[Psydotek]

For those of you with a dedicated road and tri/TT bike, what's the top tube length difference between the two?

I've been researching various frames and one thing i remember reading is that a triathlon bike usually has a significantly shorter top tube compared to regular road bike geometry. The only thing i can't figure out is just how much shorter it should be...

My regular road bike has a 55.5cm top tube. Clip on aerobars work okay but i have to move the elbow pads so far back that they're right over the steerer tube.

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[cjbruin]

This is mostly from memory but I think it's correct. My roadie (2003 Specialized Allez Pro) is 545mm and my tri bike (2006 P2 SL) is 510mm...I use the 78 degree seattube angle.

[Triguy]

I'm going to answer you the way I hate people answering questions. INdefinately(then I'll just give you the numbers)...

Top tube length is a very vague number in the world of triathlon bikes. Bikes are now made to be ridden at a variety of seat tube angles, and all of those various seat tube angles have different corresponding top tubes. So a 76 degree seat tube angle bike is actually shorter in the top tube than a 78 seat tube angle bike with the same top tube numbers but with their seat tube angles made the same.

Dan Empfield created a great chart on slowtwitch.com that compares the length of triathlon bikes from the vertical line through the bottom bracket, along a horizontal line to the headset. This is called reach.

All right now, more to the nuts and bolts of your post. I've ridden three different positions on two fairly different bikes.

My current position - slackish ~76 STA, My bike has a top tube of 53 cm and I have a 8 or 9 cm stem.

My position the last two years - steep ~ 79-80, same bike wih the 53cm top tube and a 12cm top tube with long extensions(think superman position). This position really led to plataue in my riding ability. Too steep, too stretched out, but a lot of people thought it looked good.

Original position steep ~78 degrees, a 53cm bike with a 90 cm stem. Similar to where I am now but steeper.

All in all, my perfect fitting bike would probably be more in the line of Trek Small (52cm, 76 STA, 10cm top tube). In fact I hope to get one later this summer. My road bike has a 54cm top tube.