Larger Rotor Brakes

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73dart_swinger

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How much better do the larger 11.75 inch rotors perform over the standard A-body discs? Is it a noticeable difference?
 
Good question, has anyone ever compared? It seems to reason that a larger rotor would give better stopping power, but if the caliper and brake pad are the same you really don't get any additional friction surface. All you get is more rotating mass. Looks cool but will it stop in less distance? I have the 10 3/4" rotor and have also thought of the 11 3/4" rotor upgrade.
 
I'm pretty sure you would. The 11.75 x 1" rotor is the HD rotor on the Cordobas. AREngineering made an adapter to use the Wilwood caliper with the 11.75" rotor. It saved quite a bit of weight over using the factory caliper.

spindle&caliper.jpg
 
i went from the 10.84 to 11.75 rotor upgrade. it seemed to stop better, but i am now going with the above bracket to put wilwoods on there. why? more clamping force. 4 pistons have more clamping force than a 1 piston pin or slider style.
 
Even with pad surface area being identical, I'd think that the increased diameter (without regard to other factors such as greater clamping force of aftermarket calipers or something) would increase braking effectiveness as a function of forces acting on a longer "arm". A larger rotor could be considered as a cheater pipe or a stroker crank for swept area. Without crunching the numbers, I'd guess that the increased rotational mass wouldn't be enough to cancel the positive effects of lug-shearing stopping power.

Obligatory Disclaimer: I could be missing something vital.
 
nice. that is some weight savings there! have to hold off on those till i pay off the engine bay detail i'm deep into now.

maybe by summer.
 
I've swapped from 10.75 to 11.75 in my 68 Dart. Seemed to be better.
 
Some good answers above, but the real increase in braking efficiency is due to the greater 'swept area' of the larger rotor. Because of the increase in diameter, the pad is in contact with more area (square inches of contact) of the rotor per revolution of the wheel. The larger the diameter of the rotor, the more area the pad will contact during a single revolution of the rotor. Therefore, more 'swept area'.
 
ocdart said:
Some good answers above, but the real increase in braking efficiency is due to the greater 'swept area' of the larger rotor. Because of the increase in diameter, the pad is in contact with more area (square inches of contact) of the rotor per revolution of the wheel. The larger the diameter of the rotor, the more area the pad will contact during a single revolution of the rotor. Therefore, more 'swept area'.
Click to expand...


very true. but i would think that if you also add more clamping force that would increase it above that as well.

upgrade to 11.75 rotors-better, upgrade to 4 piston caliper on 11.75 rotor- even better.
 
ocdart said:
Some good answers above, but the real increase in braking efficiency is due to the greater 'swept area' of the larger rotor. Because of the increase in diameter, the pad is in contact with more area (square inches of contact) of the rotor per revolution of the wheel. The larger the diameter of the rotor, the more area the pad will contact during a single revolution of the rotor. Therefore, more 'swept area'.
Click to expand...

This is very true but only if we are comparing rotors with the same coefficient of friction... hence if you are very rich you could buy a small carbon ceramic rotor and have enormous braking force while keeping rotation mass to a minimum! But that is only if you are very rich!
 
Sounds right, I asume it will give better stoping power but how can a pad of equal size (constant) gain more area of contact from just increasing the size of the rotor? Are you saying that the caliper pad was not making full area contact on the smaller rotor, and now that the rotor is larger, it is? Maybe I'm not seeing the science behind it.
 
I think the theory is the larger rotor has more square inches of rotor to grab per revolution. Even with the pad being the same size it grabbing more rotor per revolution SHOULD slow you down better. Thats the theory.

TopHat
 
The brakes are only as good as were the tire meets the road. Just like with engines, brakes and suspension need a balanced combination of parts.

Throwing a big cam in a stock motor doesn't do much good. Same thing with big brakes and stock sized tires, doesn't do much good.


Chuck
 
buddyralf said:
Sounds right, I asume it will give better stoping power but how can a pad of equal size (constant) gain more area of contact from just increasing the size of the rotor? Are you saying that the caliper pad was not making full area contact on the smaller rotor, and now that the rotor is larger, it is? Maybe I'm not seeing the science behind it.
Click to expand...

Increasing the rotor size means that the the moment of arm is increased, it gives you greater leverage, and with the same clamping force you get easier braking.
Now by increasing the rotor size also means that you can use bigger brake pads and hence increase the swept area which again gives you better braking.
Bigger rotors will also dissipate heat better but that does not necessarily means
better braking because the coefficient of friction is temperature dependent! For that, a graph of the coefficient of friction against temp is needed to know what we are talking about!
 
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