Hi. I have an old Orbit XL-ii road headset. Its well used and probably 20 years old. Rather than replace the bearings I am going to get a new headset. The steering tube measures 1". But, when I bought the bike, the headset had a shim between the steering tube and headset. So, does that mean I need a 1-1/8" headset? How do I know what I need?

Sounds like you have a 1" ISO Standard threadless headset.

link

Make sure you purchase a headset that matches your steerer tube inside diameter and your steerer diameter.

Thnaks. Do you mean the head tube.? the tube connected to the fork is 1" but there was a shim when I took it apart. So does that mean a 1" 1/8 headset should have been used.
Is "steerer tube" the head tube?

If the headtube on the frame was sized for a 1-1/8" headset but the bike came with a 1" steerer fork, the shim (or, more properly, reducer) would have allowed a 1" headset to be installed. If you don't want to replace the fork, you still need a 1" headset. If you are willing to replace then fork, you will have to measure the frame's headtube inside diameter after removing the reducer to be certain it was correctly sized for a 1-1/8" headset.

BTW, 1" threadless headsets aren't that common anymore but the Cane Creek 40 is available in that format. I just installed one on an old Litespeed frame.

It is possible that a 1.125" headset was used but only if the head tube was about 34.0mm inside diameter. A 1" steerer fork could be installed with adaptors/shims. But this would not be the usual or common at all. The fork crown race would need to be shimmed or a specific one with the bearing dimensions of the 1.125' headset and the crown seat diameter of a 1" headset (26.4mm or 27.0mm).

Are you sure the shim wasn't inside the stem and not overlapping with the upper bearing race (the one with the conical compression ring fitting in it)? The use of a 1.125" stem on a 1" fork is FAR more common then mixing the fork and head tube specs.

Luckily all this is moot soon enough with a few simple measurements. here's a dimensional chart to discern the different standards. Sheldon Brown's Bicycle Headset Dimension Crib Sheet Andy.

Parts to measure : the head frame, inside where the headset race presses into, fork crown race seat ..
(you have the 1" steerer tube stated)

PDX USA made Chris King headsets all are available in a threaded or threadless type ..

& the relevant top pieces are interchangeable, above the top headset bearing..

Yes, Chris King headsets are indeed still available in 1", both threaded and threadless, but are VERY expensive which is why I didn't mention them. The Cane Creek 40's are very good headsets at 1/3 the cost.

You have an FSA headset, Orbit XL_II is a model and was/still is only available as a 1 1/8" EC FSA Orbit XL II Threadless - FSA

When you say you have a shim, would go with what #HillRider and Andrew R Stewart are saying

Ok, but why is the tube on the fork only 1"? Does the size of the fork tube and headset need to be the sam?

Time for LBS.....tooo many unclear terms to follow. STeerer tube vs. steerer diameter....vs headset diameter. Must be an easy way to understand this. If the tube connected to the fork is 1", is it true that the bike should have a 1" headset?

there are 2 different steerers .. The OD of a 1" fork*, is the ID of a 1,125" steerer tube the wall thickness is 1/16"

you could use a 1" fork in a frame made to use a 9/8 steerer
and use conversion parts to make up the difference ,

but not the other way .. like 9 pints in an 8 pint pitcher doesn't work out.


There is Competing standards Too .. JIS for Japan , ISO for Europe. .. small but significant ..

* 1" forks with threaded headsets use a stem that is 7/8"

threaded 1,125" used a 1" quill stem , but Threadless stems grip the Outside of the Tube.




bene sugg : go where someone can see the task at hand, like your favorite Bike Shop.

Way too confusing.
Your fork has a 1" steerer tube.
When you say you have a shim it sounds like your frame is designed for a 1 1/8 steerer and has a 1 1/8 headset installed with reducers for the 1" steerer. This would have to include a special crown race on the fork. I'm surprised that a 20 year old road bike frame would be designed for a 1 1/8 fork.
Are you sure you are not referring to the compression ring on the top bearing?

+1 As recommended above, time for the LBS to straighten this whole thing out.

Yeah. Sorry. I meant head tube.

This is also what I think.

It might be a confusing situation at first. But after taking measurements, looking at that Sheldon Brown page I sent, and searching for parts, things should line up.

I may be wrong, but is the OP suggesting that there is a shim between the cup and the lower headtube? If so, the shim may have been inserted simply to prevent the cup from rocking in an out-of-round head tube.

If this is so another shim made of an aluminum soda or beer can might be all that is needed to secure the new cup. This type of shimming was a common fix, that worked quite well, to manage a cup/frame interface that wasn't perfect.

At this point, I don't think any of us, including the OP, are sure of what he has. That's why I thing he is overdue to take the whole thing to a bike shop and let them sort it out. We can't really do it from here and we are only guessing.

Campagnolo makes record in 1" threaded and threadless, and origin 8 has a very economical threadless cartrige headset.

Good info but, once again, no one is sure what the OP really needs.

No, we don't, but I figured I would endorse 1" headsets I've used.

here are some photos.

Do the photos help? thanks for the assistance

The photos confirm you do indeed have a 1" steerer tube (the outer diameter of the crown race is immaterial). What we don't know yet is what the rest of the headset and headtube look like and if you really have a 1-1/8" headset and shims or just a plain 1" headset too.

Show a shot of the measurement of the inside diameter of the head tube (the part of the frame that the steering tube goes into) without any headset parts...

The photos also confirm that you have the world's oldest vernier calipers...

frame is at LBS for repair