TT Bike v. Tri Bike

I believe that a tri bike has a steeper seat tube angle so that it uses more of the hamstrings than the quads to make it easier when running. 

There might be other rules for a TT bike based on the UCI rules.  I don't know all of those.

This might help some: http://www.kgsbikes.com/news/in-depth-road-bikes-vs--triathlon-bikes

The bikes are the same but may be set up differently.

In a triathlon you need to be able to run afterwards whereas in a TT you just need to go as fast as possible and nothing else matters.

Straight extensions: they allow for more leverage to be exerted on the bars, increasing power to the pedals. Not as important when you're pushing 250 watts or so, but when you're generating 400+ it's more important.

For the most part they're one in the same. Up until recently Europe based bike companies built their TT/Tri bikes to conform to UCI standards that are not in effect for triathlon. One of these standards is that the seat tip must be 5cm or greater behind the center of the bottom bracket. In order to achieve this the seat angle needs to be slack (74-76 degrees). These bikes were/are typically referred to as TT bikes.

A bike designed specifically for triathlon does not need to meet this standard and will typically be designed with a seat tube angle of 76 degrees or greater (78 being the popular choice). The steeper seat angle allows for a more forward position which in turn allows for a lower and more aerodynamic position.

Today most bike companies design their TT/Tri bikes to accommodate both markets by using dual position saddle mounts (cervelo and felt are great examples), a sliding mount (scott), or a replaceable saddle mount that allows for slacker/steeper seat positions (Orbea, Ridley, etc).

As for the use of straight bars: as already pointed out they are better for leverage then a ski-tip bar. Also many people, myself included, find them more comfortable. Lastly many people feel they're more aerodynamic, but that's open to debate.

scott

Nope.

The only reason they are set up differently is because of UCI regulations.  Otherwise they are the same thing.  The P4 you see in the Tour is the same P4 you can ride in a tri.

Position on the bike has almost NOTHING to do with how you can run afterward.  That is a myth.

Are you stating this based on personal experience? or do you know of some scientific research?  Please explain.

I don't agree, nor disagree.  But, if it is a myth, then it is like many myths, oft repeated.  I'm pretty sure I've read it in a triathlon magazine, and in articles on slowtwitch, etc.

I have not objectively tested it, but the logical explanations I've read make sense to me.

Bill

Let's just say that no one has been able to prove that a forward position is anymore beneficial to running off the bike then a slack position. I know there have been some studies, but as far as I know nothing conclusive has come from them.

Considering the fastest runners in triathlon, ITU racers, typically ride slacker angled bikes I'm not sure there's anecdotal evidence to support the theory either.

scott

As Rick pointed out, this is not true, and is a myth that has been spread for years. There is some science to the myth, you are working the muscles differently with the two different positions. Someone took this as making it easier to run afterwards, but there is nothing I have seen to support the different positions aside from UCI rules and aerodynamics.