Tom A. wrote:
- Once you start adding tread texture beyond a file tread (i.e. going to a diamond-tread center and/or small knobs), you start slowing down the pavement performance by quite a bit. All of that additional rubber flexes on hard surfaces and causes energy losses.
- In researching off-pavement Crr measurements, the data I've seen shows it's pretty clear that once on the dirt, it's the compression of the surface that starts driving the rolling resistance. Measurements with MTBs shows that the lower the pressures that can be run, the lower the Crr for a particular setup. This means that for fast performance off-pavement, you want to run the widest tires you can fit at the lowest pressures that will protect your equipment from damage.
You know, this kind of confirms something in my mind. I've ridden a Trek Stache (29x3.0) four or five times now and it always "felt" crazy fast here on FL single track which is usually sandy, loose over hard and sometimes clay. Bontrager's Chupacabra tires aren't anything special from a construction standpoint: 120tpi nylon casing and a generic 50 or 60a rubber compound. However given the likely size of the contact path, they probably don't compress the surface much compared to a 29x2.0 XC tire.
This makes me really want to try out the Continental Speed Kings now in 27.5x2.2 on my "gravel" bike :)