Despite their name, Bontrager’s R4 320 Open Tubulars are actually clinchers. They take their ‘Open Tubular’ name from the fact they’re made using the same materials and techniques as their tubular equivalents – specifically, the Bontrager tyres used by the Trek-Segafredo team of Fabian Cancellara and co.
Or at least these are the tyres Trek use when they’re not bouncing around the cobbles of Roubaix on unmarked FMB or Veloflex tyres. The R4 320 Open Tubulars are just a little cheaper, and you don’t have to mess around with glue or tape.
What that means in practice is these clinchers have exactly the same 320tpi (that’s threads per inch) construction as their tubular siblings. The higher the thread count on a tyre, the more supple the tyre will be and, in case you’re unsure, 320 is right up at the higher end when it comes to thread counts.
Softer, supple tyres conform to the road surface better than harder, more rigid ones, and they’ll grip the road better as a result.