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BMW 3-Series Run Flat Tires

3108 messages,  Last post on Apr 21, 2013 at 1:52 PM

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What is this discussion about? BMW 3 Series, Tires

Messages Page 295 of 311

#2940 of 3108 Re: Legal issues... [capriracer] by MrShift@Edmunds HOST

Jul 14, 2011 (8:40 am)

Replying to: capriracer (Jul 14, 2011 4:33 am)
I'm wondering though how limited the complaints are, or would be, once the awareness of the problem is better known.
 
What I mean is, since my friends 2007 BMW 328ix had her RFTs melt in 20,000 miles, isn't it safe to assume that just about everybody with the same car going the same distance on the same tires in the same large metro area would suffer the same fate?
 
Maybe some people only *expect* 20K on a set of tires so they don't complain?

#2941 of 3108 Re: Legal issues... [Mr_Shiftright] by busiris

Jul 14, 2011 (10:40 am)

Replying to: MrShift@Edmunds (Jul 14, 2011 8:40 am)
I'm wondering though how limited the complaints are, or would be, once the awareness of the problem is better known.
  
What I mean is, since my friends 2007 BMW 328ix had her RFTs melt in 20,000 miles, isn't it safe to assume that just about everybody with the same car going the same distance on the same tires in the same large metro area would suffer the same fate?
 
Excellent points.
 
IMO, the RFT issue (at least, as it relates to BMW) is similar to the (lack of) oil dip-stick issue. Relatively few complaints, but those that do complain are extremely vocal about it.
 
That, coupled with the fact the buyer has no option when making the purchase tends to add to the complaint issue "loudness" of those complaining. As you said earlier in regards to owners having no idea what kind of tires they have mounted (at least, until replacement time), how many drivers actually check their oil nowadays? Ask 100 people you meet at a local shopping mall, and I would wager less than 20% (and that's probably a high number) ever check their oil level on any kind of regular basis.
 
On your last statement, in theory I agree. But, reality is a different story. Even though 2 drivers in identical cars travel the same route and distances, there can be a range from little to extensive in how differently they drive that route.
 
As an example, MPG. Its not terribly hard to find forum threads with owners of the same make and model vehicle, but getting huge differences in MPG. Grandpa probably is going to get more mileage than lead-foot-Larry.
 
But, getting back to RFT's for a minute. From the physics perspective, in general, a stiffer sidewall translates into less flexibility. RFT's such as those BMW uses have stiffer sidewalls. That means that, in order to maintain the same ability to adhere to the road surface, a change in the compound meeting the road surface is required....usually a softer compound, but there may be other options. That's the theory...
 
The $64,000 question is whether or not the increased rigidity in the RFT is significant enough (and if so, by how much) to cause the manufacturer to resort to a softer (and thereby, less durable) compound in order to maintain the expected and desired road adherence...traction? Also, even if adherence isn't an issue, does the stiffer sidewall cause more wear on the tire's tread-surface?
 
Its pretty clear that a normal GFT with an external diameter of 26" will corner (ie, have better traction) at speed than a 24" solid steel wheel surrounded by a 1" thickness of rubberized tread surface.
 
Now, it may well be that RFT's don't approach any of the above limitations, but I suspect that they do, especially in environments that call for more sidewall flexing... like those who drive more aggressively.
 
Personally, I don't think the RFT issue is a "red herring", but I do think that many (but not all) who complain would just as easily get reduced mileage out of a corresponding set of GHT's.

#2942 of 3108 Re: Legal issues... [busiris] by capriracer

Jul 14, 2011 (11:21 am)

Replying to: busiris (Jul 14, 2011 7:46 am)
".......but I find it difficult to accept that 2 tires, same sized and identically named, made by the same tiremaker (1 for OEM fitment and the other for general public sales), have differences in construction........"
 
Perhaps I wasn't as clear as I could have been.
 
No, you are right. What usually happens is that a particular size of a particular model is supplied to an OEM, but both the OEM tire and the tires supplied to the general market place are the same tire. Those tires supplied to the general market place are called "downstreams" - as in they are downstream of what gets sent to the assembly plants.
 
But the point I was trying to make was that within a line of tires, different sizes would be supplied to different vehicle manufacturers - and because of the differences, you should really think of OE tires as being unique to themselves.
 
OK, onto your other posting:
 
".......That means that, in order to maintain the same ability to adhere to the road surface, a change in the compound meeting the road surface is required....usually a softer compound, but there may be other options. That's the theory......"
 
Sorry, but that doesn't work in actual practice. While the sidewall stiffnesses are different uninflated, it is surprising how small the difference is when the tires are inflated - not that there aren't differences, but that it is not as big as one might think. The net effect is that the same tread compounds are used.
 
As I have said before, there is nothing inherent in RunFlat tires that generates rapid treadwear, nor does this preclude good treadwear. It's just that RunFlats are only appearing on a few vehicles and the demand for good wearing, but lower traction, tires hasn't prompted any tire manufacturer to produce such an animal.
 
Further, many folks complain about tire wear on their new car or truck - and they sometimes post that on websites such as this one. Almost every vehicle generates some level of complaints about tire wear. The trick is trying to sort out what's "normal" and what's not.

#2943 of 3108 Re: Legal issues... [capriracer] by shipo

Jul 14, 2011 (11:42 am)

Replying to: capriracer (Jul 14, 2011 11:21 am)
As I have said before, there is nothing inherent in RunFlat tires that generates rapid treadwear, nor does this preclude good treadwear. It's just that RunFlats are only appearing on a few vehicles and the demand for good wearing, but lower traction, tires hasn't prompted any tire manufacturer to produce such an animal.
 
I'm still having a problem digesting that comment. Looked at from a slightly different perspective, I'd argue that a tire like the Michelin Pilot Sport A/S will easily out perform (from a ride, handling and absolute grip perspective) any of the all-season RFTs that BMW has mounted on the 3-Series while at the same time lasting many-many more miles before replacement is necessary.
 
With the above thought in mind, does the current technology for RFTs preclude manufacturing a run-flat version of the Pilot Sport A/S which would last as long as the GFT version?
 
FWIW, I live and drive agressively in an area with very curvy and hilly roads, and the fewest number of miles I've ever been able to put on a set of Pilot Sport A/Ss is ~45,000 miles; a far cry from what BMW 3-Series owners typically get from their OEM All-Season RFTs.

#2944 of 3108 Re: Legal issues... [capriracer] by busiris

Jul 14, 2011 (1:23 pm)

Replying to: capriracer (Jul 14, 2011 11:21 am)
...What usually happens is that a particular size of a particular model is supplied to an OEM, but both the OEM tire and the tires supplied to the general market place are the same tire. Those tires supplied to the general market place are called "downstreams" - as in they are downstream of what gets sent to the assembly plants.
  
But the point I was trying to make was that within a line of tires, different sizes would be supplied to different vehicle manufacturers - and because of the differences, you should really think of OE tires as being unique to themselves.
 
OK, we appear to be reading from the same page now. This makes sense to me.
  
  
".......That means that, in order to maintain the same ability to adhere to the road surface, a change in the compound meeting the road surface is required....usually a softer compound, but there may be other options. That's the theory......"
  
Sorry, but that doesn't work in actual practice. While the sidewall stiffnesses are different uninflated, it is surprising how small the difference is when the tires are inflated - not that there aren't differences, but that it is not as big as one might think. The net effect is that the same tread compounds are used.
  
As I have said before, there is nothing inherent in RunFlat tires that generates rapid treadwear, nor does this preclude good treadwear. It's just that RunFlats are only appearing on a few vehicles and the demand for good wearing, but lower traction, tires hasn't prompted any tire manufacturer to produce such an animal.
  
Further, many folks complain about tire wear on their new car or truck - and they sometimes post that on websites such as this one. Almost every vehicle generates some level of complaints about tire wear. The trick is trying to sort out what's "normal" and what's not.
 
Well, as I said at the beginning of the discussion, I’m certainly no automotive tire engineer. And, judging from your web-site (well done, BTW) you appear to understand far more of the specifics of the situation. And, I agree that RFT's overall have a limited exposure, usually on more "driver oriented" cars, which may have a tendency to skew the wear "data".
 
In other words, if RFT's were the only style tire available on, say a Toyota Camry, would the complaint level be the same?
 
I can't say...
 
But, I do think that, if the RFT tiremakers would make an effort to educate the public on what you stated above (and provide the scientific data to corroborate the claims) it would put many of the issues of RFT wear in perspective.

#2945 of 3108 Re: Legal issues... [shipo] by capriracer

Jul 15, 2011 (4:40 am)

Replying to: shipo (Jul 14, 2011 11:42 am)
"....I'd argue that a tire like the Michelin Pilot Sport A/S will easily out perform (from a ride, handling and absolute grip perspective) any of the all-season RFTs that BMW has mounted on the 3-Series while at the same time lasting many-many more miles before replacement is necessary....."
 
But you left out a critical item: Fuel economy (rolling resistance). Add that to the mix, and you can't say that.
  
".....With the above thought in mind, does the current technology for RFTs preclude manufacturing a run-flat version of the Pilot Sport A/S which would last as long as the GFT version?....."
 
No, there is nothing inherent that would preclude manufacturing a RunFlat version of a regular tire - and in fact Michelin offers a RunFlat version in the model you mentioned (Hint: ZP = Zero Pressure!) The question is: Is it the exact same tire or is it an OE version that suffers from the same sort of problems we have been discussing.
 
(OK, I did a quick check and it is indeed an OE tire and it looks like it is only available in sizes to fit Corvettes.)

#2946 of 3108 Re: Legal issues... [capriracer] by shipo

Jul 15, 2011 (4:59 am)

Replying to: capriracer (Jul 15, 2011 4:40 am)
"But you left out a critical item: Fuel economy (rolling resistance). Add that to the mix, and you can't say that."
 
My current car came with low rolling resistance tires and oddly enough, when I swapped them out for the Michelin Pilot Sport A/Ss, my fuel economy improved ever so slightly (per my fuel log it looks like maybe a quarter of a mile per gallon improvement on average).

#2947 of 3108 Re: Legal issues... [busiris] by capriracer

Jul 15, 2011 (5:02 am)

Replying to: busiris (Jul 14, 2011 1:23 pm)
".......RFT's overall have a limited exposure, usually on more "driver oriented" cars, which may have a tendency to skew the wear "data"......"
 
I know this is going to complicate the discussion, but low aspect ratios are required for RunFlat tires - and yes, that is why they show up mostly on performance oriented vehicles.
 
"........But, I do think that, if the RFT tiremakers would make an effort to educate the public on what you stated above (and provide the scientific data to corroborate the claims) it would put many of the issues of RFT wear in perspective......"
 
Honestly? The complaint level for RunFlat tires is interestingly pretty low. As I have been explaining before, the issues about irregular wear and noise are being driven by BMW's camber - and this existed long before and exists with other vehicles as well. This is seen by the tire manufacturers as a vehicle issue - and since their customer (the vehicle manufacturer) is the source of the problem, they don't make a big deal about. If they were to publish anything, it would be a lose/lose for them. Besides fixing the camber problem isn't going to happen! BMW is locked into that.
 
Interestingly, there was a vehicle manufacturer - I can't remember which one! - that had a sticker on the window that warned that the tires may wear out in 12K miles (or whatever it was). It's been a number of years since this first appeared and it doesn't seem to have spread - and I'm not even sure it is still done today!

#2948 of 3108 Re: Legal issues... [capriracer] by whittenberger

Jul 15, 2011 (6:28 am)

Replying to: capriracer (Jul 14, 2011 4:33 am)
Hello:
This is an excellent thread, so I was hoping to get some related advice... I've had a 2010 BMW 750Li for 14 months and have had 6 run flat tires go flat. This seems like a lot. I've driven an Arnage, Range Rover (with low profile tires) and an SL500 over the past 10 years with the same driving pattern, and I've only blown one tire over the entire 10 years.
 
I'm sure I hit pot holes - I live in PA and drive extensively in northern NJ.
 
I've noticed that all 6 tires have had blown-out side walls. Is this common for run flats? If so, what can I do to stop having this problem. I joke to my wife that it costs me $450 each time I leave my driveway!
 
Thank you for your help!
-Rob

#2949 of 3108 Re: Legal issues... [whittenberger] by capriracer

Jul 15, 2011 (6:55 am)

Replying to: whittenberger (Jul 15, 2011 6:28 am)
There is nothing inherent about run flat tires that makes them more prone to damage from potholes. This might be more about low aspect ratios - so my only suggestion would be to go to higher aspect ratios.

Messages Page 295 of 311

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