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It's really a rule meant for road racing to keep TT bikes from running a small front wheel to get closer while drafting.

The UCI has a rule that states a bicycle must have same size wheels. So they could run a 79 incher, but not a 29" front 27.5" rear. A UCI representative had an interview on here or Dirt saying they may look into changing the equal size wheel rule starting 2018. I'm interested to try anything, 29, 79, 69, even a 24 front 29 rear, why not!

Irode this bike recently with Brian,on trails i ride regularly (packed dirt, leaf covered tree roots, busy and with some small log jumps/obstacles) and rode it along the lines of dirt bike. i would throw it into corners, try and maintain corner speed and squirt it out of them. This bike rails corners and then when it comes to stamping on the pedals on the exits, I didn’t feel the usual softened bob on back end of the bike on every downward pedal stroke. On the straighter level sections, I would speed up and literally feel the rear suspension...