chas0218

So I decided to pull the trigger and convert to manual brakes. With the cam I have and the low amounts of vacuum I don't want to take the risk of someone getting hurt by not being able to stop. I mean I can down shift and pull vacuum but stopping fast is not going to really happen.

My question has to do with bore size. I have been searching and reading what people have used and I wasn't sure which bore size would be best for my setup. I will be running 99 camaro rear disk single piston and stock 86 single piston. I was looking at getting a 1.03" bore from strange or the BMR 1.03 then I saw the 7/8" smith setup might be better. I'm not planning on getting any bigger front or rear brakes just looking for the right bore size without buying 3 different master cylinders.

On a side note the BMR is for a 4th gen that utilizes 6 pistons total in its brake system where I will be utilizing 4 pistons in my brake system.

BBU.COM

Your heading the right way, a smaller bore will increase the pressure but also increase the stroke length. With 4 piston calipers all around a 1 inch bore works pretty good, with 4 piston total, you end up with a short stoke that will be short on pressure. I have done a 21mm bore (plymouth acclaim master cyl) with good results, a 6:1 pedal ratio and just under 1,100. psi from my memory.

Now the stock front calipers are low drag which need a step bore master, you should swap to a non-low drag caliper, check this thread out..

http://www.camaros.net/forums/16-bra...-pictures.html

manualbrakes.com

Hello,

Number of pistons DO NOT matter. Piston area is what matters.

Stock 3rd Gen front piston area of a single 2.5" diameter piston is 4.91 square inches.
Stock LS1 F-body front piston area of a twin 45mm diameter piston is 4.93 square inches.

Though there is twice as many pistons, the piston area is roughly the same. In other words, it takes the same amount of brake fluid to fill either of the above calipers.

Thing to keep in mind that all 3rd gen F-bodies came with LOW drag calipers and a normal, strait bore master cylinders will not work with LOW drag calipers.

For replacement front calipers, I recommend new AFCO stock replacement calipers. All other stock replacement calipers are remanufactured and they will have the same part numbers from 1978 G-bodies to 1992 F-bodies to 2003 S10 trucks. I have found they can be hit or miss in reliability.

The AFCO part number is:
https://www.summitracing.com/parts/a...5003/overview/
https://www.summitracing.com/parts/a...5004/overview/

Link is for Summit Racing, but you can buy them at Jegs, Speedway Motors, etc.

For most front calipers, you will not go over the piston area of the stock front calipers or LS1 F-body front calipers.

The LS1 F-body single piston rear caliper, is a single 45mm diameter piston, which has a piston area 2.46 square inches. This is smaller than all of the 3rd Gen F-body rear piston sizes which is around 1.89" in diameter.

With AFCO stock replacement front calipers and LS1 rear calipers, I would recommend a 7/8" bore master cylinder.

Smaller bore master cylinders give higher fluid pressure and more clamping force at the calipers, but the pedal stroke will be longer because it does not supply the same amount of volume that a larger bore master cylinder will.

BBU.COM

True, number of pistons do not matter but area does, since the poster mentioned what brakes he was using I based my response on his information, not to be confused with systems using calipers with dissimilar piston areas.

chas0218

So no matter what I will need to replace the front with the AFCO brakes. I was trying to get away with keeping my original. It's not a huge deal just a little more money, would it be worth looking into a 2 piston setup for the fronts and rears if I am replacing them. I want these brakes to perform as good as the power assist. My wife on rare occasions will be driving the car and I wouldn't feel comfortable if the car didn't behave as close to what she is used to as possible.

chas0218

Thanks for the link that really helps.

manualbrakes.com

Most of the twin piston bolt in calipers have a smaller piston area and will have less clamping force when using the same size calipers. In my opinion, the best caliper for the stock front brakes and a manual brake system is the AFCO 2.5" diameter piston calipers. It matches well with a 7/8" bore master cylinder and achieves the greatest clamping force with this combination.

To make your manual brake system better, add new rubber brake lines or stainless steel flexible lines. Old rubber lines will start to balloon with age reducing braking performance.

Get brake pads that work better when cold. This is usually a 100% organic pad, but I have heard good things about the Wagner Thermoquiet pads as having a good "cold bite"

EBC recommends the Greenstuff pads
Porterfield recommends the R4-S pads
Hawk recommends the Street/Race pads

chas0218

Okay sounds good appreciate your help.