Just got my new wheels, I want new rotors to go with them with painted calipers. I like them as big as possible, either cross-drilled or slotted. I am wondering if it will affect the braking system, how large is too large? Any recommended place to purchase them? Thank in advance

 

You could look into big brake kits that feature larger everything (Calipers rotors and brackets) which will be pricy. A cheaper alternative is to find that Company (AWR maybe, I forget) that makes the brackets for larger rotors. They move the caliper out more for room for larger rotors, but don't give the same braking power as a full upgrade. The contact point on the rotor itself is the same so the only true advantage is cooling.

To Big would be when you can't fit the wheel over the rotors... Also wieght. If you get the brackets and larger iron discs you are increasing unsprung wieight which will effect acceleration, Also defeating the advantage of lighter wheels if that is what you purchased. If you purchase two piece rotors with iron hats it won't be as much of a problem (if at all, most of the time the two piece rotors are lighter than the stock, despite being larger) You will not be able to use stock wheels if you get bigger rotors either.

 

Don't waste money on it cuz ur rotor is larger but caliper is stock. Gripping surface on rotor is as b4 but now u'd have xtra rotor surface which are not gripped by the caliper pads. Wouldn't be good in the end.
The 2 piece are sometimes not balanced or would wrap due to bad quality screws unabled to withstand the heat. Thus u'd have a wrapped rotor due to the hat's screw. It's better to buy either whole package or get the 2 piece rotors from Brembo etc.
If u have a flat, u can't use ur spare tire at the trunk cuz it won't fit into the larger caliper. That's what happened to me. I had to move a wheel at the rear to the front and chuck the spare on the rear wheel.

 

Great point about the spare...

Braking power with an increase size of rotors with stock calipers won't be better in the end. they will cool better with more rotor area diffusing the heat, but no more pad/rotor contact will be achieved over stock

 

maybe im wrong here but... you could spend $1000-$2000 for a whole new brake kit which includes rotors, calipers, brake lines, etc. and it will help a lot with braking power, or you could spend something like $400-$700 and just get bigger rotors with a caliper spacer and it will help a good amount (not as much a entire kit). The fact that they are cross drilled or slotted will help with cooling, the fact that they are bigger will help with braking. Bigger Rotors give you a further distance from the axel which means more torque = shorter stopping distances. Cross drilled brakes are good for longer harder stops, and slotted are good for many short hard stops. Both reducing heat better then stock brake rotors, reducing risk of gas buildup between brake pad and rotor which can lead to brake failure. I dont know where to get the best deal for brake kits is but try looking at www.precisionbrakescompany.com or www.rr-racing.com

 

Any test I have seen on larger brackets/rotors and not a full kit did not perform better in terms of braking power over stock. I am not sure about that torque example. I need to think about that for a while, but With a larger rotor there is more torque exerted on the pads than with a smaller one. The caliper does not move so it is only scrubbing a surface moving faster than before. If anything that would hurt it but again I am not sure on this. if anyone knows more about this feel free to correct me.

 

state college huh? I used to go to PSU too. Heres a little more about the torque thing... think of when you use a wrench to lossen a bolt. The longer the wrench (the further away from the pivit point the force is aplied) the easier it is to loosen the bolt. the same thing aplies to your brakes but in a reverse manner. The further away you put your caliper from the axel, the easier it is to brake (you will brake faster). Enlarging your rotor from the stock 11.2' to 12.2' or ever 13'(with bigger rims), the further away your caliper will be. Not changing your caliper means that your clamping power will not increase but you should still be able to break faster with just a larger rotor. Im not exactly sure how much faster your car will stop but... there will be a difference.

 

I'm going to call bunk on that theory. You will not brake any faster with larger rotors due to the increase in torque. The objective of stopping a car is to convert the car's kinetic energy into heat energy. Increasing the torque between the caliper and the axle may allow you to lock up your wheels easier but will not stop you any faster since it does nothing to help increase the connversion of kinetic energy into heat energy.

 

thank you PseudoRealityX. In responce to pollax, Hes not changing the size of his wheel, its gonna stay the same stock 16 inch rim and when he upgrades to a larger brake he will stop faster. The distance the brake pad covers as it press's against the rotor will be the same but with a larger rotor there will be less rotations. And all though there isnt any extra clamping force by the rotors themselves, the fact that you have a larger rotor will make it easier on the caliper to stop you car, giving it more stopping power.

 

That is exactly what I said in my post.

Please define stopping power. Your stopping distance will still be pretty much the same regardless of what kind of brake setup you have if you do not get different tires. I can easily lock up my tires with my stock brakes so getting larger brakes will do me no good unless I get better tires. You may be able to lock up your tires with larger brakes and rotors easier but what good is that? The biggest reason for upgrading rotors and calipers is for fade resistance.

 

Yeah I drank to much that night....

In regards to the less revolutions I don't think that is true. This is different to wheel/tire sizes and revs per certain distance. The larger rotor will make just as many revolutions as a smaller one. Think of two helicopters with different sized rotors. The central hubs are both spinnig at say 2000rpm (not realistic I don't think, but they are parked or something just showing off) and are the same size. One chopper has much larger rotors by say 3 feet than the other. IF both hubs are spinning at the same speed, the only difference is the speed at the end of the rotors. They are making the same amount of revolutions, just the longer rotors are spinning faster at the tip.

Jesse I will take your word for it with the torque arm bit and agree that it all comes down to tires.

 

It's better to leave locking up wheels/tires out of the braking equation entirely. Just focus on the brakes rotating and the braking force. As I work in the industry, I've talked to guys from AEM, Baer, and SSBC, and they all say that the larger rotor thing is almost entirely for looks. The problem with the leverage example is that (as has already been said) The outer edge of a larger brake rotor is spinning faster, and this compensates for the extra leverage from the increased caliper distance. That's why test never show much improvement if any in braking distances. Keep in mind that many tests are conducted on anti-lock brake equipped cars (wheels will not lock up). Adding slots or cross drills to brake rotors obviously improves braking performance due to improved heat dissapation (the reason why some rotors, bigger or not, will improve braking), but the only way to really increase braking force is to use more powerful calipers (more pistons or larger piston size).

 

I shouldn't say the ONLY way. You can also use better brake pads, but these may reduce the life of your rotors.

 

I'm not disputing that at all. Of course braking has a lot to do with tires. I simply wanted to leave tires out of the equation for a minute to discuss the benefits (or lack thereof) of the big rotor kits that use brackets to relocate your stock calipers outward that companies like AEM sell. All things being equal (same wheels, tires, etc) these kits won't help you much in the performance department and are mostly for asthetics.

 

Upgrading to stainless steel brake lines (braided or hard tubing) also makes a big difference in brake feel and reduces brake fade.