Threadless stem size
 

I have a bike with a 1" steer tube on a carbon fork.

I want to replace the stem but am not sure if I need to buy a size of 1" or something bigger. Im looking at an ITM 'big one" and found a good price online but dont know which size I need....Ive heard conflicting things about the way the sizes are listed sometimes...

so if the steer tube is 1", what size threadless stem do I need?

Can someone help? Thanks.

Two ways to go.Buy a 1" one or buy a 11/18' one that comes with a shim to use with a 1' steerer.

You need a 1" threadless stem for your 1" threadless fork. With threadless forks, the nominal size is also the size that the outside of the steer tube and the inside of the stem use. (edit: the shim setup mentioned by pokey works good too)

There's potential for confusion with the terminology for threaded systems, since a 1" threaded system uses a quill stem that fits the inside, not the outside, of the fork, and thus is smaller than 1" but is still nominally called a 1" stem because it fits the fork with the 1" O.D. steer tube.

Thanks guys.:beer: