Bicycle Mechanics - 25.4 handlebar on a 26mm stem??

I have a mtn bike handlebar and have a couple of options for a stem. One of them being a 26mm clamp road quill stem. The stem is one of those with the two bolts in front where you can remove handlebars without having to remove levers and tape. Is this doable? Dangerous? Shimmable?

i dont believe it is doable no, i doubt its shimmable either due to the tiny difference in diameter's.

i personally wouldnt risk it, and would simply get a stem thats designed for 25.4 bars.

Sure. Most people use a soda can to fashion a shim. Some people just run them without shims. I've got em running both ways. The pop-top type stems are pretty forgiving.

Harris Cyclery (http://sheldonbrown.com/harris/handlebars/index.html#shims) sells a stainless steel shim for precisely ths application for $11.95.

Nitto Handlebar Shims $11.95 - These beautifully made stainless-steel shims let you use a standard 25.4 mm (1 inch) diameter handlebar in an Italian size (26.0 mm) stem.

i dont believe it is doable no, i doubt its shimmable either due to the tiny difference in diameter's.

i personally wouldnt risk it, and would simply get a stem thats designed for 25.4 bars.

i agree. it may work but not worth it to me.

ed rader

I tried this using a cut up soda can, and the bar kept slipping on me. Not worth sacrificing safety imo. Maybe that $12 shim will work better, but I'm not that daring.

The problem with the soda-can shims is that you have multiple layers of a smooth-surface. This spreads out the total-friction across multiple-layers. One of those layers may have slightly less friction than another and will slide first.

A single purpose-made shim with serrated surface will grip much, much better. Bike shops usually have these by the tonne...

The problem with the soda-can shims is that you have multiple layers of a smooth-surface. This spreads out the total-friction across multiple-layers. One of those layers may have slightly less friction than another and will slide first.

A single purpose-made shim with serrated surface will grip much, much better. Bike shops usually have these by the tonne...
Yeah, I had tried one of those as well. It had ridges on the outside and a somewhat bumpy surface on the inside. It still slid, and then even started splitting into pieces when I'd tighten it further.

I have the stainless Nitto shims on a couple of bikes. They can can be trimmed so they don't show and I get no slippage at all. They are smooth, no serrations.

I have the stainless Nitto shims on a couple of bikes. They can can be trimmed so they don't show and I get no slippage at all. They are smooth, no serrations.

On those setups with shims, I've been utilizing some nice brass sheeting I liberated from work.

On those setups with shims, I've been utilizing some nice brass sheeting I liberated from work.

I've successfully used shims out of brass and out of stainless steel sheets. Usually, I fulfill my metal needs at onlinemetals.com Otherwise, soda can shims are pretty lousy, crushed by the stem clamp. A tin can shim should be better and, in fact, fit well with the thickness of 0.3mm in my memory.

You need a shim of .011" or "11 thousandths". The diameter difference is 0.6 mm or 0.023". The shim has to be half that thickness or .011". You can buy brass shim stock at most automotive supply or industrial supply stores in a variety of thicknesses. I expect .010" or 10 thousandths is the nearest common size and should work.

Handlebar shims suck. I tried the exact thing you want to do. Using shims on a 25.4 bar to fit a 26.0 clamp. Lots of slippage.

Now, shims that go on the steerer tube work ok, but shims that go on the handlebar totally suck. Go ahead. Try it.

couldn't you just lightly sand the outside of a pop can, then cut it open, sand other side, trim, assemble with crazy glue

seems like that might work

Handlebar shims suck. I tried the exact thing you want to do. Using shims on a 25.4 bar to fit a 26.0 clamp. Lots of slippage.

Now, shims that go on the steerer tube work ok, but shims that go on the handlebar totally suck. Go ahead. Try it.

I think it depends on the type of bars that you are shimming. Flat bars are no problem because there is little twisting force applied to them. I haven't had a problen using them on upright bars on bikes that are used for casual riding, but I can imagine how they could suck with drops or cowhorns.

I think it depends on the type of bars that you are shimming. Flat bars are no problem because there is little twisting force applied to them. I haven't had a problen using them on upright bars on bikes that are used for casual riding, but I can imagine how they could suck with drops or cowhorns.


Shimming handlebars suck. Period.

Shimming handlebars suck. Period.

Does not!

Does not!


Does too.

Brass isn't a good material for such a shim, its too slippery. I sucessfully used shimmed a set of north road bars used upside down as cheapo moustaches. Pop can is way too thin for this application. I made my shim from a piece of flat aluminum stock that I found lying around work that I measured with calipers to confirm the right thickness. Never had any problems with it not holding in all the time it took me to decide I didn't like the bars. I think I roughened the surfaces with sandpaper, in a direction that would be parallel to the bars, but I suspect it made no difference.