Dia Compe TT brakes levers won't tighten
 

History: I've done all my own bike maintenance for 30 years. First time installing a Tri cockpit.

Just installed a used set of Dia Compe TT brake levers on my used Profile Design T2 Wing base bar.
https://cimg0.ibsrv.net/gimg/bikefor...f24a16476a.jpg

The brakes were really loose when initially installed inside the base bar end. I started tightening them but stopped when I feared I would brake the mounting mechanism or strip out the screw threads. The brakes are usable but rotate inside the bar (with effort). I can live with this - but would prefer they stay in a fixed position.

With the brakes already being used - I assumed they had already been tightened sufficiently on whatever bar they were previously mounted on. (Of course they could have been installed on a smaller diameter bar)

In researching this issue (not much out there) I had seen one post that stated to use a large flat-head screw driver to flare out the mounting flanges.

I'd like a second opinion opinion before I attempt this "adjustment".

In general, I've found that he inside diameters of handlebars aren't very consistent. I guess one option would be to somehow shim the mounting flanges, but I wouldn't hesitate to try to flare them a little bit. It doesn't sound like it would require anything too severe to achieve your goal.

I made the adjustment to spread the mounting flanges outward and the brakes still rotates inside the base bar.

From the scratches inside the bar, it appears only the very edge of the flange is touching the bar - not a very good design IMO.
https://cimg6.ibsrv.net/gimg/bikefor...88759358bb.jpg

I wonder if a sleeve of rubber or thin aluminum would increase the flanges' friction in the bar?

What is the inside diameter of the bars? Sram and Tektro makes levers to fit >19mm ID bars.

I would try making a shim from an aluminum can first. Another option is to use a rubber bushing in place of the expanding piece on the brakes similar to what this has. Hope Grip Doctor Bar End Plugs Blue (coloradocyclist.com) Try your local hardware store. Ace usually has a supply of rubber bushings/bumpers in the loose fasteners section that might work.

The shim made from an aluminum can did the trick. Not "rock" solid - but they don't move under normal pressure.

Thanks everyone for their help!