Join Date: Jul 2004
Bikes: 08 Felt F4, 05 Fuji Team SL, 08 Planet X Stealth, 10 Kona Jake the Snake, 03 Giant OCR flat bar.
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Really, it depends. MOST of the time it will be a smaller frame, sometimes the same size. I can positively say it will never be larger than a properly fit road bike. Just as road bike companies have different measurements, the same goes for tri bikes. The rule of thumb I've always gone by is 2cm shorter on the toptube. That has worked well for my friends that don't want to be fitted, but it's not exact.
You have to take into account that your torso will be farther over the front of the bike, and your elbows will be on the pads, so a shorter toptube(or stem in some cases) will provide this.
And for comparison, I'm just over 6' and ride a 56 road bike with a 120 stem, and a 54 tribike with a 76 degree seattube angle, pushed forward to around 80 degrees, with a 110 stem.