This is the new bontrager 2013 r4 aero 700c folding clincher triathlontime trial tyre the worlds fastest tire combines the aerodynamics and low rolling resistance of the r4 tire with a new streamlined profile saving you 9 seconds over the next fastest tire in a 10k time trial more than 37 seconds faster over a 40k time trial than bontragers closest competitor they set out to create a tire that excelled in aerodynamics and in rolling resistance the result the fastest tire on the market