I have found you need to have the initial brake set at 40% for the brakes to work with our 10.5 motor class. The other thing that makes a bi difference is the motor. With a Speed Passion there is practically no brakes, LRP had some brakes and the Trackstar has awesome brakes. However my 4.5t SP has good brakes and I usually have to dial them back to 0% initial and about 70% total.
Before I got the R10, I had a Reventon Pro and I found it was much worse when it came to braking.