Converting Campagnolo Centaur CT to single chainring

[chriscross1966]

Hi folks, in my need to do something stupid I've fitted a Campy Caentaur Carbon Compact UT crank to my Brompton. Does anyone do a kit to properly fit a single chainring to it?... ATM I've got a slightly ugly bodge using washers to add the extra width to a set of KCNC chainring bolts (slightly better for the job than the Campy ones I have) but if anyone knows of a set to properly fit a single chainring to it (on the outside mounts) then I would treasure the knowledge... Push comes to shove I can make something to fit, but would rather not...

 

[chriscross1966]

The crank in situ, note ugly washer solution, there's more on the back too :-(

 

[Graeme_FK]

You could just use track chainring bolts, or shorten the collars on the existing double chainring bolts.
Both were regularly done "Back in the Day" when double chainsets were regularly used on single-ring time trial bikes. "1x" is not as recent a trend as many think :-)

 

[chriscross1966]

The track chainring bolts I could find were all M8x0.75 threads with 10mm collars, the carbon compacts use an 8mm collar threaded M6x0.75mm for no good reason other than "Campy!....screw you buddy!"....

 

[Graeme_FK]

The track chainring bolts I could find were all M8x0.75 threads with 10mm collars, the carbon compacts use an 8mm collar threaded M6x0.75mm for no good reason other than "Campy!....screw you buddy!"....

Sorry, yes, forgot the smaller tab drillings on the carbon cranks - actually if you are going to make the whole spider in carbon, including the chainring support tabs, having a bit more material around the chainring bolts makes perfect sense, and if the bolts are going to be alloy, there's logic in using a (proportionally) coarser, smaller thread. So there is a good reason.

You do need to bear in mind that you are doing something that really wasn't in the design brief ...

I just turned a female down on the lathe but it only gives about 3 turns of thread engagement with the male which I don't think would be enough in use ... so the only other workaround I can think of, that would be neater than what you have, would be to get hold of a worn-out inner ring and cut the mounting tabs off that, and file to fit neatly into the back of the spider.

 

[chriscross1966]

The plan is to make an aluminium male piece including a large flat to spread the load where the rear ring was, and make a little fixture that will allow me to turn off a mm or two on the end of the KCNC females. Have ordered the taps and dies... Have also ordered a BB facing and tapping tool from Wiggle as I'm having issues with both slop in the Hirth joint alternating with binding in the crank.... On the other hand the damn thing is about a million times smoother than the old FAG unit...

 

[chriscross1966]

Right.... a bit of research has led me to discover that I can get shim washers to fit both between the bottom bracket and the bearing cups, so I can use them to push the drive side cup out, and also that I can get bearing shims to suit the Ultratorque cups too. Between them I should be able to get this thing to work properly.

 

[oldroadman]

Ah, I give in, the Americans win again. Campy...how do we get there from CAMPAGNOLO...or Campag as known to generations of bike riders?