Front Brake Overhaul & Now Hub Rebuild Too

Yeah.

I'd ignore the Wagoneer wheel cylinder sizes, since the weight distribution of a Wagoneer is totally different from a CJ.

Look at the cylinder diameters for a '72 CJ-5 with 11"x2" Bendix brakes. These are 1.125" diam front cylinders. The force on the brakes is proportional to the piston area. A 1" piston has 79.01% of the area of a 1.125" diam piston, so the braking force for a 1" cylinder will be down by about 20% from a 1.125" cylinder. The rears on a '72 CJ are 15/16" diam. This is now 69.03% of the front, or down by 30%.

If you use the 11" brakes on the front and the 10" on the rear, both are the same width so the 10s have about 10/11 or 91% of the shoe area off the 11s. We can assume that the '72 CJ force ratio 10:7 is ideal and make a BOTEC (back of the envelope calculation) aka WAG about what size the rear cylinders need to be.

Using a 1" front cylinder, you want the area of the rear cylinder to be smaller then the front by 30%, then boosted by 11/10. So 0.6903 * 11 / 10 = 0.7593. I would make a spread sheet of the difference in areas front to rear from the different wheel cylinder sizes, in steps of 1/16".

Area = (diam/2)^2 * pi. With 1" front and 13/16" rear, (13/32)^2 * pi / 0.5^2 * pi = (13/16)^2 = 0.6602 or 66%. If you use the 1" on the front, 7/8" rear is the closest to the ideal WAG at 0.7656 or 76%.

What is the cylinder diameter of the 10" fronts now?

I'd err on the side of larger cylinders on the rear, and then throttle them down using an aftermarket proportioning valve inline with the rear brakes if you have any rear lock-up.

 

The area of a circle is the radius (half the diameter) squared times pi. When you take the ratio of two circles, everything but the diameters squared cancels. So the ratio of diameter 1 to diameter 2 is (diameter 1 divided by diameter 2) times (diameter 1 divided by diameter 2).

If it were doing this, I'd buy the 1.125" Jeep CJ front cylinders and install them in my backing plates. I'd buy 1" rubber kits and try to rebuild the 1" cylinders from the 10s. 13/16" cylinders are going to be too small. If there are no big pits in the 1" cylinders, hone them and they will probably be ok. The 1" cylinders will be too strong for the rears (87% of the fronts), but oh well. Then get a Wilwood proportioning valve and put it in the line to the rear brakes. This will help to hold off the rears in severe braking.

http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx

 

r)r)

 

I agree with fockers equation !!?

 

There is a specialized group of guys on this forum of which Tim is a part of. This forum probably would not have survived without them. Keep up the good work.

 

I fully agree with this true statement.

 

Does that tech support speak english enough to understand?

 

I don't know how much you were paying online for shoes but napa looks like it's only 17 dollars

 

And it looks like Oreillys is 19.99 for 10 inch by 2 inch cj5 shoes

 

I like rock auto, but they are not always the cheapest. I use their site to get part numbers and brands and search those. sometimes amazon is substantially less with free shipping on the same exact part.

 

I found that the cheapest source of parts is generally ... Amazon.com or eBay. Amazon is especially good if you have Amazon Prime.