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Hi - can anyone of you clever chaps please tell me the telationship between hydraulic brake pressure and braking torque for a defender front axle . A graph would be good but a factor I can multiply pressure by to get torque would be good too .  For example 50 bar pressure results in 2500 Nm torque ! Thanks 

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Wikipedia has this to offer:

"The dynamic friction coefficient "µ" for most standard brake pads is usually in the range of 0.35 to 0.42. This means that a force of 1000 Newtons on the pad will give a resulting brake force close to 400 Newtons"

https://en.wikipedia.org/wiki/Brake_lining

You'll need to create a calculation which take into account piston area, pad area, disk diameter and that coefficient. Be warned that this is an extremely simplistic model, and pretty much good for nothing more than curiosity's sake. 

 

And welcome!

Edited by lo-fi

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Pad area doesn't directly affect braking force. Larger pads are fitted to get acceptable wear and better heat dissipation.

Force on the pads is determined by the pressure in the system multiplied by the piston area and number of pistons. With the above friction coefficient you get the force on the discs. To get braking torque you need to multiply with the radius from the axle center to the center of the force applied by the  pad. The middle of the pad would be a conservative estimate.

Also curious what you're trying to work out?

Filip

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14 hours ago, Escape said:

Pad area doesn't directly affect braking force. Larger pads are fitted to get acceptable wear and better heat dissipation.

Force on the pads is determined by the pressure in the system multiplied by the piston area and number of pistons. With the above friction coefficient you get the force on the discs. To get braking torque you need to multiply with the radius from the axle center to the center of the force applied by the  pad. The middle of the pad would be a conservative estimate.

Also curious what you're trying to work out?

Filip

Resultant pressure on the pads is also going to depend on pad area - the force is going to he hydraulic pressure x piston sectional area.  Pad pressure will be that force divided by the pad area.

I can see how increased pad area helps with reducing wear, but I can't see it being irrelevant to braking capacity.  Sure, it won't be a linear relationship between area and braking effort, but there will be a relationship.  As for cooling, a bigger pad will have greater heat sink, but their composites don't absorb heat as much as the discs, which is where most of the energy goes.  However, bigger pads mask more of the disc and would thus reduce disc cooling.  The disc temperature is going to be a function of how much energy you put into it, and I can't see how pad size will affect that for a given retardation rate.

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