What controller for 8S that has a true brake??

[othello]

As your motor will spin at almost 40000rpm with 8s you should start with smaller pinions as Lutach already suggested it: 12, 13 or 14.

With a 13 tooth pinion your cars top speed will be around 40mph.

Differential Ratio: 4.6
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 13
Total Voltage: 29.6
Motor KV: 1333
Tire Diameter (inches): 5.6
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.017
Spur/Pinion Ratio: 3.54 : 1
Total Ratio: 16.27692 : 1
Tire Circumference (inches): 17.59 inches (446.86 mm)
Total Motor Speed: 39456.8 RPM
Vehicle Speed: 40.39 mph (64.87 km/h)
Estimated Adjusted Speed: 38 mph (61 km/h) - 5% loss
Effective KV Value: 1333

Here is a video with the shortest gearing (1:12,13) i used with the Jazz 55 (with 10s1p A123 around 30v and 30000rpm at full speed) and the corresponding eagletree graphs: whole run, 1 minute in detail, speed passes. There was no cogging but i sometimes noticed a very small delay (say 0.2sec) when starting from a stand still and hitting full throttle. I still use a small heatsink "glued" to the Jazz 55-10-32 cooling plate.

With better cooling mods RC-helicopter flyers push this small ESC up to 4KW.