Steve, the TA Cyclotourist triple cranks use the same set of holes to attach the middle and inner chainrings as to attach the inner ring on a double. When changing the crank from double to triple, you just need the triple hardware set with longer bolts and extra spacers, no need to drill extra holes. There was a TA model with a very large bolt circle (the Criterium perhaps), may have been a 151 BCD like 50's vintage Campy. But these also had the very small bolt circle where the outer ring attaches to the crankarm, identical to Cyclotourist, I think. The inner ring still attached to the outer ring. Even if you have one of these, which are fairly rare, the solution is to buy a full set of Cyclotourist triple chainrings, including a new outer, and bolt the new set to the crankarm.
I own both Campy NR 144 bcd 5pin and TA Cyclotourist 6pin cranksets. I want to add the triple inner chainring drill holes to both of these crankarms.
Does anyone know what are the appropriate metric tap sizes to properly thread the bolts for either Campy 36T or TA 36T inner chainrings? I have all the parts needed to accomplish this but having problems finding the proper thread sizes...
Thanks, Steve Neago