Headset Help: Shimming a 1 1/8th fork to fit a 1 1/4 Headset

Hi Everyone,

Im currently assembling a bike with an integrated 1 1/4 headset. I have a 1 1/8th fork and i'm struggling to find a way to make it compatible. Ideally a base plate shim would exist so i could place the the existing headset bearing over it.
I've looked at other threads with little luck and don't want to go down the chris king route.

https://weightweenies.starbike.com/forum/viewtopic.php?t=133626
https://weightweenies.starbike.com/forum/viewtopic.php?t=101806

Any Advice would be greatly appreciated

Thanks

Fully integrated or is a 44mm headtube with a semi integrated cup?

This should sort you out -

https://r2-bike.com/CANE-CREEK-Crown-Race-110er-Serie-EC-ZS-IS47-30-1-1-4-Reducer-to-1-1-8-Aluminum

Fully integrated

Cheers, the headset I have isn’t a cane creek but it’s worth a go

It doesn't need to be, but it'll need to be same lower bearing spec.

Thanks a million!

Reviving this rather than creating a new thread but has anyone tried shimming a 1" (25.4mm) steerer for a 1 1/4 (31.8mm) stem? I know that 1"-1 1/8 exists so surely you can do the same just with a thicker shim to accommodate the stem?

I spoke to a mechanic who was very unkeen on the idea but I've got a stem and bar combo I had planned to use and would quite like to stick with...

As steerer shims are single piece slotted, the problem is going to be compressing the shim in order to clamp everything up.

28.6mm (1 1/8”) - 25.4mm (1”) is a difference of 3.2 so shim wall thickness will be 1.6mm.

At 31.8mm - 25.4mm the difference is doubled to 6.4mm so shim wall thickness would be 3.2mm.

You may exceed the torque rating of the stem before you reach a satisfactory clamping force.

As shims to do the job don’t actually (afaik) exist and you’ll be having to make/have one made then you could go for a two piece design but poor alignment of the pieces may cause issues.

Big thanks for the detailed explanation. In my head it made sense before but now you explain it I'm starting to appreciate the issue with torque and not putting too much on the steerer. I'll obviously make sure the compression plug is correctly fitted that would hopefully prevent damage to the steerer from over-tightening but it is a carbon steerer so I'd need to be careful.

Is there anyone who might be able to make an appropriate shim for me or would it just not be recommended and I should find an alternative 1 1/8 stem?

In a pleasant turn of events, it turned out that the stem I had waiting was in fact 1 1/8 so all sorted.