Walterscot
Retro Guru
That’s right @LondonClassic, the compact chainsets with the ‘hidden’ 5th bolt have the offset 110/112 BCD. Visually the best way to tell the difference is the location of the chain-drop pin.
It's not quite as simple as that. The rings I have came off an alloy PowerTorque chainset, pretty sure it was Veloce (definitely not anything higher) and they had the hidden fifth bolt. Whether the bolt is offset I won't be able to confirm until I get back home tomorrow.I think up to Centaur the BCD was standard 110 5 hole (equidistant) for alloy chainsets.
For Chorus, Record, Centaur carbon spiders: they messed with the controls and made one of the bolt holes offset - equivalent to 112 BCD - and enough to mean you had to buy Campag rings or the expensive TA or Stronglight compatibles. The price of these is so high its often cheaper to buy a new chainset. So not all campag compacts use the same rings and worth checking.
@Walterscot do I have that right? Xenon, Mirage, Veloce,Centaur (alloy) are all standard 110 BCD and Chorus and Record and Centaur (carbon) are wonky I think.
Its no end of fun being a Campag compact chainring shopper!It's not quite as simple as that. The rings I have came off an alloy PowerTorque chainset, pretty sure it was Veloce (definitely not anything higher) and they had the hidden fifth bolt. Whether the bolt is offset I won't be able to confirm until I get back home tomorrow.