My head tube is 1 1/8" and my fork is 1". What size headset will I need?

Is this even possible? I'm pretty sure the fork and head tube dia need to match.

You need a different fork.

Or a different frame.

Isn't there supposed to be an 1/8" space between the fork and the head tube?

No. Unless you want your fork rattling around inside the headtube.

1-1/8 headtube goes with a 1-1/8 fork. The same goes for 1" HT and 1" fork.
Now, with that said, they do make "head tube reducers" - google search it and you will find plenty of options. Go for the 1-1/8 to 1" head tube reducer. I have never used this nor do I know of anyone who has used one so I cannot comment on the product.

https://lmgtfy.com/?q=head+tube+reducer
I love this link.

Your question is actually a little confusing and it is late...

Headset for your bike will be 1 1/8... if you have the right fork the steerer should be 28.6 or 30.015 mm at the crown race seat and there will be some space between the steerer tube and head tube as this has an ID of almost 34mm.

A 1 inch fork will measure 25.4 and either 26.4 or 27mm at the crown race seat depending on whether it is JIS or ISO.

You can get headset reducers to fit a 1 inch fork in a 1 1/8 frame..

Are you certain the head tube isn't actually 1-1/4" OD?

https://www.universalcycles.com/shopp...6&category=502

Here's the headset you will need in the event you're fork isn't threaded already. I'm sure there's probably a cheaper brand, but I'm too lazy too look.

^ Not necessarily. OP may have a threaded fork.

k. fixed now

Within the same topic here... Anybody know of a nice cheap SILVER Headset reducer?

Mmmm mmm mmm. Just do it right.

Chris king, Or you can get a custom crown race and headset cups from SINZ cycles, they still sell them on ebay for sure.

It was just an interesting project I thought about undertaking... Would be interesting if I could find a nice silver reducer

I was trying to go 1 1/8" to threaded 1" which king does not do... All I can find from SINZ is a black reducer, no?