Master Cylinder question

[JayDubBlazer]

I am thinking about getting this combo kit for my truck but was wondering what's the difference between the 1.00" and 1.125" master cylinder bore?

http://www.summitracing.com/parts/TFF-2132NA/

[sjarrett71]

About .125"

Just had to say it! On a more serious note, I have no idea but I hope you get your answer.

[litew8]

"The most critical factor in master cylinder selection is bore size. Bore sizes can range from 5/8 inches upward to 1 1/8 inches or more. The bore size determines the amount of hydraulic pressure and fluid volume that will be sent downstream to the calipers. The actual amount of hydraulic pressure generated is based on the amount of force coming from the pedal or booster being divided by the area in square inches of the master cylinder bore. For example, a master cylinder with a 1-inch bore has .785 square inches or bore area. ( Bore x Bore x .785) If the pedal or booster delivers 500 pounds of force to the master cylinder, the hydraulic pressure will be equal to 500 divided by .785, which would result in 637 psi going to the lines. The displaced volume capacity is then based on the length of the available stroke multiplied by the bore area. It's the same formula that's used to calculate engine displacement for one cylinder.

Generally speaking, if the master cylinder bore is too large, the driver will feel a very hard pedal feel with minimal pedal travel, and will have a difficult time generating the necessary pressure to effectively operate the brake system. If the master cylinder bore size is too small, the driver will be able to generate a lot of pressure, but the pedal may have an excessively long stroke or a very spongy feel. And if the bore size is way too small, the pedal or master cylinder may bottom out before enough volume is pumped to operate the calipers. The best advice would be to consult with the manufacturer of the brake system you will be using and work with them to pick the right size for your application."

Read more: http://www.popularhotrodding.com/tec...#ixzz1wsb3mOfn

[JayDubBlazer]

Well that makes sense. The 1.125 is about 25% bigger in bore. Does this make it 25% harder to press the brake pedal in? Is the 1.125" for a 3/4 ton truck?

[litew8]

Don't know.

[jocko]

For disks, which I assume you have on the front at least since it's a 72, a 1+1/8" would be appropriate. Either would work. 1" bore is more for 4x drums in my mind. Pedal effort should not be an issue with a boosted system. You could call wilwood as a "prospective customer" and see what bore size they recommend based on your specific setup and use that to see if you're on track.

EDIT: to answer your last question, bore size isn't really specific to GVWR (i.e. 1/2 ton vs 3/4 ton, etc). It's mostly a function of type of brake system (i.e. drum vs brake, etc)

[67chevemall]

Disc needs more than drum so it is bigger.

[JayDubBlazer]

litew8 where in DSM are you from? I am originally a southsider but moved to Urbandale in my teens.

[litew8]

From Little Italy.