Tyre question...

Just realised that I have 235/70/16 tyres on but my spare is a 265/70/16. Been meaning to get it changed before now but not had time. Now going P&P on Sunday and not going to have a chance to change it! :doh:

If for some dredded reason I have to put the spare on, what kinda damage - if any - will I do? I have a 1.5 hours drive home!

Plenty of garages open Saturday? I'd get it sorted, if you're short of money then chuck a part-worn road tyre on. The tranmission will cope okay but running different size tyres on an axle is illegal, basically.

Thanks for the reply. I will def get it changed on Saturday if I get the time. If I get a problem I'll just have to blag the local plod and hope I don't get ma ticket. At least I know there will be no lasting damage running the bigger one.

paul_c said:

Plenty of garages open Saturday? I'd get it sorted, if you're short of money then chuck a part-worn road tyre on. The tranmission will cope okay but running different size tyres on an axle is illegal, basically.

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What about these space savers like in VW's or BMW's? I thought that its O.K. as long as it just for emergency purposes.

smurphy said:

What about these space savers like in VW's or BMW's? I thought that its O.K. as long as it just for emergency purposes.

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Good question. Basically it comes down to this: strictly interpreting the law, the only tyre sizes which can be used on a car are those which the car has been type approved to use. Cars which have a space saver spare will have been approved. This might mean they've been designed with this in mind, for example have a neutral steering characteristic which makes it safe up to a certain speed (obviously not safe at the car's max speed! Hence the warning labels, often its 80kph or so). The Disco was never type approved to use different size tyres on the same axle, so it will be illegal like this. And yes....I know applying that law strictly, renders a LOT of cars on the road illegal! But there you go.

Legality is one element of this question but the other is the potential damage you could do to the diff if you run unequal sized tyres.

Basically your odd wheel will cover 15cm more per revolution than the other side of the axle, your diff will compensate for that as it will 'see' that you are constantly turning a corner - however if your diff is already worn, it may be enough to destroy it completely!

Having said that - I've just fitted 235/85's but my spare is still 235/70... If I ever need to use it i'll minimise use and limit speed until replaced - until I can afford another 235/85 for the spare that is!