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need help understanding hyd brakes!!
#1189961
03/02/12 09:27 PM
03/02/12 09:27 PM
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Joined: Aug 2003
Posts: 954
garnett kansas
rhad
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 954
garnett kansas
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i dont understand the ratio between the size of the wheel cylinders and the size of the master cyl,i have a 71 or so dana 60 out of a pickup,it has 12x2 shoes and 1 1/8 cyls,IF it had 12x3 shoes it would have 1 inch cyls,seems backwards to me,and tho this axle isnt in a dodge anymore,what is the relationship between the master size and the wheel cyl size,seems like one size master might give a harder pedal,and the other maybe travels farther???,by the way my master is also 1 1/8,rear brakes only,off road SLOW ONLY!!
thanks
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Re: need help understanding hyd brakes!!
[Re: rhad]
#1189962
03/02/12 10:55 PM
03/02/12 10:55 PM
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Joined: Jan 2003
Posts: 28,071
Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,071
Irving, TX
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You're using the master cylinder to push the fluid.
A large master cylinder can't move very far if the wheel cylinders are too small. You're moving a lot of fluid but don't have anywhere for it to go. That makes for a hard pedal.
A small master cylinder has to move more to push the same amount of fluid. That makes for a squishy pedal.
A smaller wheel cylinder means more travel at the brake pad. It sounds to me like they put the smaller cylinders on the heavy duty brakes to generate more pressure against the pad with the same pedal travel. You get more braking power with the same pedal travel. Bigger pads also give more friction for braking.
Both the cylinder and the pad would be heavy duty items. Instead of going with one, they did both.
That's how it looks to me.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: need help understanding hyd brakes!!
[Re: feets]
#1189964
03/03/12 10:53 AM
03/03/12 10:53 AM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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brakes are all about creating pressure...as is any hydraulic system.
a smaller master or larger slave is how you make more pressure for the same amount of input force.
More pressure behind the brake shoe makes the shoe push harder against the drum.
so, "heavy duty" brakes may have larger slaves or wheel cylinders.
also, keep in mind, one wheel cylinder has 2 pistons and twice the area. so a 1" bore wheel cylinder and a 1" master cylinder, are not "equal" they're actually a 1:2 ratio.
when it comes to picking master cylinder, you need to balance pedal feel with stroke volume. yes, the smaller master gives easier pedal effort, but then you need to also consider how much fluid volume you need to push the shoes out off the springs and against the drums. too small of a bore diameter, and you will run out of pedal stroke.
**Photobucket sucks**
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