Wilwood master cylinder size question...
 

Hey guys,
1970 Camaro; all the normal pro touring stuff... Twin turbo engine so no power booster on the brakes... Wilwood 14" W6A/W4A brakes. Depending on who I ask, I'm told I need a 1" or a 7/8" bore master cylinder. Which should I choose? I don't fully understand what the difference in normal usage is one way or the other?? This car will mainly be street driven with a little A/C and some drag racing...

Thanks!

There are several piston configurations on the W6A and W4A calipers, so which one do you have? There are W6A calipers with 4.04 sq inches piston area as well as 5.40. For the W4A, most rear kits would include either the 1.98 or 2.46 sq inch versions, however they're also available in 3.56, 3.90 and 4.84.

Your master cylinder should be sized relative to your calipers, the slaves in the brake system. Pedal ratio plays a role as well, however a smaller bore MC will require longer pedal travel and less effort to achieve similar brake torques as a larger bore MC, so everything is relative. In the size range being discussed here, there's about a 12% difference in output pressure and pedal travel per 1/16" change of bore size, so about 24% going from a 7/8 to 1 inch bore unit.

What are you running for pad compound? That's the other factor that seems to be overlooked when setting up any given brake system. Brake pads can make the single largest difference in brake performance of any component. The stock BP-10 pads can be a bit mild in manual brake applications IMO, so higher CoF pads would certainly be an improvement for an application that's going to see more aggressive use in Auto-x or open road course type events. The downside to more aggressive pads tends to be added dust, noise and rotor wear.

Tobin
KORE3

Hmm.... well... the short answer is; I don't know. I think I need to educate myself just a bit here... thank you!