1991 Kona Explosif 16”

[gtturbo]

Sorry it's just the steerer tube on the fork that are bigger; surely I just need to change the headset out to take the bigger steerer tube?

It doesnt work like that I'm afraid. If you frame is a 1" headtube then you need 1" forks. If your frame is 1 1/8" then you could use reducer cups to go down a size to 1". I'm pretty sure you frame is 1 1/8" though. Easy enough to check. I would just whip the stem out and check the top nut from the headset screws on the new forks.

 

[theador]

Your frame should already have a 1 1/8” headset, in which case the new fork should fit

Tried it and it definitely didn't fit. Hopefully these pics explain it. Please do let me know if I'm referring to stuff by the wrong name though. I haven't worked on 90s bikes since, er, the 90s

 

[Markybeau]

If the quill is 25.28mm ( close to 25.4mm or 1") then it's a 1 1/8th headset. It's counterintuitive.

To fit the headset the quill has to be smaller.

E.g. 22.2mm quill is for 1" headset..
28.6mm quill is 1 1/4"

 

[raidan73]

That’s an evolution 1 1/4” fork

 

[theador]

If the quill is 25.28mm ( close to 25.4mm or 1") then it's a 1 1/8th headset. It's counterintuitive.

To fit the headset the quill has to be smaller.

E.g. 22.2mm quill is for 1" headset..
28.6mm quill is 1 1/4"t

Thanks @Markybeau this is all starting to make sense.

So attached is a photo of a stem that fits the futureshock fork. The question then seems to be: Is there a headset that fits that fork in my steerer?

 

[theador]

That’s an evolution 1 1/4” fork

What bike would it have been for? Jeez I just kind of assumed they made made them for such a short period of time they’d all be the same steerer

 

[raidan73]

Plenty of companies made their forks and stems in all three sizes. Not sure I’ve ever seen one of those in 1 1/4” before though.

 

[gtturbo]

Thanks @Markybeau this is all starting to make sense.

So attached is a photo of a stem that fits the futureshock fork. The question then seems to be: Is there a headset that fits that fork in my steerer?

Afraid not. Whilst you can fit reducer cups to fit a smaller headset/fork you cant make a headtube bigger to fit a larger steerer/headset. There was someone, I think on facebook, that made some weird headset to fit a 1 1/8" fork in a 1" frame but that was all homemade and looked a lot of work for something that potentially may not be a lot of good. There are some clever people on this site so someone like @danson67 might be able to remove the existing steerer and fit the 1 1/8" you need. He's actually doing the opposite for me and replacing a steerer on some Accutrax forks to take them up to 1 1/4"

 

[theador]

Afraid not. Whilst you can fit reducer cups to fit a smaller headset/fork you cant make a headtube bigger to fit a larger steerer/headset. There was someone, I think on facebook, that made some weird headset to fit a 1 1/8" fork in a 1" frame but that was all homemade and looked a lot of work for something that potentially may not be a lot of good. There are some clever people on this site so someone like @danson67 might be able to remove the existing steerer and fit the 1 1/8" you need. He's actually doing the opposite for me and replacing a steerer on some Accutrax forks to take them up to 1 1/4"

Thanks for that; great idea, will try and get in touch with @danson67

 

[theador]

Plenty of companies made their forks and stems in all three sizes. Not sure I’ve ever seen one of those in 1 1/4” before though.

Does a 90s Hei Hei have a 1 1/4 head tube? (I can feel some massive scope creep on the Horizon haha)