Originally Posted by Bently_Coop

Just buy a new master cylinder from Rock Auto. They are not that expensive.

Originally Posted by BrakeExpert

Master Cylinder relative to the Caliper
When you go to bigger caliper than use a larger piston, you are pushing more fluid through the brake lines. Therefore, you should want a larger master cylinder to push this more fluid.
General rule is…with your stock Civic DX, with the stock front calipers, keep your 13/16” MC. Any bigger and your pedal will be too stiff.
With EX/Si calipers, use a 7/8” MC from a 96-00 EX or 99-00 Si because of the more fluid going to a larger piston.
With ITR/Legend/Vigor/Accord V6 or Integra DA or DC calipers, use a 15/16” MC from a 98-01 Integra LS to accommodate for the even more fluid. Any smaller of a MC will cause the pedal swing to be too long.
With NSX or Legend GS calipers that have two pistons, or an aftermarket caliper with multiple pistons, you’ll want a 1” MC because of even more fluid required to push all the pistons. Get the 1” MC from a 98-01 Integra GSR or ITR MC as it bolts onto the EK brake booster.
When changing out a master cylinder, be sure to 'bench bleed' it first. This involves having fluid in the resovoir and pumping it unconnected to allow fluid to fill the internals. If you don't do this, you can still bleed the car, but you may be at it all day, since air pockets may stick in there. Research bench bleeding before you attempt this on your own.
A bigger caliper usually has a bigger bracket, thus holds a bigger surface area pad. This is generally better, and that’s why on a Civic, you swap on an Integra caliper, because the piston is bigger (more fluid, that doesn’t help) but the pad is bigger, and the piston disperses its energy over more area because of a larger contact surface with the shim.

Originally Posted by Bently_Coop

I picked up a Raybestos for my 89 civic. It is a 15/16" and from a 90-91 EX sedan direct bolt on. Raybesto IMO is good quality. I can't tell which are ABS compatible either.

Not sure if you have read the sticky but here is some good information regarding choosing the correct size.



Here is another thread with decent information as well.

https://honda-tech.com/honda-civic-d...civics-364783/