Thursday 16th June 2005

Run-flat advice from tyre makers

Don't fit them to a standard car, industry body warns

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Goodyear run-flat

Fitting run-flats to a car not designed for them is inadvisable at best, according to the Tyre Industry Council (TIC).

A car’s suspension is specifically tuned for SST run-flat tyres for maximum safety, performance, handling and ride quality. SST Run-flat tyres must only be fitted in conjunction with a tyre pressure monitoring system to ensure that a tyre deflation is communicated to the driver at the earliest possible moment. Failure to do so could result in a tyre being run in a deflated condition for longer than the recommended period and the driver left in ignorance of a tyre’s condition.

Retrofitting of SST run-flat tyres may also compromise the ride characteristics of the vehicle to which they have been fitted because few older vehicles have been designed with run-flat fitment in mind.

An example pointed out to the TIC recently involved the fitment of a set of run-flat tyres to a 10 year old vehicle not fitted with a tyre pressure monitoring system. The car suffered a puncture and the driver was unaware of the deflated tyre, which was run in this state for some time, and the car failed its MOT because of damage to the tyre.

All major tyre manufacturers producing SST run-flat tyres, along with all major tyre retailers, recommend against fitting run-flat tyres to vehicles not originally designed with this type of tyre in mind.

Self supporting run-flat tyres must never be mixed with standard tyres on any vehicle.

[Raify]

Run Flats are a complete waste of time and money. I've had a terrible experience with them on my MINI. If you really have no space for a spare / space saver then you have 2 options:

1. Tyre gunk + a compressor:
Pro's - cheap, works and doesn't affect the tyre's handling / wear.
Con's - Can't fix blow outs / big holes.

2. Run Flats
Pro's - Make lots of money for tyre manufacturers
You don't have to get out of the car, while you're limping to the garage with your puncture.

Con's - Almost twice the price to buy (£160 compared to £80 for a 195*16)
Cannot be repaired. Run over a nail in a normal tyre and you pay £15 to fix it. Do the same in a run flat and that's £160 please sir. Oh no! It can't be repaired! (actually it can, but all garages claim it cannot for fear of being sued, when a repaired run flat fails, because it's been driven too far / fast on the side walls)
Terrible ride quality
Tyre wear is increased
Grip (in the wet) is bad
Try finding a place that will even change run flats, that's a mission in itself

I really don't see the point. Neither did BMW when they made their flagship M3 / M5 models...

They claim that suspension is "sepcifically tuned for run flats". What a load of horse sht Lots of car models have the same suspension, but only some have run flats (MINI for example). If they did "tune" the suspension on the Cooper S, they did a terrible job. As soon as I put normal tyres on it, the handling, ride and grip was vastly increased.
rant ends!




>> Edited by Raify on Thursday 16th June 13:24

[Raify]

[cdp]

My Leyland Princess was designed to use Dunlop Denovo run flat tyres.

Leyland claimed it would work even after significant damage to the tyre. I wouldn't like to try it.

Although I never had Denovos, I had a conventional front tyre suddenly fail at 70+mph. Thanks to Hydragas the Princess was easily and safely brought to a halt. Unlike when the same thing happened on the back of my rear engined Skoda; Big oversteer time and just good luck (a convient escape road) that prevented a big accident.

At Gaydon Museum they had a Denovo cut-away, with lots of little canisters around the inside of the wheel. Additionally the tyre was bolted to the wheel rim all the way round.

[mybrainhurts]

I had a front tyre blow out at 70 a few months ago.

Heard the bang, but had no idea what it was. Big hole in sidewall.

I drove on for at least a mile, then pulled into a filling station to have a look round. Only then did I realise what had happened.

There was absolutely no feedback at the controls to suggest the tyre had gone. I was more than a little surprised.

[sumplug]

once again we have manufactorers making us use tyres we dont really want.i remember the first time round the problems they caused.then we had metric wheels which made buying tyres very difficult and almost impossible to buy due to no supply.and the price! rediculous.

[woof]

I've got a cooper S as well - never had so many punctures on a car in my life !

what tyres did you swap to ?

Raify said:

Run Flats are a complete waste of time and money. I've had a terrible experience with them on my MINI. If you really have no space for a spare / space saver then you have 2 options: 1. Tyre gunk + a compressor: Pro's - cheap, works and doesn't affect the tyre's handling / wear. Con's - Can't fix blow outs / big holes. 2. Run Flats Pro's - Make lots of money for tyre manufacturers You don't have to get out of the car, while you're limping to the garage with your puncture. Con's - Almost twice the price to buy (£160 compared to £80 for a 195*16) Cannot be repaired. Run over a nail in a normal tyre and you pay £15 to fix it. Do the same in a run flat and that's £160 please sir. Oh no! It can't be repaired! (actually it can, but all garages claim it cannot for fear of being sued, when a repaired run flat fails, because it's been driven too far / fast on the side walls) Terrible ride quality Tyre wear is increased Grip (in the wet) is bad Try finding a place that will even change run flats, that's a mission in itself I really don't see the point. Neither did BMW when they made their flagship M3 / M5 models... They claim that suspension is "sepcifically tuned for run flats". What a load of horse sht Lots of car models have the same suspension, but only some have run flats (MINI for example). If they did "tune" the suspension on the Cooper S, they did a terrible job. As soon as I put normal tyres on it, the handling, ride and grip was vastly increased. rant ends! >> Edited by Raify on Thursday 16th June 13:24

[Raify]

woof said:

I've got a cooper S as well - never had so many punctures on a car in my life ! what tyres did you swap to ?

Pirelli P-Zero assimetricos. I really wanted Eagle F1's as I've had very good experiences with that tyre on 2 other cars, but I was in a hurry and the Pzero was the best I could find.

If you're still on run-flats, change now! You'll never regret it.

[woof]

yep - i'm do to change in the next month or so
did you also get loads of punctures ?

Raify said:

woof said: I've got a cooper S as well - never had so many punctures on a car in my life ! what tyres did you swap to ? Pirelli P-Zero assimetricos. I really wanted Eagle F1's as I've had very good experiences with that tyre on 2 other cars, but I was in a hurry and the Pzero was the best I could find. If you're still on run-flats, change now! You'll never regret it.

[Raify]

woof said:

yep - i'm do to change in the next month or so did you also get loads of punctures ?

A massive bolt in the front driver's side, and a smaller screw in the rear passenger's side. See my profile / my cars for details. If they had been normal tyres, those two unfortunate incidences would have cost me £30. In the end it cost me about £350, becuase I had to replace all four tyres.

See www.mini2.com for loads of advice / suggestions on tyres (do a search, it's been discussed to death)

[woof]

mucho gracias

Raify said:

A massive bolt in the front driver's side, and a smaller screw in the rear passenger's side. See my profile / my cars for details. If they had been normal tyres, those two unfortunate incidences would have cost me £30. In the end it cost me about £350, becuase I had to replace all four tyres. See www.mini2.com for loads of advice / suggestions on tyres (do a search, it's been discussed to death)

[armynick]

I might be wrong but I think you'll find that run-flats are mainly desgned for security vehicles to enable the driver to drive out of trouble if nessersary. (If they're being pushed onto the public then I guess it's just another angle to make more money.)

They're good if someone shoots out your tyres in order to disable your vehicle, or even lays down nails or other debris, you can then try to drive out of the ambush.

They're not fool proof but are another aid to survival and every bit helps.