So, these new EU tyre ratings...

jase1

They've only been around for a few weeks, but I keep finding anomalies.

First was the amusing spectacle of the Michelin Energy Saver which, despite being flat bottom of Auto Express's recent tyre test for wet grip etc, was the only one with a Grade A rating for wet grip.

Now, I look on MyTyres (which has just today loaded up the gradings) for an all-season tyre to possibly put on the back wheels of my car as an all-year round thing, and what do I find?

http://www.mytyres.co.uk/cgi-bin/rshop.pl?suchen=Ordern&cart_id=62010385.110.30341&ranzahl=4&Breite=205&Quer=55&Felge=16&Speed=V&Transport=P&dsco=110&sowigan=GAN&Ang_pro_Seite=20

So, the best all-season tyre for wet grip is a cheap Nankang? Really?

:rotfl:

These aren't self-assessed are they? They're done to a set standard as far as I know...

EDIT: Oh, and then the Toyo T1R (a known good tyre) gets a grade E, while a Goodride cheapy (a known not-so-good tyre) gets a C. These ratings really aren't worth the paper they are printed on are they?

Lum

Kind of like EU fuel consumption figures then?

mikey72

Maybe that's the difference.
They're done on a machine, with repeatable calibrated results.
Not by the Continental engineer on their test track, with his uncalibrated right foot, and his paycheck from Continental waiting.
I use Michelin Energy Saver, and they perform very well in the wet.

Lum

Repeatable calibrated results that don't actually reflect reality. That's certainly the case with the fuel consumption tests which can be gamed with simple things like adding a shift light.

You're right that any test done at the Contidrome is completely worthless, however.

jase1

Who said anything about the Contidrome?

Yes, AE may be unscientific, but in the manufacturers' pockets?

At the end of the day, low rolling resistance = poor grip (relatively). Good grip = high rolling resistance. It's all about the compromise.

Would you buy a Goodride in preference to a Toyo?

mikey72

jase1 wrote: »

Who said anything about the Contidrome?

Yes, AE may be unscientific, but in the manufacturers' pockets?

At the end of the day, low rolling resistance = poor grip (relatively). Good grip = high rolling resistance. It's all about the compromise.

Would you buy a Goodride in preference to a Toyo?

What's the correlation between grip and rolling resistance?

jase1

The way manufacturers typically achieve low rolling resistance is to make the tyre as smooth as possible, which is achieved with fewer blocks in the tread and harder compound.

These are two traits that have a negative impact on grip in the wet. The manufacturer then needs to get clever with the compounds to overcome the problem. In all tests that I have seen (and from personal experience) the low RR tyres are always poorer than the tyres that optimise wet grip (by making the compound softer, with differing tread patterns and correspondingly increase RR).

The 'ideal' tyre, insofar as RR is concerned, is a completely smooth tyre with no tread pattern. That tyre, of course, is a complete disaster in a thunderstorm.

mikey72

Interesting test
But how do they work out the results.
The winner, Goodyear, gets 100% overall
But the actual average is 95.97%

And as that's such a glaring mismatch, I added all the other tres results together.
The order of overall points is

Goodyear
Conti
Nexan
Vred
Dunlop
Mich
Nokian
Bridgestone

So what's the result table based on?

jase1

I was only really looking at the wet grip and associated parts (aquaplaning, wet handling etc), because frankly it's the only thing that genuinely changes between summer tyres that amounts to anything meaningful.

mikey72

jase1 wrote: »

The way manufacturers typically achieve low rolling resistance is to make the tyre as smooth as possible, which is achieved with fewer blocks in the tread and harder compound.

These are two traits that have a negative impact on grip in the wet. The manufacturer then needs to get clever with the compounds to overcome the problem. In all tests that I have seen (and from personal experience) the low RR tyres are always poorer than the tyres that optimise wet grip (by making the compound softer, with differing tread patterns and correspondingly increase RR).

The 'ideal' tyre, insofar as RR is concerned, is a completely smooth tyre with no tread pattern. That tyre, of course, is a complete disaster in a thunderstorm.

The rr is mainly a result of the deformation of the sidewall.
A softer sidewall, and the tyre deforms outwards at the base as it rolls, and this flexing is what needs to be overcome, and takes the energy.
A more rigid sidewall, and it's easier to turn.
(Hence underinflated tyres are worse for the economy, over inflated are better)

All the tread, and compound does mainly is stick to the road, a harder tyre may spin, but won't affect the rr, and a softer tyre won't "stick", when it rotates.
A softer tread may deform more, but nowhere near as much as the sidewall.

mikey72

Wet conering Nokian won 100
Wet braking Nokian won 100
Wet handling, Nokian won 100

Goodyear was 98, 94.9, 98.2
Michelin was 97.6, 90.1 94.9

Bridgestone was 88.2 for wet braking