Michelin Energy E3A or smaller Goodyear.
Discussion
The Michelin Energy E3A tyre is supposed to give about 5% better fuel economy.
The 195x65x15 Michelin E3A costs £10 more than Goodyear Hydra-grip so thats £40 more for 4 tyre.
Would you save enough to pull back that £40?.
What i would like to know is, if you bought 185x70x15 tyres instead of 195x65x15 would you save 5% on fuel because you are creating less friction?.
Surely not all make of tyres give the same ammount of grip so a excellent 185 tyre might give more grip in an emergency than an average 195 tyre.
The 195x65x15 Michelin E3A costs £10 more than Goodyear Hydra-grip so thats £40 more for 4 tyre.
Would you save enough to pull back that £40?.
What i would like to know is, if you bought 185x70x15 tyres instead of 195x65x15 would you save 5% on fuel because you are creating less friction?.
Surely not all make of tyres give the same ammount of grip so a excellent 185 tyre might give more grip in an emergency than an average 195 tyre.
Ooh, a maths question. Given that petrol is around £1 a litre and if you're lucky your car averages 30 mpg (about 6.67 miles per litre), then for every mile you drive you use 0.15 of a litre - 15p per mile. If you gain a 5% saving in economy from these tyres you'll save 0.75 pence. To save £40, you'll need to cover a little over 5333 miles to recoup the extra cost.
Now, the rolling resistance of a tyre is a small part of the fuel economy issue - aerodynamic drag is much more important. I saw details of an independent test which suggested the improvement was of the order of 2.5% - so you're looking at nearly 11,000 miles to recoup such extra cost - more if you're profligate with the right foot. In any case you might then be looking at a set of new tyres.
As for 'grip' theres very little difference in grip (measured as sliding friction rather than things such as cornering stiffness) for most tyres (the R-type tyres like the Dunlop SSR or Pirelli P-Zero C tend to have around 20% more grip than 'normal' tyres). I doubt you'd be able to tell any difference - especially on road where you won't be licking the edge of the performance envelope.
Now, the rolling resistance of a tyre is a small part of the fuel economy issue - aerodynamic drag is much more important. I saw details of an independent test which suggested the improvement was of the order of 2.5% - so you're looking at nearly 11,000 miles to recoup such extra cost - more if you're profligate with the right foot. In any case you might then be looking at a set of new tyres.
As for 'grip' theres very little difference in grip (measured as sliding friction rather than things such as cornering stiffness) for most tyres (the R-type tyres like the Dunlop SSR or Pirelli P-Zero C tend to have around 20% more grip than 'normal' tyres). I doubt you'd be able to tell any difference - especially on road where you won't be licking the edge of the performance envelope.
StressedDave said:
As for 'grip' theres very little difference in grip (measured as sliding friction rather than things such as cornering stiffness) for most tyres (the R-type tyres like the Dunlop SSR or Pirelli P-Zero C tend to have around 20% more grip than 'normal' tyres). I doubt you'd be able to tell any difference - especially on road where you won't be licking the edge of the performance envelope.
So are you saying that a Dunlop or Pirelli quality tyre has 20%more grip than a normal tyre of equivalant size, if thats the case would 2 identical cars one on Dunlop 165`s (example only)and another on cheapo 195`s go "round the track" in the same time.
Like you say the only time you might be "licking the envelope" is in an emergency stop and i can`t remember the last time i did one.
If this was the case surely 165`s would give you better mpg than 195`s with the same amount of grip.
slowly slowly said:
As for 'grip' theres very little difference in grip (measured as sliding friction rather than things such as cornering stiffness) for most tyres (the R-type tyres like the Dunlop SSR or Pirelli P-Zero C tend to have around 20% more grip than 'normal' tyres). I doubt you'd be able to tell any difference - especially on road where you won't be licking the edge of the performance envelope.
So are you saying that a Dunlop or Pirelli quality tyre has 20%more grip than a normal tyre of equivalant size, if thats the case would 2 identical cars one on Dunlop 165`s (example only)and another on cheapo 195`s go "round the track" in the same time.
No, the tyre's I mentioned are the 'trackday specials' which have very different rubber compounds that give lots more grip (in the dry) at the expensed of reduced longevity. As for lap times - yes, provided you're good enough to keep the tyre on the limit of adhesion.
What' wrong - was that answer not 100% accurate and factual - or should I have a nice extra career as a management consultant.
The longer version is yes - quite a lot. The cornering stiffness has very little to do with the rubber in contact with the road and much more to do with the internal construction of the casing and the belts. Everyone in the market is hugely propritary in this field both in terms of material and construction so you get a massive variation in properties. It's one argument for sticking with the OE tyres - the car has been engineered for them so you often (BOCTAOE) get the best performance with what it came out of the factory with.
The longer version is yes - quite a lot. The cornering stiffness has very little to do with the rubber in contact with the road and much more to do with the internal construction of the casing and the belts. Everyone in the market is hugely propritary in this field both in terms of material and construction so you get a massive variation in properties. It's one argument for sticking with the OE tyres - the car has been engineered for them so you often (BOCTAOE) get the best performance with what it came out of the factory with.
Aha. It gets complicated, then.
I assume cornering stiffness is higher than sliding friction - is it a significant percentage? Is cornering stiffness similar to the coefficient of rolling friction?
Suddenly had an image of a large porcine beast in its natural habitat with its sleeves rolled up, asking if anyone "fancied some".
I assume cornering stiffness is higher than sliding friction - is it a significant percentage? Is cornering stiffness similar to the coefficient of rolling friction?
StressedDave said:
What' wrong ...
Suddenly had an image of a large porcine beast in its natural habitat with its sleeves rolled up, asking if anyone "fancied some".
To quote a famous forensic science video, you're compataing Apples with Kumquats (no, I don't know why - it's something to do with document examination). Coefficient of friction is dimensionless (it's the ratio of friction force to vertical load) and is typically 1 for a normal road tyre (1.2 for the R-types mentioned before). Cornering stiffness has units of N/rad (or N/degree for those not working in SI units) and is the ratio of cornering force to slip angle at the contact patch. Values tend to be 3000 N/deg upwards.
I remember a magazine tyre test a few years back. They tested about a dozen family car tyres. The chief tester identified 10 out of 12 of the tyres correctly without seeing what they were but just by driving on them!
Yes there is a huge difference in carcass construction & its has a very dramatic effect on how the car handles & feels.
Yes there is a huge difference in carcass construction & its has a very dramatic effect on how the car handles & feels.
I've had first hand experience of this. When Pirelli stopped making the PZero Assimetrico in the right size for my Lancia, I fitted a pair of the replacement - PZero Nero - to the front. Instantly, the car suffered tremendous understeer where there had been none before.
After several months of cursing Pirelli for making an inferior tyre, the rears needed changing too. I had an extensive discussion with John Whalley (a Lancia specialist) who really rated the Nero, but said the stiff sidewall of the rear tyres was causing the car to try and push on, while the softer sidewalls of the new (front) tyres allowed them to "roll" on the rims more.
Against my gut feeling at the time, I trusted him and put some more Neros on the rear, and he was right - the car was transformed again. Ultimately, it will still understeer more than when it was on the original PZeros all round, but with a slightly different cornering technique you can get all four wheels doing an equal amount of work and a very "neutral" stance.
After several months of cursing Pirelli for making an inferior tyre, the rears needed changing too. I had an extensive discussion with John Whalley (a Lancia specialist) who really rated the Nero, but said the stiff sidewall of the rear tyres was causing the car to try and push on, while the softer sidewalls of the new (front) tyres allowed them to "roll" on the rims more.
Against my gut feeling at the time, I trusted him and put some more Neros on the rear, and he was right - the car was transformed again. Ultimately, it will still understeer more than when it was on the original PZeros all round, but with a slightly different cornering technique you can get all four wheels doing an equal amount of work and a very "neutral" stance.
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