Challenge gravel grinder clincher mtb tyrethe challenge gravel grinder is an off road touring tyre, which features an aggressive superpoly tyre compound to provide exceptional rolling performance and traction whatever the riding conditions'. '.strtoupper('t')o ensure complete reliability, this tyre features double pps puncture protection and a 260 tpi casing'. '.strtoupper('t')his tyre is ready to be your companion on any xc adventure'. '.strtoupper('c')oming equipped with a fast rolling diamond centre, this tyre is perfect for all around gravel and adventure riding.features use all around gravel size 700 tyre width 36mm internal rim width 17 23mm tpi 260 bead aramid casing superpoly flat protection double pps bar 3 9 psi 45 130 weight 440gtechnologies challenge handmade clinchers hcl these handmade clinchers are made from the same materials and processes as our handmade tubulars but instead of sewing an inner tube inside the casing is wrapped around an aramid bead to form a tire that fits on a clincher rim'. '.strtoupper('t')he hcl is moulded flat, not in a horseshoe like a tlr or vcl'. '.strtoupper('t')his shape allows the casing to naturally deform over surface imperfections and minimize rolling resistance'. '.strtoupper('a') tubeless tire is moulded in a u shape to make the sidewalls rigid, so the system does not “burp” or lose air when it deforms after it encounters a surface imperfection'. '.strtoupper('t')he tubeless tire's stiff sidewall compromises its ability to equal a supple hcl with a latex inner tube.buy challenge wheels tyres from chain reaction cycles, the world's largest online bike store.