Brake upgrade effectiveness

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theterminator93

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I'm sure those of us with MN12s with the factory-equipped brakes - especially those who aren't lucky enough to have the factory Sport brakes up front - will agree: the brakes on our cars aren't great! The single most common complaint is probably warped rotors - fortunately, options exist that can make that a distant memory without breaking the bank.

Fortunately in the years following the demise of the MN12, various components used on other Ford products (usually SN95 Mustangs) were engineered that community members learned could be easily retrofitted onto the MN12 chassis. The caveat is that these calipers can only be installed on MN12s manufactured for the 1993 model year or later because of a redesign of the front spindles. 1989-1992 MN12s would need to swap to 93-97 spindles to take advantage of these calipers.

For those with standard 10.8" front brakes and 15" wheels, the best upgrade option is to use the calipers from 96-04 Mustangs. These use the same 10.8" rotors but dual piston calipers made by PBR. These calipers and their brackets can be retrofitted onto 93+ front spindles with slight modification done in a couple hours.

For those who have 17" or larger aftermarket wheels, a major upgrade from the 10.8" PBR caliper upgrade is to use the (larger) dual-piston PBR calipers and 13" rotors from the SN95 Bullitt and Cobra Mustangs. The calipers are a direct bolt-on to 93+ spindles, but no 13" rotors fit the MN12 5x4.25" bolt pattern. As such, unless you are already using 5x4.5" pattern hubs and wheels, the bolt holes must be elongated into oval-shaped holes to fit the smaller bolt pattern on MN12 hubs or the rotors need to be re-drilled for our bolt pattern.

The rotor-warping issue is most prevalent with the base 10.8" rotors and factory single-piston calipers. Upgrading to one of the dual-piston PBR calipers virtually eliminates the problem of rotors warping, but as with any complete brake job - bedding in the new rotors is an essential component to longevity. Go easy on your brakes for the first several hundred miles. You could do a half-dozen hard 60-20 slowdowns in immediate succession to really heat up the rotors and pads, then let the rotors and pads cool completely prior to driving the car again.

Measuring braking effectiveness objectively from a performance standpoint (e.g. 60-0 braking distances) has never been done, however an estimation was provided years ago. In that estimate shown below you can see approximate improvements to braking effort as a result of increased pad-rotor contact area and braking force. In my opinion the increase in effectiveness between both 10.8" stock brakes and the 11.6" SC/Sport brakes and 10.8" PBR calipers and the 13" PBR calipers is understated as a result of the increased distance of the pad-rotor braking effort area from the center of the hub. If you have more accurate objective data, please feel free to share it with the BirdCats.com staff!

Stock 10.8" brakes: 100%
Stock 11.6" SC/Sport brakes: 103%
PBR dual-piston calipers with 10.8" rotors: 122%
PBR dual-piston calipers with 13" rotors: 128%

With regards to cross-drilled and/or slotted rotors, their contributions to braking effectiveness for many applications is a myth. The holes were originally engineered as a result of a need to dissipate gases that older pad materials produced under heavy braking, which is not a concern with modern products. The holes in the rotor provide less surface area for pad-rotor contact, which reduces braking surface area and thereby actually is detrimental to performance. The only benefit they would have is their lighter weight.

With regards to slotted rotors, there is a potential benefit for a performance improvement but mostly only for heavy braking applications (e.g. if you do a lot of 80-0 panic stops or hauling a trailer through the mountains). The slots on the rotors help clean off pad material faster while braking which prevents the pads from glazing over. For normal driving, however, the most obvious result will be an increase in brake dust and frequency of needing to replace pads.
 
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