Brakes Stutter right before the car stops.

I'm with Darell on this one, I can feel the cogging caused by the motor stator and the brake stutter is definitely not that. I have re-created the problem on many accounts with the car in neutral which completely eliminates the drive train as the problem. My problem diagnosis, along with others on this forum is the brake pads. They are somehow getting sticky from lack of use and this I've verified in many different ways.

Why only some vehicles have this problem is the only thing that I haven't been able to piece together yet.

Now that the weather is bearable, the next time I rotate tires and change oil (mid April), I will also be replacing the brake pads with non OEM pads. I'll post back to this thread with the results. Keep your fingers crossed.

 

That shuddering feeling is simply the gas motor shutting down and is completely NORMAL

 

<div class='quotetop'>QUOTE(sonny @ Mar 27 2007, 07:00 AM) [snapback]412897[/snapback]</div>

Ah. Then you haven't been paying attention, have you? we experience the shudder with the gas engine off just as easily as with the gas engine still running. It is most definitely NOT the engine shutting down that is causing this.

Where did we lose you?

 

<div class='quotetop'>QUOTE(sonny @ Mar 27 2007, 09:00 AM) [snapback]412897[/snapback]</div>

Dear SONNY, I think you are not on the same page we are.

 

ROTFL Darell,
I was really gonna slam Sonny about this as he's posted the same response at least 3 times. Then I figured that he wouldn't get my point. ;-)

 

<div class='quotetop'>QUOTE(unruhly @ Mar 27 2007, 06:48 AM) [snapback]412850[/snapback]</div>

Cool, I'm new to the car (second tank 51.4 MPG!) and trying to get a feel for it. Thanks for all the info.

 

<div class='quotetop'>QUOTE(unruhly @ Mar 27 2007, 05:48 AM) [snapback]412850[/snapback]</div>

That's been my thought, as well, to try some non OEM pads. I can't wait to hear what you try and what your results are. If you don't cause any positive effect, I'll be sure to try a different vendor for the pads when I get around to experimenting.

Keep in mind, however, that I have had experience where a simple tire rotation made the problem "go away" for like 6 weeks. Maybe there was some good scrubbing of the rotors or the pads when the rotation was done. I suppose my point is to make sure you don't just to a conlcuion after a non-OEM pad replacement if the problems seems to go away immediately...

Mike

 

Time for an update:

When I did the last tire rotation at 25,000, I noticed that the brakes were just barely starting to "bed" in. I decided that I should wait a little longer and check them again at 30,000 rather than try a new pair of pads. A new pair would require an even longer bedding period to determine if the stutter goes away or not. During this time, I'm actually trying to brake harder than I normally would to try to get a good even bedding layer.


Just so you know, the bedding process is where the pad material forms an even layer of deposits that actually get bonded onto the rotor from high heat. Until this happens, you will experience brake judder and this is what I think we are experiencing.
The bed-in process may not ever fully happen on our Prii because of the low use, and thereby low heat, of the friction brakes.
I'm at 28,000 now and for the last couple of months have not had nearly the severity of stuttering as before. I can honestly say that it's almost gone but the high heat of summer may also be factoring in to the lessening of the problem.

 

I have noticed this braking issue with my 2006, most often as I approach a stop sign on a downhill just a couple of tenths of a mile from my home, in the morning leaving for work. To me, it feels like I step on the brakes, and the brakes grip a bit, then lose grip (a weird feeling) for a moment or two, then regrip.

Definitely different from my 2004 and 2005 Prii, and I had the same commute.

rpm

 

My 2007 just started doing it (definitely not the ice shutdown shutter) a few weeks ago as I approached 7K miles.

Has anyone had any success with a dealer actually fixing this or confirming there's a problem?

 

My 2007 just started doing it (definitely not the ice shutdown shutter) a few weeks ago as I approached 7K miles.

Has anyone had any success with a dealer actually fixing this or confirming there's a problem?

 

Here is a curveball for the discussion - I get the stuttering when I am backing the car up.... But only when I am backing the car up at very low speed, like the last 1 - 2 feet before a complete stop. One more data point - I had the pads changed from the OEM formulation to ceramic (Hawk) the moment the car rolled off the transport truck at the dealer, so the susceptibility to stutter may be a function of pad compound.

 

Here is a curveball for the discussion - I get the stuttering when I am backing the car up.... But only when I am backing the car up at very low speed, like the last 1 - 2 feet before a complete stop. One more data point - I had the pads changed from the OEM formulation to ceramic (Hawk) the moment the car rolled off the transport truck at the dealer, so the susceptibility to stutter may be a function of pad compound.

 

I've had extensive experience with brake shudder on another type of vehicle (I don't have my Prius just yet). Many people chaulk this up to a 'warped rotor' which is rarely the case. Even high performance vehicles rarely warp the rotors, much less a street machine... I digress.

What often happens has been eluded to in an earlier post. It is an uneven bedding process where there is an abnormal deposit of brake materail in one section of the rotor and little or no deposit in another area. The result is that the pad grabs the rotor differently in these differen area, resulting in a grab/skip braking that is mistaken for a warped rotor.

My research into this topic has shown that ALL brake rotor/pads need to be bedded in with a series of agressive stops (with cool downs in between). In order to form an even transfer layer. THis is usually done by taking the vehicle to an open road where you can agressively brake from 50 to 10MPH then take the vehicle back to 50 with normal light acceleration and repat 10-12 times. Then drive at highway speeds for 15 minutes to allow the rotors to completely cool.

What usually happens is that the car is lightly driven until brakeing for a light or traffic and then sitting with the pad on th hot rotot causing an excessive transfer layer in that spot with the remainder of the rotor virtually clean. Then the transfer layer begins to build in an uneven manner. Once uneven transfer is on the rotor, it is almost impossible to get it off as even turning the rotor wil not remove this almost concrete metallic layer.

This may sound crazy and I may not have explained it well, so here is a link to a more involved description by a brake engineer.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

I hope this helps - if not just ignore me... Many people do... B)

 

I've had extensive experience with brake shudder on another type of vehicle (I don't have my Prius just yet). Many people chaulk this up to a 'warped rotor' which is rarely the case. Even high performance vehicles rarely warp the rotors, much less a street machine... I digress.

What often happens has been eluded to in an earlier post. It is an uneven bedding process where there is an abnormal deposit of brake materail in one section of the rotor and little or no deposit in another area. The result is that the pad grabs the rotor differently in these differen area, resulting in a grab/skip braking that is mistaken for a warped rotor.

My research into this topic has shown that ALL brake rotor/pads need to be bedded in with a series of agressive stops (with cool downs in between). In order to form an even transfer layer. THis is usually done by taking the vehicle to an open road where you can agressively brake from 50 to 10MPH then take the vehicle back to 50 with normal light acceleration and repat 10-12 times. Then drive at highway speeds for 15 minutes to allow the rotors to completely cool.

What usually happens is that the car is lightly driven until brakeing for a light or traffic and then sitting with the pad on th hot rotot causing an excessive transfer layer in that spot with the remainder of the rotor virtually clean. Then the transfer layer begins to build in an uneven manner. Once uneven transfer is on the rotor, it is almost impossible to get it off as even turning the rotor wil not remove this almost concrete metallic layer.

This may sound crazy and I may not have explained it well, so here is a link to a more involved description by a brake engineer.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

I hope this helps - if not just ignore me... Many people do... B)

 

I agree that brake bed-in is a component of the problem.

The more I play with my brakes, the more I am convinced that at least in my case, I have another issue going on.

When the problem shows itself and I have come to a complete stop, if I stab at the brakes and then slowly release, about 90% of the time I get a little squeak or bark from the area in front of the passenger. If I get this squeak/bark to occur, the problem stay away for any stops for typically about a half day. Then it slowly returns.

likewise, if I don't do this "stomp and squeak" maneuver, the grabby brake stops continue until I do a "stomp and squeak".

I don't believe that the amount of brake bedding has much bearing on the mode that I am experiencing, but have a sneaking suspicion that it may be related to the brake actuator noise TSB. In reading other threads talking about "brakes barking" and the like, I would tend to equate the noise described there as the noise I experience which makes my stuttering go away for awhile.

The next trick, of course, is getting the pattern to show to a tech

Mike

 

I agree that brake bed-in is a component of the problem.

The more I play with my brakes, the more I am convinced that at least in my case, I have another issue going on.

When the problem shows itself and I have come to a complete stop, if I stab at the brakes and then slowly release, about 90% of the time I get a little squeak or bark from the area in front of the passenger. If I get this squeak/bark to occur, the problem stay away for any stops for typically about a half day. Then it slowly returns.

likewise, if I don't do this "stomp and squeak" maneuver, the grabby brake stops continue until I do a "stomp and squeak".

I don't believe that the amount of brake bedding has much bearing on the mode that I am experiencing, but have a sneaking suspicion that it may be related to the brake actuator noise TSB. In reading other threads talking about "brakes barking" and the like, I would tend to equate the noise described there as the noise I experience which makes my stuttering go away for awhile.

The next trick, of course, is getting the pattern to show to a tech

Mike

 

At 35,000 miles now and it's still doing it.

I guess I have to actually back off on my brake bedding theory now as it just can't possibly be the "cause" of the problem, although it may play into the symptoms of it somewhat.

My second theory... A sticky hydraulic relief valve?
There's an accumulator for hydraulic fluid which is at full pressure. OK. So, the brake computer controlls how much pressure to apply to the brake cylinders and when to let off on the pressure. So, you could assume that this is controlled by two hydraulic valves one that opens to apply pressure from the accumulator side, and one that opens to relieve pressure back into the low pressure reservoir to begin the pressure cycle again.

Perhaps the valve or the device that modulates the relief valve, or even the computer itself, is not functioning correctly. To me, this seems like something that would be easy for a tech to diagnose if we could just get one to get in there and spend the time on it. I for one don't want to give up my car for a week or two without knowing if there's going to be any positive outcome or not.

 

At 35,000 miles now and it's still doing it.

I guess I have to actually back off on my brake bedding theory now as it just can't possibly be the "cause" of the problem, although it may play into the symptoms of it somewhat.

My second theory... A sticky hydraulic relief valve?
There's an accumulator for hydraulic fluid which is at full pressure. OK. So, the brake computer controlls how much pressure to apply to the brake cylinders and when to let off on the pressure. So, you could assume that this is controlled by two hydraulic valves one that opens to apply pressure from the accumulator side, and one that opens to relieve pressure back into the low pressure reservoir to begin the pressure cycle again.

Perhaps the valve or the device that modulates the relief valve, or even the computer itself, is not functioning correctly. To me, this seems like something that would be easy for a tech to diagnose if we could just get one to get in there and spend the time on it. I for one don't want to give up my car for a week or two without knowing if there's going to be any positive outcome or not.

 

I have an 08 and it has this problem. It has done it from day one, and I am going to have it checked out. The car now has about 1000 miles on it.