Car tyre speed rating question

[orange71]

Any reason why I shouldn't get an H rated tyre (rated for 130mph) for my diesel Saab which is never likely to approach that sort of speed, rather than a more expensive V rated one (150mph)?

 

[suburbanreuben]

Yes. If you have a crash, your insurers may decide not to pay out, since you have fitted tyres not meeting manufacturers requirements. It's not just about top speed.
The only valid excuse for fitting a lower rated tyre is when fitting winter tyres, although Vredestein do a W rated winter tyre...

 

[orange71]

Thanks - just did a bit of googling and this seemed to be the generally accepted answer.

 

[REKIBorter]

The speed rating must be the same as that which was fitted to the car from new, it's the law (unless there is a change of use ie. snow tyres mentioned above). Don't think of it as a maximum speed the car will never be driven at. It is more to do with the torque the car can generate. In other words replace like for like. I have worked on the technical side of the tyre industry for nearly 25 years so if you need to know more pm me.

 

[SF Klein]

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[REKIBorter]

ZR looks a bit misleading, why have a tyre with speed rating of W-168 and Y-186 when ZR rates at 149mph+

ZR rated tyres do not have load ratings marked on the tyre, the load and maximun speed rating are certified by the manufacturer, this certificate can be viewed on request. Saying that I have never seen one or been asked to get one. And remember that a speed rating is more to do with the torque the vehicle can generate and not the maximum speed the vehicle can do.

Some may be confused by H & V appearing out of alphabetical order in the speed rating sequence. This dates back to the late 60's and early 70's when radial tyres were speed rated S - standard, H - high and V - very high.

I'll get my anorak :roll:

Tyre, easy, just squirt rubber into a mould and get a donkey to stick them on your car. If only it was that easy.

 

[SF Klein]

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[REKIBorter]

Some diesel powered cars have XL (Extra Load) rated tyres. A diesel engine is much heavier than the equivilant sized / power petrol engine so the tyres fitted need to be able to carry more weight. The difference in power between diesel / petrol engines in similar car models is not enough to warrant a higher speed rating on the diesel engined versions. Most diesel powered cars have the top speed restricted.

 

[SF Klein]

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[REKIBorter]

Not just the top speed the vehicle. My own car is diesel powered, has 204bhp but is electronicaly limited to 130mph max. It has W rated tyres fitted.