I am about to buy a 2012 Cervelo P2, I am 5'10" 1/2 and 32" inseam.This is my first tri bike and I am not sure/I have no experience on how these bikes are supposed to feel when you are riding them. I currently have a road bike (Specialized Allez), it is a 56 and fits well. The LBS recommended me a 54 for the P2, since they offer a fitting with the purchase. However, they only have a 54 in stock and I'm wondering if they recommended that size for that reason. I tried the bike and it seems ok, but again I have no experience with these types of bikes nor I have the opportunity to try a 56 (only LBS in town that has Cervelo) to see of it feels better. Do you think that given my height and inseam I am better fit for a 56 or a 54?Thank you for your help!
it's hard to tell, as each person's fit is a little different, but a P2 in a 54" is a pretty reasonable choice for someone your size.
But let's say- just for fun, that you are right in the middle and can be fit on either the 54 or 56.
On the larger bike, you would need to lower your seat a little bit more, relative to the frame, so your front end would feel like it's a bit 'higher' up. On the smaller bike- your seat would be raised and the cockpit would be relatively lower- allowing your torso and head to be in a lower, more agressive position.
so the smaller bike would, all other things being equal, give you a more agressive riding position. torso length, lower back flexibility and arm length (specifically the distance between your shoulder and elbow) are all pretty important measurements- along with inseam of course. If your bike shop measured these parts of you- it's likely that they've picked out the right size. If they didn't- then they might have made a good educated guess, or maybe they're just foisting their stock upon you. But- even if they were nefarious- a P2 54 is a fine steed.
Here's the problem... height and inseam are both quite poor indicators for bike fit... so many other factors come into play that you can take 4 people of exactly the same height, one fits perfect on a Cervelo P2C 54cm, another fits the 56cm, the third can't fit well on either, but the P3C fits fine (shorter head tube), and the forth, well doesn't fit any Cervelo well, but fits perfect on another brand...
You're about to spend some serious money on a bike... do it right and get a bike fit FIRST and then buy the best fitting bike for YOU.
Thank you very much for your replies!I went to the LBS again, got properly fitted and they insisted that the 54 was my size. Although I wanted to try the 56 before spending that much money I went ahead and purchase it (first time in this store, but they seem pretty honest). I just came from my first ride and, even though I still need to work on my aero position (first tri bike), the bike feels great!Thank you very much for your help!