I was fitted for a P2C recently and had a choice between a 54 with a 120mm stem and a 56 with a 90mm stem. The 56 seemed to feel a bit more comfortable but there really was hardly any perceptible difference. Is there a rule of thumb when choosing between sizes? I have a longish torso so while the 54 was right for my inseam length, the top tube seemed a bit short. Is there any downside to going to the larger size?
I think that most riders will go with the size down especially if there is no issue with clearence for your knees while out of the saddle. the reasons are usually as follows: Smaller frames are lighter, and stiffer than their big brothers, and for a tri bike a 120mm stem is wel within acceptable giudelins and will make the bike feel less twitchy (although a 90mm stem is not really that short)
Mostly though if you have the opportunity to ride both frames, jsut pick the one the feels the best.
As long as you think you will never want to ride other than where you were fitted, then it is what it is. If you expect to evolve a steeper or shallower position, then I'd go with the 56 or 54 respectively.
Gbot,
What’s interesting is that the difference in top tube lengths between the smaller and the bigger is only 1.5 cm (54 has a top tube of 53cm and the 56 has a top tube of 54.5cm (assuming you’re set up steep - we’ll assuming lots and lots of stuff). Yet the stem length differences noted are 3 centimeters. That seems odd to me. I can’t help but wonder if the seat clamp was in the same hole for both bikes…if the bars (probably Vision) were spec’d the same, etc.
There is a proportion of sorts that goes with bike frame sizes and stem length. I, personally, think that a 120 stem on a 54 is a hair outside the bounds. Just as a 70mm stem on a 60cm bike would be a bit extreme. But that’s just littl’ ole me a FIST certified fitter who fits about 150 bikes a year and who stands 6’1" and rides a 56cm P2C with a 90mm stem - just me thinkin’ out loud.
Ian