TT frame size

[Jonah]

I'm looking to buy a Planet X track bike for TT.  I'm just under 6' 1'' and could use the M or L sizes.  Please could anyone suggest which frame size would be better suited to TT?

[Rhys W]

I had a steel TT bike custom built to my measurements a few years ago, and it turns out the top tube is identical to my "perfect" top tube length which I'd arrived at by trial and error over many years. So, I'd go for the one that is closest to top length to your most comfortable road bike.

Having said that, many carbon TT frames I've looked at come up rather short, putting me on an M, which would leave only a couple of cm of seatpost showing.

[uphillbothways]

Don't buy a TT bike without getting professionally fit, it's a complete waste of money if you don't get the position right. A properly fitted steel frame is far faster than a badly fitted Cervelo P5. Andy Wilkinson's frankenbike shows that you can be very competitive on a machine that is in theory completely unsuitable as long as you get the fit right.

There are no simple biometric rules, because the main sizing criteria are your flexibility and core strength. You'll need to take into account the distances you'll be riding and the code under which you're competing - UCI, CTT and ITU rules lead to very different setups. A rider who takes a small frame for 10 milers could suit a large frame for Ironman distance triathlons.

You can figure out the right fit by trial and error, but a brand new bike is a really expensive way of doing it.

[Jonah]

Thanks for the advice

[Gruby Mits]

Don't buy a TT bike without getting professionally fit, it's a complete waste of money if you don't get the position right. A properly fitted steel frame is far faster than a badly fitted Cervelo P5. Andy Wilkinson's frankenbike shows that you can be very competitive on a machine that is in theory completely unsuitable as long as you get the fit right.

There are no simple biometric rules, because the main sizing criteria are your flexibility and core strength. You'll need to take into account the distances you'll be riding and the code under which you're competing - UCI, CTT and ITU rules lead to very different setups. A rider who takes a small frame for 10 milers could suit a large frame for Ironman distance triathlons.

You can figure out the right fit by trial and error, but a brand new bike is a really expensive way of doing it.

  Most sensible advise ever!