Why do tyres have silly speed ratings?

[fjord]

Why does my diesel bmw have tyres rated for speed of up to 180mph?

It seems all common tyres have W/Y ratings, when in reality, theres no car on the road which will be using these types of tyres and able to reach those speeds.

So, why do normal regular cars have tyres on which are rated to such high speeds? Is there a reason?

[Zod]

Don't you like to have a margin of safety?

[nsi]

I fitted winter tyres to my BMW 7 series last year. They had a speed rating of 149mph.
I took it on a trip around Europe, including Germany. I did 149mph and the car was still pulling, but I eased off because I'd reached the limit of the tyres.

HTH

[fjord]

Zod said:

Don't you like to have a margin of safety?

A 100mph margin of safety?

[Chris944_S2]

fjord said:

Zod said:

Don't you like to have a margin of safety?

A 100mph margin of safety?

They sell the same tyres in the UK and Germany...

[TA14]

because the marketing guys think that that is what the punter wants and it will sell the cars. You bought the car so maybe they were right.

[sebhaque]

I would guess the tyres are the same ones as sold over on the continent, being German. Since it's more than likely at least one 3-series diesel will reach Vmax on the Autobahn, it seems fair.

I just checked the tyres on my Corsa and next door's Aygo, the Corsa's tyres are rated for 131mph, and the Aygo's for 118mph. About right, I think.

Not to mention that larger tyre sizes tend to be shared by cars of varying performance, so the tyre someone fits to their 1.6 Astra may also go on an E36 M3 (this probably isn't true, but you get the point).

[MX7]

It might be more economical to give all the tyres the same rating, than to make 2 or 3 different specs.

[Dog Star]

My car is most annoying in this respect. 151 top speed. So 2 mph too fast for V, so now has to have 186 rated Ws. Daft.

[Tango13]

Dog Star said:

My car is most annoying in this respect. 151 top speed. So 2 mph too fast for V, so now has to have 186 rated Ws. Daft.

Typo?

W = 168mph

Y = 186mph

[scorcher]

absolutely ridiculous having tyres rated to 180 mph plus. I mean the speed limit is 70 mph in this country.
Hang on though, what's the point in having cars that go faster than 70 ? Absolutely crazy this country!

[TA14]

Tango13 said:

Dog Star said:

My car is most annoying in this respect. 151 top speed. So 2 mph too fast for V, so now has to have 186 rated Ws. Daft.

Typo?

W = 168mph

Y = 186mph

Yes and he can fit V rated tyres if he wants to as long as it's appropriate for the driving that he does, which for most people it will be - crops up frequently on the TVR forums; if in doubt a quick call to the ins co will confirm.

[Frances The Mute]

The speed rating isn't all about terminal speed. It's about the forces that the vehicle can generate so the construction has to satisfy this.

In addition, whilst tyre constructions are getting much more specific, there is an ever-increasing breadth of the vehicles they have to be fitted to. As such, they have to satisfy the market demands.

[PoleDriver]

So where do those of us who have cars capable of speeds in excess of 186MPH get our tyres from then?

[ED209]

How does a tyre know how fast you are going?

Surely the load on a tyre cornering hard at say 60 mph will be greater than doing 150mph in a straight line?

[TA14]

PoleDriver said:

So where do those of us who have cars capable of speeds in excess of 186MPH get our tyres from then?

Usually the same plce as any other tyre: a good tyre retailer selling Z rated tyres.

[Pistom]

scorcher said:

absolutely ridiculous having tyres rated to 180 mph plus. I mean the speed limit is 70 mph in this country.
Hang on though, what's the point in having cars that go faster than 70 ? Absolutely crazy this country!

This is what I would expect from a member of BRAKE. Go hang your head in shame.

[PoleDriver]

TA14 said:

PoleDriver said:

So where do those of us who have cars capable of speeds in excess of 186MPH get our tyres from then?

Usually the same plce as any other tyre: a good tyre retailer selling Z rated tyres.

A Z rated tyre is guaranteed above 149 MPH

[Finlandia]

PoleDriver said:

TA14 said:

PoleDriver said:

So where do those of us who have cars capable of speeds in excess of 186MPH get our tyres from then?

Usually the same plce as any other tyre: a good tyre retailer selling Z rated tyres.

A Z rated tyre is guaranteed above 149 MPH

Isn't 187mph above 149mph then?

[McWigglebum4th]

Max rated speed of the tyres on my old landrover

30Mph