Run Flat tyres.

[GS]

Can anyone tell me if Run Flat tyres can be repaired at all?

I've just been out in a Mini which had a puncture. Small screw through the centre of the tread area of an almost new tyre. The owner said that it would have to be replaced, I don't know ant different, but it appears to be a really expensive puncture.

[GS]

So lets say if the driver noticed that the tyre had been punctured and stopped there and then so that there is minimum damage, is there anything to stop the driver from just adding a can of sealant into the tyre and setting of again? I know that the sealant is only supposed to be a 'get you home' fix but I also know of tyres which have been used for years after the sealant has been added. Does the sealant harm or damage the tyre in the long term?
By the way, how does the car know that the tyre has been punctured, can the car detect that the punctured tyre is rotating at a different speed to the others?

[zadocbrown]

So lets say if the driver noticed that the tyre had been punctured and stopped there and then so that there is minimum damage, is there anything to stop the driver from just adding a can of sealant into the tyre and setting of again? I know that the sealant is only supposed to be a 'get you home' fix but I also know of tyres which have been used for years after the sealant has been added.

I don't think I'd feel easy in my mind until is was properly repaired. Imagine if the seal gives up just when I'm braking hard for a bend!

Don't fancy it.

[jbsportstech]

There's no legislation, or indeed reason why one couldn't be repaired. The bit that does the 'run flat' is the sidewall. The main tread band is identical technology to a normal tyre.

As dave said subject to the side wall having to been driven on (Ie tyre very flat or completly) and the damage is within normall repair are why not.

[GS]

So lets say if the driver noticed that the tyre had been punctured and stopped there and then so that there is minimum damage, is there anything to stop the driver from just adding a can of sealant into the tyre and setting of again? I know that the sealant is only supposed to be a 'get you home' fix but I also know of tyres which have been used for years after the sealant has been added.

I don't think I'd feel easy in my mind until is was properly repaired. Imagine if the seal gives up just when I'm braking hard for a bend!

Don't fancy it.

zadocbrown do you use second hand tyres? Do you buy second hand cars and not change the tyres? If you don't change them, how do you know someone has not done this already to the tyres on a used car???

[kfae8959]

By the way, how does the car know that the tyre has been punctured, can the car detect that the punctured tyre is rotating at a different speed to the others?

It detects a drop in the pressure of the air in the tyre. When you inflate the tyres, you "reset" the run-flat system, and it takes those pressures as its benchmark.

[zadocbrown]

I don't buy 2nd hand tyres. On my car the fronts were on when I got it (though won't be for long). So, of course I can't be sure what someone else has done to them, though there's no sign of damage. I'm not quite paranoid enough to chuck them just in case, but I wouldn't knowingly live with anything other than a professional repair.

[Octy_Ross]

In 2003 - I had a car with no spare and just a can of stuff.

I got a nail in a Goodyear Eagle F1 (in a car park - was fine when I left, flat when I got back) - it had only done about 1000 miles (from new) so wasn't too interested in binning it, but took the car into the local tyre place... showed them the can (can't remember now, what it was). I asked them the best course of action - they stated then that the spray sealant stuff was as good, if not better, than a standard repair and the car could be driven as normal.

They also added the stuff would prevent them from doing a normal repair as it adheres to the inside of the tyre and stops the proper repair from doing so.

I did so (drove normally), the tyre seemed fine until it was EOL 9000 or so miles later.

When they changed it, I watched (better than telly anyway!) and the inside of the wheel was covered in the spray stuff. Still impressed with it to this day and wonder if it's worth replacing (or augmenting) the spare with a can.

Of course, I drove and still do so, in a namby pamby fashion so perhaps I wasn't as hard on the tyre as some would be

[waremark]

GS asked how you know if a car with runflats has a puncture. I think all such cars have a 'tyre pressure monitor'. Most use the ABS sensors to compare the rate of rotation of the wheels, and to flag a warning if one starts to rotate faster than the others.

A much smaller number of cars have pressure sensors which transmit pressure info by radio. These can display your individual tyre pressures as you drive.

On gel sealant products, I suspect some aftermarket products claim to achieve long life repairs. However, my BMW's instruction book says of gel repairs (I do not have runflats, nor do I have a spare wheel): 'After applying the gel, do not exceed 80 kph, and have the tyre replaced as soon as possible'.

Unfortunately, I cannot remember what the tyre was like after the time I had to use tyre gel.

[MikeG]

Googling came up with this,

Puncture repairs to Run-Flat tyres (only Michelin ZP)
(Minor tyre repair to the BSAU 159 standard)

The position regarding puncture repairs to run-flat tyres is muddled. Most tyre manufacturers state that their run-flat tyres should not be repaired under any circumstances. The reasoning behind this is that when a run-flat tyre is punctured the weight of the car is supported by the specially strengthened sidewalls. These are designed to carry the weight of the car and withstand speeds of up to 50 mph for a limited distance. However the exact nature of the damage, the speed at which it occurred and the distance subsequently driven are all factors that would effect the internal integrity of the tyre and it’s subsequent safe use of the tyre following a repair. As these “known unknowns” (Thank you, Donald) represent a serious safety issue the policy is that repairs are prohibited.

Michelin however have had a change of policy and now state that their run-flat tyres can be repaired as long as there is no visible internal damage and no more than one repair per tyre is executed. As some Michelin run-flat tyres carry a sidewall notice prohibiting repairs the company state that this should still be complied with. Consequently Michelin run-flat tyres can be repaired, once, if the sidewall does not contradict the new directive.

The Michelin run-flat tyres directive is in question and answer form and is as follows:-

Why may Michelin ZP be repaired?

We have examined many ZP tyres after they have been punctured in order to establish a position on reparability. This statement is the result of considerable study to ensure that ZP tyres may be repaired safely.

New Michelin ZP tyre lines, such as PRIMACY HP ZP, are repairable once and once only following the same rules as standard car tyres such as Michelin PRIMACY HP. Michelin have prepared this statement which dealers should follow when dealing with the repair of ZP tyres. However, it is the dealer’s responsibility to decide whether an individual tyre is repairable or not.

What about existing ZP versions of tyre lines such as Pilot Primacy, Pilot Sport PS2, PILOT Alpin PA2?

Existing ZP tyres from tyre lines such as PILOT SPORT PS2 / PILOT PRIMACY / PILOT ALPIN PA2 are still considered NON-REPAIRABLE when, “Do not reuse or repair the tires after a low or zero pressure operation” or equivalent is written on the sidewall.

Pirelli on the other hand adopt a completely different approach and state that their run-flat tyres should not be repaired under any circumstances. Their directive is as follows:-

After low pressure warning is shown, the condition of the remaining tyres and the TPMS should be immediately checked by a specialised dealer.
A tyre should always be changed and not repaired after a loss of pressure, as it is not always possible to establish the time and conditions under which the tyre has been used with insufficient inflation pressure.

Damaged Run-Flat tyres, or Run Flat tyres that have experienced a loss of pressure should be immediately replaced with another Run-Flat tyre of identical size and service description (Load Index and Speed Code). Pirelli recommends that a tyre of a different type, or which contains a different load index or speed code, should never be mounted on the same vehicle.

After a loss of pressure, the rims should be inspected to ensure they haven’t been damaged. Damaged or deformed rims should always be replaced prior to mounting a new Run-Flat tyre.

etyres' position on the repairability of run-flat tyres is that we will comply with the official policy of the manufacturer concerned. We will therefore carry out minor repairs to Michelin but not to other brands. If the position of other manufacturers changes will comply with whatever recommendations they may make.

With regard to tyre sealants, my car does not have a spare or a space-saver tyre but a compressor and a bottle of sealant. While having some new tyres fitted recently I asked wether a repair can be done after using this 'gunk', the reply was that the tyre would be ruined and cannot be repaired, , probably due to the reasons outlined above.

Mike

[TripleS]

At the risk of causing further mutterings about Ned Ludd from my friend at Ware, I ask again if technology is yet in a position to give us satisfactory characteristics by the use of solid tyres. This originally occurred to me after seeing some tyres that were of such low profile that it almost looked as if the rims were on the deck anyhow!

What I thought was that you might use a hard(ish) material in the tread area, combined with a softer material or combination of materials in the rest of the tyre, such that this might behave similarly to our current pneumatic tyres.

This might be all nonsense of course, but it would at least relieve us of the worry about deflations. I'm not sure how we'd get them on and off the wheels, but I expect something could be worked out.

OK, OK, so I've taken leave of my senses, again. 'Twas just a thought.

Yes folks, I too enjoyed the film "Crazy People".

Best wishes all,
Dave.

[GS]

GS asked how you know if a car with runflats has a puncture. I think all such cars have a 'tyre pressure monitor'. Most use the ABS sensors to compare the rate of rotation of the wheels, and to flag a warning if one starts to rotate faster than the others.

A much smaller number of cars have pressure sensors which transmit pressure info by radio. These can display your individual tyre pressures as you drive.

On gel sealant products, I suspect some aftermarket products claim to achieve long life repairs. However, my BMW's instruction book says of gel repairs (I do not have runflats, nor do I have a spare wheel): 'After applying the gel, do not exceed 80 kph, and have the tyre replaced as soon as possible'.

Unfortunately, I cannot remember what the tyre was like after the time I had to use tyre gel.

Thanks for this waremark

Today I noticed that the warning system in the car, a Mini, went off what appeared to be quite early, although it could not inform the driver which tyre was deflating. We had time to drive about 1/2 a mile then pull in safely. By this time the tyre still looked OK. It was still hissing away merrily and obviously still had some air pressure in it. The tyre was not noticeably warmer than the others and continued to hiss for about five more minutes. I fully accept that 'hissing' is far from a scientific method of establishing the remaining pressure but the point I'm trying to make is that I think the warning system had gone off before any great damage to the tyre had occurred. I think it would have been possible today to safely stop and insert some gel into the tyre before too much damage had occurred. I am curious to know exactly how the warning system works and just how sensitive it is. It must be very sensitive to wheel revolutions and this could help to prevent excess damage.

[MikeG]

At the risk of causing further mutterings about Ned Ludd from my friend at Ware, I ask again if technology is yet in a position to give us satisfactory characteristics by the use of solid tyres. This originally occurred to me after seeing some tyres that were of such low profile that it almost looked as if the rims were on the deck anyhow!

What I thought was that you might use a hard(ish) material in the tread area, combined with a softer material or combination of materials in the rest of the tyre, such that this might behave similarly to our current pneumatic tyres.

This might be all nonsense of course, but it would at least relieve us of the worry about deflations. I'm not sure how we'd get them on and off the wheels, but I expect something could be worked out.

OK, OK, so I've taken leave of my senses, again. 'Twas just a thought.

Yes folks, I too enjoyed the film "Crazy People".

Best wishes all,
Dave.

Is this what you had in mind

Your a visionary Dave, "Twas just a thought", tis a Tweel developed by Michelin.

[jbsportstech]

One of my conti sport contacts got a small nail in it in the repairable zone and was properly reapired about a 14 months 20k ago and its has been sound and has been fine up to speeds of 140mph on a track.

I did soem freelance work on hospital job and the senior qs got himself a z4 2.2 and didnt know anything about cars. He wheel spun it everywhere and in within amonth his back tyres where knackered. He went to some back street garage his dad used and put about £580 of michelins on the back axle, he was bragging how good these where until I told him they where supposed to be run flats BMW void your warrenty on those if you dont use those.

[GS]

................... he was bragging how good these where until I told him they where supposed to be run flats BMW void your warrenty on those if you dont use those.

Not according to BMW they don't.

What I've been told is that if I want to remove the run flats I can but if I wanted to sell the car or part ex it back to BMW it would either have to have run flats fitted or the price would be dropped by the cost of a set of run flats.

I have been told by three BMW garages that the tyres do not effect the warranty, although some people have suggested that it might be worth informing the insurance company in case they view it as a modification away from the manufacturer's specifications.