Bicycle Mechanics - Aero bar clamping problem

I help a novice triathlete with her bike. She had an '88 Centurion Ironman, Nitto B115 bars, and bought a cheap set of Ascent aero bars, which worked just fine. She moved up from C&V to a 2006 Team Fuji carbon with a Fuji bar, clamp size 31.8, but the bar itself is a lot smaller in diameter than the Nitto.

On the Nitto, the toothed shims worked just fine. On the Fuji bar, they are still way too big.
The gap between the bar and the clamp just too big for the shims to fill.

Do they sell different size shims alone, or does she need to find a new set of aeros? I'm a C&V guy, so the modern stuff is unk to me.

Thanks.

Does the Nitto bar have a longer clamp diameter section (25.4 mm? 26.0 mm ?) than the Fuji's 31.8 mm diameter section which could neck down to the regular 23.8 mm bar diameter much sooner? If so, the areobars may be able to clamp to a 25.4 or 26 mm section on the Nittos but are too large to clamp to the 23.8 mm section on the Fujis.

The Nitto's have a wide sleeve, but we clamped the aero's just outside the sleeve, no problem.

Why it won't do so on the Fuji is beyond me. I even unwrapped some of the tape to get a wider stance, just too small a bar, I guess. The shims do not touch each other in the top/bottom of the aero clamp, but their diameter is just too big.

I've got some shims from some other aero's I may try. Thanks for your time.

I didn't ask but is the Fuji's bar also carbon? Many carbon handlebars are not rated for use with clamp-on aerobars. If the bars are Al, it should not be a problem.

Generally aero bars clamp to the bulged stem of a bar with road bar specifications. That is, 26.0mm for traditional bars or 31.8 for modern OS bars. To the best of my knowledge, aero bars are not intended to clamp to the outer (23.8) section of any bar. This may be a matter of strength or leverage as you move farther out the bar.

Companies that make a lot of aero equipment (Profile Design etc.) also make a series of bars with extended stem areas so that aero bars can be clamped on a little farther out if the rider desires that setup for comfort. Some of the cheaper OS bars that I have seen, have a stem area taper so close to the centerline that fitting aero bars is almost impossible.

When you change over to base bars instead of road bars, this problem is a little less likely as most base bars have a wider stem area.

They're aluminum, so I guess I'll see if she wants to change bars. It just goes from 31.8 to 23.8 so fast, there's no way to get the clamp on. The Ascent aero's worked pretty well for a low-priced bar, but we'll make some changes and see what happens.

I have a set of Profile's in 31.8 with a much wider base, and a Richey Pro 25.4 26.0 that I'm sure will work fine, but she'll need to use a different stem, which I have, but I'm not sure I want to trade my 3T Forgie for her Fuji. I don't use aero's, though, so it may be a decent trade.

Thanks so much for your help, guys.