[QUOTE=FBinNY;17629106]I'm a bit confused by the post. Have you actually measured anything?

I ask because clip-on bars are usually mounted so the clamps are about 6" apart, or roughly 3" from center. That's beyond the clamp bulge, so both 26mm and 31.8mm bars would have already been reduced to the grip/brake clamp diameter of 15/16" (23.8mm), and that's what the clip-on bar clamps would be.
I obviously am not the best mechanic out there or I wouldn't be asking a stupid question like this. I tried to mount the clip ons on my handlebars and they will not tighten down nearly enough. My handlebars are 26mm. I know I could change the bars out relatively cheaply, I was just trying to find a way to make it work. I asked a mechanic at the bike shop and he said they usually shim it with something like another poster mentioned, but they are $15 apiece and they didn't have any. He said some people shim them with an aluminum (soda) can-honestly. I am pretty experienced with using aero bars. I have a TT bike and have done triathlons and many time trials. I'm not gonna be racing on the SS, just looking for a way to get in a different position occasionally. I'm doing a cross state ride in June (300+ miles in 3 days) and I'm doing in on the SS.