[Terza]

So... A thread on a Croatian BMW forum about RFT's was started and there is a guy claiming that when switching from RFT to non-RFT you definitely must do some changes on the suspension geometry, or the tire wear will be uneven and the handling of the car will be compromised. I wouldn't normally give any meaning to such a claim, but it's coming from a man who really knows a lot about cars and is doing some amateur racing/slaloming and builds his own cars. Granted, he doesn't work with the newest BMW's, but he does have an extensive knowledge of car dynamics, setups, etc.

I've told him that for my E92 I've got non-RFT winter tyres with which I've done exactly 12.000 km last winter and they have 8/6mm of thread left and the wear is really even. The tyre change is done at an authorized dealer, and they've also never mentioned the need for any suspension geometry changes. Also, I've said that there was never a mention on the e90post forums about that, and there is tons of people going to non-RFT.

But, seeing as the guy has credibility, I've decided to raise the question here: when changing to non-RFT's, is a change on the suspension geometry needed? I'm thankful for any input from you guys...

Cheers...

[Serjames]

technically the standard or the MSport suspension would be designed with the extra sidewall stiffness inherint on RFT's...

but I don't see that a significant geometry change would be relevant really ? unless you are Seriously working the tyres and suspension... i.e. racing ?

SJ

[E92Fan]

There is no change in geometry, if the change to non-RFT uses the same dimensions of tyres. There is a change in suspension response, due to the difference in weight of the tyres and the stiffness in sidewall, but that has nothing to do with geometry.

[Terza]

Ok guys, thanks.

[agh!]

When BMW deliver an E60 5 series from the factory on 19" wheels which are not available with run-flats, you get proper tyres and a space saver, are they changing the suspension in anyway at all?
I don't think so

I've driven 24,000 miles on Continental Premium Contact 2 standard tyres after 14,000 miles on Continental Premium Contact SSR (run-flat) tyres.

The run-flats had outside edge wear on the fronts by 9,000 miles eventually ditched for standard Conti 2's at 14,000 miles.
Now the car is nearly at 38,000 miles and I do see outside edge wear on the fronts again, but it's taken 24,000 miles to get there.

The only side effect of non-run-flats I've experienced is a subtle amount of extra body roll - barely noticeable - and the elimination of tram-lining and bump skip, better ride etc. etc. of course