You may have heard the news that Michelin is working on designs for an airless tyre. The possibility of never having to change a flat is tantalising, but the concept is still several years away. Until then, we have run flat tyres. So, what are they and how do they work?
You guessed it: run flat tyres are so named because they can be driven even if they’re punctured. They achieve this through the use of reinforced rubber that prevents the tyre from collapsing upon a sudden loss of pressure. Self-supporting tyres (SSRs) have a tougher, thicker sidewall that holds its shape upon deflation, while another type of run flat tyre has a supporting ring of hardened rubber that prevents a collapse.
What are the advantages of run flat tyres?
Firstly, the most obvious advantage: you don’t have to pull over and change the tyre straight away. Run flats are designed so that you can continue driving to a service centre and have the tyre changed safely.
The second advantage is a follow on from the first: you don’t have to change a tyre on the side of the road. Not only is this always a huge inconvenience, but it can be unsafe if there’s no wide shoulder or carpark to pull into. Run flat tyres also save you from hanging around for roadside assistance.
Thirdly, if you experience a puncture, the toughened nature of run flats lends the car greater stability. In other words, the driver will maintain greater control over car’s handling, and more able to negotiate obstacles.
Another important advantage is the reduced risk of blowouts. A blowout can occur for several reasons, including underinflated or worn tyres, too heavy a load, or a particularly nasty pothole. Whatever the cause, blowouts are sudden, frightening and dangerous. Fortunately, the reinforced sidewall of run flat tyres greatly reduces the chance of your tyre rupturing and rapidly deflating.
The fourth reason is more about convenience than safety. Because a run flat allows you to continue driving to a service centre – you guessed it – there’s no need to carry a spare tyre! Hooray for extra boot space. Plus, the reduced weight helps with fuel economy (albeit marginally).
How far can you travel on run flat tyres with a puncture?
It depends on the tyre. Manufacturers will always have guidelines for you to follow. As an example, though, the Continental Self Supporting Run flat (SSR) allows you to continue driving for up to 80 kilometres at a top speed of 80km/h. Unless you’re in the middle of nowhere, that gives you a very good chance of reaching a service centre.
Can I have both run flats and regular tyres on my car?
No, we strongly recommend that you don’t. Not all tyres behave in the same way; they have different characteristics and different handling. If you mix and match on your car, you’ll end up with unpredictable dynamics. Plus, it actually makes the car unroadworthy. So it’s all or nothing; you either have four run-flats or four normal tyres, but you cannot have a mixture.
Can I fit run flat tyres myself?
Not really. The thicker, stiffer side-walls make it almost impossible to remove and refit the tyre without a good quality tyre changing machine. Tyres such as the Continental Self Supporting Run flat are technologically advanced products which should be mounted by a certified Continental trained tyre specialist.
The walls on run flat tyres are very rigid, and so you may not even notice a puncture; for this reason, we recommend the use of a tyre pressure monitoring system (TRMS), which will alert you when there’s a loss of tyre pressure in the tyre. If a professional fits the tyre and the monitor, you’ll know all components are functioning correctly.
Can my vehicle be fitted with run flat tyres?
Depends on the make and model. Some cars have been approved by the manufacturer for SSR tyre use, some not. Bring your car in to Eastern Tyres and we’ll tell you if run flats are appropriate for you, and what type.
Here’s where you can learn more about the Continental Self Supporting Runflat.
Can run flat tyre punctures be repaired?
Yes and No! Some manufacturers allow it, but some don’t! The issue is when a run flat tyre is flat and you have been driving on it, the side-walls become damaged.
If there is any evidence of ‘creasing’, ‘cracking’ or deposits of rubber inside the tyre, then a repair must not be carried out as these are signs that the tyre has been running at very low or zero pressure for an extended amount of time. If there are none of these signs above, then it is generally okay to proceed with the repair.
This table outlines each tyre manufacturer’s ruling on repairing run flat tyres
|MANUFACTURER||REPAIR POLICY||ADDITIONAL PROVISIONS|
|Bridgestone||Permitted||Only if 15 PSI maintained|
|Continental||Does not recommend||Invalidates subsequent warranties|
|Goodyear||Permitted||One repair maximum for H-rated & greater speed ratings|
|Michelin||Permitted||One repair maximum|
|Pirelli||Not endorsed||Refer to company’s road hazard program|