Any way to use 1" stem with 1 1/8 fork
 

I have some bull moose bars I'm trying to put on an early 90s trek mtb. But the trek takes a 1 1/8 threaded stem and the bull moose have a 1" threaded.

Is this impossible? Thx

They sell shims for that. If you can't find one, sometimes they come with threaded to threadless stem adapters.

It's a less direct and less secure connection, but it is possible.

There is no way to put a 1" stem on an 1 1/8" fork, but you may find shims to put your bars on an 1 1/8" stem. You may also be able to find an 1 1/8" stems that fits your bars, but everything is mostly for 31.8mm bars these days.

What are you talking about? You can absolutely put a 1" stem in a 1 1/8" fork with a shim. Bullmoose bars don't take stems, the stem is integrated with the bar.

I have no idea what you mean by a shim, but when I think of a shim i think of a piece of metal used to make a smaller part larger. If this is what you mean by a shim then it would be physically impossible to put a smaller diameter part onto a larger diameter part by adding to the diameter of the larger part.

Think old school quill stem and it makes sense. I haven't seen a shim to adapt a 7/8" quill stem (1" steerer tube) to a 1" quill stem (1 1/8" steerer tube). Someone must make one?

Threaded or threadless Headset/fork?

Threaded headset the bearing adjustment is taken care of

1" stem has a 22.2 MM OD, 7/8"; a 1.125" fork has a 1" 25.4mm ID

the difference is 1/8" diameter, or 1/16" radius.

so a tubular shim would have a 1" OD, 7/8" ID. 1/16" tube wall thickness

and have a slot cut in it , so as the wedge in the stem is expanded the sleeve will expand within the fork.

I have seen such pieces made, with a lip edge around the top so as to shoulder on top of your headset.

It is a relatively simple thing for a machinist to make, Chicago certainly has machine shops to do small jobs.

You'd both be correct if we were talking about threadless forks, where the stem clamps to the outside of the fork's steerer tube. But Chris is talking about a threaded fork and quill stem, where the stem goes inside the fork's steerer tube. A 1" stem will absolutely insert into a 1 1/8" fork and you can safely shim it for a proper fit.

The trick will be to find the right shim. There are 1" to 1 1/8" shims out there, but most of the ones currently available are designed for threadless stems. They're not long enough to engage the length of the quill and the wedge. Shims made for quill stems are longer, plus they have a lip at the top edge so the shim rests in place and doesn't fall into the steerer tube while you insert/adjust/tighten the stem. At a glance, I couldn't find any shims available on their own, but I did find them included with some stems or threaded/threadless adapters like this one.

+1, I ran one of the reference adapters for a year or so then switched it out for another that had a sharp shoulder rather than that long taper which I though looked bad on the bike. Never a problem with either.

Yes, bullmoose bars have an integrated quill stem. Yes, there are adapters made to adapt a 1" quill stem to a 1 1/8" fork. I have a bike set up that way. The adapter is a slotted stainless steel tube. It is very secure and there is no reason why it shouldn't be. I got it online, but I don't recall where.

appreciate all the help, esp skydog for linking to one.

Except Sky dog (& oj)is using Outside diameters not Inside ones

the stem goes inside on quill stem types , the stem grips the Outside on a threadless fork.

is the one he linked to not the right shim?

No, skydog is right. That's the kind of threaded to threadless adapter I was saying that you can find the shims with. Make sure the wedge is inside the shim when you install for obvious reasons.

Looks like you also have to buy the quill to threadless stem adapter, as a Package to get it .

Maybe a Bike Shop did an adaptation for a customer and did not need the shim tube and so would sell it separately.

It Is Chicago after all, Not a one Horse town.

there is a shop or two nearby I'm going to check with

problemsolvers sells locking steam spacers.. might want to incorporate one of these in your weird stem setup

soma fabrications used to sell an adapter specifically for this during the fixie era

What a Rube Goldberg solution!!! OP, get a new set of bars that are compatible with whatever stem you choose, appropriate to your threadless steerer. Cheesh, this thread is a head slapper...

I disagree. What he is attempting to do is perfectly reasonable and not uncommon. I also had some vintage Nitto/Richie bullmoose bars that I wanted to use on a Trek MTB. A 1" to 1 1/8" quill adapter shim was a perfectly satisfactory solution.


Maybe the problem is that you and others don't understand what he is trying to do. I think it's been made perfectly clear that he's not dealing with a threadless steerer. He said so in his first post.

Oh. I see now. I'm sorry. Yes, a shim would work in this case. My bad.