AJH

http://www.e90post.com/forums/showth...190162&page=12

http://www.bbc.co.uk/watchdog/consum...ice/bmw_latest.

norsecarnut

While they may shift that force, it takes a certain amount of force to cause damage. Again, if you took the same instance, the same speed, pot hole, etc, and tire sizing, an impact that has so much force that it causes a stiffer sidewall tire to bend a rim, would destroy the tire and/or rim if hit with a non-run flat tire.

I have used several different brands and sizes of rft and they are simply not so stiff as to be stronger than the alloy!

If you take a taller sidewall tire, it is more able to deflect, and will not do what you are saying. If you take a short sidewall, like 19" on a E93, the pothole that is bad enough to push your tire into the rim enough to damage it, would have shredded the tire and dented the rim if it weren't a rft.

You simply cannot have both in this argument. Meaning, if it's bad enough to do what you think happens when using a rft, then the same set or parameters will be worse for the non-rft situation.

I can understand your annoyance with the tires, it's like they are supposed to protect your wheels, themselves, etc. However you may not have considered the reality of hitting the same bad edge with a low profile non-rft.

norsecarnut

Yes, more nonsense. You are missing the point. People, including you maybe, drive harder because you have this idea the rft tire is indestructible. These people are driving like morons and actually bringing the damage upon themselves.

If you drive like a sensible person, simple pretending you have delicate non-rft, then these issues won't occur. I know all about the rft issue on the low profile 19's. As I said, we had the exact problem ultimately on our 328iT with staggered 19's and RE050A rft. And gues what, I drove it harder than I would have had I been on non rft.

I will also say that if you drove the same tire size, on non rft, the situations that are harsh for the rim would be shredding tires.

Yes, maybe it's better to shred tires, or slow down than to crack rims.

The end of it all is that how people drive is the ultimate cause to any issues.

AJH

I see your point.
The issue seems to be from people who say they have not run over potholes. Rather than one large catostrophic pot hole, that would react indeed be as you described, but more of general usage. The thousands of smaller bumps on the road, the rigidity of the runflat, the shorter sidewall and the camber of the wheel all contribute to the cracking of alloy rims. I believe a standard tyre would be more likely to absorb normal day to day impacts better than a runflat. In 17 years of driving I can only remember hitting one pothole and had one blowout. Ive had lots of punctures but 99% of the time you can pump it and drive to the nearest garage anyway. Runflats are overated

narvselius

Nonsense indeed...or do you have research to vindicate this statement?

norsecarnut

Now that's an entirely different thing and I can see the issue. I assume this is really just a problem on the lowest profile versions, not "normal" sidewalls like a 5 series 18".

I just put rft on our Audi and went to a slightly taller size, slightly, only .3" more total but it's also plenty of room, and less camber than bmw have. The rims additionally are stronger than some of the bmw light wheels. On a Z car this rim would result in a short sidewall but on the Audi it's a 245/45x18 tire.

For the E61 I went up to 245/45x18 which actually ads about .5" to the sidewall! This should keep me from having any of the stress induced issues you mentioned.

It seems if I ever go to a 19", that it ought to be a non-rft, but I think instead I'll go with an 18" staggered 8"/9" style 89 or 32. I like the inherent durability you get from sidewall, plus then you can use the rft without issues.

AJH

AJH

No, it's a secret

narvselius

What? Secret- go tell Assange!