Brakes Stutter right before the car stops.

Newbie, first post, hello.

My very new '07 has the stutter too. It was delivered to the dealer in Atlanta in late December 06, and I bought it the very next day, so this is basically current production (minus time in transit from Japan). The car was so fresh the rotors hadn't grown any rust yet (and with 2 miles on the odometer, it certainly hadn't rusted and then been rubbed off by the pads!) . I've put 2000 miles on the car in 7 weeks, and haven't noticed any change in any of the conditions I mention between mile 2 and mile 2000.

When it does the stutter, I almost always three quick thumps in succession... reminds me of being on a plane with a kid kicking the back of your seat. This is not a bumpy ICE stop or start, either; I get those occasionally and know the difference. If I make a prompt (graceless) stop, like I might if I were in a hurry, it doesn't do it. I enjoy making buttery smooth starts and stops, though, like a limousine driver should, and when I stop like that I usually get the three thumps between about 2 mph and the actual end of the stop. It seems like it only happens when the ICE is off, though, which I don't think I've heard anyone else mention. I'm still experimenting with my technique to see if I can work around it. I'm not sure I want the dealer to look at it; in my experience mechanics almost always do collateral damage when they do take something apart (broken plastic clips, new rattles, mangled trim, etc.) and at this stage I'd rather leave my very new car unmolested.

I do ALSO get the barking. I'd already concluded that it was part of the electrohydraullic brakes. I've had several cars with ABS solenoids that would cycle just after start-up (one did it the first time you reached 18 mph). That's one of the most consistent times my Prius will bark- right at start up when I'm putting my foot on the brake, selecting D, and releasing the parking brake. Granted the ABS solenoids in my previous cars sounded more... metallic and clattery, but since it will also do it if I push heavily or repeatedly on the brake pedal while at a stop, I'd concluded it was the brakes. It's loud enough that passengers will notice, but the brakes work fine otherwise and it seems to be widespread and consistent. I've also read enough here to make me conclude that this is a cold weather thing, so I assume given my climate and a late December purchase, this is only going to be noticeable three months of the year in this area.

Other than an OK-but-not-perfect factory wheel alignment (I had the dealer check it, they found it to be "in spec" but after they tweaked it to be closer to perfect, the car doesn't wander anymore), the car is perfect. I do notice these quirks- the stutter, the occasional rough ICE shutdown, the barking) but they haven't detracted from the euphoria of getting not just a new car but for the the first time ever, a new car that was EXACTLY what I wanted. The behavior of this car is amazingly familiar for how vastly different its mechanical systems are, compared to the vehicles we are used to driving.

 

I have noticed similar behavior as you mention, wyounger, about it happening less when you simulate something close to a panic stop...

What I have noticed is that when it is flaring up and giving me grief (since it doesn't happen all the time), if I am a complete stop and push hard on the brake pedal several times until I hear the "click click click" of the accumulator (?) building pressure, it does not happen again until that "built up pressure" bleeds away again. If the problem/stuttering comes back, stomping on the brake pedal a few times while at a standstill makes it go away again for awhile.

I'm guessing that means that when the brakes are "fully charged hydraulically" (?), releasing pressure on the brake pedel to effect a smooth stop actually interacts with the brake pads differently. Why this seems to have a connection with smooth stopping ability, I can't say.

I mentioned it to an interested local Prius tech one day (the stuttering, not the more recent behavior I noticed which seems to align somewhat with what you've experienced), I hope to get back to him one day to show the problem and the new way to make it go away. There have indeed been occurrences where my "stomp on the pedal at a stop" technique has not made the problem go away, but it seems to work at least as reliably as the "shift into neutral and clean your rotors" technique.

One other fun bit of data, I pulled the front wheels off one day when I had a particularly stuttery week and scrubbed the outside of hte front rotors with some fine steel wool. There was certainly some rust and road gunk built up. This made the problem go away for two days.

There's clearly a connection (obvious from this thread) to dirty/rusty/gunky rotors, but it seems like there is something else at play too.

I've had this problem for the life of my 15k miles on my 2006.

Mike

 

Hello, I have the same thing happen with my 07, Its nothing that bothers me. I summed it up to the brakes being extra grippy.
This always happened in my more performance oriented cars,...My '02 Stratus R/T had the carbon metallic brake pads that had the same problem,My '02 A4 had the same issue, along with my S10. the only thing that the three cars had in common was, the Carbon Metallic pads.

Eh, The car stops and thats all that matters to me

 

Speaking as an owner of a 2006 Prius and an Audi A4 Cabriolet..... may I suggest something other than the brakes. (So what's an A4 got to do with it?) You see, both cars use a CVT (Continuously Variable Transmission) for the drive train. Mind you the cars are very different, one a V6 performance car, the other a small gas engine with Hybrid drive. The A4 has a very slight stutter when coming to a stop, around 2mph and less. It's something we've learned to live with. It might have something to do with these CVT drive trains. Very different technology than typical auto-transmissions that use torque converters and belts. The CVT doesn't cause gear to gear shifting lags and engine ups/downs as you accelerate. Check around the forum, because this is only my suggestion. The feel of a Prius is different in many ways. Our new Prius has that same feel coming to a stop like the A4 and we've never felt this characteristic is a huge problem.
Best of Luck with your car.... cheers.

 

Well, there is a new thread with a post about a prius not being able to stop his car. He got off the highway, and went to the gas station where he ran it into something at the station and it spark a small fire. Thank goodness they were able to put the fire out.

There may be something definitely going on with the brakes.

Wonder if there will be a recall?

 

Mine does it too. I am guessing it's normal.

 

Same thing 2007. 1063 miles Just before it stops shutter. Asked service writer at Dealership. He said he was familar with the symptoms, but did not suggest a solution.
My guess:
I don't have one.
somebody will figure it out.

As a side note Consumer Reports listed the Prius stopping distance as 145 feet. About 10' more than average of the recent cars I have owned. Anticipate!

 

My 2005 Prius didn't do this, my 2007 does. I was hoping that as the pads bedded in it would go away, but no luck. At 6000 miles it still does it. I doubt it has anything to do with the regen braking system at all.
I really think it feels like a different brake pad material was used in the newer cars, and it has a higher amount of "stiction" (yes it's real word) than the earlier pads. I'd suspect a different formulation of brake pad would change or solve the problem. It may even be a symptom of pad glazing, in which case just removing the pads and roughing them up with a file would solve the problem. Once I get some time (sometime in April) I'll try this and post the results.

 

22,000 miles and it's just as bad right now as it ever has been. Yesterday I did three neutral hard brake stops on the way home from work. Cleared it up on the remainder of that trip but it's back at it this morning. To be frank, it's really getting on my nerves now that I can't make a smoothe stop.

 

I took three first graders on a field trip yesterday. One said, "I like this car, but why does it bump when we stop?"

 

<div class='quotetop'>QUOTE(narf @ Mar 8 2007, 03:31 PM) [snapback]402309[/snapback]</div>

I just want to offer another data point: My (second half of the year) 2005 has never had single problem of this nature. The silkiest smooth stops you'd ever want.

So it's something that changed after the late-year 2005s.

Good luck figuring it out!

 

Hi All,

Yep, happened to me too. Why, because of my reflex to feather the brakes just before stopping. This is left over from driving a hydraulic friction brake car. If you maintain, or increase pressure just before stopping in a standard car, the car will jerk to a stop as static friction takes over between the brake pads and rotor.

In the Prius, it switches from electric regeneration braking, to hydraulic friction brakes at 7 mph. If you feather the brakes at that point, it introduces a oscilatory decision point as the friction brakes have much less power than the regeration brakes. Or at least its common in Prius that the force gains are allot less for the friction brakes.

What to do? Just push harder at 8 mph, rather than feathering the brakes. No more stutter!

People told me it was just normal break-in. But I believe its just normal driver familiarization. Since now I have realized that I am subconciously pushing harder on the brakes as I come to a stop, rather than feathering the force to the pedal.

 

<div class='quotetop'>QUOTE(donee @ Mar 8 2007, 07:22 PM) [snapback]402564[/snapback]</div>

Again, I have owned both a 2005 and 2007 Prius. I know how to use the brakes on a Prius. There is definitely something different about the 2006/07 brakes. It's not the 8mph transition. The brake pads actually grab, stick, and release several times at the instant just before stopping. You can keep it from happening by not stopping smoothly, (making a fairly hard stop), but there is clearly something not right.

 

Can I still email to the gmail account?

Sputnik's got this braking shudder/studder thing. It is nearly a near (he'll be 1 on Monday) and I still get it but it isn't often.

 

<div class='quotetop'>QUOTE(hockeybrat @ Mar 9 2007, 04:41 PM) [snapback]403011[/snapback]</div>

Lowspeed was the one collecting VINs and he has since traded in his Prius due to the fact that he could not get satisfactory results from Toyota on this problem. I doubt he is still on PC nor using that gmail account.

 

<div class='quotetop'>QUOTE(unruhly @ Mar 9 2007, 06:04 PM) [snapback]403016[/snapback]</div>

Thanks!

I've gotten used to it now, it is just a little annoyance though.

 

<div class='quotetop'>QUOTE(narf @ Mar 9 2007, 02:13 AM) [snapback]402631[/snapback]</div>

I have 2006 and I have over 30K miles on it. It was stuttering pretty badly. Yesterday I forced Prius to use mechanical brakes from high speed by putting it in Neutral a few times and then I washed the car. No more stutter. At least for the last two days. I am certain that it will come back soon.

 

I have had the thump-thump occur as well but the first time that it happened, I developed a theory. Have any of you ever twirled the rotor of a high performance remote control electric motor and felt the thump-thump as the magnets passed each other? I believe that this is what's happening with our cars. At slow speed, you are able to feel the magnets pass each other. If you rapidly brake past that point, it's not as noticeable. Just my theory, what do the experts think?

 

<div class='quotetop'>QUOTE(Chris Robson @ Mar 23 2007, 07:41 PM) [snapback]411325[/snapback]</div>

This "expert" thinks "NOPE!" That very "cogging" happens in my Rav4EV, and I'm quite familiar with the effect. While it is a brilliant guess at the problem, I'm pretty confident that this is not what happens in the Prius. If this were the case, the cogging would happen under power as well as with braking - and it doesn't.

 

<div class='quotetop'>QUOTE(darelldd @ Mar 23 2007, 10:09 PM) [snapback]411361[/snapback]</div>

I'd like to take another look at this "cogging" thing. I did a little experiment today and drove down my empty street. I applied the brake for a gradual stop and received the thumping effect. I let off the brake and felt a few thumps, but not as severe. I did this several times and was even able to sustain the effect at very low speed (<1MPH) both stopping and starting. The thumps are very consistant, much like the magnet effect. Looking at the simulation at http://eahart.com/prius/psd/ , A speed of around 1 MPH produces an MG2 speed of between 33 and 65 RPM, which coincides with the pulse that I felt in the car. I think vehicle speeds just over 1 MPH increases the frequency of the pulses above a level that can be felt.