Raighne

I would have to be really, really sure of that...

fraseman999

some great posts guys. well i know what im going to do. As soon as these runflats go down im going to get rid of them and put non runflats on. And if you have standard suspension then try them without runflats and see how it handles. Dont like it go back to runflats. Its that simple.
I missed something out in my first post, the guy from bmw said they sent them down to thruxton racing circuit in england and they fitted runflat tyres with small incendiary devices and as they drove the car they replicated a blow out and the car skidded ect. They were told that at that speed with a normal tyre the car could have somersaulted.
Since i have never had a blow out im not too worried.

"Better make way" if thats a pic of your car speedo. You better stick to runflats! lol

My source at bmw guys. bmw customer service 0800325600 Richard. Guy says hes the only Richard at that number so never gave second name.

BetterMakeWay

No man, not my pic, but a pic of a 535d none the less. Although i also tried it, i assume that the lower weight of normal tires compared to RF which are waaay heavier will result in a slightly higher top speed as that's sprung mass and it counts quite alot
But even at 250ish if you have a flat tire because of a puncture i presume even in normal tires that won't be too dramaticly, it's not like it looses pressure in a fraction of a second, it will loose the pressure gradually and the flat tire warning will pop out, in which case no sane will keep accelerating. Only an explosion will make a big difference, when i assume that run flats will be a tad safer but won't do miracles. I had a blown tire with run-flats (explosion) at 160 and it's a bit scary none the less.

katheikia

Run-flats are crap period...

KAF

If you think about the dynamics of a tyre you can see why the grip is less secure on poorer surfaces.

Think of F1 cars, they have tyres with incredibly stiff sidewalls to handle the stress put on them through acceleration, braking and cornering at high speeds.

Yet on surfaces we would consider to be as smooth a a billiard table, the drivers complain of 'bumps' causing lack of grip.

The fact is, for a tyre to have good grip it needs the maximum footprint on the road all the time, if anything interupts the contact area a loss of grip results.

When a tyre goes over a ripple or lump on the road surface the tyre needs to deform and reform around the imperfection on the road allowing the rubber to mould over it and remain in contact with the road.

With a very stiff walled tyre this does not happen as well, instead the moulding of the tyre over the imperfection is less complete and there is a reduction in the amount of rubber in contact with the road.

So the tyre skips as it hits imperfections in the surface on bends or when braking or accelerating hard. This is what F1 drivers complain about.

But they have to use tyres like this or they will not get the steering response they need and the tyres will fail due to heat build up, hence the problems at the US GP a couple of years back.

The same principle applies with hard walled RFT's and our roads. Less than perfect contact footprint on poor road surfaces leads to reduced grip, but a tighter feel to the initial turn in.

We have the choice of not using such hard walled tyres and many of us prefer the grip during the bend.

Note - this is nothing to do with the suspension set up, nothing you do to the suspension will affect the ability of the tyre to deform and mould itself to the road surface.

Engineer the suspension all you like, but the weakness in current RFT technology is the excessive stiffness of the tyre and its inablity to mould to the road surface like a regular tyre.

mmwaly

I had Dunlop RFT in my first 525i then had Bridgestone Potenza in my second 525i, the Potenza was softer and less noisy, both were in 17 inch wheels. Recently I switched to Continental non RFT, great improvement in comfort and ride quality.

baadaaboo

Changed the RFT to non-RFT today, know what?





It is 11ty billion times better!! Recommended!

Nova Invicta

Maybe with the revamped 2007 model car they have revised the suspension / geometry for the run-flats, evidentially and yes it is a new model they have done exactly that with the new MINI.
The recent Dunlop RFT replacements I have do appear to be less noisy than the ones they replaced but cannot say why.

Boarder

If BMW is changing their suspension setup to accommodate the performance of RFTs, then they are taking crazy pills.

Build a car around the tires? Bass Aackwards.

KAF