Tapered for to non-tapered frame?

If you measure a 44mm internal diameter and it's a zero stack/semi intergrated headtube then it's just a matter of fitting an external cup headset assembly (EC/44) at the bottom.

If your bike has two small lips visible above and below the headtube then they're the outer edges of cups that are pressed into the headtube.

To convert to use a tapered fork an external cup assembly houses the wider diameter 1.5" bearings underneath the headtube instead of inside it.

The top doesn't change from a standard semi intergrated (ZS/44) assembly.

It only works if the frame uses a straight 44mm head tube (which would use zs headset cups top and bottom for a 1 1/8" straight steerer). It's physically impossible if the frame uses a straight 34mm head tube.

The Jabbers of the time were a basic frame so no outer 'lips' it's simply a straight headtube from top to bottom. I currently have a standard 1 1/8 Cane Creek headset installed. It's not the integrated kind. So I think that means the internal width is 34mm....correct? So if it's possible, I would need a 34mm internal cup.

Crash_FLMB said:

The Jabbers of the time were a basic frame so no outer 'lips' it's simply a straight headtube from top to bottom. I currently have a standard 1 1/8 Cane Creek headset installed. It's not the integrated kind. So I think that means the internal width is 34mm....correct? So if it's possible, I would need a 34mm internal cup.

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Do the math. It is physically impossible to fit a tapered fork into a frame with a 34mm headtube, regardless of the type of lower headset cup you use.

34mm = ~1.34"

I haven't measured it as the fork is still installed. The outer diameter is 44mm. No worries Harold, sorry to 'bother' you. Feel free not to post on this topic again.

Crash_FLMB said:

I haven't measured it as the fork is still installed. The outer diameter is 44mm. No worries Harold, sorry to 'bother' you. Feel free not to post on this topic again.

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The ID is what matters.

Headset Standards | Park Tool

Crash_FLMB said:

I haven't measured it as the fork is still installed. The outer diameter is 44mm. No worries Harold, sorry to 'bother' you. Feel free not to post on this topic again.

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You're asking if a 1.5" tube will fit through a 1.125" hole... ask your local shop if they have a Park Tool headtube stretcher.

Someone I met mentioned they were going this route so I was just curious if it was possible. Now I know it's not.

- considering how much hell my old straight headtube frame has been through for over 10 years, I despise the companies making forks for not continuing to make straight steerer forks - finding good replacements is really hard for my Ti frame.............

For those who think I was completely off my rocker, I got the idea from videos like this. So while it may not fit on my frame, I wasn't completely off balance by asking this question.

This is confusing because some say it could work by having the bottom headset cup hold an external bearing meaning the bottom cup would go into the 44mm (inside diameter) of the headtube and the part of bottom cup that extends outside of the headtube that holds the bearings would be bigger than the headtube external diameter by a bit (1.5" - 1-1/8"= 3/8" or 9.525 mm) the top would remain the same. It makes sense that it could work but after reading all the articles I am still unsure. The reason I am interested is because I have a 2013 Giant Revel 29er 1 which has a straight headtube and I have a fork from my 2021 Giant XTC advanced which is a Rockshox SID which has a tapered steerer tube.

If your bike has a 44mm id straight headtube it will accept a tapered fork. If it has a 38mm id straight headtube it will not.