Brakes grabbing

drive by wire baby!!!

 

actually that is when regen cuts off and its at 8 mph

 

I've been noticing the same problem. New '05, bought it in August, and it's now about 3800 miles, and I've just started noticing the grabbing/sticky brakes at low speeds. I'm pretty sure it never did it before. I'm planning on bringing it up when I take it in at 5k for the first service, I'll let you know if they say anything.

-Orgus

 

I have noticed the exact same issue with my 2005 Prius with 9k miles. Anybody have any diagnosis from a dealer about this?

 

Hi there.

I feel there are two different effects being described here. Sticking and grinding versus 'grabbing'.
Grabbing as described above never occurred to me.
Sticky and grinding noise in low-speed stops or starting to roll again with stop-and-go traffic situation happens all the time. A bit annoying, but not a bug, I suppose. Though it can be quite embarrassing to sit in your most advanced car, gently smiling at the rest of the traffic jam, when suddenly you roll off with a creaking sound befitting a Ford T-Model Like a jetplane pulled by horses...
The effect is that which you usually observe with new brakes. It's some form of micro-jaggedness between the friction parts of the brakes causing vibrations. It wears off with use when the surfaces of the parts are ground to snugly fit to each other.
Blame it on the reduced wear of the Prius braking components.

When I was driving user-serviceable cars *grin*, I used to fix this by applying copper paste to the backside of the brake callipers where the plunger pushes on. This gives damping and lubrification eating up the vibrations which caused the screeching noise.

Best regards from germany

Edit: Thinking about the grabbing sensation: may also be an effect of the jaggedness (also caused by rust and dirt). Could be caused by the way friction works physically (try to pull a wood block over sandpaper;moves smoothly if you pull fast, but if pulled slowly it starts to jerk; more force needed to get it moving again once it stopped, so it 'grabs'). The copper paste won't solve this. Though I could imagine that it has some effect in reducing the grabbing to an extend by reducing the friction on the backside of the brake callipers

 

One thing that happened with my brakes- this may not be what you all are talking about, but it's certainly something that can happen:

As soon as I drove my '05 for the first time, I noticed the brakes didn't feel right. Now, this car replaced a '99 Prius, so I was used to the "quirkiness" of the braking system. The brakes also did not feel like the ones in the '04 Prius that my dealer let me borrow for a few weeks while they were building my car for me.

When I would get close to stopping, applying gentle and even force to the brake pedal, there would be a point where if I added just a tiny bit more pressure, the brakes would grab as if I had pushed about 2 or 3 times as hard. It made for really jerky stopping and anyone riding with me would probably think I was a pretty lousy driver.

I took the car to the dealer and they also noticed the difference compared to other Prii. It took 3 different tries to get the problem fixed. Since I'm not a native Japanese speaker, I was never really sure exactly what they were replacing during each of the 3 times I took it to them. I know they thought it was a computer thing at first, but that was not it.

Finally, they replaced what I inturpreted as the "actuator," but since I don't know much about brakes, I'm not sure if this is what it is called in English.

Anyway, since they replaced that part, my brakes have felt just great. So, my point is, unusual braking in the Prius might actually be resulting from a defective part somewhere. So if something feels extra strange, you should have it checked out.

 

good information to keep in mind, thanks for the post. a lot of people who post here sometimes sound as if they are just not used to the various hybrid adjustments. of course, a detailed explanation does involve a lot of typing when its all one way print i guess so its hard to tell if they are describing something that is normal or not.

 

I Agree.
I also like to thank you for this quite important input. I believe it is up to anyone to decide for himself if observed oddities are worth a pitstop.
I figure as a guideline: try the algorithm posted by hobbit (shift to 'N' while driving and firmly brake a few times - observing traffic and security of course). If there is no change afterwards have the brakes checked.
'Never meddle in the affairs of brakes, for they are subtle and quick to anger', if I'm allowed to quote

Thanks to hobbit, my brakes are clean now. No more embarrassing screeches in stop-and-go. And no further need to blush...very much improved my self-esteem

 

UPDATE, I took a look at the rotors and they were rusted a bit where the pads make contact. I adjusted my driving style so as to use the friction brakes when below 9 mph and it has lessened the "sticking". I think "sticking" is more accurate than "grabbing". So, since I drive a lot on the highway I don't make many stops. I have adjusted my driving style when coming to a complete stop to use the brakes rather than glide the entire way. It only makes sense that the brakes will get rusted if they are not used and not to completely "baby" the stops.

 

Update --

Took it to the dealer over the weekend. Described the problem and left them the car. The diagonosis? "Operating within factory specifications." I pressed them on the issue, and they didn't really have any further explanation. Overall, they weren't that helpful, so I think I'm going elsewhere for my 10k-mile checkup.

While it's frustrating, I don't think it's unsafe. I'm hoping that time and wear will get it to the point where it no longer sticks at 7mph and less.

-Orgus

 

Hey everyone,

I think what is being reffered to here and now other posts is different than what you are talking about. A few people on here have my exact problem. Here it is:

Drivers side front brake: when coming slowly to a stop, 2-4 "grabs" happen. The best way I can describe it is its like the ABS kicks in at a slow speed and cause the front left breake to go "grab, grab, grab, then stop" It is quite annoying when it keeps happening. For me it happens a lot of the time but not all the time.

let me know if anyone figures it out. so far the dealers have not been able to help. I will show them next oil change and see if they can fix it.

paul b

 

Warped rotors? This could cause a pulsating grabbing with light brake pressures, but might not be noticable on hard stops. Since during moderate to light stops, the regen braking is used all the way down to 8 or 9 mph, then you would only use the disk brakes for the last 10 to 20 feet or so. If the rotors are warped, you would get a grab for each tire rotation that occurs while the friction brakes are engaged.

The warped rotors might not be noticable during heaving braking because enough pressure is applied to the pads from them to ride flush against the warped surface instead of hopping over the valleys.

Try shifting into neutral and then using light brake pressure. If this indeed disables regen as stated in earlier posts, then you would probably feel the pulsing all the way down from 25 mph to 0 if the disks are warped.

 

DJFrugal, The grab-grab-grab-stop definitly sounds like a warped rotor. Your problem seems to be different than the sudden grab of the brakes as the stopping car passes 8 MPH when the hydryolycs kick in, that most of us are talking about. If you have access to a lift, or are willing to get out the jack, jack up the front, one side at a time, enough to get the tire off the ground. Give the wheel a good hard spin with your hand and listen to the brushing sound the brake pads are making as they rub on the rotor. If one is warped, you will hear it immediately

 

This is as close to a 100% description of what I am experiencing. At 15k I had the dealer look when they rotated the tire but they said they could find nothing wrong. I do notice that when I use the friction brakes more it lessens and with more experience now I can modulate the brakes to lessen the number of times it happens.

My concern is the long-term after warranty situation. Since I drive 90% + on the highway I plan (hope) to keep my prius for 150k.

Anyone else have an update? :blink:

 

I'd like to pick up this thread again. This is too important to drop:

I took my Prius in today, not checking Priuschat.com first, with the sticking/grabbing sound and feeling occuring. I've had my 2006 for only a little over a week.

I was told, by the Service Manager, that the car is working "according to manufacturer specficiations." He went on to say, what I've heard is the usual, "the Prius has many new sounds and feelings -- it's unlike any other car." While that's certinly true, I'm beginning to feel it's a cover-up for a larger re-occuring issue with the vehicle.

I remembered that I had a friend who worked as a mechanic at my local dealer (who will go un-named). He said that this problem is to the level of a Service Bulletin" on all 2003-06 Prius' (though it's not official). He said that all certified mechanics are told, at least in his shop, to say automically, "the car is performing accoring to manufacturer specs."

I truly feel this is a problem and we don;t know the whole truth. I'm not suggesting it's to the level of a lawsuit, just that we Prius lovers aren;t being told the whole truth.

When driving any modern automobile, espcially as modern as this one, we shouldn't have to put up with a feeling of sticky brakes, grabbing and releasing and causing the passenger and driver an uneasy feeling -- no matter the cause.

I'm consider my options. Appreciate any advice on next steps.

 

Have you tried the smooth-stop-in-Neutral trick to clean the
rotors/drums off?
http://techno-fandom.org/~hobbit/cars/prius-log/003.html
search for "sticky"
.
_H*

 

Yes, thanks. But, I did that already. While that did reduce the "grinding" noise, it didn't touch the "sticky" and grabbing." I'm truly baffeled.

 

What does this mean? You'll return your week-old car?

 

No, didn't mean to imply that. I LOVE this car. There's just got to be a solution to this problem and we as consumers aren't receiving a fix because there's not been enough grumbling. That's my take, anyway.

 

Through careful modulation of the brakes I can reduce the number of times that this occurs. The fact that my ears tell me it is only coming from the front driver side is perplexing. I also noticed more brake dust on this side, although it is an observation that may be biased by my belief. I have 16k and I got until 35k to address this under warranty.

Next time I bring it in I am going to be a bit more forcefull and see what happens. :blink: