But the surface area DOES effect the calculation of the coefficient of friction therefore a higher CF does effect your formula.

 

I know it goes against everything that's seems to make sense, but that's not correct. Surface area plays no part in any calculation relating to friction. I didn't want to believe it when i took my first physics class either, but it's true. Surface area is is for heat dissipation, which can affect the coefficient of friction if the material breaks down at high temperatures, but at the end of the day the surface area isn't in the friction calculation. Bigger rotors shed more heat and provide a greater moment allowing for quicker breaking. (try stoping a spinning bicycle tire with your finger at the hub vs the rim.) it is also interesting to point out that cross drilled rotors provide for easier stopping because the holes reduce the moment of inertia which the brakes are fighting. It does seem strange though doesn't it. I blame he wider is better commercials.

 

Has to be. When something is rubbing on something else causing friction if you increase the surface area of either part there is an increase in the number of molecules interacting resulting in more friction. Simple physics.

Try a drag test for yourself. Take a section of old tire maybe 6 inches square and put 30 lbs on it evenly distributed, tie a rope to it, and drag it down a concrete road or driveway with a strain gauge attached.

Then repeat the test but make the tire piece one foot square. If you don't get an increase in the strain gauge reading I will EAT THE TIRE CHUNK.

 

I can't tell if you're serious or not, but this post is chock full of misinfo.

 

Not to break up this little lovefest, but today's price for the OP's brakes on eBay is $80.74 w/ free shipping.

http://www.ebay.com/itm/07-08-09-Honda-Fit-FRONT-BRAKE-ROTORS-CERAMIC-PADS-/390174246347?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item5ad83285cb

 

just paid $60 for Honda pads.... should've read this thread before

 

Misspelling maybe, misinformation? Please elaborate.

 

Tell you what, I'll save on the postage, you do the test, and I'll explain why you are eating rubber. Which if you believe surface area has anything to do with friction, you are probably used to.

First let me say that you have the right idea, this is exactly how the test would be performed, and by measuring the force, and knowing the normal force, you have calculated the coefficient of friction. You are welcome to put surface area in the calculation. Lets say resistance = coefficient of friction times surface area, times distributed mass. Lets keep the numbers simple. Lets say we have a coefficient of friction of (.5) a 10 pound 10kg mass, and in the first experiment a one square foot piece of material. The second experiment is the same, but with a 2 square foot piece of material. So our formulas are. X=(.5) x 1 x 10/1. That comes out to 5. The second is x = (.5) x 2 x 10/2, which magically also comes out to 5. Sorry, I don't have a better way to express multiplication on an iPad. The point is, if you increase surface area, you are reducing the force applied per unit of that area, and the net effect is the exact same. So no, once and for all, surface area doesn't effect the resistance due to friction.

Think of a train, really small contact patches with the rail, and metal to metal accept when they are sanding. Motorcycles, one wheel power delivery. Might be wide, but its curved, so the contact patch is still very small. Ever notice how they accelerate best when on one wheel? It's because the entire weight of the bike is on that wheel increasing the resistance from friction allowing more power transfer to the ground.

If nothing else google it.

This is my last response in this conversation. Have a nice day.

 

I'm not going to get into the physics side of it, but what I have always been told and read (which still doesn't mean it's correct):

Surface is for heat dissipation as Garrett said. The only time added surface area will help with friction is if (in this case) the caliper/pad size is increased to create additional friction against the rotor. That's why you can have larger rotors, but if you have the stock calipers, it will just help with heat dissipation. Now it's not to say it will not help with stopping under extreme circumstances where the rotor is hot. Less heat means better stopping (usually) and is why you'll read tests where they test a cold rotor against one after multiple hard stops so you can compare the stopping distances. If you want to increase breaking under all circumstances, a larger rotor and caliper it's required.

Just my 2 cents but would love to know if I'm wrong.. always up for learning if I don't have it correct

 

You and I are correct I was referring to the surface area of the PADS.

 

Yep I figured both you and Garrett were on the same page but this is why you gotta love the internet cuz it complicates things sometimes