On Tue, 20 Feb 2018 23:49:48 +0100, Emanuel Berg
wrote:

Ian Field wrote:

Hard tyres last a long time but don't grip
well - soft tyres have grip but wear rapidly.

Yep.

They should put the tire hardness on the tire
just like the size and intended preassure!

https://www.bicycling.com/bikes-gear/components/know-your-rubber-quick-start-guide-mountain-bike-tire-design
See section under "Tread Compound":
Markus Hackmeyer, product manager at Schwalbe, feels that
hysteresis is a much more important measure than durometer:
"From our point of view the compound hysteresis (also known
as viscoelastic properties) is much more important than the
durometer. That means the durometer only can not define
the compound properties. That is the reason we do not state
the durometer values of our compounds."

The rubber hardness is also not uniform over the tire surface.
For automobile tires, it would not do for customers to notice that the
hardest rubber yields the most miles per tire. Rubber tires also
become harder as they age.
"Degradation of vulcanised rubber products..."
http://www.polymerjournals.com/pdfdownload/991052.pdf

Buy one of these:
https://www.ebay.com/sch/i.html?_nkw=rubber+hardness+meter
For bicycle tires, you want a Shore A gauge:
https://en.wikipedia.org/wiki/Shore_durometer
I've been conducting some disorganized rubber hardness testing for
about 5 years. So far, I've found nothing interesting, conclusive, or
worth announcing.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558