Cut Down RF Brake Pad

[racing08]

Some guys run a cut down rf brake pad to reduce the braking on that corner of the car is that a good thing to do or will it loosen the car up too much on entry just looking for some opinions?

[LRtireCHANGER]

I have seen late model setup books that tell you to change out master cylinders for the front or rear as the track changes. rf cutoff valves are pretty common on a dirt car in any class. I don't see why using different brake pads to affect the handling of the car would be any different than the changes that I have listed. If the car is tight on entry, I would say that using and aggressive pad on the lf and a less aggressive pad on the rf would be an acceptable correction to your handling problem.

[RaceEngineer]

Some guys run a cut down rf brake pad to reduce the braking on that corner of the car is that a good thing to do or will it loosen the car up too much on entry just looking for some opinions?Friction force is independent of surface area. If you decrease surface area, you increase pressure. Friction only is affected by coefficient of friction and normal force. You would need a different pad material to make a difference. Unless you made the area small enough to overheat the pad. Then it would not make a difference until the pad was cooked.

[ZERO25]

Some guys run a cut down rf brake pad to reduce the braking on that corner of the car is that a good thing to do or will it loosen the car up too much on entry just looking for some opinions?

Ive done a couple different things on stock cars depending on the rules. Ive put a rivet head, with diff size holes, in the line at the frame fitting and Ive put a brass needle valve. Of course, you'll have to experiment a little with the adj on the valve.

[stock car driver]

yes I always cut them down on the rf, since 1997, I also always ran organic on the rf.. dirt and pavement racing.

[racing08]

Thanks for the info guys I currently have my rf pad cut down and its just a stock pad what Im looking to do is tighten the car on entry when its dry so I thought about putting a full pad on which would be the same compound as the other 3 corner do I need to be concerned about the rf wheel trying to lock up on the slick?

[95shaw]

The thought process should be, will the heaviest loaded tire, on entry, on the front, lock up first?

[racing08]

Ok 95shaw now that you say that Im not concerned never looked at it that way for some reason

[95shaw]

The balance of traction at the front should be the real consideration for limiting braking forces at the right front.

Glad you caught my drift.

[RaceEngineer]

This here is a case of thinking something works, so in your head it does. An old racing wives tale as well.

[smokem2024]

Where do you cut the pads down? In the center? Outside edges?

[RaceEngineer]

Where do you cut the pads down? In the center? Outside edges?I'd leave the material as far from the Piston as possible. That way the metal part of the pad will warp and cause your pistons to have side load in their bores. Then your pistons will egg the bores. This will cause leakage. Then you will finally have less brakes at that wheel.

[stock car driver]

You need pad material over the piston, you dont need any out on the ends unless your rules dont allow grinding the pads.

[smokem2024]

Thanks for the info.

[oilman]

One thing I have done in the past which technically would be legal if you can't cut pads is to have someone with a brake lathe cut grooves into the rotor, therefore reducing friction surface.

[RaceEngineer]

One thing I have done in the past which technically would be legal if you can't cut pads is to have someone with a brake lathe cut grooves into the rotor, therefore reducing friction surface.Getting the gas out from under the pad INCREASES braking.

[stock car driver]

One thing I have done in the past which technically would be legal if you can't cut pads is to have someone with a brake lathe cut grooves into the rotor, therefore reducing friction surface.

Grooves in the rotor would give you MORE surface area and more braking..

------------ normal rotor

grooves on a lathe ---^--^--^-- GAINING surface area

[RaceEngineer]

Grooves in the rotor would give you MORE surface area and more braking..------------ normal rotorgrooves on a lathe ---^--^--^-- GAINING surface areaFriction is still independent of surface area. And dependent on normal force.

[RaceEngineer]

https://www.google.com/imgres?imgurl=http%3A%2F%2Fhyperphysics.phy-astr.gsu.edu%2Fhbase%2Fimgmec%2Facmfb.gif&imgrefurl=http%3A%2F%2Fhyperphysics.phy-astr.gsu.edu%2Fhbase%2Ffreeb.html&docid=_uSCA6Za0CsLlM&tbnid=xpvcw1E-yjWAUM%3A&vet=1&w=349&h=213&bih=511&biw=360&ved=2ahUKEwjFnJ21idXiAhWCGDQIHX_wC94QxiAoAnoECAEQI Q&iact=c&ictx=1

[stock car driver]

Friction is still independent of surface area. And dependent on normal force.

your a idiot congrats you made my ignore list, seen enough of your stupid posts on here, why not go get a hobby this isnt yahoo chat this is all but dead forum for help what was your last user name and the one before that and the one before that on here?

bye bye felicia

[RaceEngineer]

your a idiot congrats you made my ignore list, seen enough of your stupid posts on here, why not go get a hobby this isnt yahoo chat this is all but dead forum for help what was your last user name and the one before that and the one before that on here? bye bye feliciaContinue to spread your misinformation. I could care less. Many thought Galileo an idiot. But, they were the idiots. You can't beat the laws of physics.

[turtle1hp]

Friction force is independent of surface area. If you decrease surface area, you increase pressure. Friction only is affected by coefficient of friction and normal force. You would need a different pad material to make a difference. Unless you made the area small enough to overheat the pad. Then it would not make a difference until the pad was cooked. I was digging for information when I came across this thread and thought I might put my 2 cents in to help clarify differing opinions on this subject. I would agree that the smaller pad surface area would increase the pounds per square inch distribution of the actual brake caliper pressure at the brake pad contact point, on the rotor. But does that actually increase, or decrease the actual braking force for that rotor? I would think that reducing the surface area (friction area) would reduce the friction, causing less braking force for that rotor. An example of reducing friction area: (perfect world scenario) Car has 4 tires that are 10 inches wide that are all equally loaded, creating the same amount friction, or grip, when corning. Everything still the same, now change one of the tires to a 5 inch wide tread. That tire has a reduced surface/friction area. This reduction of friction area is a reduction of grip for that corner of the car when cornering. The same should happen if you reduced the friction surface of a brake pad. Less friction......Just my 2 cents...

[MasterSbilt_Racer]

I was digging for information when I came across this thread and thought I might put my 2 cents in to help clarify differing opinions on this subject. I would agree that the smaller pad surface area would increase the pounds per square inch distribution of the actual brake caliper pressure at the brake pad contact point, on the rotor. But does that actually increase, or decrease the actual braking force for that rotor? I would think that reducing the surface area (friction area) would reduce the friction, causing less braking force for that rotor. An example of reducing friction area: (perfect world scenario) Car has 4 tires that are 10 inches wide that are all equally loaded, creating the same amount friction, or grip, when corning. Everything still the same, now change one of the tires to a 5 inch wide tread. That tire has a reduced surface/friction area. This reduction of friction area is a reduction of grip for that corner of the car when cornering. The same should happen if you reduced the friction surface of a brake pad. Less friction......Just my 2 cents...

Tires are a much more complex system than a simple friction calculation. You changed the spring rate, the ability to channel debris out from under the tire, the number of edges in contact with the ground (edges and surfaces have different friction values) and a million other things.

The only way you change pad size and affect braking power is if you remove material from the outside only (reduce the effective diameter of the rotor) or reach a higher operation temperature that then reduces the coefficient of friction.

The calculation of friction force is simply coefficient of friction times normal force. That's it. No areas are involved. The first measurement to come into play is distance from center of rotation to center of brake pad. This is because now your force is applied at a distance. This is a torque stopping the wheel.

[turtle1hp]

Tires are a much more complex system than a simple friction calculation. You changed the spring rate, the ability to channel debris out from under the tire, the number of edges in contact with the ground (edges and surfaces have different friction values) and a million other things.The only way you change pad size and affect braking power is if you remove material from the outside only (reduce the effective diameter of the rotor) or reach a higher operation temperature that then reduces the coefficient of friction.The calculation of friction force is simply coefficient of friction times normal force. That's it. No areas are involved. The first measurement to come into play is distance from center of rotation to center of brake pad. This is because now your force is applied at a distance. This is a torque stopping the wheel. As far as the example of the tires, we could have used asphalt slicks to simplify the variables involved. I was just trying to find another subject matter as an example, to resemble a reduction in surface area. With your statement about the reaching a higher operating temperature, made me put thought into the tire surface area theory. That smaller tire will have grip, till you push it hard enough that it will start over heating compared to the other 3 tires. Once overheated, that is when it will not have the same grip. Thank you for your input, that had me put some thought into the "cause and effect" for the loss in grip. I also understand your point about removing pad material to simulate a smaller diameter rotor and I agree with that. That will reduce the brakes "leverage" that would be applied to the rotating wheel and tire. I guess it boils down to, if you want to reduce RF braking force, 1) you need have a smaller rotor diameter, to reduce the leverage, 2) you need a smaller caliper piston, to reduce the clamping force applied to the RF rotor, 3) you could use a RF proportioning valve, to reduce the line pressure going to the RF caliper, 4) a less aggressive pad material on the RF compared to the other pads being used. Am I forgetting anything??

[MasterSbilt_Racer]

As far as the example of the tires, we could have used asphalt slicks to simplify the variables involved. I was just trying to find another subject matter as an example, to resemble a reduction in surface area. With your statement about the reaching a higher operating temperature, made me put thought into the tire surface area theory. That smaller tire will have grip, till you push it hard enough that it will start over heating compared to the other 3 tires. Once overheated, that is when it will not have the same grip. Thank you for your input, that had me put some thought into the "cause and effect" for the loss in grip. I also understand your point about removing pad material to simulate a smaller diameter rotor and I agree with that. That will reduce the brakes "leverage" that would be applied to the rotating wheel and tire. I guess it boils down to, if you want to reduce RF braking force, 1) you need have a smaller rotor diameter, to reduce the leverage, 2) you need a smaller caliper piston, to reduce the clamping force applied to the RF rotor, 3) you could use a RF proportioning valve, to reduce the line pressure going to the RF caliper, 4) a less aggressive pad material on the RF compared to the other pads being used. Am I forgetting anything??

I think you have summarized the situation perfectly. Any would work. It's what can you get away with, within your rules.

[stock car driver]

When I went to a modified I cryo treated my rear rotors to try and get some longevity out of them and they became worthless, zero braking..

So after that I cry treated my rf rotor to reduce braking on that corner coupled with organic pads that rotor would be cold compared to the other 3.

my rules didnt allow 3 wheel brakes

Just another fyi to share.