... (235/45/R17 W), she has a set of Michelin Pilot Sport's at the moment and the front's are almost down to 2mm tread depth. As cash is tight I have been looking at mid range tyres. I found this website which is a test on 50 tyres that underwent a wet and dry brake test from 100KMH and it shows some interesting results.
Well, you know what will happen with this method; you'll select tyres that are good in braking, and not in anything else. provided that you are happy with that (and it is better than having tyres that aren't good in braking...).
Its from these results that I started to look at the Kumho Ecsta's (came 15th in the test) and the Nankang NS20's (came 21st). Looking on the black circles website, it seems there aren't many tyres that offer low rolling resistance and hence better fuel economy. Samples shown below (prices are per tyre inc fitting).
Nankang £80 'E'
Kumho £95 'C'
Hankook £109 'B'
So I had pretty much decided on the Kumho tyre..
Well, 'E' rated isn't that good for fuel economy; you could hardly consider that a fuel economy tyre. 'C' or 'B' are obviously better.
The trouble is that if you go for fuel economy, you'll get better fuel economy and worse grip. Now this may not be too bad with 235/45/17s, because that's a reasonable amount of rubber and it doesn't have to be the softest, squidgiest, rubber to get a reasonable amount of grip. And that's not at all bad, if you are happy with the trade-off that you are making.
So I had pretty much decided on the Kumho tyre, but has anyone else noticed any difference with fuel economy when using different brands of tyres? The 'B' rated Hankook is the most fuel efficient tyre offered by Black Circles.
Yes. Well, the easiest thing is note the temperatures that the tyres run at on a trip at normal cruising speeds on an extended trip. So, out with the optical pyrometer, and you can definitely see a difference, but it is difficult to know how that relates to, eg, fuel economy (but it does confirm that it isn't just bull droppings). As far as I could tell, on my old Cougar, there was about 1 mpg difference between (relatively fuel efficient) Michelin Pilots and (not as good, but not the worst tyres for FE by any means) Kumho (KU19s) on the front. The trouble with that was that the precision of measurement was about+/- 1 mpg, so that would be anywhere between 0 and 2 mpg, but 1 mpg seemed like a decent estimate.
Now if you take the Official A....G classification at face value (which I don't), there is the possibility of making a calculation (which, again, will be pretty approximate, but there you go), As far as I can tell, and per tyre (not pair, or four tyres) and over 9000 mixed miles qnd relative to 'A' rated tyres (and I don't care that you can't find them, because I sort-of understand why, although I do not understand why 'D' tyres don't exist, but that's life for you)
A B C D E F G
£, @ 1.40/l 0 26 57 - 91 128 1 63
(with the original info from some tyre website or another, and, ultimately, who knows about them, too).
But, if you want a reasonable first order estimation, I can't do better than suggest that, per tyre, and over 9000 miles (roughly my average annual mileage) you subtract the two relevant figures from one another. Its a bigger number than I might have expected, but that's what happens when you do the multiplying thing by a relatively big number.
On the one hand, it does look as if paying a little extra for fuel economy tyres can pay for itself, on the other you pay upfront and receive back in trivially small amounts over an extended period. And lose grip...
As they say 'you pays your money and you takes your choice'.