Bicycle Mechanics - 1" threaded to 1 1/8" threadless

I have an older mountain bike that appears to have a 1" threaded headset set-up ( designed to look like a 1 1/8 style ) and I'd like to convert to 1 1/8 threadless. I have a Surly 1 X 1 rigid fork, Cane Creek headset, all the spacer hardware, and an Easton EA50 stem ... and would like to use them on this older (early 90's) bike. Are they interchangeable or are the headseat sizes (dia) different (<---always)? If it wasn't so cold out right now, I'd go out and start removing a few things and putting the calipers and ruler to it... It's about 5 above out right now and the garage is mighty frosty to work comfortably. Any ideas about this? Thanks...

Edit: The old bike headset (frame) measures dang close to the outside dia of a newer bike with a 1 1/8 arrangement SO...I was wondering if it is not gonna work in ALL cases? Probably so but, just curious.

You are stuck with 1" size unless you modify the the frame of your bike by replacing the head tube. As a retired shop teacher 1" and 1 1/8" are not the same size. Roger

You are stuck with 1" size unless you modify the the frame of your bike by replacing the head tube. As a retired shop teacher 1" and 1 1/8" are not the same size. Roger

Are you implying that's a dumb a** question? LOL (kidding) As an engineer I'd have to concur...generally speaking. What I wasn't sure of is if the headset arrangement/lock rings/etc. somehow necked down the opening the extra dia. allowing for a 1" headset...AND, if removed, would the opening in fact be larger to accomodate a 1 1/8" threadless fork/set. I haven't had it apart *AND* if you just do a quick-and-dirty test and put the old Mitoya digital caliper on the headset (frame tube body) of the old bike and compare it to a 2007 Motobacane frame that has a 1 1/8 set-up... They are approx. the same dia. +/- .004. I don't understand that and that is what peaked my curiosity (without putting tools to it and finding out with a true inside dia. read. If you could see the headset, it doesn't look like say....an old 1" quill stem headset. I wasn't sure if this would apply in all circumstances. I take it it does by your response. Thanks!


B.S. CEE 1990
M.S. CS 1992
Ph.D CS 2001

It sounds to me like you've done the preliminaries. I think that you're going to have to take it apart for an internal measurement or trial fit to know for sure.

It sounds to me like you've done the preliminaries. I think that you're going to have to take it apart for an internal measurement or trial fit to know for sure.


I think you are absolutely right. Strange. Until I came across this situation, I would have thought ( as was sugested to me above ) that each were distinctive sizes. This got me to thinking I could be wrong in some circumstances so, I put it out there. Thanks to all again.

Are you sure the quill stem is a 1"? A 1 1/8" quill stem was also made, not very common, but made.

Are you sure the quill stem is a 1"? A 1 1/8" quill stem was also made, not very common, but made.

Yeah. I'm also thinking there used to be a "devaluation" headset to adapt a 1" fork onto an 1 1/8" frame.

Yeah. I'm also thinking there used to be a "devaluation" headset to adapt a 1" fork onto an 1 1/8" frame.
http://www.chrisking.com/headsets/hds_devo.html
or this for alot cheaper
http://www.choppersus.com/store/product/635/Headtube-Reducer-1-1-8-to-1%22/

Yeah. I'm also thinking there used to be a "devaluation" headset to adapt a 1" fork onto an 1 1/8" frame.

It sure looks like it's just 1". I haven't taken it out and measured it. However, I did put the calipers on it right at the uppermost lock ring and got 0.998 so I figured it was. Probably the only way to take the guesswork out of it is just rip 'er apart and go to town measuring the inside dia. of the head tube.. I would have already if it wasn't so cold out. I'm being a sis and staying in where it's warm. (Floridain transplanted to midwest..not used to below zero wind chill and 10 degree garage temps) This was helpful info though. It makes it worth exploring further. I just took an uneducated guess that maybe there was some kind of adapting going on since the outside head tube actually measures the same as one w/ 1 1/8 fork. Just knowing it's a possibility.....

if you want to use a 1 1/8 stem on a 1' quil you can get an adaptor part at nashbar and many other sites just search it, i know one of my friends did that when i sold him some OS bars because they dont make too many quil stems with OS clamps. But the adaptor will deff work if this is all you are looking for

you can buy a 1" to 1/18 converter thingy. Slide it into the 1" threaded tighten down now you have a1 1/8 thread less. Go on line to any mail oprder bike parts company they cost about $10-20. I got on last year for an old bike. works great but heavy

+1 on an adapter. granted, i do prefer threadless but its a far easier solution than a new headtube.

If you measured the outside diameter of your quill stem and it was 1", then you already have a 1 1/8 headset. A 1" headset would have had a 7/8" stem dia. You didn't say exactly what it was that you measured, but if you were using calipers just above the lockring, I can't see what else you could have been applying them to!

If you measured the outside diameter of your quill stem and it was 1", then you already have a 1 1/8 headset. A 1" headset would have had a 7/8" stem dia. You didn't say exactly what it was that you measured, but if you were using calipers just above the lockring, I can't see what else you could have been applying them to!

+1
That's what I was thinking while going through the thread.

The OP can still get an adapter to convert to threadless. He just needs the 1 1/8" instead of the 1".

I would concur that whatever the OP measured makes a big difference.

My 2003 Giant Sedona DX had 1 - 1/8 threaded, with a quill stem. I replaced the fork and headeet, and now run 1 - 1/8 threadless.

I am ambivalent in the threaded vs threadless question. However, in choosing a rigid fork, I didn't have to be picky about steerer tube length, which is why I made the change to threadless when I replaaced the fork.

Don't confuse the 1 1/8" threadless stem with a quill stem for a 1 1/8" steerer. Two different beasts.

A 1 1/8" quill stem has an outside diameter of 25.4mm (1"), it fits inside the steerer with will measure 1 1/8" on the outside. If this is what you have then your bike is a candidate for replacing the current setup with a threadless 1 1/8" setup.

AASHTA (http://sheldonbrown.com/harris/stems/1-1-8-quill.html)

It sure looks like it's just 1". I haven't taken it out and measured it. However, I did put the calipers on it right at the uppermost lock ring and got 0.998 so I figured it was.

Measure the flats on the top hex nut. 30/32mm = 1" , 35/36mm = 1 1/8" , 40mm = 1 1/4"

I agree with the above, if you measured .998" then you have a 1 1/8" stem. The measurement for a quill stem is the outside diameter of the steerer tube, not the actual size of the quill stem. As mentioned above, my 1" quill stems actually measure 7/8". This sometimes causes confusion when buying a new quill.

You should be good to go with your conversion.

Don't confuse the 1 1/8" threadless stem with a quill stem for a 1 1/8" steerer. Two different beasts.

A 1 1/8" quill stem has an outside diameter of 25.4mm (1"), it fits inside the steerer with will measure 1 1/8" on the outside. If this is what you have then your bike is a candidate for replacing the current setup with a threadless 1 1/8" setup.

AASHTA (http://sheldonbrown.com/harris/stems/1-1-8-quill.html)

Thanks a million for pointing that out and for the ref. to the link. Once again...Sheldon's site has exactly the info I was looking for. He sure will be missed.