BBB chainring will not fit As a follow up from my previous question I decided to change my Campag Veloce 53T chainring. I bought a BBB 50T chainring. I tried to fit it over the weekend but it wouldn't fit.

I think the problem is that the original chainring is about 3mm thick where it bolts to the crank arm and the BBB one is 4.5mm. Below is a photo showing the gap where the chainring will not sit flush against the mounting points, and a diagram attempting to explain where the problem is.

I've had a look at Campy tech docs and can't find anywhere specifying the width of the chainrings at that point. I assume the BBB one just isn't compatible. Or have I missed something?
When Campagnolo introduced their 11 speed high end groupsets they re-engineered the chainset and introduced 'Micro Precision Shifting' and that new bottom bracket design amongst other features. Whilst they were at it they put the new (and thinner) chainrings on the 9/10 speed groupsets, including yours. Not that yours is compatible with 11 speed - you would have to replace the chainrings for that.

And yes, they have created a bewildering array of parts that are a compatibility minefield, making one suspect Shimano are not so bad after all...

Your BBB chainring is for the earlier 9/10 speed systems and sadly won't fit. Your best option is to put the 53T back on there until you can devote the man-months needed to research, afford and buy a genuine 50T Campagnolo MPS chainring.