[kaishang]

What the BMW M-division does is not relevant for non M cars. M cars have a number of design objectives but maximum safety at the expense of maximum performance is not one of them. If you want maximum performance, RFTs aren't it - but very few people ever use maximum performance and they would be better off with additional safety.


Tire blow-outs and motorway accidents.
Martin JL, Laumon B.
Source
French National Institute for Transport and Safety Research (INRETS), Bron, France.

"During the period from 1996 to 2002, 60,397 vehicles were involved in crashes with property damage and/or injury on a French motorway network of 2000 km. It was observed that 6.7% of these accidents involved tire blow-outs. In 87% of cases, only one vehicle was involved in the accident. Tire blow-outs occurred in 6.5% of cars that represented more than 80% of the vehicles involved in crashes."

[HighlandPete]

Originally Posted by doc_ab

I don't know enough about the technical aspects of suspension and set ups but I changed from RFT to NON RFT about 6 months ago and on my 19" tyres the ride is smoother, less harsh, quieter, no tramlining. I have a can of tyreweld and AA membership.

Typical of what users find.

I posted the following comment in another forum on "Why do BMW fit run-flats?"

Only my opinion, but is a considered one after talking 'face to face' with a BMW Technical Engineer and a Bridgestone Field Engineer.

I've researched this subject as much as anyone, I'd say...

My conclusion from reading all sorts of information, technical data and opinion, there is not one main reason.

Safety is a key element, seems when focus groups are asked about their driving concerns, the ability to drive on to a safe point after a puncture, is high on drivers priorities. Very valid and I'd agree with that for many situations. But even that view can be skewed by how the question is asked, wonder if the folks were told it would compromise the driving abilities of the car.

There are the emission issues, (anything to shave CO2 figures) and more scope for design changes in car construction.

But as the M Division and Alpina have clearly shown, RFTs were just not up to the job as a driver's choice, particularly for the enthusiastic driver. Hence not used, says it all really. BMW and Bridgestone shot themselves in the foot, IMO, at the Bridgestone 'G3' launch when in context of the testing, really admitted they hadn't got it right before, as "with G3 you wouldn't know the difference" between a normal tyre and the RFT. Before that time they were defending "you shouldn't notice any difference" with RFTs to conventional tyres.

From my own perspective, a RFT is a square peg in a round hole, how can a primary suspension component (which a tyre is) be changed without drastic re-invention of the rest of the suspension system? That is taking BMW and the tyre makers time, VDC and the like, seems to be getting there, even the F10/11 5-series shows they have taken two generations (E60/F10) of development and still not 100% there.

There is feeling the new F30 3-series may be there, but there are still reservations, until the testers drive basic (non VDC) cars on UK roads, then the verdict can really be made, as to whether BMW and the tyre makers have really sorted the driving experience.

I sense the rest of the industry are waiting to see if BMW can get it right, before they seriously move to RFTs. Some others make a 'soft' attempt at offering RFTs, or 'Extended Use' as Mercedes do on some models, with a more conventional tyre, with very limited drive on capability. Wonder Why?

HighlandPete

[kaishang]

Originally Posted by HighlandPete

Typical of what users find.

(big wheels, sport suspension; harsh ride)

It may be typical of what people with a sport suspension and 19-inch tyres find but most BMWs do not have this combination.

Before I had a 330d with 17" wheels, standard suspension and RFTs I had.....
another car with 19" wheels, sports suspension and conventional non-RFT tyres. You know what, driving the BMW with RFTs was a revalation afterwards. It was so smooth, it soaked up bumps, I could drive straight over potholes and it still goes around corners fast.

[HighlandPete]

Originally Posted by kaishang

It may be typical of what people with a sport suspension and 19-inch tyres find but most BMWs do not have this combination.

Before I had a 330d with 17" wheels, standard suspension and RFTs I had.....
another car with 19" wheels, sports suspension and conventional non-RFT tyres. You know what, driving the BMW with RFTs was a revalation afterwards. It was so smooth, it soaked up bumps, I could drive straight over potholes and it still goes around corners fast.

That may not say much for the other car's suspension and wheel set up.

I was running 17" RFTs on standard suspension and I can assure you it was not a very nice ride at all. Wasn't a typical BMW driving experience, lacked the planted, secure, predictable feel I'd always had in a BMW. You just didn't have precision of line, purity in the steering, or even decent road feel. never mind the ride quality or tyre grip levels.

I got involved in a 3 user situation, through my dealer. They had my car, one user from Glasgow, (whose wife refused to drive the car as she hated the way their 3-series drove) and one in Edinburgh, reporting (without each other knowing) virtually the same problems. We were all long time BMW customers, so they took us seriously. BMW Technical came up to the garage for an internal meeting, to try and pinpoint what was the basis of the issue. They were almost at the point of letting one of us try an 18" wheel set, as we were all on 17", but at the last moment BMW backed out and left us all to sort our own problems.

I bought a second set of rims and fitted them with non RFTs and proved all the issues were RFT related. I tried to get BMW to come and run a 'back to back' test to show them the car couldn't run up here on RFTs, without issues. Bridgestone sent up an engineer who rode with me, and clearly saw the limitations. He agreed with my assessment and we concluded the RFT had very tight working parameters, too tight for my typical driving to cope with.

I had the benefit of swapping wheel sets at any time and driving the car, so could go trouble shooting, assessing conditions, looking for faulty suspension, or loose steering, would be indentified, if it wasn't a tyre issue.

RFTs would only start to run properly when the car was loaded with 4 adults, or when the ambient temperature went above 18 degrees. Even then predictability was still lacking. Simply, they just didn't work on roads I typically drive.

HighlandPete

[HighlandPete]

Ooops, duplicate post.

HighlandPete

[225_AB]

I do know of 2 people whose tyres have delaminated when they were running RFT. the risk of a blowout is tiny.

[kaishang]

Originally Posted by HighlandPete

He agreed with my assessment and we concluded the RFT had very tight working parameters, too tight for my typical driving to cope with.

What is it about north Scotland driving which is different?

[HighlandPete]

Originally Posted by kaishang

What the BMW M-division does is not relevant for non M cars. M cars have a number of design objectives but maximum safety at the expense of maximum performance is not one of them.


Tire blow-outs and motorway accidents.

Don't quite follow why an M-Car should have a lower safety approach, should be higher, due to the very nature of a higher performance car. Particularly as they use the same roads and at same speeds as most of us drive. Plus the M-division engineers are, IMO, the very guys who could tame the RFT, if anyone can.

Strange thing, M-cars can ride better at the speeds we all use. I thought many BMW drivers have a BMW because it is a driver focused car. So to corrupt that drive seems to go against the whole ethos of a BMW. Then I suppose the typical customer these days isn't buying a BMW for the drive qualities, thus allowing BMW to get away with inferior dynamics.

It is often these every same drivers who are writing in the reviews, that they can't see what all the fuss is about with a BMW, "they ride and drive so poorly".


As to blow outs, statistics can be read in different ways, according to context. Other research has shown even blowouts have identifiable causes and I remember reading that only about 1% of blowouts/tyre failures are caused by issues outside of driver control. (Actual tyre structure failure/objects on the road, etc.). The rest are down to tyre care, correct pressures, badly worn/damaged tyres, wrong specification, all preventable ahead of a blowout. So we can do a lot ourselves, to minimise our blowout risk, mostly by simply tyre checks, running the correct pressures and replacing tyres before they become vulnerable, or even illegal.

HighlandPete

[HighlandPete]

Originally Posted by doc_ab

I do know of 2 people whose tyres have delaminated when they were running RFT. the risk of a blowout is tiny.

Some of this is down to running low pressures, often to try and get a softer ride. Riding on the sidewalls (is using up the run on flat properties) and causes the tyre structure to overheat/additional stresses and delamination is under way. One other identifiable reason, the typical 'inner wear' isn't spotted in time and the structure ruptures and again shreds the tyre.

BMW have built in additional risk factors, which are so easy to overlook as an uninformed customer. There is this feeling and perception, the car will tell the driver when it is running a flat, or the pressures are low, so even less tyre checking and pressure adjustment.

So is safety improved, or are the risks now higher, for the average user, running RFTs?

HighlandPete

[HighlandPete]

Originally Posted by kaishang

What is it about north Scotland driving which is different?

Personally I don't think my 'typical' roads are in isolation to a lot of UK roads. Just that most of my driving is on the same sort of surfaces. The Bridgestone guy did comment, when he arrived, that he could see where I was coming from, I remember him saying they were a bit more challenging, than most would be driving on, as we have such varied surfaces, camber changes, broken edges and a lot of varied undulations due to subsidence, etc.

When I test drive any BMW from my dealer, down in Perth, I drive out on the M90, get a bit of motorway feeling, then cut across to Stirling on the A91, surfaces typical of my local roads and then back up the A9 trunkroad for typical dual carriageway surfaces. So get a good feel for what the car is really like, without bringing a car back home. The A91, as anyone who uses it will know, has some "very interesting" road surfaces.

But it isn't just up here, I'll give an example of a section down south I've used several times in my car on the RFTs, which gives the same sort of corruption to the car. Cutting across from the A419 below Cirencester via the B4696 to Wootton Bassett. Road surfaces are similar to many of my local roads.

Now we could say I'd be better moving away from BMW, to a softer riding car like a Merc C-Class, but having driven BMWs on these same roads, which do drive properly, without a second thought to the ride quality, suspension dynamics, or purity of steering, does tell me it isn't the BMW chassis, but the tyres. Proven by removing them.

Just a thought on the latest F30 3-series, the RFTs being sorted. Steve Sutcliffe of AutoCar, believes we may be through the worst, but he is reserving judgement until he tries a basic suspension/wheel setup on UK roads. Yes like many others acknowledge, UK roads do offer a different set of challenges to suspension engineers, so whether a non VDC F30 will ride and drive properly on RFTs we have yet to see.

HighlandPete

[scousesnail]

Interesting nobody has mentioned what the Insurance implications might be, do you need to inform you provider as I am thinking of changing my wheels as well as the tyres and wondering if this counts as modifying the vehicle. Am I better to change just the tyres and keep my BMW runflat wheels or change both wheels and tyres.
I agree the handling must get better with non runflats as the handling on my E93 isnt anything to write home about now and the tramlining is attrocious and my wife refuses to drive it as it is so unpredictable and has frightened us both on occasions.

[Hotcoupe]

Originally Posted by scousesnail

Interesting nobody has mentioned what the Insurance implications might be, do you need to inform you provider as I am thinking of changing my wheels as well as the tyres and wondering if this counts as modifying the vehicle. Am I better to change just the tyres and keep my BMW runflat wheels or change both wheels and tyres.
I agree the handling must get better with non runflats as the handling on my E93 isnt anything to write home about now and the tramlining is attrocious and my wife refuses to drive it as it is so unpredictable and has frightened us both on occasions.

Changing your wheels to aftermarket wheels is a modification.

Changing tyres is arguable in my opinion,if the tyres match the specifications/sizes of the OEM tyres bar being runflats I don't see a problem,I'm not sure all insurance companies would agree with me though,so it's best to speak to your insurer if it's causing you concern.

By the way,your OEM wheels are not 'runflat' wheels,you can fit non runflats to a wheel that has runflat tyres fitted to them,so just change the tyres.

I'd still tell the insurer though

[kaishang]

I'd take the philosophy that if your tyre is listed on the tyre placard, then that satisfies your insurance. The tyre placard doesn't say anything about RFTs or no RFTs.

[Hotcoupe]

Originally Posted by kaishang

I'd take the philosophy that if your tyre is listed on the tyre placard, then that satisfies your insurance. The tyre placard doesn't say anything about RFTs or no RFTs.

Excellent point Mr.Plato

[Stringbag]

One reason BMW fit RFT tyres - weight.
Fitting run flats allows them to ditch spare tyre, jack, wrench etc.
Less Weight = less co2.

Nothing to do with safety - that's just marketing. The chances of a blow out at speed are negligible. More likely to get hit my lightning.

I have just changed from RFTs (the best on the market - ps2 ZPs) to normal tyres (conti sport contact3) and the difference is remarkable. Just run over a few cats eyes to feel the difference. it is that noticeable.

[rich1068]

I disagree. Weight isn't the issue when BMW could, like many manufacturers, just supply you with an electric pump and a bottle of goo.

[jada07515]

well after reading this cant wait to ditch the run flats tomorrow!!

[rich1068]

I haven't followed this thread but my winters are non-RFT and the difference is noticeable. That said, the ride on my Michelin RFTs is (I think) pretty good.

[Hotcoupe]

Originally Posted by Stringbag

One reason BMW fit RFT tyres - weight.
Fitting run flats allows them to ditch spare tyre, jack, wrench etc.
Less Weight = less co2.

Nothing to do with safety - that's just marketing. The chances of a blow out at speed are negligible. More likely to get hit my lightning.

I have just changed from RFTs (the best on the market - ps2 ZPs) to normal tyres (conti sport contact3) and the difference is remarkable. Just run over a few cats eyes to feel the difference. it is that noticeable.

The only reason BMW fit RFT tyres - profit.
Fitting run flats allows them to ditch spare tyre, jack, wrench etc.
Less parts = more money in the coffers.

Apologies for hi-jacking part of your post Stringbag,but I swopped my rose tinted specs for transparent ones quite a few yrs ago

[scousesnail]

Thanks for all the comments, not sure what you mean by OEM wheels as my wheels are the original BMW wheels and are deffo runflat wheels and have the extra bumps in the middle.

My twopenneth on the reason BMW use run flats is purely for marketing, your average suit or lady driver does not want the hassle of having to change his/her own wheel or even spray sticky rubber compound and then blow the tyre up and get nails and clothes etc. dirty in the process and would much rather take the car to a dealership or tyre bay and have it repaired by somebody else. My friend was pursuaded of the benefits of all of this when he changed from Land rover to BMW a while back......unfortunately they neglected to tell him how much it was to have a tyre replaced as repair were "not possible" with run flats. He is a building site surveyer and six week in, 3 punctures and £1100 lighter he wasn't in least impressed and several heated conversations with the dealership he got some of his money back and and insurance policy as a good will gesture.

[YvesD]

Not wishing to tempt fate but I've only had one puncture in 26 years of driving.

Cant justify junk flats on the basis of that statistic

[Stringbag]

Originally Posted by jada07515

well after reading this cant wait to ditch the run flats tomorrow!!

Let us know how you get on!

Hotcoupe is right - they are only on there for profit reasons, not safety.
If they were, They would be on every car for sale in the USA.