Triathlon - TT versus Triathlon Frame

Often the terms Time trial and Triathlon geometry are used interchangably - is this correct? Are there differences between time trial bikes (more laid back seat post, stiffer frame, etc) versus bikes made for triathlons? I'm currently looking at the Isaac Joule and I'm just wondering if it is a strict TT frame or if it was designed to provide some comfort over a long ride.

Any thoughts on Isaac bikes in general?

I have not seen any differance in frames between TT or Triathlon frames. They are actually the same. Look at the Cervelo P3C. Team CSC uses them for TT, yet pro Ironman Triathlete Lisa Bently uses one...

Ain't Tri frames more lax?

Meaning something like Softride is OK to use where in TT it's not?

Generally......

A triathlon frame is 75 degrees or steeper, some getting up to 81 degrees. This helps with the bike to run because you use different muscles to run.

A TT frame can be anywhere from 73 degrees to 81 degrees. My TT frame doubles as my Tri frame solely because I am not going to buy a slack angle bike just to ride a few TT's a year. I also make plenty of power in a steeper angle. The term is generally used interchangeably because 99.9% of people use their tri bike as their tt bike. Now, uscf rules state that the nose of the saddle must be 5cm behind the bottom bracket. That is why you see CSC riding a P3 with the nose of the saddle cut off and riding a steeper angle. As far as I know, there is no such rule in triathlon, so you can ride bikes like the P3 and Softride.

But it basically comes down to preference and where you make the most power in the aero position.

And to answer your question, the Joule, with a 76 degree angle, is considered steep and would "technically" fall into a triathlon category, but would also be a fine bike for TT's.