What limits a TT bike geometry from becoming basically a front-recumbent?


New Member
Jan 9, 2007
I know that recumbents are not allows in races, I suppose due to less safe speeds in flat/down hills. But, are there rules preventing a TT bike from having, say, the pedals behind the rider instead of below? He'd be prone and his wind signature would decrease markedly because he'd now be pushing up/down, but his body parallel to the ground.
The short answer is, yes, there are strict rules for what defines a TT bike (as well as road bike). Moving the cranks behind the rider would be illegal.

The Union Cycliste Internationale (UCI) is the governing body over international cycling. They have very specific rules on equipment. Most national cycling governing bodies have subsequently adopted those rules.

Here's a link to the UCI rulebook containing the specifics (chapter on equipment starts on page 54):

All the UCI rulebooks and guidelines can be found here: