TT vs road bike sizing

weapons

I am considering delving into the world of tt bikes and wondered if anyone had a rule of thumb for sizing between road and tt frames. I know the best way is to go to a shop and get sized properly, but I am only doing initial research for now so a rough and ready rule of thumb would be good at this stage.

I currently ride two road bikes, one with an effective top tube length of 510mm with a 130mm and another with a top tube length of 535mm and 100mm stem.

What sort of top tube length do you think would be suitable for me on a TT bike? Is the top tube length the best measurement to be looking at?

Many thanks in advance

danowat

General concencuss says that a TT bike should be about a size smaller than your road bike, however, I ride a 58cm Allez on the road, and have a 58cm Slice TT bike, which fits fine.

moonshine

so for a smaller top tube than on your road bike.
I ride a 54cm Felt F3 with a 545mm top tube as a road bike.
my TT bike is a Planet X stealth in Small with a 510mm top tube

G

hopper1

Before buying a TT bike/frame, read this.

Then use the links to compare what you have with what you want...

chrisw12

Yes, I'd say top tube length is probably the biggest factor when choosing a tt bike. You can get some margin for error with stems and some aero bars, but it's nice to get a good neutral position to start with then use the bar/stem to get an extended position or a tight position when you fancy experimenting for aerodynamics and comfort.

hopper1

Not necessarily shorter top tube length...
'Stack Height' and 'Reach' are the main measurements to consider, but reach is also affected by the Seat Tube angle... The steepeer the angle the further forward you will be over the BB!
On like for like angles, then Top Tube can be factored in, but adjustments have to be made for varying ST angles...

chrisw12

Don't know if you were responding to me but I didn't say shorter top tube length.

When I think about it, it's all bit of a minefield. I was lucky in that I started off with a road bike which by using different seat posts, angled and different length stems and very adjustable tri-bars I was able to get a good(ish) position. When I then bought a dedicated tt bike, I've just transfer measurements across.

My method is to put tip of saddle in line with bottom bracket then get a reach measurement to end of aerobars and a drop measurement from pads to seat. That way I haven't got to worry about any angles.

I don't think I'd buy a bike unless I had measured the reach myself.

hopper1

chrisw12 wrote:

Don't know if you were responding to me but I didn't say shorter top tube length.When I think about it, it's all bit of a minefield. I was lucky in that I started off with a road bike which by using different seat posts, angled and different length stems and very adjustable tri-bars I was able to get a good(ish) position. When I then bought a dedicated tt bike, I've just transfer measurements across.

My method is to put tip of saddle in line with bottom bracket then get a reach measurement to end of aerobars and a drop measurement from pads to seat. That way I haven't got to worry about any angles.

I don't think I'd buy a bike unless I had measured the reach myself.

Not aiming it at you, Chris... It was mentioned in earlier posts...

weapons

Thanks all, that's really helpful

moonshine

hopper1 wrote:

Not necessarily shorter top tube length...
'Stack Height' and 'Reach' are the main measurements to consider, but reach is also affected by the Seat Tube angle... The steepeer the angle the further forward you will be over the BB!
On like for like angles, then Top Tube can be factored in, but adjustments have to be made for varying ST angles...

yes, the angles and everyhing are clearly related ... but have you got a road bike and a TT bike?
If so, what are the top tube measurements?
Is what I said wrong? Does your TT bike actually have a longer top tube than your road bike?

Interested to know.