In a car industry that just keeps on growing and growing, it can be easy to get confused by a lot of the terminology and features that get thrown about. Run flat tyres are just one example of that.
Which is why we've put together a nifty little guide to help. We'll be telling you what run flat tyres are, what their purpose is, how they differ from regular tyres, and how far you can drive on them if they do get punctured.
Plus, with a growing number of car manufacturers including them as standard in their new vehicles, it can be very important to know.
So, let's get to it!
What Are Run Flat Tyres?
Just to be clear, run flat tyres don't stop punctures. Instead, they're designed to make it possible for your car to stay on the road long enough after a puncture so that you can safely reach a repair shop.
In the event of a puncture, run flat tyres will keep you on the road for around 50 miles (at a maximum speed of around 50mph) before becoming fully deflated. Because they’re made to support your vehicle even when they contain no air, run flat tyres help you maintain better control than conventional tyres in a complete air loss situation.
Which means no more hazard warning lights on the hard shoulder and no more stopping at the sides of busy roads waiting to be roadkill. Yep, run flat tyres mean that if you get a puncture on a cold, dark night, there's no need to perform an uncomfortable tyre change by the edge of the road. Instead, you're safely off to the nearest garage to get the tyre replaced (not repaired, and we'll tell you why later). Which isn't the case with conventional tyres, which when punctured require you to stop and fit a spare tyre yourself or have your car towed away (at quite some cost, if you don't have breakdown cover in place).
First developed by tyre manufacturer Michelin in the 1930s, run flat tyres entered the public market in the 1980s and are becoming more and more common as time goes on.
How Do Run Flat Tyres Work?
What makes run flat tyres so durable is that they have a reinforced sidewall construction to provide extra support should the worst happen and you get a puncture.
The reinforced sidewalls mean that run flat tyres can temporarily stay rigid despite a lack of air pressure. The tough rubber inserts allow the tyre to temporarily hold up the weight of a vehicle after a puncture. That isn't the case with a standard tyre, which would just collapse in the event of a puncture due to its sidewalls needing that constant air supply.
Just be advised though that most cars which have run flat tyres don’t come with a spare tyre, which can either be a good or a bad thing. But probably a good thing, because your vehicle's weight will be reduced and your fuel economy will be better as a result.
So if run flat tyres are designed to withstand the immediate effects of punctures (for a range of 50 miles, at least), then how are you meant to actually know when one of your tyres has been punctured?
Tyre Pressure Monitoring System (TPMS)
Well, that's where the Tyre Pressure Monitoring System (TPMS) comes in.
Designed to monitor the pressure in each tyre, this system will alert you of a puncture due to detecting the loss in air pressure. Normally, you'll see the alert on the centre console of the dashboard and it'll remind you to stop driving after 50 miles. You don't need to worry about setting it up yourself, because every car that's compatible with run flat tyres already has one of these systems installed.
Obviously, detecting a puncture on run flat tyres without TPMS would be virtually impossible given that they're designed to keep working even whilst deflated, which makes TPMS a very important tool to say the least.
How Far Can You Drive on a Run Flat Tyre?
Like we say, they'll usually keep you on the road for around 50 miles following a puncture, but the exact range can depend on variables like driving speed, vehicle load, road conditions and more. To be on the safe side, we'd recommend going slower rather than faster in the event of a puncture, even with run flat tyres.
Can Run Flat Tyres Be Repaired?
Unfortunately they can't, and that's the one potential downside.
They reason you can't just patch them up after a puncture is that once a punctured run flat tyre has been driven on, its strength and sidewall has been compromised and it loses its structural integrity, making it unsuitable for repair. And if a repair is attempted, it's highly likely that the tyre will simply get punctured soon again due to uneven wear and a loss of rigidity.
That's why most leading tyre retailers and auto shops will refuse to repair a fun flat tyre following a puncture. Also, most manufacturers advise against it.
Can You Use Run Flat Tyres on Caravans and Trailers?
You can't use them on a caravan or trailer itself (as neither caravans or trailers are currently fitted with TPMS, and only TPMS vehicles can use run flat tyres), but you can use them on a car that's being used to tow a caravan or trailer.
However, we'd still advise you to take particular care when doing so. The extra weight that's added by a towed vehicle can put any tyre under additional stress, and that's especially true of run flat tyres. To stay safe, it's recommended that you reduce your overall speed and distance travelled whilst towing with run flat tyres. Because even if you observe the set speed limit, you could still run into problems with the stability of your car and the towed vehicle.
As extra reassurance, it's best to check with your vehicle manufacturer's handbook for additional detail.
Benefits of Run Flat Tyres
We've already touched upon the main advantages, but just to summarise them more neatly for you, here they are again:
- No need to change tyre in a dangerous roadside situation (motorways especially)
- Gives you enough time to reach a garage in the event of a puncture
- Provides more stability than conventional tyres after puncture
- Vehicle weight reduced by having no spare wheel
- Less prone to blowouts (a rapid and potentially dangerous loss of air)
And the disadvantages ...
- Can't be repaired (needs replaced after a puncture)
- More expensive
- Can't be used on caravans and trailers
Lifespan of Run Flat Tyres
The materials involved in the making of run flat tyres are similar to those for conventional tyres, so expect their wear rates to be comparable.
Just make sure that you're popping down to the nearest air machine regularly (at a supermarket, for example) and keeping the air pressure in your tyres topped up. That's always the best way to ensure that they get the longest life possible.
Can You Mix Conventional Tyres with Run Flat Tyres?
Conventional tyres are a lot less expensive than run flat tyres, so this can be tempting, but it's generally not a very good idea.
If your car originally came with run flat tyres, then it is possible to change to conventional tyres. But if the vehicle was designed exclusively with run flat tyres in mind, then bear in mind that you could be left stranded without a spare.
It's often the case that run flat tyres come as ‘Original Equipment’ – in other words, the tyres which the car is fitted with upon leaving the factory. What this means is that the car’s designers will have repurposed the space that would otherwise have been for a spare tyre, with no spare tyre cavity and therefore no spare tyre.
Summary
So, a ton of paragraphs and roughly 1600 words later, you now hopefully know what run flat tyres are and what they can do for you and your lease car. They'll certainly come in handy in the event of that pesky puncture which none of us ever wants, but which is bound to happen at least once in our driving career.
Two things to watch out for though: just be wary of mixing them with conventional tyres, and be aware that once punctured, a run flat tyre can't be fixed and has to be replaced.
As always, happy leasing!
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