I'm in the market for a tri bike and have been shopping around too. I'm 6'2" and 200lbs and I've been told I would need a 58cm tri bike. I've got a 60cm road bike right now if that helps at all.

Good luck

Tri-Sooner-

just curious what size road bike did you ride compared to your Tri-bike?

I hope that the 58 wasn't more comfortable just because I am use to my 62 Road Bike.

Maybe the LBS would match the online price...worth asking.

Good call, I should have been more explicit. Another trick is asking the owner for a discount for paying cash, if this is an option for you. They'll sometimes pass on the savings of not having to pay the credit card company their fee; they have no reason not to.

My $.02: More comfortable = faster. Remember you're talking about a 2 cm difference in tube length; you can dial in the fit by adjusting stem length, aerobar length, seat forward position & height, etc. I concur wth TriSooner: Since you test-rode them both, go with what "feels" the best. For what it's worth, I'm 5' 11" and I was also between a 56 and 58. I went with the 56; the fact that I have a freakishly-short torso (and a 34" inseam) may have played a role in getting the smaller frame, i.e. it "felt" better. Hope ths helps/makes sense.

Yeah, definitely see what a tri fitting says. Another thing to keep in mind is how low you can get on the different bikes. Now you'll probably stay fairly up, but with time and comfort you may find yourself wanting to get your front end lower, and with a 58 it might not be possible.

Discomfort on the 56 might be not being used to the tri position -- it feels pretty different to me than my road bike position. But both are great for different things.

Legs/trunk length ratios vary from person to person but..

I am 6'2.5" and ride a 58cm P2SL, I did a 182km ride on Friday and it feels just fine.

:)
I got fitted / measured for the 58cm frame by a certified Cervélo dealer: Kelowna Cycle.
In case it helps, I have a 34" inseam on my jeans.

PoC

I can't tell you how similar my situation is to yours. I am probably closer to 6', same pant length. I think the bottom line is we are smack dab between two sizes and could probably go either way with equal success.

The thing that really had my head spinning when i bought my Felt (very similar geometry) was that the forums and serious folks all stated 56, go 56....smaller, more aggressive. I went into the LBS with my mind focused on 56 is the size I had to get. The store even suggested a 56 to start with. I ended up finding a pretty comfortable position on it and I bought it. Here is where it got a little interesting though. As I rode it around that day I took inventory of my position. I had my aero bars at their maximum extension and my seat post in the rear position, that is where I was comfortable. The problem is these bikes are not really designed to be in the rear seat post, they are made to be in the front seat post hole. I started looking at geometry on the bikes and realized the forward position on the 58 is the same distance as the rear position on the 56. Now I could move the seat forward on the 56 and go to a 120mm stem but I felt that would put my weight pretty far in front of the bike. The 58 would give the same exact reach, while still getting me forward on the seat post, but distribute my weight more evenly over the bike. I could also go down to a 100 or 90mm stem if I want to drop the front lower or compact my position.

Sorry for rambling on. I guess my point is to not let "guidelines" weigh too much into your decision and trust the comfort. I switched to the 58. The only thing I can possibly think of that I gave up is the ability to go quite as low in front...but it is comfortable now and I can always start removing spacers if I want to go lower.

Trust your body, not the general consensus. Besides, Cervelo's own website puts the rough estimates for a 56 from like 5'8 to 6'1, and a 58 from like 5'11 to 6'4. I might be off a bit but not much. You will likely get the same fit either way.

The road bike is interesting. I have an old Bianchi that is 60 and it is too big even though i rode it for years. I have actually been cramming onto my wife's 54 without much problem. I think I am sort of a strange bird because I have actually found myself more comfortable on smaller road bikes, but larger tri bikes...and I know that totally defies conventional wisdom.

Right now I have only been doing sprints. I plan to add in a longer distance event next year as I don't feel quite ready to tackle them yet.