Hopefully swapping to standard tyres

[craigsup]

Jimboka said:

Strange. Wife's BM on RFTs has never cracked an alloy.
So not consistently..
(Goodyear Eagle F1 now, far superior ride. Very Harsh & more expensive Potenzas previously)

Just seemed to be a common occurrence when google searching around BMW alloys + runflats. I suppose I'm just glad that it's only one alloy and it's not a large bill

The alloy that my tyres are going on are these:

[anonymous-user]

craigsup said:

Jimboka said:

Strange. Wife's BM on RFTs has never cracked an alloy.
So not consistently..
(Goodyear Eagle F1 now, far superior ride. Very Harsh & more expensive Potenzas previously)

Just seemed to be a common occurrence when google searching around BMW alloys + runflats. I suppose I'm just glad that it's only one alloy and it's not a large bill

The alloy that my tyres are going on are these:

You should google a bit harder. Several manufactures, including Mercedes and Jaguar have similar issues to BMW. Nothing to do with RFTs, all to do with pointlessly low aspect ratios.

[Swervin_Mervin]

REALIST123 said:

craigsup said:

Jimboka said:

Strange. Wife's BM on RFTs has never cracked an alloy.
So not consistently..
(Goodyear Eagle F1 now, far superior ride. Very Harsh & more expensive Potenzas previously)

Just seemed to be a common occurrence when google searching around BMW alloys + runflats. I suppose I'm just glad that it's only one alloy and it's not a large bill

The alloy that my tyres are going on are these:

You should google a bit harder. Several manufactures, including Mercedes and Jaguar have similar issues to BMW. Nothing to do with RFTs, all to do with pointlessly low aspect ratios.

I can't believe that the RFTs don't play a very big part though. All 4 of my wheels (18" style 193) were egg shaped and I only found out after switching from RFTs to non-RFT. Subsequently the one with the worst damage cracked, on a flat spot in the rim.

The sidewalls are so stiff that the bump absorption must be practically non-existent, so all that load from hitting a pothole or whatever is transferred directly to the wheel rim. Some will obviously get absorbed through the suspension (and I think they're now better at tuning the suspension to cope) but the initial hit is taken by the wheel.

Added to that, I reckon the RFTs hide any obvious sign of damage, in terms of vibration when driving. The sidewalls are so stiff that they effectively keep the tyre more round, despite the wheel perhaps being out of shape a little. That then becomes apparent when you switch to non-RFT.

Well, that's my theory anyway.

[craigsup]

REALIST123 said:

You should google a bit harder. Several manufactures, including Mercedes and Jaguar have similar issues to BMW. Nothing to do with RFTs, all to do with pointlessly low aspect ratios.

I don't need to google harder - I have no interest of Merc or Jag, only BMW. During my googling (or apparent lack of), the common response to people's cracked BMW alloys were the stiff side wall of RFT causing increased vibrations to the alloy thus deteriorating them quicker. Added with a large impact (going over a speed bump too quickly etc), the RFT causes the crack.

I'm not saying the alloys are absent from blame, but in my opinion majority of the blame lies with the RFT.

Edited by craigsup on Thursday 4th February 10:08

[JNW1]

REALIST123 said:

You should google a bit harder. Several manufactures, including Mercedes and Jaguar have similar issues to BMW. Nothing to do with RFTs, all to do with pointlessly low aspect ratios.

I suspect the cracking is probably due to a combination of things; I'm sure you're right when you say low aspect ratios are part of the problem but I think that's almost certainly exacerbated but the stiff sidewall construction on run-flats (plus of course the lousy state of many of our roads!).

[craigsup]

Just thought I'd do an update.

Got my alloy repaired and the new Goodyear Eagle F1 Asymmetric 2's fitted. I've done about 150 miles in them so far and they are so much nicer than the RFT. The ride is much comfier; going over small potholes / bumps in the road doesn't crash the car around any more. The cabin noise is slightly less as well (not much of a difference though). I'm not going to comment on grip as of yet, simply because I've done so little mileage and they won't have worn in yet.

Never going to go back to RFT.