I am a 5 foot 10 male with a 32 inch inseam I am in the market for a new tri-bike and I listened to everyone on this forum and went to get fitted by a Fist certified & Serotta certified fitter. The fitter put me on a Serotta size cycle and took some measurment and then recommended that I would fit on Cervelo P3C 51 cm. Because this seemed smaller than I would have guessed I went to see another Fist Certified fitter, who actually put me on the P3C (size 54) and watched me ride it on a trainer (he also measure various of my body’s angles while on the trainer). This fitter told me that I should be on a P3C 54 cm, not a 51 cm and said that I could fit really well on the 54 cm. He said a 51 would require too long of a stem. The previous fitter said 54 would be too big. I am now pretty confused. I have two so-called experts saying two very different things.
My questions is how do I determine which size bike to go for? Any thoughts would be appreciated. Also, I would be curious to know, for those of you riding P3Cs what size frame did you buy and what is your height and inseam. I am curious to see what people with similar body types as me riding. Many Thanks.
You will fit multiple bikes. Your position should stay the same, but the bike can increase and decrease in size underneth your…at the same time you “size” the components to maintian the position.
I think it also depends on the lifetime of your bike is going to be. Again, from my fitter:
As you get older, the front end of the bike comes up and back in a arc. You want a bike that will last a long time, plan on this before hand.
Anyways…as I am no expert, I would be interested in what the position was on a 51cm as oppossed to a 54cm. That seems like a HUGE size difference to me. If the positions are identical, then its going to come down to bike handling and stability. A long stem and tiny bike under you is going to be really squirrelly!
Well, I just looked at the P3C geometry, and I would be on a 54 configured for 78 degrees with a 105mm stem - but I am 6’0 with longish legs, short torso.
My questions is how do I determine which size bike to go for?
Maybe not the norm for most fitters but seems to me that a fit specialist should be using some kind of video to provide the customer with a visual aid during the session so that the results are immediately obvious as to what has been done. In a situation where you are riding a fit bike or a P3 on a stationary trainer for XX minutes, you should be able to judge from how oyu look on the bike just as much as how you feel.
Based on your height (and mine being similar) it sounds like you really fit in between the two sizes. That means both would probably work. You need to decide if you tend to ride more steeply than the typical 78 degree setup and how rigorously you want your elbows directly under your shoulders. If you ride steeper than 78 then the 54cm might make more sense as your effective seat angle would shorten up the top tube length.
Personally I’d lean towards the smaller bike even if that meant using a 120mm stem. I hate being stretched out, but that is just me. Most people in triathlons seem to end up on bikes that are too big.
FWIW, I’m 5’9" (not sure of my inseam at the moment, but normal proportions) and I ride bike with a 52.5cm top tube at 75 degrees, shortened by sliding the saddle forward. My effective seat angle is more like 78-79 and my effective top tube length is more like 50-50.5cm. My shoulders are directly over my elbows which I like.
I haven’t looked closely at the P3C geometry, but 3cm is a big jump between sizes.