Triathlon - Bike Sizing Question

I'm finally shopping for a tri bike after racing my road bike last season and the first few races of this season. Right now I'm looking at the Cervelo P2SL, Felt S22, and QR Kilo. Trying to stay around 2k.

My LBS finally has the new Kilo so I went to check it out yesterday. They had a Kilo in a 52 and Tequilo in a 55. I think the geometries of the frames are the same. I didn't have time to test ride yet but got to sit on each in the store and get a feel for them. I could probably fit on either frame with some adjustments and wanted everyone's opinion. I'm about 5'11", almost 6'. The 55 felt a tad on the large side but will probably be fine with a shorter stem and bar adjustments. The 52 was a tad small but will probably be fine with a longer stem and some bar adjustments.

So what would you do? Shorter bike with longer stem? Longer bike with shorter stem? Any reason for one or the other? Any side effects from either of these setups you can think of?

The geometries are different. The 52 has a 52cm toptube, while the 55 has a 54cm toptube. The 52 has a lower/shorter headtube, which means you will be lower in front. That's great if you are flexible, but some can't ride like that. Your best bet is to ride the two back to back and choose from there. The optimal choice would be to get fit, then buy from there. Generally, you would ride 1 size down from your road bike size. i.e. if you ride a 56, get the 55 and if you're on a 54, get the 52.

And if it fits, I generally would pick the shorter bike with longer stem due to handling. But, unless you are some physical freak, the 55 which has a 54cm toptube should fit fine.

Thanks. I'm actually on a 58 road bike now but it is a bit big and should probably be on a 56. The 55 more likely my pick as the 52 did have a rather short top tube. Just wanted to make sure there was nothing else I was over looking. I'm not particularly flexible so the bigger size will likely work better. I didn't have my shoes and pedals with me but when I go back for test rides I'll be sure and ride them both and make sure.

Thanks.

Yeah, just for comparison I'm 5'9" and I'll ride a 52/54. I would think the 52 would be a little on the small side for someone a couple inches taller.

I ride a 51cm P2 SL and am 5'8" The 54 was a little too big for me. Not sure if that will help you.

Yea. I sat on the P2SL as well. The 54 felt perfect on that one so I'm thinking the 55 for the QR will work best. I've got to go back with some more time and my pedals and shoes and spend some real time on all of them. I have no preference so I'm going to just go with whatever fits best. All 3 bikes are close enough in spec I'll be happy with any of them. Thanks for the replies.

Standard general rule of thumb is one size down from your road frame size. Though it can vary on how aggressive a postion you will/can ride...

My road frames are 56 (best) or 57cm. My Cervelo P3 alloy is a 52cm.