TT sizing

marmatt said:

in regards to a TT bike,is it advised to get the same size frame as you would your road bike or would you get slightly smaller(52 instead of 54)Thanks, MC

I think the trend is slightly smaller. I think it gives you more handlebar-seat drop. Something else too, but I am not sure.

Bobby,

Give him a link to Budgie's Tri page. He has good articles on bike set up.
http://www.trysport.com.au/articles.htm
See also the page of "Athlete's Bikes".

You generally should have a shorter top tube due the aero position that we assume on these bikes. Also, the seat tub angle is more upright to put you into a power position. These are all things to consider when purchasing your frame. You can also opt to have your TT Frame custom made exactly to your body measurements. 🙄

marmatt said:

in regards to a TT bike,is it advised to get the same size frame as you would your road bike or would you get slightly smaller(52 instead of 54)Thanks, MC

marmatt said:

in regards to a TT bike,is it advised to get the same size frame as you would your road bike or would you get slightly smaller(52 instead of 54)Thanks, MC

Depends on the individual frame geometry and the way you ride. The key issue usually ends up being "cockpit length" or reach, which is the distance from the saddle to the bars. Most people need a shorter top-tube when using aerobars for the same saddle height. Also a shorter headtube or lower rise stem may be needed to get the bars low enough, again depending on how you ride. This is affected by how steep of a relative seat angle you ride, though.

This question comes up a bunch, so you might want to do a search. But this is what i found when trying to convert a road bike to TT use, and eventually building a dedicated TT bike. The length of the top tube isn't a huge issue (you can just get a shorter stem), the major issue for me at least was getting my seat far enough forward (because of a 72 degree seat tube angle). And also being able to get low enough in the front end. In a perfect world where we are all more flexable than we need to be our goal would be to get our back perfectly flat, with a standard road bike that is tough because you are sitting far back behind the BB and therefore your hip angle is closed, and if you could get low enough you would have your legs hitting your stomach, so a TT bike puts you more forward, so you can raise your saddle, roll your hips forward opening them up, and therefore get your back flat. So with a road bike i ride a 58.5 top tube with a 130 mm stem, and my TT bike has a 56.5 top tube with a 130 stem. The TT bike has a much shorter(3cm) head tube, and that is the reason i went with the smaller frame, not the top tube lenth (in my mind i could adjust that with a shorter stem), so take a look at the other frame dimensions on the frame you are looking for, not just top tube. As far as i'm concerned the head tube measurement is super important, because it's hard to get lower in the front than the head tube will allow. Everything else can be adjusted with more spacers, longer/shorter stem, seatpost with more or less setback, etc. Sorry for the long winded response, but this is a somewhat complicated thing.