[GC0215]

As per title, recently changed to non runflats (Goodyear Assymetric 5 on rear, Hankook Ventus fronts) and there is a persistent crashing/wobbling from the rear end, like I'm driving over potholes but only at certain speeds. I've had the wheels balanced twice at 2 different garages and both say they are perfectly balanced- any ideas as to what's going on? Any/all help greatly appreciated

[roger55]

Maybe the tire shop bent a wheel on their tire machine. Check them for runout.
You can do it on the car easily. Using a dial indicator would be the best way.

[Eddamoo]

A buckled wheel should show on a balancing machine though.

Sticking brake caliper maybe? Can you feel any warmth from the wheel after a drive?

Either way it sounds dangerous. I would suggest taking it to a specialist.

[teaston]

Sounds like something in the complex 5 link rear suspension may have failed, maybe a ball joint or bush.

[roger55]

Originally Posted by Eddamoo

A buckled wheel should show on a balancing machine though.

Not necessarily. Balance machines don't check for runout. I know technology does change and maybe there is a balancer now that does but I haven't seen any do that.
I don't know what BMW tolerance is for wheel runout but most figures I've seen are max .050".
I'd want to stay south of that number though.
Run-flats might accentuate being able to feel a runout that is off. So it's also possible he hit something and bent a wheel a little and didn't feel it with non run-flats and does with his new tires.
Anyway, it's easy enough to check and rule it out. I'd sure do that.

[adam.b]

swap left <> right wheel and see if there is any difference.

[NanasBack]

Pretty sure those tyres are directional.

You can't just swap the wheels.....

[GC0215]

I did think it was something in the suspension as the ride has changed too. I'll get it booked in today at my local indie and see what they find. Thanks for all your inputs

[Eddamoo]

Originally Posted by GC0215

I did think it was something in the suspension as the ride has changed too. I'll get it booked in today at my local indie and see what they find. Thanks for all your inputs

Ahh could also be a snapped spring then. Pretty common at this time of year with cold weather and potholes.

[Alscoob]

Originally Posted by NanasBack

Pretty sure those tyres are directional.

You can't just swap the wheels.....

Tyres stated are asymmetric thus not directional, they have an inside & outside so can be swapped side to side. Although once bedded in you should ideally maintain the direction of rotation.

[NanasBack]

Originally Posted by Alscoob

Tyres stated are asymmetric thus not directional, they have an inside & outside so can be swapped side to side. Although once bedded in you should ideally maintain the direction of rotation.

Just checked on my Eagle F1 tyres (in the garden shed) and you are correct.
There is no directional arrow.

The Vredstein Wintracs which are still on the car, do have a rotational arrow.
My mistake.

[GOF_430d]

GC0215 what tyres did you have on the rears before you replaced them?
I ask because I went from the original fitment ContSport5's to Goodyear Assymetric 2's and the ride is so much softer than before and I'm still on runflats.

My car is much less taut than it was before [increased flex in the sidewalls] but I can no longer feel all road surface changes like I could before which is a definite plus for me living in N London where the roads are littered with speed humps and potholes - I honestly believe that the council leaves the potholes as they are better at reducing the speed of vehicles than speed humps.

[GC0215]

I had standard Bridgestone S001 runflats- same ride quality as wagon wheels

[Alscoob]

Originally Posted by NanasBack

The Vredstein Wintracs which are still on the car, do have a rotational arrow.
My mistake.

Good choice, I have the same

[HighlandPete]

Originally Posted by GC0215

As per title, recently changed to non runflats (Goodyear Assymetric 5 on rear, Hankook Ventus fronts) and there is a persistent crashing/wobbling from the rear end, like I'm driving over potholes but only at certain speeds. I've had the wheels balanced twice at 2 different garages and both say they are perfectly balanced- any ideas as to what's going on? Any/all help greatly appreciated

Have you had the suspension checked out yet?

If nothing wrong, like a broken spring, (normally that would show with a slightly different ride height on the corner with issues), it could still be a wheel. A Road Force balance should identify the problem.

[HighlandPete]

Originally Posted by Alscoob

Good choice, I have the same

Vredestein Wintracs were brilliant on my E91.

[GC0215]

Originally Posted by HighlandPete

Have you had the suspension checked out yet?

If nothing wrong, like a broken spring, (normally that would show with a slightly different ride height on the corner with issues), it could still be a wheel. A Road Force balance should identify the problem.

I've not been able to with the lockdown. Car hasn't even moved since Saturday! I guess it'll just have to wait... At least I've still got the wife's Note to use if needs be