time trial bike size?

davidtarmac said:

hi, i am now shoppind to buy a time trial bike and i don't know what size to take. some people say the same size of my road bike and others say smaller. what is the truth???? some body please help me!

david

Don't waste your time listening to some drivel on the internet, go get fitted properly. It's well worth it since if you're on the wrong sized frame on a TT bike it is guaranteed to hurt. Gonna hurt anyway ...

There isn't a general rule. The idea of getting fitted is very good. In my own experience, I needed to have a top tube 3 cm's shorter than my road bike to fit properly. Moreover, my aero bar pads needed to be 3cm lower than my road bike bar tops to be comfortable and aero. This might be unusual, I really don't know. But it just shows you the kind of variation you can have b/t your road and tt bike. Look too for aero bars and seatposts/seats with lots of adjustability (Profile Design T2 and Richtey Prologue are two of several clip on's with lots of adjustability) . Finding the right position will involve a lot of trial and error. At least, this is all in my experience.

davidtarmac said:

hi, i am now shoppind to buy a time trial bike and i don't know what size to take. some people say the same size of my road bike and others say smaller. what is the truth???? some body please help me!

Okay, here's some drivel:

Forget the so-called professional fit ...

How in-/flexible are you?

How is your "tuck" position?

Unless you buy a ready-to-ride (e.g., Trek) bike, you're going to need to buy a saddle & bars ... BUY them, first.

PUT them on ANY frame ... and, that bike on a trainer. Get on the bike for 15+ minutes in the TT position.

Tweak the bars & saddle's fore-aft position.

Is the top tube long enough, or too long?

Find another frame which has a longer/shorter top tube ... repeat.

Keep tweaking until you are comfortable (for 30+ minutes) on the setup -- look for a TT frame whose top tube suits the position YOU deem to be acceptable for 30+ minutes ... for a LONGER TIME if you are using the bike for Triathlons.

FWIW. I reckon for a dedicated TT bike, you'd want a bike with a "shorter" seat tube than on your ROAD bike (unless you are riding a "compact" frame) where your saddle is 7+ inches above the top tube BECAUSE the idea is to have a smaller headtube which will subsequently allow you to get more aero -- that may be a frame with the same length top tube as your ROAD bike, or not.

thank you guys for your help!

david