On tyres you have speedratings. What exactly does it mean? If you go over it will it blow up after a long run? Or even blow up very fast if you exceed it with let's say 30mph?

Speed ratings. Is that the maximum speed at the maximum load or the maximum speed at any load? Is there a derating curve for load?

i'm too lazy to look it up but the tyre bible (google it) will probably cover it.

I seem to recall its something like 10 mins at that speed without the tyre failing ..... which surprised me as i was expecting a lot more. Luckily i never intend driving the tin top at its max speed.

(not that the manufacturers are claiming at 10:01 the tyre will explode, just that it won't at 10:00)

One important thing to remember is SVA. If you're tyres aren't rated for the max speed you say the car is capable of you get handed a fail.

That could be very expensive if you've been over enthusiastic at application time (I've been told design weight and max speed are very difficult to get changed once they are in the system).

The tester disagreed with the design weight, so he put down on some form or other what he thought they should be, then asked me to sign it.

No great issue really, unless you're out on your figures.

"All tyres are rated with a speed letter. This indicates the maximum speed that the tyre can sustain for a ten minute endurance without coming to pieces" Tyre Bible.

10 minutes? Shocking.

Reminds me of the comment made on Top Gear, when test-driving the Veyron at full speed:

"At this speed the tyres will only last 30 minutes - but it doesn't matter, as a full tank of petrol only lasts 15 minutes!"

TYRE SPEED RATINGS TABLE

Steve

design weight? how do you get that???

is it the car with the fattest person that will fit and a full load of shopping?

quote:

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Originally posted by Mr Whippy
design weight? how do you get that???

is it the car with the fattest person that will fit and a full load of shopping?

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There is a proper formula in the SVA manual - they allow 75Kg per person, which is quite skinny! There's a luggage allowance per person, etc.

My 600Kg car ended up with a design weight of 800Kg on the official records.

David

[Edited on 24/12/07 by David Jenkins]