Bontrager’s Team Issue GR1 tyres come in 35mm or this 40mm width, and are designed principally for gravel use. I tested the larger size.
Built on a 120 TPI casing, the GR1 has Bontrager’s Inner Strength supple, lightweight Nylon inserts protecting the sidewalls, and its tread comprises rubber compounds of durometer 60a and 52a (this number determines softness of the compound). My 40mm test tyres weighed 410g each.
Fitting the GR1s on to my Mavic Allroad Pro wheels was about as simple as tubeless tyres are always meant to be, but rarely are.
They were fairly easily pushed in to place by hand, and then 40 psi from a track pump seated them first time. They too stayed in place while adding sealant, and measured 41mm wide once inflated.
The Bontragers’ rounded shape gives them wonderfully consistent handling, with predictable transitions from upright to any cornering angle.
Hundreds of small, shallow, angled tread blocks bite in to every surface for confident grip in loose, dry conditions, and do a decent job when things are damp too, but sloppy mud is a step too far.
They roll fast on tarmac with no buzz, and feel supple and responsive.