The cars from the 60s where exactly known by their braking performance.
Also, they would do a lot of lift and coast to save fuel (a great race pace should be about 5 seconds slower than raw car pace, 10 seconds would be a good pace "Gurney developed a strategy (also adopted by co-driver A.J. Foyt) of backing completely off the throttle several hundred yards before the approach to the Mulsanne hairpin and virtually coasting into the braking area"), from GT40 to the next successful car at the endurance scene, the 917, there was a performance jump of about 8 seconds (5 if you consider the 7.0 liter Mark IV). As for brake specs, the Cobra and early versions of the GT40 used a very rudimentary solid brake disks and three piston calipers and on those days the wheels were pretty small, 15 inch on both cases, the brake disks had to be pretty small also.
On sprint races, the GT40s weren't as dominant as in endurance races, the Lola T70s and later the Mirage M1s gave them a run for their money.
Of course, nothing of this as to do to, prior to update, the braking was ok, now it isn't. My guess is that PD realized the handling of this old cars shouldn't be as easy as it was before.
