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Vintage Bullmoose bars on my 90's Trek

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Vintage Bullmoose bars on my 90's Trek

Old 10-03-18, 09:18 AM
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kiblam
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Vintage Bullmoose bars on my 90's Trek

I recently received some vintage bullmoose handlebars to put on my trek 8000. The issue is the stem that is welded to the bars has a diameter of 21.1mm. The trek needs a stem with 25.4mm. I'm a broke college student so I'm trying to find an affordable and correct way to get these bars onto my bike. Any help Would be greatly appreciated. I'd post a picture but the forum won't let me until I have reached 10 posts.
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Old 10-03-18, 09:50 AM
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Basically you want to take a quill style stem for a 1" fork and put it in a 1 and 1/8" fork.

I don't know a way to make it work.

The good news is that a 1 and 1/8" quill stem plus handlebar are cheap. If you have a bike co op in your area, you can get the parts for about $10. Maybe nothing, just a straight trade for the bullhorn.
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Old 10-03-18, 11:13 AM
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It would be pretty straight forward to machine a shim that fits inside the 25.4 ID steerer and has it's ID that allows the 21.1 stem to fit.

https://stockcarsteel.com/aluminum-t...m-round-tube-1 This is a stock list with a 1" OD and .083" wall AL tube shown. If my math is correct this tube would likely only need minimal OD sanding to have it slip inside your steerer. The ID is .about .003" oversize WRT your stem's quill. So no machine shop tooling needed after all. Get a foot, make 3 shims and offer the 2 left over to cover your cost. Andy

Forgot to add that the shim will need to have about 2.5" of it's length slotted to allow it to expand as the stem's wedge is tightened.
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Old 10-03-18, 11:56 AM
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Originally Posted by Andrew R Stewart View Post
It would be pretty straight forward to machine a shim that fits inside the 25.4 ID steerer and has it's ID that allows the 21.1 stem to fit.

https://stockcarsteel.com/aluminum-t...m-round-tube-1 This is a stock list with a 1" OD and .083" wall AL tube shown. If my math is correct this tube would likely only need minimal OD sanding to have it slip inside your steerer. The ID is .about .003" oversize WRT your stem's quill. So no machine shop tooling needed after all. Get a foot, make 3 shims and offer the 2 left over to cover your cost. Andy

Forgot to add that the shim will need to have about 2.5" of it's length slotted to allow it to expand as the stem's wedge is tightened.
Sand the sleeve's OD to size; then slot the sleeve to fit inside the head tube.

After you have the parts fitting correctly.

Get a 1.125" shaft collar to functionally replace your current stem, set up your threadless steerer in your headset first, and use the shaft collar to clamp the system together, remove the star nut (or compression plug); grease the inside and outside of your aluminum sleeve, push into the steerer so that it is flush with the top, insert stem, adjust height and square up with front wheel, tighten bolt to pull wedge.

The grease is so that you can take it apart in the future (see stuck seat posts for why).
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Old 10-03-18, 12:25 PM
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It wasn't until the late 90s that they came threadless.

I still think the best option is a cheap stem and handle bar at a co-op.
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Old 10-03-18, 06:52 PM
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Originally Posted by rosefarts View Post
It wasn't until the late 90s that they came threadless.

I still think the best option is a cheap stem and handle bar at a co-op.
I didn't take the OP's first post to say he needed a bar/stem but that he wanted to use the bullmoose one instead. Andy
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Old 10-03-18, 07:49 PM
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Find an old junk bike like a Schwinn Varsity, an old Ross, or a Murray. Maybe a BMX bike. They all used .833" stems (of which 21.1mm is the metric equivalent). Cut the steerer tube off a bit above the fork crown and below the threads and you have your shim stock. Hacksaw or Dremel a slot through the tubing wall and for its full length and you now have a shim with an external diameter of 25.4mm (1") and an inside diameter of .833", your 21.1mm. Grease up the Bullmoose stem and insert into the shim, then grease up the outside of the shim and insert into your Trek's fork steerer. Go ride.
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Old 10-04-18, 01:15 PM
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I like the idea of buying the tubing and making my own shim. I wonder if that is the best option or if I should try and sell the bars and get some new ones that fit correctly.
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