Jeff Liebermann wrote:

https://www.bicycling.com/bikes-gear/components/know-your-rubber-quick-start-guide-mountain-bike-tire-design
From the same paragraph as the above quote:
Hysteresis A dynamic measurement of energy
loss in the rubber compound, this can also
relate to rolling resistance or tire
"grip." A 70sA compound typically has
little energy loss, while a 40sA has
a large percentage of energy loss.

BTW what notation is 70sA and 40sA?

--
underground experts united
http://user.it.uu.se/~embe8573