Question about big brakes

[Hopalong]

I've been gone a while so please bear with me if this has been asked before.  The question is this:  At what point are brake rotors too big?  My thought is that as rotor sizes increase, so does rolling resistance.  I've been looking at different brake kits that are available, but wonder if I really need a 13" rotor on the front to acomplish what I want.  What I want is a system that is bigger than stock, for looks and performance, without going over board.  My idea is a 12" rotor on the front, and maybe a 11 1/2" - 11 3/4" on the rear with good four piston type calipers (wilwood?  It will be a fair weather car).  I hope to do some local autocrosses and some ocasional drag strip action as well.  I understand that the larger rotors offer a better heat sink, which makes sense on a (road) race car, but is it just "wow" factor on a street car?   

[NoMope Greg]

Rolling resistance doesn't change with the size of the brake rotor - only with the size of the tire.  The larger rotor may require you to use a larger wheel, solely so that it can fit inside.  By way of example, I've converted my car from drums to front discs, requiring me to switch from 14" to 15" tires.  Larger rotors also weigh a little more, increasing unsprung weight.  In a road-racing situation, that may require more damping in the shocks to soak up the increased tendency to oscillate when undergoing a change in load.  In your case, unless you're intending to do some serious autocrossing with an idea of some track time later on, the extra inch won't be worth the extra $$$. 

[HP2]

I'll second what Greg said.

The larger rotor allows you to put more leverage into braking, thus stopping you faster. Think of it like the good ole' cheater bar for breaking nuts loose; longer bar for more leverage and torque, bigger rotor for more leverage and torque. The greater the torque, the faster the car slows. So large brakes are functional.

With a 15" wheel, the biggest rotor you can use is a 12.12. This is so large you will have to use an aftermarket caliper with a thin bridge and a custom bracket to mount them on to get the clearances just right. I don't think any one out there offers a 12" kit for mopar spindles. You probably could piece one together from the Wilwood catalog with some careful parts selection and a buddy who is a machinist. FWIW, Nascar uses 12.12 rotors.

Anything bigger than that requires a larger diameter wheel. However, with the number of 13" kits at there, it may be a cheaper route to go 13" with new wheels rather than trying to fit a 12.12 rotor in the stock wheel.

The largest stock rotor is 11.75, which is bigger than most the 10 inch kits you see on the aftermarket right now. For anything but all out road racing, this would be sufficient, and even then cooling ducts and special pads will get you a long way into the road course action with a factory set up.

[Hopalong]

Thanks for the info guys!  I was looking at Baer's kit that offers 12" rotors on both ends (fronts are thicker).  I like the idea of 12" rotors so that I can use 16" wheels if I should get serious about racing it (drag or autox).  I was planning on using 17" wheels for normal driving for the looks and good street performance.