Suspension after tyre change

E90

I just got new rear tyres fitted, moved from run flats to standard. Drove about 30 miles on them and am noticing the car seems to be rolling/bouncing a bit, definitely not as solid as the run flats. The car is a 2005 BMW 320d msport.
Does the suspension need to be altered after moving from run flats? Being an msport it has different suspension than standard. Any other ideas what could be causing this?
thanks

Saab Ed

Possibly but it's more likely that you just need to adjust tyre pressures. I'd bet that will solve it.

Cee-Jay-Cee

Run flats and regular tyres give totally different ride comfort/quality. Regular tyres allow more bounce as the side walls are not rigid like run flats. The standard suspension is not adjustable, just ensure you have the tyres inflated to the correct pressure.

HandsomeDan

Changed all four run flats on an SE E90 for standard tyres myself. The turn in is is slightly less sharp around town all right, but certainly not bouncy or anything like that.

Some lads do over-inflate standard tyres when changing to regain some of the sharpness - maybe you could try that?

E90

the tyre has a 40 sidewall, didn't think there would be that much difference. I'll try changing the pressure, not sure what they are at at the moment As the tyre place fitted them. If I knew this was the case I would have stuck with ru flats, its an unnerving amount of bounce, certainly doesn't feel safe.

monkeypants

First thing to do is check the pressures. I've never gotten tyres replaced and driven away with them at the correct pressure. Last time one tyre was overinflated by 12psi.

Yeah, i think your just too used to the hard run flats that the regular tyres seem bouncy. What tyres are they?

E90

cisk wrote: »

Yeah, i think your just too used to the hard run flats that the regular tyres seem bouncy. What tyres are they?

They're hankook ventus. The old ones were Bridgestone potenza RF. Both 255 40 17.

keithsfleet

You wouldn't have a knackered shock or anything? Bit of a coincidence to go the same time you change tyres but would be worth a look.

fasttalkerchat

Did you see the old wheels being removed. They could have rusted on and needed a sledge hammer to get them off.

Nissan doctor

The suspension on your car is tuned for the run flat tyres so obviously will feel a lot different with much softer non runflat tyres.

The handling can be effected too as the car will bounce more over bumps then the suspension can react to.

Its odd that most people buy a BMW because they are 'drivers' cars and then set about ruining the ride and handling by messing with a set up that costs millions to develop.

foggy_lad

Check for bulges/blisters on the side walls of the tyres and also check the balance on all 4 wheels

Nissan doctor

foggy_lad wrote: »

Check for bulges/blisters on the side walls of the tyres and also check the balance on all 4 wheels

How would they effect the softness of the suspension?

corkgsxr

id be going for pressures. there cant be that much of a difference

E90

E90 wrote: »

the tyre has a 40 sidewall, didn't think there would be that much difference. I'll try changing the pressure, not sure what they are at at the moment As the tyre place fitted them. If I knew this was the case I would have stuck with ru flats, its an unnerving amount of bounce, certainly doesn't feel safe.

E90 wrote: »

They're hankook ventus. The old ones were Bridgestone potenza RF. Both 255 40 17.

40 profile 255s is plenty of sidewall to be fair
If you didn't notice the extra give I'd have been surprised.

bazz26

I switched to non RFTs over a year ago on my E90 M Sport and other than having to carry a spacesaver wheel in the boot I cannot see any disadvantage to switching over. There is definately an improvement in handling and comfort running the non RFTs but there is no rolling or bouncing from them. Mine are 255/35/r18 on the rear btw.

galvo_clare

Nissan doctor wrote: »

The suspension on your car is tuned for the run flat tyres so obviously will feel a lot different with much softer non runflat tyres.

The handling can be effected too as the car will bounce more over bumps then the suspension can react to.

Its odd that most people buy a BMW because they are 'drivers' cars and then set about ruining the ride and handling by messing with a set up that costs millions to develop.

I never understood why BMW adopted runflats so early. The E60, as far as I'm concerned, has suspension best suited to normal tyres but it would seem the marketers held sway and runflats were fitted.
I had a 2006 SE on 17" wheels and the ride was acceptable on runflats.
I swapped to a 2008 M Sport and test-drove a version on 19" wheels with normal tyres.
My car has the standard 18" wheels and came with runflats. It only took me six months with the car to change to conventional rubber and it has transformed the car. Even my wife and other passengers noticed the change.
The ride is much, much better and there's a slight loss in sharpness but barely noticeable.
I have to say that the current 5 Series, the F10, has a very nice ride, even in M Sport trim. The same goes for the current 3 Series, but I still maintain they jumped too early.

galvo_clare

E90 wrote: »

I just got new rear tyres fitted, moved from run flats to standard.

Just noticed this. Did you just change the rears to standard tyres? If you didn't do all four then there's your problem.
The two types have totally different characteristics and mustn't be mixed.

Nissan doctor

galvo_clare wrote: »

Just noticed this. Did you just change the rears to standard tyres? If you didn't do all four then there's your problem.
The two types have totally different characteristics and mustn't be mixed.

That's actually a very good point that I didn't pick up on when reading the OP. Run flats on the front and standard tyres on the rear will have the car all over the place as the front and rear will have completely different reactions over bumps etc.

E90

galvo_clare wrote: »

Just noticed this. Did you just change the rears to standard tyres? If you didn't do all four then there's your problem.
The two types have totally different characteristics and mustn't be mixed.

Yeah that's probably it then, the front still have a fair bit of thread on them, might just have to bite the bullet and get rid of them for standard tyres.