Brakes Stutter right before the car stops.

My 08 does this too, but not every time, just some times. I have about 2800 miles on the clock, figured it was just part of the freaky braking system in the car.

 

Personally, I suspect that is the ICE shutting down.

 

It's not the ice turning off.

I've tested it out on a slope going backwards in neutral while the engine is already off (verified by a scangauge)

 

My 08 does this too. Its definitely something to do with the breaks.
I thought it was something, but not sure that is was anything worth mentioning... I will pay closer attention now. Please let me know if anyone has figured this one out.

 

My '08 had been doing this for the first 1300 miles. After I did a lot of driving a few days ago the problem has gone away. I think the problem might be, as others have suggested, that "stuff" builds up on the rotors. I only put about 6k miles per year on my cars, and with the prius I am somewhat fanatical about trying not to use the brakes unless I really have to, and braking very gently when I do. I would suggest the idea proposed by others of putting the car in neutral while braking to try to "clean" the rotors.

 

Same problem with a 2005. Just before stopping at low speeds, and especially under wet conditions, the front brakes "bite". I bought this car used with 10,000 miles and now have 25,000. I assumed this was an imperfection in the pads and that the problem would pass with use, but it hasn't. I just got a "brake special" flyer from my dealer, so I'm using this to replace the pads. If that doesn't correct the problem, I'll complain to Toyota.

Marc

ps; I'm replacing the crummy Goodyears that came with the car at the same time (but not through the dealer). Brakes and tires seem like a curious place for Toyota to skimp on the quality of an otherwise outstanding car.

 

yup i got the brakes grabbing effect that happens once in awhile, my rear brakes lock up BAD and i hear a THUMP along with the ABS light blinking on/off.

sometimes it goes away sometimes its there, i just brake with neutral to prevent it.

i will check my brakes soon anyways since its my next chapter

 

I have noticed a shudder in my 2008 when coming to a slow stop, but I had always attributed it to the hybrid synergy drive trying to balance regen, friction braking, and electric-only coasting, like when you first release the brakes, ie. parking lot navigation. I have had, on a couple occasions, a need to stop suddenly... deer in the road, etc., and have noticed no issues with coming to quite an abrupt stop. You also have to bear in mind that the regen system creates the most resistance at the highest RPM of the wheels, therefore the slower the wheels turn, the lower the regen resistance. Try this simple experiment, connect both leads on a small electric motor and try to spin it, you will notice that you can turn it very slowly with ease, but the faster you try to spin it, the more it resists.

 

My 08 Touring Edition has done this since I drove home from the dealership. 800 miles now...
I, like many others, assumed the brakes needed broken in. That didn't fix it.
I then assumed it was some function of the hybrid system. From this thread, that is possible buyt not likely.
Not a "serious" issue but enough to monitor and test ideas.
Everyone, keep this thread alive and communicate your findings.

 

Marc - Did you get your pads replaced? Notice any difference?

It feels to me like a slightly more 'slippery' brake pad would help the issue.

I've also noticed that when I am at a stop and release the brake pedal VERY slowly, I can make the car lurch every so slightly and then come to a stop, and then keep taking pressure off the brake pads, and the car will roll smoothly. It's almost like one side is still grabbing while the other releases, but ever so slightly...that would also tend to explain the front end shimmying a bit back and forth when I the brakes are misbehaving...

Mike

 

Got the same problem on a new 2009. Issue has been occurring since the day I drove it off the lot and has been happening every day since. Stuttering from the brakes when coming to a slow, smooth stop at the 0-5mph mark. Passengers in the vehicle have commented on it repeatedly. I'll be taking it to the dealership sometime next week.

 

I suggest that you try accelerating up to around 40-50 mph on a road with no traffic behind you, then shift to N and brake moderately to a stop. Repeat a few times. The point of this is to clean the brake friction surfaces. Then see if your brakes still stutter as you describe above.

 

2008 prius it dose it sometimes even when i did a test drive

 

please let me know what is going on with that i get the same thing on my 2008 prius also / but i had gone to the dealer for the gas meter was showing 1/2 tank of gas but i fill up a full tank of gas and still did not go up too full tank on the meter on the dash the dealer had too reset the computer and it is all find for now .

 

I was going to post about this a while ago but decided the brakes needed to break-in and I was not breaking hard enough. The front brakes shudder when stopping gently and just before the car stops. (it's not the ICE - it turned off some time ago)

Has anyone else noticed that one side of the brakes is affected more than the other? I'm convinced this is only happening on the drivers-side and wonder if there is a problem with the breaks not self-adjusting properly because they're used so lightly.

I'll try to 'bed them in' as suggested a few times in this thread... after they put some gravel on the ice.

 

I have just purchased an 04 Prius that does the heavy braking thing, when the regen just goes off, when comming to a full stop.
Not all the time though, I have not quite pined down the pattern yet.
Previous owner sent it in for repair but did not get a good result.

I am not aware of the computer doing the breaking for me? I was guessing the the vacuum pump may be coming on, giving an extra bit of un-expected braking?

 

A good site to look at is Hobbit's Prius Training manual (for service technicians). This is really just his presentation slides but it's still quite understandable.

The Prius has a dual-circuit braking system. Your braking force, if everything is working correctly, merely changes the pressure on a couple of pressure sensors, and moves a piston in the Stroke Simulator (otherwise the pedal wouldn't move at all). The computer interprets that pressure (along with other sensors if you have VSC) and decides how much braking force to apply to each wheel. It asks the HV ECU how much regenerative force it can supply, using as much of that as possible, and adds hydraulic braking via the second hydraulic circuit to make up the difference.

The brake accumulator contains pressurised hydraulic fluid to do the actual work. You can hear the pump working - it's a whirring noise, noticeable particularly at startup and after shutdown (shutdown de-pressurises the accumulator). Electronically-controlled valves control the flow of brake fluid.

The car does not have a vacuum pump. You would lose all assist when the engine stopped, and the Prius engine doesn't generate a lot of vacuum anyway.

The cut-over seems to be at about 7mph (probably 10km/h + 10% speedometer overread), where the HV ECU stops regen braking and starts the creep function instead. If you brake slowly and smoothly, and don't encounter any bumps or have to swerve, this is the first point that hydraulic braking occurs. As a result, the brake discs tend to rust through under-use. It takes many, many miles for the pads to even bed in properly.

If the Skid Control ECU detects a fault, it opens two valves which connect the two hydraulic circuits, and brake master cylinder pressure is used to brake the front wheels only. There is a large bank of capacitors next to the auxiliary 12V battery, in the boot, to provide a short-duration backup power supply in case the 12V system fails while the car is in motion.

 

Judging by the number of posts, this is not an unusual issue nor limited to one particular production year. My '08 brakes normally and steadily until I get down to about 3 -4 mph, then it feels like I have suddenly increased the pressure on the brake pedal. I have learned to anticipate this and back off on the pressure on the pedal just as I get to that low, nearly stopped speed.

Lots of good theories why this happens, but the bottom line is I can accept it as being "normal" (or perhaps a better term: "typical") and I can live with it.

 

This started happening to my shiny new '09 Prius It started after about 130 miles.

I tried the neutral braking suggested in this thread this morning and it went away for a short while, but came back towards the end of my drive. I didn't really get to try it on a nice downhill slope though as I was doing my regular commute, but I'll try again tonight and see how it goes.