Just wondering. Took delivery of a 60A Maxxis High Roller today, and the rubber feels more tacky than a DTC Nevegal, which is supposed to be 50/60 on the shoulders/centre respectively. Is it just some kind of residue from the manufacturing process, or is it actually tackier?

They often feel especially tacky to touch when new – run it for a while and then compare them.

Ah ok, will do…

Plus it appears Maxxis reckon their 60A compound is special:

Only Maxxis has exclusive use of the Exxpro polymer, created by Exxon. Our engineers have blended Exxpro with our own MaxxPro elastomer, which allows soft tires to have a long tread life without compromising the increase in traction that soft compounds provide.

All MaxxPro tires benefit from 100% perfectly dispersed carbon black.
Maxxis’ technology allows for the carbon black molecules to be ground smaller and thus more closely arranged than carbon black found in other manufacturer’s compounds. The result is a smoother tire surface that wears longer than traditional compounds. Maxxis’ perfect dispersion of carbon black also minimizes cut growth in instances where the tread becomes torn or cut. The tire also rolls faster as a result of the rubber recovering more slowly after shaping itself to the terrain. MaxxPro is one of the many technological advantages brought about by our more than thirty years of producing bicycle tires.

But then they would say that.

The numbers refer to shores hardness which is a standardised test so they are directly comparable assuming they’ve all used the same test. There are different test methods for different materials. They’re all rubber so should all be the same. HTH

Thanks, that does indeed help! So strictly speaking its a hardness test? Just wondering aloud, would it be possible for two different rubber compounds to possess similar hardness but different friction coefficients?

Somebody on NSMB had an actual durometer meter (funny that) and tested different compounds. There seemed to be quite a lot of variance between claimed values and reality.

Apart from that there is of course differences in the rubber itself, for example Continentals Black Chili compound is not so good only because of the durometer, actually the softness varies quite a bit from one model to another (Rain King is softer then Rubber Queen is softer then Mountain King).

two different rubber compounds to possess similar hardness but different friction coefficients

Yes, all things being equal softer rubber = higher coeficient of friction, but very rarely are all things equal.

You could start off with a really hard compound and try and make it sticky, or a really soft compound and try and make it long lasting.

well: http://en.wikipedia.org/wiki/Shore_durometer

but: The material under test should be a minimum of 6.4 mm (.25 inch) thick.

so: is every sausage the same length?