As tech-minded readers may already know, double chainring cranksets for roadbikes generally are described as either “standard” meaning a 53 tooth big ring and a 39t small, or “compact” with a 50t/34t combination. Compact road cranks have a 110mm bolt-circle-diameter which will accommodate rings smaller than 38t, down to a 34t….except for Campagnolo. No, they decided to make the their compact BCD 110mm for four of the bolts and the fifth “hidden bolt” (positioned behind the right crank arm) lies a little further outside a 110 circle. Why?
Stupid, stupid, stupid. I remember years ago when I first started wrenching, the old hands would bitch about Shimano creating ridiculous standards. I would like a Campagnolo designer to explain to me what performance benefit could possibly come from placing one of the five bolts 2mm outside the 110 BCD. A rational person could only assume that they did it to make their cranks incompatible with other manufacturers’ chainrings (though Specialties TA does make some). I have to say that I am personally offended….you suck Campy!
The Campy ring situation puts a crimp in my attempts to tailor custom bikes to suite a customer’s needs. For instance, no one makes a Campy compact compatible cyclocross chainring guard. But I’m not going out like that. I took a Campy 50t ring, ground off the teeth and combined it with a 46t Campy ring. Voi la!