[Ron Sutton]

Originally Posted by BANKO

Ron, thanks so much for running the numbers, I appreciate you showing me that every little detail matters in the system.



If I have a goal of running Wilwood J or H on the track and E's on the Auto-x / street can I do the following: 0.875" bore on the front, 0.875" bore on the rear dropping the line pressure via my existing proportioning valve to what a 1.0" bore would provide?

I'm running the Wilwood high volume master cylinders that run in (0.75", 0.875", and 1.0" bores, no 13/16" available). I have a duplicate set of 0.875" bore master cylinders and would like to put them to use instead of buying another new MC.

So the system would be:

Scenario 1: Street / Auto-x

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix E
Rear: Hawk HP+

Scenario 2: Track Only

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix J or H
Rear: Hawk HP+

Hey Josh,

The proposed packages you laid out work for the street & AutoX events ... if you put a 1" M/C on the rear. Do not run a .875 M/C on the rear even with a PV.

You end up with a LOT of braking force ... total = 3893# ... with a natural 67.4% front & 32.6% rear bias ... that can be fine tuned with the Wilwood pedal system you have.

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For the road course track days, the combo you proposed does not work ... but I showed it anyway ... obvious by the big red letters.

With almost 5000# of braking force, you would just lock up the tires. The F/R bias doesn't work either.

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The 2nd chart shows the same street & AutoX set-up ... but shows the Track Day set-up with different brake pads.

4387# is still a lot of braking force. You will need good tires ... like Hoosier R6's or comparable ... or you'll constantly be on the edge of lock up.

This package uses:
Wilwood BP-20's in the rear which are an excellent rear pad with their steep CoF curve. For the front, either PFC's new 12 pad or Porterfields R4 pad. I know the R4 has a nice flat curve from 450 to 900 degrees, which makes for predictable braking.

I "believe" the new PFC 12 has the same CoF & flat torque curve ... and should last longer. It is an endurance pad with medium bite that was on the 2013 Daytona 24 Hour Overall Winner.

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Tip:

For road course racing, front brake pads ... with a flat torque curve in the operating range your running ... provides predictable, consistent stopping ... even when you're braking differently ... shorter/longer, softer/harder ... for different speed corners.

For road course racing, rear brake pads ... with a steeper climbing torque curve in the operating range your running ... provides the best overall stopping performance ... because the rear brakes don't bite so hard when you first get on the brakes ... and then brake progressively harder the longer you're on the brakes ... which the car can handle.

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