Stem/Bar Adapter 31.7-->26mm
 

I have a 31.7mm stem I want to use with some older 26mm handlebars. Is there some type of adapter that will clamp around the bar and allow me to use this stem? I think I've seen it come with certain stems but I don't know if there is a universal one or not.

Stem shims are fairly common.

You may find that the bar creaks when you use the shims. A possible fix would be to wick cyanoacrylic cement (Krazy-type glue) between the bar and the shim, NOT between the shim and the stem, while everything is clamped together, to immobilize the joint. Be very careful not to glue the shim to the stem! This is commonly done to quiet creaking sleeved bars, which is essentially what you are creating.

I have a 26.0mm clamp stem and I am in need of a 31.8 mm clamp stem. What size stem you have, maybe we can trade? I believe mine is a 100mm, 3T brand.

Yep, had to order mine from Amazon though. My LBS told me that "they" (whoever they is) make such shims for seat tubes but not for handlebar stems. This, after I had already found what I needed on line but checked with the LBS to try and eliminate the shipping time.

Re : Shims, QBP has over size 31.8 type stem to either 26mm or 1" bars ..

but the LBS may not have them in stock, but can order and save you shipping.

Or just go on eBay and buy the correct size stem for $10.