Yes, that's the critter. Externally it will look the same as what you have now. The bore size increase will allow you to apply more pressure on the brake shoe.

 

Just bought two of them. My local NAPA had them in stock.

Pretty inexpensive way to upgrade the rear brakes. Now I just need to do as the front of this thread says and upgrade the front disks and pads.

 

http://www.ssbrakes.com/

thats the correct website..

 

hey yall waht do ya think of the powerslot brakes. The reason so is becuase 4 wheelparts is giving you a set of free brake pads with the purchase of 2 brake rotors. if they are good then i might ****** em. ya know it cant hurt to have an extra set of BP around.



Also what are yall talkin about with the GMs rear brake, what exactly does it do and what will it help, hard to put on or not. will i need new brake pads with the transfer. Thanks and sorry just dont understand. Thanks

BNB

 

anybody want to fill me in here



BNB

 

Regarding the GM wheel cylinders. It is a matter of hydraulics. The stock wheel cylinders on my 01 Ram have a 1" cylinder that pushes on the pistons which push the shoes against the drum. The GM Cylinder has a 1 3/16" cylinder. This translates to a stronger hydraulic action against the brake pads. However, I have not done the work yet or the calculations to see if the stock master cylinder fluid volume to the rear brakes really does translate into a stronger hydraulic action at the shoes. The same volume of fluid that pushes the 1" cylinder must now push 1 3/16" of fluid in the new wheel cylinder. That means the pistons will travel less in the new wheel cylinders and may actually reduce the braking action.

Once I get the calculations completed I'll post the results. Sorry for being so technical.

 

OK, I completed the volumetric calculations and it will take about 1/2 teaspoon more brake fluid into each wheel cylinder to push the 1 3/16 pistons the same distance as the 1" pistons. I based my calculation on each piston in the wheel cylinder moving approx 1/4 inch to fully apply the brakes.

That means the Master Cylinder needs to push 1 teaspoon more volume toward the back brakes to get the same movement of the pistons in the 1 3/16" cylinders as the 1" cylinders. Maybe I am getting too deep into this, but when pushing this additional teaspoon of brake fluid pushed to the back brakes the Master Cylinder will also be pushing an additional teaspoon of fluid to the front brakes.

Here is my assumption. I think the increased volumetric need of the 1 3/16" wheel cylinders will cause additional braking to occur in the front brakes as well as the back brakes unless the proportioning valve in the Master Cylinder is modified to accomodate the extra need of the back brakes without affecting the front. I think this mod will cause the front brakes to wear quicker and could cause them to lock up easier. That is why it seems like there is better braking with the larger wheel cylinder.

Unless somebody can poke holes in my numbers, I am taking the GM Wheel Cylinders back tomorrow.

 

turkeyhunter, that is the kind of thought I've been waiting for. I appreciate the effort you've put into this. Do you have experience in fluid power?

I did the mod this spring, but originally had 15/16" cylinders, and so far haven't had any problems with the rears or the fronts locking. I have noticed it doesn't nosedive as bad, so I think it's a little more balanced.

I was trying to compare other setups, ie 3/4 ton Dodge and also some Chev setups and how they utilize different MCs and varying piston sizes for the front and rear. I don't have the patience for the math to balance out the hydraulics. I was hoping there was someone experienced with designing hydraulic systems that might chime in, but that never happened. I did notice that DezlDemon has done some interesting work on his rig, switching to a 1" MC I think. I've been contemplating that move also.

I think I can use a higher line pressure without lock up. I'm also wondering what sort of modifications you had in mind for the proportioning valve. Didn't really want to go the adjustable route. I don't fully understand how they work to know which way to proceed with that, but perhaps a valve, or just the guts of one from something with rear discs would be a step in the right direction since maybe the caliper pistons have a larger diameter than my original wheel cylinders. Does the p-valve work on pressure or volume? I thought it was pressure.


The GM work trucks I used seemed to stop better.

I'm just looking to provoke some thought on this, but I'll probably just get flamed I'll try anyway

 

Shepard,
The Masster Cylinder pushes volume into the brake lines, which in turn pushes on the pistons in the wheel cylinders. As the resistance to the piston movement increases ( the brakes are pushing against the rotor/drum and braking the vehicle) the volume builds up more pressure as you push harder on the brake pedal. So in reality it is both items, but pressure is the main factor in how hard your brakes apply.

One thing I did not calculate was how much effect 1/2 teaspoon of brake fluid would have on each front disc brake caliper. The cylinders in those are much larger than rear wheel cylinders and the movement of the front caliper cylinder may be so minor with the extra volume that it is irrelevant. I looked at my trucks front brakes when I got home from work and I have 2 cylinders per caliper and each is about 2 1/2 inches diameter. Each would absorb about 1/4 teaspoon and this is what is making me re-think a proportioning valve mod would be required. I am starting to think the replacing of the 1" wheel cylinders with 1 3/16 inch wheel cylinders would have an overall positive effect on braking.

Would need to take more time to do full calculations regarding front vs. rear effect. I am just making my best guess based on what fluid engineering training that I have had.

 

Cool. So is it the building of the line pressure that works the p-valve? If thats the way it is you should be able to put more pedal (volume) to the rears before the pressure would be equal to what it was with the original cylinders, correct?

If you look at Rockauto.com you can get a measurement for caliper pistons. Most of the brake parts there have dimensions.
I'm stuck with single piston calipers so my results probably won't be as good as yours.

Thanks for the reply.