caboosemoose wrote:Is it really true that tyour insurance is void if you are using mixed tyres on the same axle?
Personally, although I would not choose to run mixed tyres on a single axle on most occasions, I generally think that the dangers of doing so are usually overstated. If you think about driving in wet or damp conditions, the difference in available grip, side to side, can be hugely variable, regardless of what tyres you are using - much more variable than the relatively small difference in grip and other characteristics that results from using two different tyres on the same axle. Even when road conditions ae dry there are a huge number of factors that can lead to a large grip or stability differential, side to side, even if you are using matched tyres. I think you'd be hard pressed in most circumstances to notice the impact of mixed tyres on your car's stability.
To be clear, I obviously favour using matched tyres and I'm not suggesting that anyone should actually do anything else or saying that Liquid's excellent advice isn't generally worth following. But I personally don't think that mixed tyres are a that big deal in safety terms - the style 32 rims I bought have mixed rear tyres with lots of tread of them, so I am going to run them over the winter and replace them in the spring. I really don't think there's any point in changing them now.
Having said all that, I would probably be a lot less comfortable with running mixed tyres on the front axle...
Bit late in responding to this
The bottom line is balance. There will be very few situations where the conditions experienced by the car will be different from one side of the vehicle, to the other.
Maintaining the same tread pattern will minimise the risk of any shortcomings due to the environment. Differing trewad depths are also very important. A difference of 3mm and over between axle pairs have a huge affect on braking ability and water clearance.
Granted with most modern high level cars, on board computers will calculate many variables in order to appropriate the required power to each wheel, so this does minimise the issues to a degree.
It's common sense to a degree, that the same tyres should be worn on each side. Not everyone will notice the difference and not everyone has the capability of pushing their cars to the limits where the differences can be found, but there is irrefutable evidence that matched pairs are far less likely to see you in trouble on the road. These are the findings that our insurance compaines pay a lot attention to.
As far as legalities are concerned, insurance companies will investigate this area thoroughly if an accident is believed to hold the tyres as a contributory factor. Like your yearly premium, every insurer is different. With road safety getting increased funding and public awareness, it will only be a matter of time before some concrete legislation will be passed in favour of these sorts of actions.
As an example, Porsche have a series of tyres that are specific for their cars from all manufacturers. These have the denotion N0, N1, N2 and N3. They have a directive whereby all the four tyres must be exactly the same on their vehicle (save for sizes on wider rears) otherwise their warranty is invalidated.
Imagine how annoying that will be when 6 months after someone buys their 911 Turbo, their N2 tyre pops and all that is available is N3's. That's four new tyres and a light wallet for Mr 911.