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sp250 tire size

Ian Slade
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Joined: Sat Feb 13, 2016 9:54 am
Location: Scotland

Re: sp250 tire size

Post by Ian Slade »

All the 175/80 R15 tyres seem to be S rated (112 mph) so not suitable, in 185 the Vredestein Sprint Classic ( 185/70 R15 89H ) seems to be the best bet, it is a common tyre for the Porche 911 of around the 70's vintage so should be available over the pond
https://www.tirerack.com/tires/tires.js ... um=87HR5SC
or
https://www.ebay.com/itm/VREDESTEIN-Spr ... 2569645914
Owner since the 70's, Genghis is slightly to my left.

Stevesv8250
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Joined: Tue Mar 02, 2021 10:07 am
Location: Hullbridge Essex. Uk

Re: sp250 tire size

Post by Stevesv8250 »

Why are tyres that 112mph rated not suitable?

Chris_R
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Location: Twickenham

Re: sp250 tire size

Post by Chris_R »

There is a view that tyres fitted must be at least capable of the maximum speed of the car. That was the original manufacturers specification since they don't know how fast you will drive the car. In Germany it is also the law. In the UK you are only required to fit tyres capable of the use to which they are being put. There is no law that requires tyres in the UK to be capable of the maximum speed of the car since the national speed limit in the UK is 70mph and on a public road no one legally can go faster than 70mph and of course being a law abiding citizen you would not dream of breaking the national speed limits!
There is also a myth that insurance companies can refuse to payout if you have lower speed rated tyres than the maximum speed of the car. You would not be breaking the law by fitting them and insurance companies would not be able to penalise you either since you are totally within the law. Apart from speeding, the only law you would be breaking if you exceeded 112mph would be the construction and use regulations. If you crashed at 120mph then the insurance company might be able to deny payout on those grounds but at 70mph they could not. The other aspect is the load rating that you need to look at but I imagine that an SP250 will never exceed any tyres load rating.
Therefore if you never exceed 110mph on a public road, S rated tyres will be satisfactory from a speed rating point of view.

Ian Slade
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Joined: Sat Feb 13, 2016 9:54 am
Location: Scotland

Re: sp250 tire size

Post by Ian Slade »

It was explained to me some years ago that the speed rating was more to give a easy measuring system based on a cars performance, therefore the higher rated tyre would have a stronger carcass and able to withstand the stresses of acceleration and cornering, just because you are limited to 70 mph it doesn't mean you drive the car 20% lower than its capabilities, the same stresses can be experienced by the tyre except the centrifugal stress at the higher speed
Owner since the 70's, Genghis is slightly to my left.

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