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Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 14, 2012 at 12:30am

There are shims to go from 1" THREADLESS to 1-1/8" threadless and these are not really hard to find online.  Problem Solvers makes one -and I'm sure most LBS's could order one for you too.  These can be used on a threaded fork as long as you have a longer steerer and can put the shim BELOW the threads.

Putting the shim over the threaded part of a threaded stem is very dangerous because the steer tube at this point has been weakened by the threads and the stress of riding will cause the stem to snap at the threads.  Please, for your own safety do not attempt to do this unless you have a long enough steer tube on a shorter head tube where you can put the threadless stem and shim below where the threads start -effectively cutting the threaded part of the steer tube off and creating a 1" threadless stem.  The threaded portion is not strong enough to support a threadless clamp.  The threads are only strong enough to hold the headset bearings tight while the quill stem reaches down beneath and inside the threads and is supported by the wedge that is below the threads -not putting the leverage from above like how a threadless stem works.

The correct way to convert from a threaded 1" fork & steer tube to a 1-1/8" threadless bar stem is to use a quill adapter such as this.   you can then put a few shims under the stem and even hide the top headset race nut and locknut with a plastic sleeve if you so wish.

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Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 14, 2012 at 1:28am

Oh, wait.  I didn't have enough coffee this morning and misread and misunderstood what you wanted to do.  

You want to use a 1" quill stem inside a 1-1/8 threaded steer tube.   That's a different animal indeed and everything I said above is totally not helpful.

A 1" steer tube will usually have a 22.2mm inside diameter (ISO/JIS) while a 1-1/8 is 25.4mm ID.

They make 2-piece handlebar shims that do this but it would be a difficult installation to get them to drop in just right.  I don't think anyone makes such a shim any longer but it is possible that a seatpost shim that is 1.6mm thick can be adapted to work and squeezed down with a little cutting to make the notch larger so it can be squeezed into a smaller diameter.  

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Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 14, 2012 at 2:44am

I think the easiest way to do this would be to buy a couple/3 pair of the handlebar shims and after inserting the quill loosely into the over-sized steer tube drop them down along side the quill.  You might need to use something to push them down far enough or maybe put something inside the steer tube first to keep them from falling down too far if you want the quill up higher.  Something like a short chunk of 3/4 PVC pipe or maybe a 1/2" PVC coupling -whatever was just the right size to fit inside the 25.4mm ID.   You might need to add an extra set or two of shims above the first pair as  they are not very tall -depending on how large of a frame you have and how tall the steer tube is.

Then tighten down the quill and test to see if you got it good and firm.   

I think this would work if you were wrench-worthy and used your head.  It'd be a PITA to adjust later and may not be lawyer-approved -but it would work I think.

This is just for entertainment purposes only -do at your own risk.   I'd never do such a thing on a customer's bike.  On my own bike -hell, I'd try it if I couldn't find the right shim and just had to use the 22.2mm quill  in the 25.4 steer tube. 

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Permalink Reply by Kevin Mulcky on May 14, 2012 at 3:21am

Behold, The Soma Quill-inator!

http://store.somafab.com/soqu.html

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Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 14, 2012 at 3:39am

...the fug?

That has got to be strangest/coolest thing I've seen for bikes in a long time!

+1

Kelvin Mulcky said:

Behold, The Soma Quill-inator!

http://store.somafab.com/soqu.html

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Permalink Reply by Lee Roy on May 14, 2012 at 9:53am

I thought this would be both impossible and dangerous, if done at all.

The Quill-inator is ingenious!

 

+1

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