I was pleasantly surprised with the brakes when I first test drove the GIII Prius -- considering all that was going on ----I found them to be rather "normal" But I don't like how the brakes work when you apply them and then go over a series of bumps -- I'm not sure what is going on ... but the ABS is clearly pulsing/ modulating the pressure -- with a diminished brake force the result. I have a route that takes me over a flat metal two lane bridge with gradual ramps at each end (that go over canals) -- then a smooth RR crossing on one side ... each of these transitions has a series of small bumps plus two pedestrian crossings. It is all 25mph .........So you come off the bridge --- starting down the ramp and apply the brakes.... The car slows down or at least does not speed up -- then the bumps ...... if someone approaches the crosswalk and you push on the brakes harder at the same time the car hits the bumps -- nothing more happens? You have to really hit the brake pedal. I know Toyota had an issue with some of the controls on earlier models. Anybody have this happen? It is a bit unnerving.
It is not a problem with the controls but a characteristic of regenerative braking, losing traction in at least one of the wheels and then transitioning to ASB. Search on here for brakes, brake delay or ABS and you will find multiple threads on this subject. It can be unnerving until you understand what is actually happening and then know what to expect.
Braking torque is generated by MG1 (a motor/generator) during light and moderate braking. This is a good thing because it recovers energy rather that dissipating it as heat. The issue is that this braking is applied to only to the front wheels and it is applied through differential gearing. So if one wheel slips during braking, then all braking is effectively lost until the ABS kicks in or the driver applies additional force on the brake pedal and forces the application of the caliper brakes. This can occur very quickly (minimal reaction time) since the driver’s foot is already on the brake pedal. So, to me, there is no safety issue. The best solution would be to add a motor/generator for the rear wheels. This would both mitigate the effect of skidding by a single wheel braking while providing much improved winter mobility. I would expect that Toyota could readily sell this feature as an extra cost option.
