Wilwood Manual master cylinder Bore size ?

[karolko]

I was wondering if any of you boys have some experience with the bore sizes that wilwood offers with their manual master cylinders.

i currently have factory front discs and drums in the rear, but will be upgrading to wilwood drag brakes in the front and discs in the rear.

I local friend use to run a 1 1/16 bore and he said it doesn't have enough pressure, so will a 1' or a 7/8 bore be best suited for my application.


Thanks alot guys.

Adrian

 

[Bent6]

Go with the 1" bore and set it up with a 6:1 pedal ratio.

 

[karolko]

Will,

do you have a similar setup on your street car, and how is the pedal feel? Do you think running the 7/8" will not give me enough volume.

If you are running this setup, how far down is your pedal before the car starts breaking hard?

Thanks for your help and advice Will.

Adrian

 

[Bent6]

Hey Adrian. I am about completely re-engineer the suspension on my street car and will be upgrading the brakes while I'm in there. I plan to use all Wilwood equipment with 10 inch front rotors and 12" rear rotors. I spoke in length with a tech at Wilwood about the MC volume needed and they are advising a 1" bore with this setup. I will be completely eliminating the factory proportioning valve and using a manual adjustable valve. As far as the 6:1 pedal ratio, this is from Wilwood's website and explains it pretty well.................


Pedal assembly ratio, or mechanical leverage is the ratio calculated from the length from the pivot point of the pedal to the center of the foot pedal (A), divided by the length from the pivot point to the master cylinder pushrod (B). Refer to the figures below. Mechanical leverage is simply a means of increasing the brake force without increasing your leg effort. As “A” gets longer and “B” gets shorter, the mechanical leverage increases brake force without pushing harder on the pedal. The disadvantage is that the pedal stroke also increases, requiring you to push the pedal further. With a 1” master cylinder stroke, a 100-pound push onthe pedal, and the pedal having a 4:1 ratio, the force is 4 x 100 = 400 pounds, and the stroke is 4 x 1 = 4 inches. With a 100 pound push on the pedal, and the pedal having a 6:1 ratio, the force is 6 x 100 = 600 pounds, and the stroke is 6 x 1 = 6 inches.

Here's the link if you need to see the diagrams Wilwood Disc Brakes for Racing On Track, Off Road, and Street Performance

I think the stock pedal ratio is close to 6:1 - good starting point at any rate and it all comes down to personal preference in the end. Good luck.

 

[karolko]

Hey Will,

I took some time to read through the wilwood website and what has me a little confused is that wilwood states that the optimal pressures for brake claipers is between 900-1200 psi.

How does the master cylinder increase brake pressure. Is it simply a cross sectional area multiplier that also increases brake pressure.

Example 1" bore in the master cylinder and the outlet line are 1/4" for argument sake. Does that mean that the pressure is multiplied by 4? That seems too easy. I need to go back into my old physics books. I know that is a formula for this.

Hopefully i have explained myself...Probably not

Adrian

 

[karolko]

i found this formula on the internet...

To figure how much pressure your master cylinder is putting out:
C = pedal ratio
D = pounds of pressure apply by your foot
E = area of you master cylinder
F = pounds of pressure out of the master cylinder
C X D /(divided by) E = F

Example: If you have a 1" master cylinder the area equals 1/2" x 1/2" x 3.14 = 0.785 Square Inches. So, 100 pounds (of applied foot pressure) X 6 (pedal ratio) divided by 0.785 = 764 pounds of pressure.

i did some quick calculations and this is what i came up with:

100lbs=764lbs at brakes
110lbs=840lbs at brakes
120lbs=917lbs at brakes
130lbs=993lbs at brakes

I do not know the validity of this formula, but i will keep looking to verify. It seems that 120-130lbs at your foot will yield a good pressure for the brakes.

thoughts?