best i can measure they are 10 3/4. is it worth going up to the 1" bigger rotor? i know surface area is everything,but what is it going to cost me to pick up a damn inch?!
Its not the surface area thats the big difference, its the diameter. The 11 3/4" rotors use the same calipers, so the pad area is the same. There is a slightly larger overall area (as the pad sweeps out a larger area due to the increased diameter), but the biggest change is the diameter. For a 10 7/8" rotor your radius is 5.4375, for a 11.75 its 5.875. Now the pads are what, 2" wide? Figure 1" less to the center of the brake pad. So, on average, instead of multiplying your braking force by 4.4375 your multiplying it by 4.875. So, you're looking at a 9.85% increase in braking force.
~10% increase in braking force! And of course, as you mentioned, you have a larger surface area for cooling. You'd think the larger rotors would weigh more too, but I found my drilled/slotted eBay rotors to weigh almost the same as my 10 7/8" stockers.
As for cost, its not that bad for a stock setup. If you use the 11 3/4" caliper adaptors from a later car they can be found on eBay in the ~$100 range usually. And then its just the rotors, I paid $140 for mine, shipped...
This is of course provided you have the '73 up style spindles. If not, you'll need those too. And this is using stock calipers, not aftermarket ones, which would obviously increase your price tag. Upgrading my Challenger to 11 3/4" brakes made a noticeable difference in stopping, it completely corrected my stock too-much-rear-brake bias issue that the Chally's had, and then some!
