The master cylinder that doesnt exist! - GMC 1 3/4" bor

[Steve-SKO]

Why not just take a MC off another truck and use it. I have a Triumph that has some sort of Ford MC retrofitted to it.

 

[frank-id]

Master cylinders

These units can be swapped in relation to need. Increasing the bore size will operate a system more slowly, using a smaller bore will make more pressureand reacts more quickly. I once used a Corvette cylinder, because the original was not available on a RV with 6 ncylinders. The swap was a great change. The cost was reasonable and the volumn was a good fix. The cylinders can also be line bored and honed to any near size. The machining is not cheap, but nice to have a standard bore for later repair. Frank

 

[the_experience03]

Ok, Frank...I'm a little confused here. A bigger master cylinder will displace more fluid in a given amount of pedal travel than a smaller one. This means it will apply more pressure at the shoes/pads than the smaller cylinder, but will require more effort at the pedal itself. I know this much from some fairly simple fluid mechanics and personal experience with brake swaps, but can you clarify what you mean by saying one will react faster? It seems to me that the bigger one will react faster because for a given amouint of travel it is going to profide more fluid. I know that's what I swapped a bigger one into my truck. I didn't like th e idea of the pedal going 3/4 of the way to the floor before it could establish enough pressure.

 

[frank-id]

Cylinders and prerssures

A large volumn cylinder will not make the same pressure as a smaller bore cylinder. Let's create a big argument. Please show me some test data.
I have my view and you have yours. The basic intent of my post was to offer some resolution to a brake problem that was unsolvable. Do ya wanna argue? Frank

 

[the_experience03]

Whoa Whoa Whoa...back down theere...I was looking for clarification as to what you meant. I was simply curious about what you meant about reacts faster. It is unfair to say a small bore makes more pressure than a large bore...there is more to it including amount of travel (total fluid displaced) and the force applied to the pedal itself. Yes, a smaller bore has a higher multiplication factor, but because it displaces less fluid it will have a harder time increasing pressure at the shoes/pads themselves. Like I siad...that is why I swapped cylinders....I wanted less pedal travel. In order to make pressure you need to have an increase in force over an area of the system without a corresponding increase in volume. With your brakes your volume remains the same until the pads make contact with the rotors. It might not seem like much, but it is significant enough to matter. At the point the pads make contact I will give you that it is true that the smaller M/C will apply more pressure given it's greater multiplication factor. However, it will require a tremendous amount of pedal travel to do so. Otherwise we'd have Geo Metro master cylinders on our buses. That is where I get hung up on saying that smaller master cylinder is faster to react. I'm not saying you are wrong. I JUST WANT TO KNOW WHAT YOU MEANT.

I'm not trying to start an argument at all and I apologize if you felt like I was attacking what you said. I am, however, still looking for clarification. It is important to take all factors into consideration when doing brake swaps as they are the most essential system on the bus in my humble opinion.

 

[Jarlaxle]

From personal experience on 2 vehicles: a larger MC bore size will INCREASE pedal effort; however, it will also REDUCE pedal travel needed for the same pressure at the wheel brakes. I did the swap on one vehicle due to brake fade...basically, as the brakes heated up & the pedal dropped, I ran out of travel. This was a factory flaw, since the car, being a performance model, had larger brakes than the regular version, but the same master cylinder. Swapping to the larger one totally fixed the fade problem.

 

[the_experience03]

Me too, Jaraxle....swapping to bigger calipers didn't leave me with much reserve travel. A new bigger MC along with a new dual diaphragm booster meant that my pedal travel was reduced, my pedal effort was reduced, and my braking force was increased. Pretty cool 8)

 

[Jarlaxle]

Me too, Jaraxle....swapping to bigger calipers didn't leave me with much reserve travel. A new bigger MC along with a new dual diaphragm booster meant that my pedal travel was reduced, my pedal effort was reduced, and my braking force was increased. Pretty cool 8)

I didn't have to replace the booster (MC donor used the same one, anyway)--but what a difference. Best $30 I ever spent. I just saw I didn't say what it was: the car was a 1985 Shelby Charger turbo, with a 21mm master cylinder. Swapping to a 24mm MC (basically, a Caravan part) was the fix.

 

[oldog12]

Hey jmaes...

Where in Highland MO is this "Amazing Big Truck Junk Yard"?

If you have the name of the place and the address/phone number, I for one would like to know about it

 

[oldog12]

THANKS