What's going on with the run flat failures? - My assessment.
I hope to impart some facts and solicit comments and suggestions on the idea of going to 18" instead of 19".
I suffered a sidewall bubble on one of the 245/40/19 Goodyear LS2 run flat tires on my 535i X sport as many others have. It probably happened at 1000 miles when I hit a "minor" pothole at 60 MPH in Northern VA. I researched my options by talking to two BMW dealers, four independent local tire dealers, Tire Rack, and Goodyear consumer relations. My conclusion is that the failures occur because it is a low profile tire not because it is a Goodyear or because it is a run flat. I know that others feel differently, but I came to this conclusion after talking to tire dealers that have no agenda and derive no benefit from misleading me. In fact it would benefit them to sell me a new set of four tires which I indicated I might do rather than wait for a replacement. These dealers have considerable hands on experience with all brands of tires and have encountered an unusual number of low profile tire failures in CT this winter due to the road conditions.
One thing is that none, except Tire Rack and the BMW dealers have had much experience with the 19" Goodyears since there are comparatively few around. So there is a possibility that the Goodyears are more prone to failures than the other brands or have manufacturing defects, but Tire Rack doesn't think so.
Here is an expansion of what I found:
This tire in this size was made specifically for the F10. It is only made in Germany and no other vehicle uses it.
1. Why It Happens
It could be a manufacturing defect if it happens within the first six months or so of tire use. It is more likely due to an impact from a pothole or some other obstacle that causes the tire to compress until the inside of the tire hits the wheel. Judging by the fact that most people on the forums associate the bubble with a pothole or other impact I'd say that it is impact in most cases. When the rim hits the inside of the tire, the inside of the tire gets bruised or cut and this is readily observable when the tire is removed from the wheel. I received this explanation from a few of the tire dealers and there is a good write-up at
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=159.
2. Why Does This Particular Tire Seem To Fail?
We read about it on the BMW forums so we don't see the whole picture of other cars or tires. I asked the four independent dealers and Tire Rack if the problem was peculiar to the LS2's or the fact that they are RFT's or because they are low profile. Each one had the same answer - low profile. The local dealers said there were an enormous number of low profile failures this winter and RFT's were no better or worse than the other low profile tires. The four tire dealers plus Tire Rack said that run flats could theoretically be better because of the stiffer sidewall, but they have not observed that. My take is that going to non-RFT's will not improve the failure situation and may worsen it.
3. Replacement Availability
There are no 19" LS2's at any U.S. Goodyear owned store or warehouse and it will be at least four weeks before the stock is replenished. Tire Rack says six weeks. The other tire dealers and BMW dealers say at least four weeks. According to one tire dealer who checked with the home office there are 1100 19" tires back ordered and as of March 25 are on the way to a German port for shipment to the U.S.
4. Solutions
One BMW dealer indicated the problem was more prevalent with 19" vs 18". The four tire dealers and Tire Rack had mixed answers about going to 18". They all said that theoretically there should be an improvement, but some said not a dramatic improvement and others that they really didn't expect a real world improvement at all. I wonder if the U.S. suspension is tuned for the 18" and replacing four wheels and four tires is a long term fix. The 18" wheels are the standard 535i configuration for the M-Sport package in the UK with 19" offered as an option. Of course we only get a pseudo M-sport suspension and 19" wheels in the U.S. and it may be tuned for the 19" combination.
5. Goodyear Road Hazard Warranty
It is good for 12 months and includes replacement and installation. It does not include balancing, old tire disposal, and taxes. It is subject to wear limitations. Presently, Goodyear is willing to replace my four tires with four from another manufacturer because of the lack of Goodyear stock. Unfortunately the only RFT's in the 19" size are summer which I don't want. I could go to 18" if I wanted to buy wheels.
6. My Solution
Well I don't really have one. So far my BMW dealer hasn't indicated what they could do for me other than put me on a list. Goodyear seems anxious to make things right and they set me up with a local independent dealer to negotiate a solution, but I can't find an acceptable solution. Most of the tire dealers said I probably could get by with the bubble until a replacement arrives, but no guarantees. A failure would not be catastrophic because of the RFTs. At the moment I'm hanging on with what I have and hoping for the best. I am also toying with the idea of going to 18" wheels, but am not sure about the impact on ride and handling.