Hi,
The other week I asked about tyre rat>The D rating isn't used, so in practice, for fuel efficiency it tends to
be a choice of C or E. I assume any manufacturer whose product was
>borderline would make the effort to get it into C rather than E but that
>may mean that C is not much better than E. The economy is a lab test and
>formula for rolling resistance so it probably isn't significant for stop
>start urban driving. The difference between E and C might amount to 3-4%
>fuel saving in favourable circumstances.
>
>Wet Grip, again D isn't used, Some are rated A in one sizes and B in
>another. I haven't noticed anything less than C, but maybe because I
>have ignored the cheaper brands. Difference between one grade and the
>next may be about one car length in stopping distance in the wet. But
>again, based on lab tests etc, so difficult to tell how much real >difference.
I was surprised I could not find any official (gov.uk) web sites about this.
I was interested that class D is not used. According to the blackcircles faq:
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D is being omitted to make a clearer distinction between good and bad tyres! This does mean the gap between Michelin C rated and Uniroyal E rated isn't as big as it would first seem. I can't work out the resistance/fuel rating. The same url says that G tyres will use 6L more over 600 miles.A page at Kwikfit:
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says much the same thing: 0.5L per 60 miles. I'm sure this all adds up if you drive tens of thousands of miles, but even so, it doesn't seem like a very big difference and I wonder whether other aspects of driving would account for bigger differences in fuel consumption, i.e. could someone driving smoothly on G tyres use less fuel than someone stop/starting and accelerating and braking hard in the same car on A rated tyres?Perhaps this rating is nothing to get worried about?
The wet rating sounds like it might be more useful as each letter adds a car length before the car stops and this could make the difference between hitting something and not. It would appear than neither class D nor G are used though.