The "Infamous" Breaking Gear

But we are not comparing engine braking to mechanical braking. We are comparing engine braking to regen braking.

 

This is simply not true. I understand the thinking that goes into this line of argument, but it is faulty. From a friction and control standpoint, there is absolutely no difference between ordinary regenerative braking and B mode braking. Both work only through the front drive wheels, and both work through regeneration. The difference is only in the use of the regenerated energy. In B mode some of it is discarded as heat through air pumping, while in normal regeneration it is used to charge the battery.

Both B mode and normal regeneration suffer from using only the drive wheels. This is done through a differential, so loss of traction from a single front wheel means loss of braking.

Friction braking, on the other hand, independently brakes all four wheels. Loss of traction at any one wheel still leaves the other three braking. In addition, the friction braking system has ABS, which will help maintain directional control. This is why the Prius falls back to friction braking when traction is lost.

Tom

 

I agree that if there was an easy way for cyberprius (she started this thread) to use dedicated friction braking, it would give her 4 wheel brakes, (at the loss of some energy) which would increase her safety. Given the steepness of her descent, I bet she is getting substantial friction braking, no matter what strategy she chooses.