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Run Flat Tyres

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malana3 | 12:36 Sun 21st Jan 2018 | Motoring
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When I took delivery of my car six years ago it came without a spare tyre or the space to carry one, just an aerosol of sealant and an electric pump. With a disabled wife who has frequent, timed, hospital appointments I have dreaded having a puncture. The time has now arrived to replace all four tyres and the thought has occurred to replacing them with run flat tyres. Is this a simple replacement or are there other things to consider, i.e. fitting to my existing rims or handling etc? In the event of a puncture, what are the limitations of use of a run flat tyre?
Any replies will be gratefully received.

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The most important aspect of this decision is whether your car has a tyre-pressure monitoring system (TPMS). It is ESSENTIAL that you have a working TPMS system on your vehicle if you have run-flats fitted (see below) TPMS became a legal requirement in the UK (and EU) for new cars from the start of 2014. They were an extra (sometimes optional) prior to that....
13:35 Sun 21st Jan 2018
I’m not sure that run flats can be fitted to your existing rims, and it would be expensive to change the wheels.

Mrs Hymie has run flats on her vehicle – not long ago she suffered a puncture, which resulted in the rim cutting through the tyre (despite driving less than 5 miles with a flat tyre). I have recounted this story to others, who report the same experience with run flats (tyres ruined once they suffer a puncture).

In one case, it resulted in the vehicle being stranded since the breakdown company could not source a replacement run flat tyre.

So based on my experience (and others), you will be no better off with run flats verses ordinary tyres (other than the run flats will be much more expensive).
Perhaps consider buying a jack and a spare wheel. There might be a spacesaver wheel available if luggage space is essential for you.
The most important aspect of this decision is whether your car has a tyre-pressure monitoring system (TPMS).

It is ESSENTIAL that you have a working TPMS system on your vehicle if you have run-flats fitted (see below)

TPMS became a legal requirement in the UK (and EU) for new cars from the start of 2014.

They were an extra (sometimes optional) prior to that.

Run-Flats have a limited life at zero pressure. Usually 80km and a maximum speed of 80 kph (50 mph).

They are designed to feel as comfortable at zero pressure as they are when fully inflated, so you cannot tell from the driver's seat that you have a flat tire. (and they do - I have driven many different types of run-flat in my time)

Thus ,there must be some kind of warning system to alert you to the low-pressure situation.

Without that warning, you risk destroying the tire and causing a serious accident.

No responsible tire fitting service will fit run-flats if the vehcle does not have a working TPMS system.

You can buy after-market TPMS systems. I personally use this system:

https://www.nonda.co/products/zus-smart-tire-safety-monitor

others are available.

Most Run-Flats from the major brqnds (Michelin, Bridgestone, Goodyear, Continental, Hankook etc) are designed for use on a specific vehicle. The best one (in my experience) designed for general after-market use is the Bridgestone Driveguard.

If you need any more info, pls ask further questions as normal.


In response to HYmie, yes - all run-flats can be fitted to existing rims.

The only exception to this was the Michelin PAX/PAZ that was developed a couple of decades ago and then withdrawn because they could not fit it to existing rims - it needed a speciaised rim. It was used for the last time on the Bugatti Veyron, as I recall. Tyres (not rims) at over £1000 a throw
I have a further question.

I have a C3 Picasso, 2017, bought in the UK and it has no tyre pressure warning system. Why would that be?
Are you sure it’s not just sat there in the background Doooogie?
https://enginepartsdiagram.com/how-to-reset-citroen-c3-picasso-tyre-pressure-warning-light/
Well I'll be hornswoggled! I've never seen that warning light, or rather never noticed it.
My routine pressure check regime must be keeping me from needing a prompt. :)
Thanks, Z-M.
Run flat tyres are the work of the devil....the side walls are very strong and if you go over even a small pothole the shock can transfer to the alloy wheel and crack it.Do as Hoppy says at 13:22
Hi Ryzen

we-e-ell maybe not the work of the Devil.

There is no question that early generations had a very harsh ride. The whole point of a radial tire is to de-couple the sidewall from the tread - and that gives a more comfortable ride.

With a self-supporting sidewall (most modern runflats), the tread is coupled back to a reinforced sidewall, which results in a harsher ride. In theory.

In practice, tire makers realised this is an issue and now you have to be a very sensitive soul to feel the difference when the tire is fully inflated. Some of my friends who are professional drivers claim to tell the difference, when driving performance cars at the limit around a track but I am not entirely convinced.

Of course they can tell the difference between a de-flated run flat and a fully inflated regular tyre.

I'll be honest, I can barely tell the difference. For modest cars at modest speeds, there is effectively no difference in handling or ride quality between an inflated runflat and an inflated regular tyre.

I will agree that on a performance vehicle with 25-series tyres (those very low-profile tyres), then a pot-hole or roadbump taken at speed can transmit to the rim and crack it. But on a 205/55R16 (the most common size in the UK) there is no risk of that at normal speeds and under normal conditions.

Of course, driving up a kerb at speed counts as abnormal.

The OP expressed a desire for runflats. I'm trying to explain the issues around them.

Personally, I don't have runflats and would not fit them. The reason is mainly expense. Punctures are quite rare ( every 50,000 km on average). The vast majority of those punctures are slow-release events, and a decent pressure warning system will help you manage that situation without the need for a runflat.

Runflats will probably save your life if you sustain a front-wheel puncture while driving at speed (60 mph upwards) on a curve. But that is an extremely rare event.

The key reason for buying runflats are safety and security, as mentioned by the OP, or security driving (VIPs who might get their tyres shot out by kidnappers) or concern over becoming immobilised in 'unsafe' areas.

Those issues don't apply to me, or probably to you. But they might to the OP.
Kidas...thanks for the response. BMW have had many headaches with regards to run flats and 19"alloys.
Yes - I agree. BMWs - especially the performance models are an issue - they tend to have the low profile tyres - in 40- or 45-series, and I know the BMW user group discussion boards have been alive with complaints about over-harsh ride; noise and difficulty at first (and later) replacement.

It's why I said the Driveguard is a better product. BMW chassis engineers specify a highly responsive tire with lower levels of comfort (harsher ride) in order to deliver the performance and handling that their drivers demand.

I happen to know the engineer at BMW who made the decision to convert the company to Runflats.

He quit BMW and moved to Bridgestone and has just retired. He regards the runflat decision at BMW as one of the greatest achievements in his career

I get the impression the OP does not drive that kind of vehicle. I might be wrong, but thanks for the comments - certainly adds an extra dimension to the thread.
Kidas...the runflats were on a 530 GT we had.When we changed to an M5 we found they had gone back to conventional walls ...even though there was a +300HP difference.
Indeed. BMW listens to its drivers.
Since Rudi left, there has been a softening of their approach to runflats. Now the base models tend to have runflats fitted as standard, but the option packs, especially on the sportier models are normal tyres.

As I said, Personally, I see no need for them. But some people put a high value on mobility and safety in the case of extreme situations.

There is no single solution for all customers. Some like the insurance value of runflats; others (including the two of us) do not see the benefits.

Today runflats are around 5-6% of the total EU market for replacement tyres. A lot of that was driven by BMW replacement sales, but the percentage has held pretty steady for around a decade. I don't expect to see much change in that figure over the coming few years.

Probably we will see a move away from runflats on sporty vehicles toward low-end vehicles. As TPMS systems get better, people (and car makers) will realise that runflats introduce one compromise too far.
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Thank you all for your responses, very informative and I've learnt a lot.
Not sure yet what my final decision will be but whatever it is, it will be based on sound knowledge. Once again, thanks to you all.
I have no personal experience of run flats, but I wold definetely encourage you not to rely on the compressor and tin of glue method. That's what my Focus ST came equipped with, (I think as a cost cutting measure for Ford). I quickly bought a space saver and jack on Ebay and carry them in the boot, (no spare wheel well either!). I have seen plenty of tests of the repair and inflate methods which were all dismal failures, plus I believe that the tyre cannot then be properly repaired as the inside is full of the gloop.

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