Run Flat Tyres - What Are They & How to Identify Them
Ellie Dyer-Brown, 1 year ago
5 min read
- Tyres
- Car ownership
FixMyCar discusses everything you need to know about run flat tyre technology.
Tyre brands invest heavily in research and development to ensure their tyres include the latest and greatest technologies. This is excellent news for motorists, who have more choice than ever when we need to buy tyres, but it also leaves us with an ever-growing list of features to familiarise ourselves with.
For example, if you’ve spent time researching tyres, you’ve probably come across the term “run flat” or some variation. Invented in the 1930s, run flat technology wasn’t introduced to the public market until the 1980s, and since then, it has exploded in popularity.
Despite the prevalence of run flat tyres, many drivers have only a vague understanding of how this technology works and whether a punctured run flat tyre can be repaired. If this sounds like you, fear not! Your questions are about to be answered.
Contents
How to identify run flat tyres
Can run flat tyres be repaired?
Are run flat tyres more expensive?
What are run flat tyres?
Tyre punctures are depressingly common. You’ve probably had one before - I know I have. In fact, they are one of the biggest causes of breakdowns, along with dead or faulty batteries. Wouldn’t it be great if, after your tyre sustained a puncture, it could just…keep going? Well, that’s what run flat technology is for.
Run flat tyres are engineered to support the weight of your vehicle following the loss of some or all tyre pressure due to a puncture. This solution is a temporary fix designed to get you to a garage or somewhere you can safely replace the tyre.
How do run flat tyres work?
There are two types of run flat systems you should be aware of.
Self-supporting run flat
Self-supporting run flat (SSR) tyres feature a reinforced sidewall, supporting the vehicle when air is lost. You can keep driving up to the distance and speed specified by the tyre manufacturer.
The sidewall of a tyre supports the car's weight, absorbing shocks from the road and potholes while keeping the tyre sealed to the wheel rim.
Support ring run flat
Support ring systems use a rigid rubber ring or an alternative structure to support the vehicle’s weight when the tyre loses air.
How to identify run flat tyres
Run flat tyres will usually have specific labels or markings on the sidewall. Here’s what to look for:
ISO symbol - There is a run flat symbol designated by the International Organization for Standardization (ISO), which consists of the letters RSC (Run-Flat System Component) inside a circle. You will find this on the tyre’s sidewall.
Tyre markings - Most run flat tyres will have a marking on the sidewall, though this may vary between manufacturers. Look for abbreviations like SSR (self-supporting run flat), RFT (run flat technology) or ROF.
Owner’s manual - Your owner’s manual should state whether your car is equipped with run flat tyres. You could also check the manufacturer’s vehicle specifications.
Manufacturer’s designation - Some manufacturers have their own branding for this technology, such as Bridgestone, which uses the term “DriveGuard”.
Read this guide for more information about understanding tyre markings.
While some vehicles have run flat tyres as standard, not all do, and some may offer this technology as an optional extra. If you’re unsure, it’s best to consult an expert mechanic.
Can run flat tyres be repaired?
Tyre technology has come on in leaps and bounds, but unfortunately, it hasn’t come far enough to make it possible to repair most punctured run flat tyres. I say most because the answer to this question is a little more complicated.
Generally, once the tyre has sustained damage and supported the car's weight, its structure becomes compromised. It’s also more difficult to spot any secondary damage, so additional harm to the tyre wall may be hidden, in which case a repair will not sufficiently restore the tyre to safe working order.
Most mechanics will refuse to repair a run flat tyre and offer to replace it; this is the best and safest option.
However, you should check the guidelines outlined by the tyre manufacturer. Most tyre companies advise against repairing run flat tyres. But Goodyear, for example, states that its run flat tyres can be repaired by a qualified professional after a thorough inspection and analysis of the tyre’s history. If there are any doubts, it should not be repaired but replaced.
Are run flat tyres more expensive?
One of the significant downsides to run flat tyres is that, yes, they are more expensive than regular tyres, sometimes by as much as 50%. The price also depends on choosing a budget, mid-range or premium tyre manufacturer.
Check out these guides for more information:
Are run flat tyres worth it?
If, like me, getting a blowout on the motorway sounds like your worst nightmare, run flat tyres might be a good choice next time you’re choosing a set of tyres. Before making that decision, consider the benefits and disadvantages below.
You must only use run flat tyres if your vehicle has a tyre pressure monitoring system (TPMS).
If your car doesn’t monitor tyre pressure, you could end up driving on a punctured tyre for far longer than you should, as you’d have no way of knowing something was wrong.
Benefits of run flat tyres
Run flat tyres have a range of benefits, including:
Run flats are more stable after sustaining a puncture than regular tyres.
You can keep driving - you don’t have to change your tyre in uncomfortable or dangerous conditions.
Cars with run flat technology don’t need a spare tyre, leading to better fuel economy because your vehicle carries less weight.
You don’t have to change the tyre yourself or call for roadside assistance.
Disadvantages of run flat tyres
There are some downsides you should also be aware of, such as:
They provide less ride comfort due to stiffer sidewalls.
They are more expensive to buy than regular tyres.
You can only drive a limited distance after a puncture before replacing the tyre.
They may result in reduced performance due to the stiffer construction impacting cornering and handling capabilities.
Run flat tyres are not as widely available in all sizes and for different vehicle types.
Can you mix run flat tyres with regular tyres?
There are no laws about mixing run flat tyres with regular tyres. That said, it isn’t recommended because doing so may negatively impact vehicle handling. Since run flat tyres have a more rigid construction, they may affect the braking and steering of your car when combined with softer tyres.
It’s a good idea to buy a set of four run flat tyres rather than one or two.
How far can you drive on a punctured run flat tyre?
The following factors may influence how far you can drive after sustaining a puncture:
Vehicle weight
Car model
Tyre manufacturer
Driving conditions
Driving speed
Run flat tyres allow you to continue driving a limited distance at reduced speeds with a puncture. Each tyre brand has its own recommendations, but it’s a good rule of thumb not to go further than 50 miles at speeds not exceeding 50 mph (this advice also applies to driving on a space-saving spare tyre, as discussed here).
Buy your next set of tyres
Whether you decide to buy run flat or regular tyres, FixMyCar has thousands of options and a network of mechanics ready to fit them. Select the tyres you want, choose a fitter in your local area and enjoy your new tyres.
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