today's run-flat tyres: 500 miles while flat?

Today I was amusing myself with a pleasant eyelid movie (no, not that sort).

I've won the really big lottery, millions, and after a lifetime of frugality I lash out and do something crazy. I buy a nice new Rolls-Royce Phantom, and drive it across Australia, more 2,500 miles, to show it off to some family members. I'm out on the Nullarbor Plain, halfway between Perth and Adelaide, and I a get a puncture. The runflat tyre handles it fine, so I stop, look for the spare. Whoops, there isn't one. The wheels are so bloody big a spare would fill up the entire trunk. No worries, the handbook says the runflat is good for 100 miles at 50 mph. Only thing is, the nearest place I can get another tyre, or get this one fixed (if you can) is well over 500 miles away.

Will I make it?

Can I get one of these things repaired at any small town with a tyre dealer so I can carry on?

Or will my shiny million-dollar set of wheels need a tilt-tray recovery vehicle?

And to make matters worse I don't have satellite telephone, and there's no cellphone reception out there. So do I get a passing motorist to call in a help call for me in the next town, and spend a night or two sleeping in the bloody thing?

Or maybe better, set fire to it.

I'm fairly serious about this. Could a flat runflat make it say 200 or 300 miles at 50 mph?

Anyone know. There are some seriously lonely places in Australia, and if you can't take a million-dollar limo outside the metropolitan area, what the hell use is it?

Well if you can afford a Rolls shirley you can also afford a sat phone. Or you can afford to have another car ("security") trailing you with servants and spares, wherever you go. Or you could sacrifice luggage space and carry a full sized spare. Whatevs. Punctures are so rare that it rarely makes any sense to lug around a full sized spare unless you go off the beaten path or are into hardcore 4X4 action. How may people carry spare spark plugs and fuel injectors with them? The typical driver these days won't even know how to change a tire even if there was a spare.

There are some seriously lonely places in Australia, and if you can't take a million-dollar limo outside the metropolitan area, what the hell use is it?

This must be what they call 'a rhetorical question'.

I had the thought because I have driven that route - many times - and I have had punctures in these remote places, even on bitumen. Once I got a puncture, put on the spare, realised I didn't have a spare any more and, you guessed it, twenty miles further on got a second puncture, this time a bit of shrapnel left by another vehicle scopped a half inch hole from the sidewall. I had to thumb a lift to Nullarbor Station carrying the best of the two to get the repair (tube in a tubeless, what else?), and thumb back, all the while leaving a fully loaded car parked on a desert road vulnerable to any passing pilferer for half a day.

Mostly I've been lucky - just one tyre flat. I learned from the experience, and next time I went down the junkyard and bought a spare wheel and tyre complete and tossed in the boot along with the official one. And yes, got a flat miles from anywhere, slow leak not a puncture, but had the reassuring knowledge that I still had a spare.

All you need is a slow leak from a dodgy valve (had those too, even new ones) and you're in trouble.

So it looks like the answer is: if you have a car with a set of runflat tyres and no spare, don't travel more than 100 miles from civilisation.

Seriously, can a runflat do more than 100 miles at 50 mph? Why only 100 miles? I assume it's heat buildup, or maybe it's to frighten you into buying a new tyre.

Edited by Terry Walker, 10 May 2010 - 15:02.

True if you are going out of the way it only makes sense to include certain spares yourself even if they were not part of original equipment. I have seen different usable ranges quoted for runflats (no doubt vehicle weight also comes into play), likely it would last more miles at a slower pace. I have never abused a runflat to the end of its usable life after having a puncture, but it is not as if one would fail at precisely 100 miles. The range seems a like a safe suggestion.

And this limitation could be due to weight of the runflat itself, the longer it has to last without air the heavier it might become. IIRC earlier runflats were very heavy compared to ordinary radials of similar size. I once lifted a Michelin runflat (don't recall the size) and thought this thing would not be out of place in a gym.

This has been a major problem for some years, and not just topend exotica. Here in Oz and lots of other countrys this problem with run flat spares or skinny spares is a huge problem. The cars are designed for an urban enviroment and should be left there. So they are really useless for long remote distances.
As I am a car dealer this has caused grief for me with customers who insist on a full size spare, more so on standard models with bigger aftermarket rims eg 17s where the car was fitted with 14 or 15 originally. Though the original tyres are at least a proper tyre which are a similar rolling diameter. Lots of common cars these days are built like that, both because of space considerations and cost cutting. The miniscule run flats have NO excuse ever being on any car, they are dangerous and should be outlawed. There was talk of that happening here but it has not happened yet [and may not ever ofcourse]
Tring to get a puncture fixed even in more populated areas these days is hard unless it is business hours, most retail petrol outlets do not do them at all now so you need a tyre service which can add hours to your commute. I have been there and done that on a Saturday in a major town between Adelaide and Melbourne on a saturday morning. 2 1/2 hours wait [they were flat out and that is not unusual] which really stuffed up an 8 hour trip. I had to get it done as i was coming back on Sunday and would hate to travel without a spare.
Buy a car with a proper spare if travelling long distances and if going bush carry two and really the Nullabor is low risk bush

I suppose car designers and builders don't realise that apparently civilised western countries like Australia are vast, with enormous distances between major towns even on major highways. Using my hypothetical example, there is only one Rolls-Royce dealer in my home state of Western Australia, and that is the only source of the giant RR tyres. Major centres like Bunbury (120 miles away), Geraldton (300 miles), Kalgoorlie (300 miles) and the Pilbara iron ore towns (well over 1,000 miles) definitely don't stock them.

I've driven the Nullarbor route about 40 times, and seldom had any trouble, but if you do, you're a very long way from anywhere. The time I felt seriously vulnerable was when I rode a BMW motorbike there and back, no spare of course.

Funny how sales guff sometimes fails to mention the crucial issue of the spare. I wondered if the Bentley had runflats too, so I looked up their site. No mention of wheel OR tyre size in the "technical information", nor whether there's a spare wheel. I'm none the wiser.

I'll stick with my Silver Shadow with its full size (and standard 14 inch size) rubber. And it's full size spare wheel. Too many of today's new cars are purely urban shopping trolleys, not real cars.

I finally found the Bentley spares setup under "options". No spare, but a repair-inflation kit for emergencies. Spacesaver spare optional, standard in some markets, presumably where the law says you have to have a spare.

So much for a long-distance cruiser. Long distance only within Monaco, I guess.

Tring to get a puncture fixed even in more populated areas these days is hard unless it is business hours, most retail petrol outlets do not do them at all now so you need a tyre service which can add hours to your commute.

Buy one of those puncture repair kits, then. Very handy to carry one on the long trips. It's easy to fix punctures in radials yourself, and given how much shops charge for this simple job a kit pays off quickly indeed. Although I cannot see most people (particularly women) getting their hands dirty, most would rather stand at the side of the road for hours and scream into their mobile phone.

... or equivalent.
I carry a can of the goo in the Fraser as I don't carry a spare either.

Buy one of those puncture repair kits, then. Very handy to carry one on the long trips. It's easy to fix punctures in radials yourself, and given how much shops charge for this simple job a kit pays off quickly indeed. Although I cannot see most people (particularly women) getting their hands dirty, most would rather stand at the side of the road for hours and scream into their mobile phone.

Don't forget the compressor.

Don't forget the compressor.

The problem you have with modern cars at highway speed is the tyre is stuffed before you realise it is going down. I lost 2 tyres in aweek like that on the same stretch of freeway. Somebody must have dropped a box of tek screws as both were the same size tek.

I have a plug set here in the workshop but find that with my lack of expertise I probably fix 1 out of 2 tyres. And some modern tyres dont seem to like a cold patch on the inside anymore either, they do not stick so you either scrap the tyre or put a tube in it.

When I go bush in my Landcruiser I always carry 2 spares. Murphys law if you are prepared you never have a problem. Though have had one puncture a trip on a couple of trips.

Although I cannot see most people (particularly women) getting their hands dirty, most would rather stand at the side of the road for hours and scream into their mobile phone.

The problem you have with modern cars at highway speed is the tyre is stuffed before you realise it is going down.

This is one scenario where TPM can prove very helpful, if pressure reading goes below a certain point it can flash alarm on instrument panel to draw attention.

When I go bush in my Landcruiser I always carry 2 spares. Murphys law if you are prepared you never have a problem.

Indeed better be safe than sorry. No harm in carrying extra spares, particularly if you are going off road.

I have heard stories of Porkers being brought back to the city from the bush on tilt-trays, but I have no firsthand knowledge - may be just urban myth stuff, but then again ...

I have heard stories of Porkers being brought back to the city from the bush on tilt-trays, but I have no firsthand knowledge - may be just urban myth stuff, but then again ...

I have seen one, but not tyres. It knocked a hole in the sump. Really pretty dumb taking a low slung sports car into that area.Flinders ranges. Though a normal Falcon or Commodore would be ok, carefully.
I bet the tow bill was huge, like 400km from an accepted Porsche repairer. From what I saw I suspect the engine was ok as it was dry sumped.