Not sure if I can mount bar-end shifter on bullhorns
 

I bought these handlebars

Amazon.com : Retrospec Bicycles Pursuit Bull Horn Style Lightweight Alloy Handlebars for Track Bike, Black : Bicycle Bullhorn Handlebars : Sports & Outdoors

they're great handlebars, and much to my surprise can mount mountain bike 22mm shifters.

But they can't hold bar end shifters.

Now, the clamp size on these is 25.4. Does that mean that if I get one with clamp 31.8 I'll have better luck? OR maybe these are just unique handlebars?

Depends on the bar inner diameter where the bar ends mount. If the ends are still meant for 22.2 grips and levers then no the bar ends sill won't fit. But it the larger clamp sized bars also have a larger end diameter and the ID is compatible the bar ends might fit. So you have some homework to do. Find out the 31.8 clamped bar's end size. Andy.

Can't find any info on that. Have to look at pictures of them and guess.

Yes, this is the cost of mail order purchasing. You sometimes have to guess. Andy.

Bar-ends will mount on some 22.2 (7/8") ends. I've done it on several bikes. Your problem may be the "cheap" bars. Higher quality bars will be thinner walled tube and accept bar end shifters.

I could , if I wanted to ..

MTB bars are 22.2 mm (7/8 inch)
Road bars are 23.8 mm (15/16 inch)

Bar end shifters are made to fit inside the wider gauge road bars. You can mount thumb shifters anywhere on your mountain bars, but probably not bar-ends.

31.8 vs 26 vs 25.4 mm is the clamp diameter, where the stem clamps to the bar. The clamp diameter is independent of the grip diameter.
There are 7/8 in MTB bars with 31.8 mm clamps, and there are 15/16 in road bars with 31.8 mm clamps.

Cheap track bars aren't concerned with fitting shifters. They are made for track bikes that don't have shifters.

I have these handlebars. I think they are more designed for MTB and Hybrid riders to convert handlebars on the cheap without having to change their stems, brakes, and shifters to accommodate road bike sizes (23.8mm). On the downside, this may make installing barcon shifters difficult. On the upside these bars allow for ridiculous set-ups like mine - SRAM grip shifters on bullhorns. Not nearly as unwieldy as they look, although I only use this for commuting.

http://bikeforums.net/attachment.php...hmentid=402445

Maybe you could ream the ends out to fit the barcons. The Specialized BB-1 dirt drop style were made like this. I have a coupla bikes (CB Zip & Volpe) with barcons on Scott AT-3 bars.

Volpe:

http://bikeforums.net/attachment.php...hmentid=402516

Another issue is that many bullhorn bars curve up at the tips, and while the barends may fit the diameter they may not fit because of the curve...Try cutting the up-curve off.

or use a reverse Brake lever .. for racing Triathlons there is a brake lever with a shift lever on the side of it. 2 in 1..

and for thick wall Carbon bars there are external mounting shift levers

My Latest Wanky Set-up
 

^^^This^^^ I've got a pair of junk fixie bullhorns that have an ID too small for bar end shifters.

I got a pair of Profile Design Wing-something base bars. Tried using bar ends and cross brake levers. It worked, but I wasn't real happy, especially using them in town. The shifter on the ends of the bullhorns sucked and the brake levers weren't handy to get to.
http://i155.photobucket.com/albums/s...2/DSCN0909.jpg


I switched to TRP brake levers and moved the shifters to Paul Thumbies. Much better.
http://i155.photobucket.com/albums/s.../K2Rack021.jpg

The only thing was the TRP levers, they worked great but not for my short fingers. I changed to some Shimano BL-TT78, or something, that have adjustable reach and they fit great. The shifters are where I can get to them with my thumbs and are a lot more practical than having to reach so far to get to them. Especially on hills it was awkward. With this set up I can pull both levers towards me, the left drops to the small ring and move the right three clicks----with my cassette it equals one lower cog if I stayed on the big ring. It's quite quick and easy.

The up-turn on the ends is like the horn on drop bar hoods. The whole base bar feeling is like riding hoods. My old back with its compression fractures doesn't like drops at all and there's no sense fighting it. The last road bars served no purpose but to fit the fancy brick columns at my main grocery store to lean the bike on.

Are the Pual Thumbies on their respective sides?
 

I'm looking into doing this for a Shimano Nexus 8 - so I only need one 8 gear shifter. So, I can't really tell from the photo, bit is the Right Paul Thumbie on the Right side and the Left on the Left or are these swapped? I think they are normally not used in this configuration so I'm trying to figure out which Thumbie to buy (the right or the left) so that I can mount it like you have on the right side. Is your right Thumbie marked right or left?

Now that is crazy! I like the outside-the-box thinking :thumb: