Front Derailleur Braze-on Tab Measurement...
I was wondering what the correct distance is supposed to be from the center of the bottom bracket, to the braze-on (front) derailleur tab?
This is a 80s style, NOS Italian frameset (SL tubeset, and fully lugged)...
I don't recall where I found this, but it has been tremendously helpful as a beginner and drawing frame plans by hand (finally putting all those high school pre-CAD drafting classes to use.)
Gives data for basically all Shimano components to help position things in the framebuilding process. Especially helpful to plan out crank/chainring clearance.
Originally Posted by jharley
Thank you so much!
Here are the numbers from the Campagnolo website. We are talking about a lugged Italian frameset after all. I just copied and pasted the numbers from the chart. The measurement in mm is from the center of the BB to the center of the slot in the brazeon. The next number is the chainring size associated with that measurement and the string of seven numbers is the list of compatible chainrings.
140 mm 48 45,46,47,48,49,50,51
142 mm 49 46,47,48,49,50,51,52
144 mm 50 47,48,49,50,51,52,53
146 mm 51 48,49,50,51,52,53,54
148 mm 52 49,50,51,52,53,54,55
150 mm 53 50,51,52,53,54,55,56
152 mm 54 51,52,53,54,55,56,57
Cissell, I only do lugged work and measure off the top of the BB shell once I have the ST pinned into the shell. If you are working with the Sachs tab, locate the reference hole and place it at 90° from the front at your preferred distance. Make a little stick with a mark for quick work. You can see I've used paint sticks. You can +- it a mm for customer needs. This advice is based on standardizing your parts. You can see what I use below. I just stuck a stub in a shell for illustration purposes, but you can get the idea. I use 119mm for my stick. You can also see I have another stick for placing bottles where I like.
Good luck, Craig