Front tires slip on bumps- sometimes

This is normal for turd gen prius. There are places around town that has bumps and dips that will cup my tires as I drive over them, some of them are present on downhill roads. I purposely do a hard regen over the dips and bumps to feel it slip to refresh how I will react if there is a car in front of me if I am in ever in such situation. Others have reported in here for rear ending others after hitting a pothole because of their brakes slipped right after running over the pothole.

 

Because it’s never killed anyone and if Toyota was to release this Information, no one would buy it.

Trick: It’s just like falling toward at knifes, just angle yourself in ways where your not punctured, just only cuts that can be bandaid up with minimal blood loss.

 

just push harder on the pedal, it's counterintuitive

 

The known issue involves the ABS-triggered transition from regen-only to friction braking. That means it is triggered only when you are using light to moderate 2-wheel (front) braking. And it is only momentary, so you should have functioning brakes again, all-wheel this time, within a fraction of a second. Don't release the brake pedal, just stomp harder.

Numerous startled drivers have mistakenly or reflexively released the brakes. I suspect the few folks who did hit something, panicked and released for too long.

The known problem doesn't happen when the car is already in 4-wheel friction braking, which covers all hard braking. If you are close enough to be at risk of rear-ending a vehicle in front, then you should already be in harder 4-wheel braking, and this problem doesn't happen.

Traditional non-hybrids don't have this 2-wheel braking mode. They always use 4-wheel friction braking, so initial ABS transitions are far less obvious and intrusive.

If your brakes are releasing or 'pausing' under hard braking, then you are experiencing something different.

 

On our 2nd Gen car, the Traction Control light will flash briefly when this occurs. The first few times it happens, it is a little scary, but it always happens at low speed (~7 mph, I believe), and it is so brief that I don't believe it adds much to the car's stopping distance. It's just that momentary feeling of loss of control that makes it seem worse than it really is. I suspect those who have blamed rear-ending someone on it were more than likely going to hit them anyway, at the speed they were traveling. FWIW, I don't believe I've experienced this on the Gen 4. Perhaps this defect (aka "feature") has been corrected somewhat on the later generation cars.

 

For Gen3, that is the minimum speed for regeneration to function, so is also the minimum speed for this issue. But I have run into it at all speeds up to about 30-ish. I am not aware of any upper speed limit, but the window where it is possible is much smaller at highway speed, because the maximum possible regen force is inversely proportional to speed. (Regen has a power limit, force equals power divided by speed.)

I sometimes also feel the cutout when slowing down through 7 mph to a stop on smooth surfaces, as the transition isn't always perfectly seamless. But this 7mph transition mismatch doesn't happen all the time, and is always much smaller than the ABS-triggered bump events.

Agreed. Plus, it happens only under light-to-moderate braking force, which no rational driver should be using when stopping distance is sparse.

Hitting someone under these conditions is not a speed issue, but a failure to use anywhere near full available braking force.

Folks who are deliberately using just light braking while aiming to stop only a couple feet behind the car in front, and then either freeze or release instead of escalating their pedal force when this bump-induced 'pause' hits, are at risk for an expensive surprise.

 

A similar jarring interruption will occur on the power side of the performance curve if any slip is detected in the front wheels. This is to protect the half axles and other components of the drive train from over-torque when wheels re-engage with the surface. You will see the yellow Traction Control light blinking a couple three times. Something else to be aware of in this high-tech vehicle.

I keep a mental map of all the braking hazards where I drive such as cattle guards, uneven surface transitions, dirt and gravel, and ponding areas when (if) it rains. If you don't know your route this well then I suggest some very careful driving, which is what everyone should be doing anyway.

 

if this is the mantra here, wonder if the Tesla “auto pilot” sub forum has the same.

 

Just suggestions. As always, YMMV.