Stretched tyres, legal and safe or not?
"It's a long stretch."
Are stretched tyres safe? This is a question we get asked over and over again.
There are 2 schools of thought on this subject and we aim to cover the pros and cons in as open and unbiased way as we can.
Firstly a bit of an introduction. What is a stretched tyre?
This is a tyre which has been fitted to a much wider rim than it was originally intended or designed to fit. Stretches vary from an inch to around 3 inches. It has gained a lot of popularity in VW circles and the look is really starting to take off.
The benefits of stretched tyres are that they look great (this is a matter of subjective opinion though). They also allow you to run much wider rims without having to alter the arches or bodywork as no part of the tyre may protrude from the bodywork.
We have heard many horror stories including the increased risk of blow outs, or sudden deflation and the extra risk of kerbing your alloys. We have even heard of track days where cars running big stretches would often lose tyre pressure and "blow out".
So lets look at the two main arguments for and against them.
Stretched tyres are dangerous and risky - the argument against.
The arguments against stretched tyres will cite that tyres are designed to fit a specific width of rim. Tyre makers will not warrant their products fitted outside of tolerances and the speed ratings will typically be a few steps lower than a correctly fitted tyre.
The load bearing wall of the tyre is designed to be at around a 90 degree tangent to the rim and under cornering this allows a small degree of vertical 'wobble' which aids cornering feel and grip.
They will state that stretched tyres are no longer within this ideal tolerance and probably 80 or 70 degrees from the rim so subjected to extra stresses and strains. They are also more likely to pop away from the bead when the pressure drops than a standard fitting tyre.
On heavy driving, a stretched tyres wear pattern, will be different to that of a standard tyre with a greatly increased edge wear. The narrower tyre width also reduces grip and traction - most people fit wider tyres to increase the grip and this seems diametrically opposed to that philosophy.
Stretched tyres are perfectly safe - the argument For.
Modern tyres and especially low profile tyres have much thicker walls and are more than capable of handling the extra loads they might be subjected to. In a pneumatic tyre the car is resting effectively on a bubble of air so the actual walls of the tyre are less important when it comes to strength.
If the tyre pressures are maintained correctly there should be no risk of the tyre popping off the rim under cornering. A lot of those with stretched tyres run with much higher pressures than a conventionally fitted tyre.
Lots of people have stretched tyres on their cars without any problems at all. The narrower footprint argument is also immaterial as generally speaking the rim size has been increased and standard tyre widths are used.
Now unpicking these 2 arguments is not going to be easy. There are going to be lovers and haters of stretched tyres and neither side is going to back down.
They are getting more popular and the craze is really catching on. As with any modification one has to examine the parts used and the dimensions involved.
It is fair to say that the larger the stretch the greater the risk of having a problem with your tyre. We can also say that those who drive hard or use cars on tracks subject the car to a lot of extra wear and tear.
So the use of the car also comes into it.
Whilst one make of tyre might be ideal for a stretch, by virtue of the tread pattern and sidewall construction another may prove woefully inadequate. Different rim sizes and tyre profiles also have a bearing on this issue.
We would have to concede that stretched tyres can be perfectly safe in some situations where the stretch is not excessive, the car is not driven too hard and the tyres are properly maintained. The risks of damage from a kerb also needs to be mentioned as most tyres give a degree of protection to a rim. Personally I don't like the look and do not recommend them from that point of view.
There is also the question of whether these tyres are legal. We are obviously based in the UK and we know that regulations vary from state to state and country to country. But from a UK MOT test point of view (as at the time of writing) there are no points raised specifically concerning stretched tyres.
Insurance companies may not be happy though and tend to take a cautious view of any modifications made to a car. If an accident happened that could be directly attributed to the stretched tyre there will certainly be questions raised about the "did the insured take reasonable steps to maintain his vehicle in a road worthy state" clause. As with any modification always notify and get your insurers approval or you would invalidate your policy cover.
It is also worth noting that the Motor Vehicles Approval Regs 2001 section 16 state that tyres should be of a nominal size appropriate to the wheel to which it is fitted. The police have also taken a dim view of these in the past and issued warnings and penalties under various construction and use clauses. We would also refer you to the more recent "road vehicles (Construction & Use) regulations 1986", and specifically Regs 24 to 27 concerning tyres.
The lack of specific legislation either against or for stretched tyres does not add to the clarity of this issue. "Appropriate" in our mind rules out excessive stretches. Tyre manufacturers specify suitable width rims for their tyres as further guidelines to those wanting a "stretched look". Speed ratings are also nominally lower on stretched tyres in use so this needs to be born in mind.
Personally I'd leave majorly stretched tyres to show use only. There is a degree of common sense required here. Check your tyre makers specifications and don't go to the extreme. I'm sure tyre makers will pick up on this trend and provide specific stretch designs that are suitable for this type of look.
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