Brake Failure (and an accident in a snowy day)

This isn't enough to wear out the initial (but still not great) winter ability of A-S tires. But now that you live in Philly instead of LA, real winter tires are probably a good idea.

#1: LEAVE A LOT MORE SPACE FOR STOPPING AND TURNING! Expect stopping distances to be 4X to 10X longer than when dry, though it will vary enormously in different conditions. Turns also demand strong steering traction to prevent sliding out, so take them much slower.

#2. Learn the 'Stomp And Steer' rule for ABS. Stomp hard on the brake and keep holding it down, while continuing to steer in the safest direction. Don't pump brakes the way we once had to on ice with pre-ABS cars, unless you know that all wheels have locked up (which has happened to me only a very few times since ABS).

#3. Get real winter tires. Nothing can possibly give you traction even close to normal dry road conditions, but winter tires will beat others.

This seems like the root cause, lack of winter driving experience in the new geography. The first time sliding will nearly always be a shock. Your driving reflexes and styles will need to be reprogrammed.

Not only is it OK, it is nearly essential if you want to be driving in winter conditions. Your mind and body need some training in how the car responds. Your previous experience simply doesn't cover it. Some old habits and practices and reflexes that were acceptable in the old environment may need to abolished in this new environment, and replaced with new or modifed methods.

In a wide safe place, start with straight line stops. Moderate at first, then as hard as the slick surfaces allow. When comfortable with those, try stopping while turning.

 

I am sorry that you had an accident in last Thursday's snow. I was driving in it also, trying to negotiate my way home in the Phila suburbs. I had my F250 with very aggressive tires, which is my go-to vehicle when the weather is bad. Interestingly enough I specifically recall immediately noticing that the roads were very slippery. Conditions were bad, and my immediate instinct was to go into super-safe mode -- exercising extreme caution to avoid an incident. There were many cars that had trouble just negotiating the main roads, with a few in ditches or off the road entirely.

Fortunately, I made it home safe and sound without any issues, after taking four times my normal travel time. Even while being extra cautious, it's still possible to have an accident when conditions are that bad.

I hope you're able to get through this, get your Prius fixed quickly, and put it all behind you as soon as possible.

Good luck.

 

No it is NOT. If that's what you wanted, ABS would not be needed.

ABS stands for "anti-lock brake system".

It is specifically designed to keep the tires from completely locking up.....by applying and releasing the brakes in milliseconds.

And there is no reason to think that the ABS system on the Prius works any different or worse than any other make or model.

 

Interesting Thread.

 

Jalopnik link illustrating traction on ice by tire type.

Regarding weather in the Philadelphia area last week, the fundamental problem was that the weather rapidly reduced the actual cars-per-hour traffic handling ability of the roads to about 5% of their normal numbers. This happened without a corresponding 95% reduction in the actual traffic attempting to use said roads.

 

Most of the responses on here are clueless. You did not slam the brakes at all and you completely braked properly. This is a common problem with the gen 3 Prius. Loss of brakes when hitting a bump. It happens to me too every time I brake to turn to the street where my workplace is just because the road is bumpy before the turn. This is a big issue and I've been saying this since 2014. Toyota should take responsibility of this brake problem and add it to their recall. Again, this is a big safety issue and it is totally not the driver's fault. The brakes just simply loses traction when you hit a bump WHILE braking. BIG BIG BIG safety issue but Toyota won't own up to it. Fail.

 

Finally, I was reading through the thread waiting for someone to mention the problem with Toyota's brakes over bumps, I agree, hit a bump, lose your brakes, combine that with ice and you have an accident waiting to happen.
Had a gen3, the op's gen3 also has a bump problem, not as bad as the gen2, but, adding ice and an unfamiliarity with prius brakes....
I had a gen2, there's one stop sign on a bridge just after a bump, once you go through a stop sign on a dry road, well, it only takes once, when it's icy you know what to do.
I also run studs winters, got rid of the gen2, now have a prime, with studs, the studs are for stopping on ice.

 

I've never "lost" my brakes when going over bumps. They're still where Toyota put them.
I believe you feel you "lose your brakes" over a bump because the wheels are off grounds????
I speed up for the speed bumps and then brake just before hitting so the front end rises to reduce the slam.
Then hit them again so the rear rises. But have never felt them not working. Even on a bumpy road while
slowing or stopping, the brakes work well.

 

If I understand his description of the situation correctly, YOU are absolutely, totally wrong.

In a situation where loss of traction is likely to occur and you have an ABS equipped vehicle, pumping the brakes in an attempt to regain traction is precisely the WRONG thing to do.

And a lot of cars with ABS will exhibit "skid control" actions on one wheel IF you are going too fast and hit a bump that is big enough.
That should be your clue to slow down.

Sounds to me like it is YOU who needs to get a clue.

 

Sorry, but this is only a momentary loss (I think BobW measured about 0.6 second, before the recall that shortened it), only when transitioning from regenerative-only to all-friction braking, only during light-moderate braking.

It doesn't last anywhere near as long as OP's slides persisted. It doesn't happen with hard braking, which is what OP should have been doing when that close to a collision and/or when ABS is needed. And it doesn't repeat when one holds the pedal down hard, it repeats only when one 'pumps' the brake and applies just light-to-moderate pressure.

In short, this Prius regen braking transition issue has little relevance when driving properly for the conditions and leaving adequate margins. It matters only to those who are tuning their stops to land just a couple feet behind the car in front with no safety margin and no escalation when something goes wrong, a poor practice even on dry road and an invitation to disaster with the compromised traction of foul weather.

 

You're talking about the way the car switches from two-contact-patch regen braking to four-contact-patch friction braking if the sensors suggest the two patches might lose traction. Which is pretty much what you'd want it to do. This is one of the most-discussed, and yet somehow least-searched-before-discussed, Prius behaviors on PriusChat. Goes all the way back to gen 1.

For future searches (in case searching is a thing in the future), there's more detail in this post.

-Chap

 

folks, you are not supposed to brake hard while hitting a pothole. this wipes out front suspension when tires lock. yes, prius' reaction to that is worse than average car, but it's preventable.

 

Another "Prius brake" issue I've noticed, at least with ours: once in a long while, right after start-up, in reverse, the brakes are ULTRA-touchy. The first time I noticed, I was backing up in a parallel parking space, preparing to leave. As I got close to the car behind I touch the brake, and at first I thought I'd misjudged and tapped him: the car just stopped on a dime, no modulation, off or locked, take your pick.

Anyone else notice this?

 

I’ve noticed that or the brakes are hard and the pedal isn’t responding on startup and backing up.

I put it in park and let it sit for a couple of seconds and retry.

That works for me.

 

In my 2010, yes, once or twice. But never in my 2012, now at 84k miles.

 

It's another symptom of the "surface rust" that develops on the rotors and maybe the drums too if you have rear drums.
Yes I've noticed it......on several different cars.

 

Wondering if the touchiness in reverse is that there is no regen braking. The mechanical brakes are engaging directly - and probably very effectively if there is any surface rust. It also is true that right after a start, the accumulator should be fully charged at max pressure.

 

That snowy day around Philly, as others noted, roads were a total mess. Everyone forgot how to drive in the snow, the roads glazed over, and the afternoon commute turned into a total nightmare with cars stuck and accidents everywhere. Just a bad day to be on the roads if you had to be out there. Sorry to OP they had a problem.

 

Agreed.... Weather conditions dictated that everyone leave enough gap for maybe 2 semi trucks between every single car.

But it's Philly so everyone was packing it in like sausage on any other day. Completely predictable outcome.

I think it says a lot about our vulnerability as a nation when that many people can't afford to miss work.

 

I get this in my Subarus, and very strongly doubt that it is what I felt in my 2010 Prius, which was traded in at 35k, much less than I've rolled up in my 2012.