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      05-28-2016, 03:36 AM   #1
Lancelot
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Need some advice: a bit wobbly when pulling straight

Hi

I'm looking for advice as to why, when pulling straight, the car feels a bit wobbly, that is like uncertain if it's going straight or left or right.

When pulling at max power it does stay straight but you can feel that it's not super stable, I'd like to resolve that.

I understand the principle of an RWD car of course, but under dry conditions with normally used tyres (30% used i'd say) of rather good quality (Goodyear Eagle F1 Asymmetric 2 runflats), I would expect more confidence.

I thought of a few reasons... what do you think?
- Are the tyres not wide enough to grip at the front? at the back? running a default 225/35/19 - 255/30/19 setup.
- Are the tyres not good enough? I'll move to Michelin PSS when the time comes, perhaps sooner if that comes into play.
- Am I lacking a limited slip diff? Is the open diff distributing power unevenly on the left/right of the rear axle?
- Is this an aerodynamics issue? Should I have try a front lip to help push the front to the ground?

Here's a picture of the car if that's helpful (no spoilers, M perf bumpers)


Thanks!
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      05-28-2016, 11:11 AM   #2
Gixerste
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If everything is okay your car should feel rock solid when accelerating especially in the dry, Goodyear's are good tyres. I'd check to see if they have worn the same across the tread and maybe get the suspension/steering checked.
PS just noticed your tyre sizes they should be 225/40/19 and 255/35/19 not 225/35/19 and 255/30/19 the sizes you have on are for the e9* models at least in England they are ?

Last edited by Gixerste; 05-28-2016 at 11:18 AM..
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      05-28-2016, 11:33 AM   #3
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Sorry my mistake i do have the tyre size you mention.

Thanks for your help, the tyres look evenly used i'll check again more in details
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      05-28-2016, 01:25 PM   #4
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by your brief description, I agree it sounds most likely to be a suspension issue or misalignment. Did this suddenly begin and, if so, was there any incident such as a curb hit, etc?
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