Brake problems????

same thing happened to me one time as i was backing out our inclined driveway... this is my first prius, I think its just us getting used to using the brakes. (too sensitive for me)

 

I had this problem this happen this morning. I put it back in park, pumped the brakes about 5 times, put it in drive and the brakes didn't grab anymore.

 

It almost sounds like the hill holder function is kicking in.
Page 243 in main manual

 

I wouldn't think the hill holder would activate if you're in reverse.

 

Hi All,

This sounds like rusty brake issue. In the Prius, it rarely uses the friction brakes, and as a consequence they can get grabby when the rotors get a coating of rust on them.

Allot of Prius people will shift into neutral coming into a stop below 40 mph on level terrain. This forces the car to use the friction brakes, and cleans them up. Do this a few times and the braking action should smooth out. Its pretty much SOP with a Prius to do this after heavy rain/sloppy driving. I have added flush wheel covers, which reduces the incidence of rotor rusting, but such wheel covers are not good in a mountain driving area.

 

Based on the demo of hill-start assist at our pre-launch event, on about a 1 in 4 hill, the car doesn't move at all (the car did roll back when hill-start assist wasn't used). I wouldn't describe that as 'grabby'.

If you brake relatively lightly - about 1mph/sec at 70mph, 2mph/sec at 30mph, 3mph/sec at 20mph - the car can perform your braking needs entirely through regeneration (and frictional losses). The friction brakes only get used starting at about 6mph, which is only 2.6 metres per second. One revolution of the wheels is a little under two metres, so it's unlikely that the discs complete much more than one revolution if you're continuing to slow to a stop. That's not really enough to clean off road debris and water, and smooth off the disc's surface.

 

I see the same thing occur at low speed maneuverings. Whether in D or R, if i am crawling along, it seems to me that (unlike in a traditional car, which has the engine pulling you along as you use the brakes), the engine/battery stops powering the car at low speeds, and then the brakes feel very grabby. This is especially noticeable to me when I am stopped, and then trying to reverse into a parking spot. When I try to inch back the last few feet. At that point, the car seems to either stop, or want to lurch forward more than I am ready for. As I gently apply the brakes, the car is no longer propelled, so it then comes to jerky stop, instead of being able to smoothly inch back.

This does not seem to happen in any other circumstance other than when I am just trying to move 1 foot forward, like at a light, or backing up. When I drive, and use the brakes, all is good. They look clean, so I am thinking that the 'rust and debris' comments here have nothing to do with this, but instead it is a finicky brake pedal in the Gen 3 at low speed?

 

I had a somewhat similar experience today at a gas station. Shut the car off while waiting for a pickup in front of me filled up. Started the Prius w/ foot on brake, it lurched forward and I smashed on the brake to keep from hitting the truck in front of me. Brake pedal seemed to go all the way to the floor but car did stop. I assume that I had put the car in D. What was all of that about?

 

Has anyone experienced this type of brake problem?...

Theres plenty of pot-holes here in NYC, when I am braking on a slight downhill and run over some minor bumps, the car feels like it accelerates or someone rear-ended. I dont get any whiplash, but a sudden forward jerk when you are expecting to slow down.. Is this a common CVT transmission behavior when your are rapidly deccelerating?

If it this was like a manual transmission, it would feel like the hard clutch engagement during up-shifting at high RPMs. A little scary if the front vehicle is too close to you and you need that braking power with no "hiccups".

 

Also, does anyone else uses the foot- parking brake when parked or starting the car? I've driven manual vehicles before so it comes as second nature to always have the parking brake on. It does ensure that if you brakes are not responsive, the parking brake is still doing its job.

 

The car can move a bit when in Park, as there's a bit of distance between the teeth on the parking gear. There's a chance that some movement will occur when the engine starts - while it does its best to absorb the torque, this is where the engine is least predictable. The car shouldn't be able to move further than the next tooth on the parking gear, but to prevent movement, set the parking brake.

 

1999-2002 GM full size trucks did this also so I am doubtful it is the CVT. In fact, sometimes my trucks wouldn't slow down after the jostle of the bump and the brakes would go almost to the floor. It is disconcerting to be sure.

 

I have the same issues and it is very scary and dangerous. No matter how hard I hit the brakes, the car lurches forward over bumps in the city. If there was a close call over bumps you'd ram the car or pedestrian pretty hard, as it seems like the brakes just give up.

I think it has something to do with ABS, but that's just my guess. I have never ever liked ABS systems so I could be biased.

 

I have the same two issues.

1. When I go over a pothole as I am applying the brakes (stop sign just ahead), the car accelerates slightly, which is quite scary when others are waiting at the stop sign.

2. The brakes grab (and the car seems jerky) when I am backing slowly out of the driveway.

2010 Prius IV with navigation. Only 135 miles so far.

 

Do you actually see your speed increase on the speedometer?

 

this was in another thread

i think when you are braking, say decelerating from 25 through 20 to 15 or so (above 7) and you hit bumps, the traction control says oh sh*t i'm losing grip and the regen function stops, so you are not accelerating per se, but decelerating less so it feels like a surge