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The S (7.5in) brakes are significantly better than twin leading shoe brakes. They aren't as good as 8.4in brakes but these would require larger wheels.
7in 997/998 Cooper disks (the earliest Cooper disk brakes) are unlikely to give better braking than the '78+ twin leading shoe setup. In fact I'm told they are far worse but they are also rare. These used a 7in rotor and 2.120in pads.
The next generation Cooper disk brakes used the same size rotor but a different calliper with a 2.335in wide pad. They seem to be the equivalent or maybe just slightly better than the twin leading shoe brakes.
They tend to be listed as 997 Cooper and 998 Cooper, but I don't think the changeover came at exactly that time, however some sources say some 997s had the later brakes other sources say early 998 had the earlier type.
The real problem wasn't the pads though (or the callipers which are also different). It was the thickness of the disk, the Cooper disks faded badly due to their inability to disipate heat effectively. The S type disks are not only larger they are thicker as well.
You will need 'S' callipers, discs and drive flanges.
"AFAIK there's no vented Cooper S disc available.
When you use 8.4in vented discs and turn them down to 7.5in, watch out - they don't fit onto the Cooper S drive flanges. You can use Metro flanges but the offset between them is different, i.e you can't use turned down 8.4in discs with Cooper S callipers.
The difference in offset between 8.4 discs and Cooper S is about 7mm."
Best of both worlds - cold stopping power is preserved, and you still have brakes after the standard pads reach heat-fade temperatures. At in-between temps, the setup is near optimal.
The only downside is you pay twice as much since you have to buy two sets of pads.
Ford used this arrangement as standard on some
Thunderbirds, probably the supercharged ones.
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