I’m trying to get my fit dialed in on my new P2k. For what its worth, I’m 6’1" with a 58cm P2k. I’m young, flexible and thin. Currently I’ve got my saddle even with the BB which puts me around 78 degrees.
I got my fit roughed in using the 90 degree angles and the upper part of my back parallel to the ground. So tonight I got around to Dan’s formula for arm rest drop. My saddle is 30.25" from the BB. I converted that to 76.835 cm. Dan’s formula then suggests C=12.9986cm which I converted to 5.1175" I took all the spacers out from under my stem and the lowest drop I can get is 3.5"! I’m measuring from the top of the saddle to the top of the armrest using a level.
Do I have to reverse the stem so that it is pointing down? This seems really low, but this is my first real tri bike so I don’t have a frame of reference. Please tell me that I’m making a stoopid mistake somewhere with the formula or measuring the wrong place.
I wouldn’t be surprised if you’re young, flexible and have to turn the stem to make it lower. I’m having to use mine with no spacers, a 17(? flat) degree negative stem and still can’t get it as low as I’d like with the regular Profile bars, had to modify them a little to get lower… but for most people being a little higher isn’t going to kill them as much as being a little too low.
You are on a bike with 700c wheels, so it would make sense that you would have to have the stem in the orientation that keeps your bars low to get the desired drop. I use stems that have a 10 degree rise. Since the headtube is at an agle of about 73 degrees, my stem goes up at either a 7 degree or a 27 degree angle depending on orientation. It depends on your choice of stem how it works for you.
I didn’t run the numbers, but off hand your calculations seem reasonable.
Turn the stem, remove the spacers, be happy getting your Cervelo - I’m still waiting for mine… It’s no problem using a stem upside-down.
You need a big (long) frame since your upper body is very long (Your seat is at exactly the same height as mine - but you are 2" higher= 2" longer upper body. ) Then you probably need a 58frame to get the correct length of the top tube.
You guys nailed me, I am very long in the body so I have to use the 58 cm bike to get a long enough top tube. I reversed the stem and took out all the spacers and I get exactly the drop the formula suggests.
My question really centers on is 5.1" of drop really the correct amount for a 30.25" saddle height? It just seems really low. I guess I’ll find out, I’ve got a long brick tomorrow.
Dan’s formula is correct, it is bodies like mine that can’t get in that position that are the problem. My bars are way too high right now. I think I need to do a little yoga before Lake Placid. Your body will tell you soon enough what the right bar height should be.
I would say that most likely your frame size is correct.
You used the formula correctly, your calculated drop is entirely reasonable.
The Cervelos are equipped with flippable stems for exactly this reason, to flip them if necessary. There is a wide range of positions people ride in, and so you need the 2" difference that flipping the stem offers to accomodate those positions.
If anything, pointing the stem down would have to be considered the “normal” position, so no worries about doing that. Of course, both positions are equally fine, it’s just that traditionally stems would point down. Just to give you an idea, my body is quite the opposite from yours, I am 6’3 but with long legs and a short torso, so I am on a 55cm with one 10mm spacer and the stem flipped upwards to get a 13cm drop from the saddle. Works perfectly.
If you’re riding lower in front tomorrow for the first time, you might find that your neck is uncomfortable during the ride. You’ll be bending you’re neck up more to look up the road. For me, it takes a couple of rides during spring to get used to the “tri” position. If you’re slightly uncomfortable at first, don’t give up on the position right away because you’ll probably adapt to it soon enough.
My question really centers on is 5.1" of drop really the correct amount for a 30.25" saddle height? It just seems really low. I guess I’ll find out, I’ve got a long brick tomorrow.
Be very careful about making assumptions about your fit on the bike if you are doing a long brick tomorrow on a bike you are just now getting on. In fact, I’d recommend you didn’t do a “long” workout until you’ve got more time in the saddle on this bike. You’re setting yourself up for injury. And then you’ll blame the bike for your injury/discomfort when it is simply a matter that you haven’t adapted to the position yet.
He’s not the odd one out, I am. 6.1 with his saddle height is really normal for a 58cm P2K or P3, and all his info indicates that he will find his position on his Cervelo with a very normal number of spacers and a very normal stem.
And even though my proportions are rather unusual (I’m the same height as Lothar Leder, he rode a 61cm, I’m a 55cm), in the end my set-up is also technically correct.
Yes, the 55cm has a lot of drop for somebody like me with an 84-85cm saddle height, but a flipped up stem has a lot of stack so in the end I only use the one spacer. I’m not a fan of using more than 40mm of spacers, but one almost never has to. The way we made our bikes, they are low enough for almost anybody (even Tyler uses a spacer) yet withthe 17 degree stem we provide it can also be positioned high enough for virtually anybody. It’s one of the reasons why we rarely get requests for customs, if you do the geometry properly you can fit a wide range of people and positions. But you have to use common sense, match up the frame and stem with your needs.