I was visiting my friendly neighborhood Cervelo dealer yesterday, and while I was just there to “browse”, I started talking to the owner about sizing. I am interested in the P2K, but they didn’t have any in stock so I couldn’t actually try one on.
He put me on a 55cm One in the 78 degree config which seemed a little compact, and told me that for the P2K I could go two ways - I can fit a 58 with a slightly shorter stem or a 55 with a slightly longer stem - both assumed a 78 degree position. If I wanted to go with the 76, I would need a very small stem on the 58, but could still do it.
He felt it would be better for me to go with the 55 and the longer stem, but I was concerned that this would put too much weight on the front end of the bike and throw off the weight distribution. Any thoughts on this? Better to go bigger or smaller on the frame? Also, anyone know the rationale behind the 3cm differences in sizing?
Cant comment on your situation but my LBS suggested I go with the bigger one b/c a) I will have too many spacers and b) the owner of the LBS is from the Dan E school of tri fit and without a much longer stem I would be riding a very shallow angle, which he did not believe was optimum for me. I fit on either a 51 or 54, and you can get 53 TT on both depending on how you are set up. It works really well, and is very stable.
Provided that standover height isn’t an issue (or getting low enough on the front end), the larger 58cm ride is going to be more stable with a shorter stem than the smaller 55cm with a longer stem.
On the other hand if the bike is just a bit too small it is easier to make it bigger than trying to make a bike too big smaller. I’d want to get on a 58 and/or 55cm before dropping a $. After all better safe than sorry.
You should email Gerard on this. Where’s Tom Demerly when we need him! I’m a perfect size 54 on a P2K but my wife was half way between a 51 and a 48. The shop told us to go to the 48. Works fine for her.
What are your exact options here? What is a “long” stem? Is the choice between a 55cm with a 120 stem or a 58cm with a 100 stem? Does your position fit within the Slowtwitch rule for elbowpad drop? If so, then the choice for the 55cm is fairly easy in my opinion. If you’re deciding between a 55cm with a 140 stem or a 58cm with a 120, then the choice for the 58cm is fairly simple as well. If you’re in-between, then I would make it depend on how aggressive your position is.
You have to remember that the steering geometry of this bike is very robust, you will never get too much weight on the front wheel. The geometry is such that even in the fully forward position handling is very good, in fact as slowman has frequently pointed out, the geometry of the P2K really revolves around its 78 degree position, not its 74 degree position. For more info, also check the thread on the Soloist geometry from last week, the same tricks were used on the tribikes. I think it was called “bike design” or something like that.