Rotor Swap

[BD-VX99]

I'll have to admit I'm surprised that a '96 rodeo would have larger rotors. The VX's are large enough that you can barely fit a 15" wheel. But if you do the swap you're going to have to fab new caliper brackets to handle the increased diameter. And if the calipers you use can't accept larger pads to cover the additional swept area then you're wasting effort. It's a two-part deal: bigger rotors need bigger pads. Otherwise you'll actually reduce your braking power as the same amount of pad is attempting to stop a rotor further out meaning it has greater force to overcome than if it was gripping nearer the axle. Simple leverage works with braking too.

Joe, I think you may have it backwards on that last point. Unless I'm totally looking at this wrong. The brakes apply a force in the opposite direction to which the rotor is spinning, about a lever arm the equal to the radius of the rotor (actually ~2/3 of the way through the pads contact patch). The negative torque applied at the centre of the wheel is equal to the radius times the breaking force (based on the hydraulic squeezing force and the frictional coefficient of the pad/rotor). Increasing the radius, increases the amount of negative torque that can be applied to the wheel using a given caliper/pad. Is there something I'm missing there? I don't think bigger pads change the applied frictional force, as the same hydraulic force is now being applied over a larger surface area. I was under the impression that bigger pads just distributed the negative effects on the heating and wearing surfaces. Anyways I've been wrong before but if I am this time I'd like to understand it better.

[Joe_Black]

It's sorta had to describe in text, at least for me. But imagine a spinning disc in front of you that you want to stop for your hands. Would you place both hands on either side and press, using as much of your hand as possible or just squeeze the outer perimeter with your fingers? Using your entire hand to cover as much area as possible provides more friction and distributes heat over a greater area as well. Using just your fingers on the outside will either burn them or you'll be unable to hold on.

In relation to brakes you want pads that cover the full rotor, which can't happen if the calipers aren't selected or mounted properly for the application.