hi im 6ft 1 inch and buy 33 inside leg,do i go for a 55.5 frame or 58.5 size frame please?

Road bikes are like suits; go try it on.

Sorry – it all depends on the bike. For example, I’m 5’7″ and ride a 56cm Cube.

It’s all about the top tube, innit..

As above, they’re all different. I’m 5’10.5″ and ride a 54cm Raleigh with a 110mm stem.

Some like cubes & trek size up small, others big / strange.

Cockpit length also is something that needs to be considered as well as TT lengthy. Centre of post to back of hoods thus dictating reach

do giants come up small then,im not sure has the guys at the bike shop donot seem to no,i feel a 55.5 small but a 58 may be like a barn gate

I’d say you’re exactly smack bang in the middle assuming you’re average proportions. Go and find a local bike shop that knows what they’re doing and sit on a few 56 and 58cm bikes till you find one you like.

[edit] Giant’s are compacts aren’t they? I’d say you’re most likely to want a 56-58cm top tube and ignore the seatube length. As above ask in a good bike shop with plenty of sizes to try out.

It’s not even consistent within brands.

I am 6′ with 33″ inside leg, and ride a Giant TCR in M/L which is 53.5

I can’t see how you would need anything above a large (55.5), but a M/L would probably be more suitable.

Giants are a compact frame, a M/L equates to a conventional frame size of 57 to 59, and has a top tube of 57cm. A large is equivalent to a conventional 58 to 60 and has a top tube of 58.5cm. I think a large would be too big for you based on the top tube length.

You really need to try the bikes though.

OK thank you to all who helpedm me will do

there is a very good sizing chart on Giant’s website – a lot more detailed than most manufacturers

also a frame that is on the small side can be adapted to fit, one that is too large cannot