drum brake backing plates with only two attaching screws to the axle tube flange ? i take it that the shoe anchor bolt pin is what holds the top of the plate to the axle tube flange ?
Are the F body 7.5" axles the only ones with this design ?

Would S-10s have the same design or any caprices in the 80s, or ?

since what year has this design of plate been used on these ?

what im trying to do is upgrade from my 3/4" bore cylinders up to 7/8 or 15/16, but the problem is that camaros use clip on style cylinders and are only 3/4" bore, all of them from what i have seen in applications look ups. Others are screwed on conventinally with two screws, so.,,, I am hoping to locate a donor 7.5" axle vehicle in the 80s or 70s even that have the same style of attachment for the backing plates ot the axle tube flange.

anyone ?

thanks for anything !

 

Enlighten me.... Whats the point of the larger cylinder and does it require changeing the prop valve or Mc?

Thanks,
R

 

Look at A & G bodies (Monte Carlo, RWD Cutlass, etc.) 78 up. They use the clip-in WCs.

If you put in a larger wheel cyl you will end up requiring considerably more fluid to work the rear brakes, which will make your brake pedal go alot lower. The relationship of MC diameter to WC diameter is a situation almost like gears; it changes the relationship of applied force to distance moved (the product of the 2 always remaining the same). Decreasing the MC/WC ratio will cause the MC to have to deliver more fluid to push the WC the same distance, which means the pedal will have to travel that much farther. I doubt it's a real good idea.

 

RB83L69

Kinda off the subject of bigger rear brake cylinders, but I'm one of the people involved with the C4 and LS1 front brake upgrades.

The LS1 style front caliper has two 1.75 pistons, and the C4 has two 1.5 pistons. I realize it will take more fluid to move the bigger pistons the same distance. My question is that with more area for the fluid to work against (1.75 vs. 1.5), will that result in more braking pressure applied to the pads?

 

Yes.

Another way to think of the piston diameter ratio thing, is to consider it as a form of "leverage". Small MC -> large slave cyl = lots of leverage (i.e. low force but lots of motion has to be applied)

 

http://www.chevyhiperformance.com/techarticles/49418/

That site and some stuff I've read on G body rear drums seem to think going from a 3/4" cylinder to a 7/8" or 5/16" cylinder make the brakes work better. But from what I understand it just needs more fluid to actuate the cylinder making the pedal drop lower and feel softer. Thats doesn't seem like something I'd want to do.

But I also found this while poking around on the net.

A basic principle of fluid physics is that the larger a caliper or wheel cylinder piston, the more force will be applied. Force = P x A, where P is the hydraulic pressure in pounds per square inch and A is area of the piston in square inches. This is one of the reasons for calipers with multiple pistons. By increasing the number of pistons, the total area is increased, creating more force.

Therefore, the larger the rear wheel cylinders, the MORE apt they are to lockup, given the same pressure. The statement about increasing the MASTER CYLINDER bore size to reduce lockup on the rear brakes is more correct.


I am confused

R

 

I dont know if I understand this correctly, but the way I am seeing it the larger diamiter cylinder will allow more pressure, but the pedal will have to travel further to get it. The only way I could think to get around this would be a larger master cylinder bore. Does this sound right?

Ben

 

Makes sense to me if you pump out the same pressure with enough volume to compensate for the larger cylinder it would make for better brakeing.

R

 

I had a long talk with Dave at Wilwood today. He's a tech rep and I asked him about this. I'm working with him on a project and I worked this subject in during our conversation.

We are correct that is takes more pedal travel to move larger caliper pistons when using the same master cylinder.

He also said it's better to have more movement than less because of more pedal feel and more braking predictability. He said human can judge moving pedal distance easier than judging the applied force to a brake pedal.

He also told me that with twin 1.75 caliper pistons, a 7/8" or 15/16" MC could easily feed these. Does anyone know what size our MC piston is?

 

If we increase pedal travel with larger rear drum slave cylinders how will this affect the front disc brakes?

R

 

I have kind of thought about this too. Depending on how much difference in pedal travel there really is I wondered if the pressure from the front brakes would get to firm before you really got much stoping action from the rear. If this is the case you could just use an adjustable prop valve.

 

I had a thought. The Prop valve mod that uses the 5/8" -18 plug. With disc brakes it makes the rears lock just before the fronts. Now if we used the plug with the spring and Valve/plunger could we make the stock Prop valve an adjustable prop valve just by turning the plug in or out?

R

 

Ok, did some looking and came up with this info. I haven't went through it, but I think it's got all the info we need to answer our master cylinder questions.

It's from a Dec. 2000 car craft tech article. You math guys look it over and let us other dummie's know what you come up with ok?

http://www.carcraft.com/techarticles/76680/index3.html

 

Yet more usefull info on brakes.


http://www.carcraft.com/techarticles/76680/index2.html