Time Trial Bike Sizing

[andycarter]

I'm thinking of buying a time trial bike. Nothing fancy and something that leaves plenty of room for upgrading in the future. I found an article in Cycling Plus a few months back that tested a cheap Guess frame. I've now found them on the internet but have no idea how to go about deciding what size to get.
I'm 6'2" and ride a 58/59cm road bike but I have read things that suggest for a TT bike for someone my size I can go as small as a 54cm. Does anyone know (without spending lots to be professionally sized) how I'd go about working out what size I'd be?

[Jon H]

You're fairly tall, so should be able to get a good time trial position fairly easily. Shorter people (me included at 5' 8") can have problems getting low enough at the front because of the head tube length limiting how low the bars can go. That's not usually a problem if you're tall, because you start off from a higher position. The general idea is to get your torso horizontal, upper arms vertical and forearms horizontal. That's a good starting point anyway. You can tweak the position with different length and angle stems and headset spacers (as long as you don't cut down the steerer too much). It's better to start off too high and go lower as you adjust to riding in a time trial position. If you go too low you might find you can't produce the same power as you can on your road bike, or you restrict your breathing. I'd say the most important measurement for a time trial bike is the top tube length, and this will normally be shorter than for a road bike, but don't go too short or you run into problems with hitting your knees on the bars when riding out of the saddle.

Hope those ramblings are of use. Sorry I can't give a definitive answer on the frame size, but there are so many variables.