Have you experienced the "grabby" brakes?

Yes, experienced it. Once, in reverse, going down a very gentle incline, after parking overnight. Shifting to Park and back to Reverse fixed the problem and braking was immediately normalized.

 

My experience was basically the same as rachael's. It has only happened once in the month or so that I've owned my Prius.

 

I've experienced it 3 or 4 times. Always after pressing the power button to start the car, then pressing it again to stop it (e.g. to go back in the house to get something I forgot), then starting it again and shifting into reverse. As soon as I finish backing out of the driveway and shifting to D, the problem disappears. I can also press the P button and then shift into R to make it disappear.

 

Have not experienced it.

 

I've experienced it a couple of times after parking overnight. Both times I was backing up out of my driveway

 

It's simple: it is due to rust on the brakes built up from shipping from Japan to its destination. (Or letting the car sit for a while.) You encounter it at low speeds, like creeping in a parking lot, because above 8 mph you'll either be using regenerative braking or you're braking hard enough (and have enough momentum) that there won't really be any grab.

Just run the car up to speed, put it in Neutral (no regen braking) and brake firmly, should eliminate it. Or it will go away naturally.

I experienced it perhaps twice in the first two weeks of owning the car and never since, just like everyone else I've ever heard about.

I've encountered the same thing with non-Prii over the years, usually after the car has sat for a week or two and it's rained.

EDIT: People describe fancy situations with shifts and offs and ons "triggering" the grab, but then they only have it once or twice and never again. Odd isn't it? My guess would be that the braking they did rubbed the rust off and the off-on-wave-a-rubber-chicken didn't actually accomplish anything.

It's possible that models with the anti-slip-back feature (breaking assist, or whatever it's called) might engage the mode accidentally in reverse, I guess, and shifting out of D and back would no doubt clear it, but...

 

Well, that might be your guess, but you'd be dead wrong. I'm an experienced mechanic and I know the difference between rust on the brakes and a software glitch that activates the brake assist, or some similar phenomenon. Once you've experienced it, you'll know too. But in the meantime, keep on throwing those guesses out. Good stuff.

 

Maybe it's rust on the software. Try shifting back and forth from octal to hexadecimal a few times. If that doesn't fix it, try an eight bit rotation on each byte.

Tom

 

Twice reversing out of my driveway in the morning. It went away after I put it in park and reverse the second time.

 

Oh qbee, you and your silly math talk. Kids these days!

 

Wife just got back from a 2000 mile trip and was describing how the car would shake while she was backing up, Happened twice. Both times after sitting over night. Wouldn't think there would be rust on the rotors after rolling 1500 miles in two days. Told her to take it to the dealer but thought I would check here first to see if anyone else had experienced it. Still going to have her take it in if for no other reason than to document it.

Just went out and looked and felt the rotors,,, slick and clean.

 

My brakes have been very very smooth.

 

I've experienced grabby brakes while backing down the driveway. It's happened more than once and I have 1,050+ miles on my V. Alarming at first, now it doesn't freak me out. What is weird is going over a bump in the road while braking and the ABS kicks in and the Prius lurches forward faster (momentarily) instead of slowing down.

 

I HATE that lurch! Happened to me the other day as I was entering a parking lot from the street. Went over a metal grate that triggered the 'lurch' and felt like we were shot into the parking lot. I know everyone says it is to be expected, but it sure doesn't feel right.

 

No, we've had the car for 2 months, used the brakes a lot, live in a very dry climate, and park indoors. The car rarely sits more than overnight without being used. The problem still occurs, intermittently as always. The feel is nothing like rust or debris or any mechanical issue with the brake mechanism. I suspect a software/firmware problem. I am sure Toyota will come out with a fix soon.

 

Just picked up my Prius Friday night, and Saturday afternoon I had grabby brakes while backing out of my (very slightly sloped) driveway. I assume it will stop doing that with time.

 

Yes, experienced it twice in 3 months. One time going forward and once backing out. On both occasions sitting in the car for 2 to 5 minutes before hitting the on button. The brake primes when you open the door but if you do not start right away it seems to "unprime" itself and cause the grabby brakes. Maybe someone else has a better explanation...

 

Backing out of a somewhat sloped driveway, I experienced unexpected acceleration (backward, foot not on the "gas") as I eased off pressure on the brake pedal. I pressed the brake, stopped more abruptly than expexted.

Easing off even more gently, the same thing happened 5 times.

Finally, I re-booted and the problem went away.

Maybe, the Hill-Hold feature was turned on and I did not see it.
Is the Hill-Hold only designed for use when going forward (in Drive)?