View Full Version : Front brake bore sizes HELP!!!!!

12-10-2012, 9:30 PM
Let's see if I can get some help on this one...
I'm currently trying to install a complete front brake set up on my custom Paughco. Since this is my first build, a question of the front brake bore size has come into question. The front caliber I purchased has a banjo style fitting on it, and the bolt/bore on the caliber is 3/8. Now trying to purchase a master cylinder, and lines that will work, all I see available in bore sizes is 3/4 and 5/8. Since I can't imagine a brake line with a 3/4 brake line fitting on it, what is this bore size describing? All I know is that I need a master cylinder assembly, and line that will screw into a 3/8 hole.

12-10-2012, 9:38 PM
Those sizes refer to the internal diameter (the bore) that the brake piston rides in, that moves the fluid when you squeeze the brake lever.

12-10-2012, 9:52 PM
This makes a lot more sense. So when choosing a master cylinder set up, what are the pros and cons of 3/4 over 5/8, or vice versa ?

12-11-2012, 3:54 AM
It's about feel. You also might have an easier time finding information if you started spelling caliper properly.

12-11-2012, 1:31 PM
The bore size of the master cylinder depends on whether you are using a single or two front rotors. I think in general, the typical master cylinder bore size is 11/16" for two rotors and 9/16" for a single rotor. I don't think the banjo bolt size makes any difference so long as it fits correctly in the caliper or master cylinder and you have the correct size banjo fitting.