Master Cylinder Bore Size

[Z69]

Which master cylinder bore size should I get with a 2.75 caliper bore, 6:1 pedal ratio, manual front disc/9.5 drum rear? Wilwood has been giving me advice ranging from 1-1-1/8. They can’t seem to understand that stock these cars have a brake pedal stop for a manual setup. They keep trying to get me to order a compact master with a built in pushrod which isn’t needed. I thought 1” was for a stock manual drum and 1-1/8” was for power disc. Wasn’t sure if 7/8” would be good with the caliper piston size being that it’s on the larger side according to Wilwood. But according to the internet a stock piston is around 2.9”. I know 7/8” would be softer but will increase the pedal travel compared to a 1”. I’d rather have a softer pedal to be honest. Thanks.

[Sinnister69]

Read this

https://www.onallcylinders.com/2017/08/18/ask-away-jeff-smith-using-master-cylinder-math-solve-brake-pedal-woes/

[malibudave]

With the specs you gave, I would recommend a 15/16" bore master cylinder as a minimum. A smaller bore will give you less pedal effort, but the pedal stroke will be longer. If you have a racing seat (ie Kirkey), or a very firm seat with more support than cushion, you should be able to go to a 1.0" bore. The 1.0" bore will need more effort, but a racing type seat will give you more leverage to press the pedal as you will not be pushing yourself back into a plush seat cushion. Let me know if you have any additional questions. [email protected]