Just looking on the Black Circles website to see what tyres they have, and what they have to say about those tyre rating letters, A-G (first I'd heard of them to be honest!). And they have this to say -

 

"A tyre's rolling resistance score ranges from A to G. Over the life of the tyre, fitting an A rated tyre could save you up to 6 litres of fuel when compared to a G rated tyre." Hmmm, a 6 litre saving over, say, 20,000 miles. I can't get too excited about this! Obviously they can't mean this, so what do they mean?

 

And then, for braking distance -

 

"A tyre's wet grip capacity is expressed in Grades from A to G. The difference in braking distances between each grade is roughly 3m - an average car length. This makes average stopping distance between an A and G rated tyre 18m. That's 4 car lengths."  Er, wouldn't that be 6 car lengths, by their own arithmetic?

 

Hopefully somebody from Black Circles can tidy this up a bit

 

 

How many cars have you seen that are only 3m long?

Thanks for opening that particular can of worms

 

Yes it's BlackCircles own rubbish spiel, but it's I think a misunderstanding of the official regs.

 

If you look at the official EU tyre labelling regs (see https://www.gov.uk/guidance/eu-tyre-labeling-regulation-guidance-for-business-and-industry) there is an official tyre industry guidance booklet you can download.

 

On fuel efficiency they mention the difference between A and G being around 7.5%. So depending on how much 'the life of the tyre' is, this might be true - but i'd be a bit annoyed if my tyres only lasted through two tanks of fuel

I can only assume that someone's managed to calculate that 6 litres of fuel is 7.5% of one vehicles fuel tank, and then totally misunderstood what they are trying to calculate/write  

 

On the wet grip they are correct - difference from A to G is stated officially as being 18m stopping distance when braking at 50mph. But yes the math even by their own calcs is well off.

 

There is one big but to all this though... since there is no official or conformed testing across all tyres and the testing and labelling is left up to individual manufacturers, the whole thing is pointless anyway. One manufacturers C might correspond with another manufacturers A etc etc. Really it's meaningless - at least the BlackCircles descriptions are amusing if nothing else!

Edited 8 February, 20179 yr by Girardi

3 hours ago, KenONeill said:

How many cars have you seen that are only 3m long?

 

Quite right, I didn't think to check that! My Yeti is 4.2m. Even a Fiat 500 (SWMBO wants one) is 3.5 m. So their "4 car lengths" (for 18m) is reasonable, they just need to change the "roughly 3m - an average car length" bit.

"There is one big but to all this though... since there is no official or conformed testing across all tyres and the testing and labelling is left up to individual manufacturers, the whole thing is pointless anyway. One manufacturers C might correspond with another manufacturers A etc etc. Really it's meaningless"

 

Wonderful, just when I thought I'd found a useful point of comparison! Thanks for the warning.

tyrereviews.co.uk has links to all the tyre group tests run by German Auto magazines so you can at least see how 10 or 20 tyres compared to each other.