05 Prius Front Brakes "Grabbing"

Hi Ken, from Bill in Oregon...

You should have almost no brake wear at 17,000 miles. Since the friction brakes are used so little, in our damp climate the disks can rust fairly quickly. Have a look through the front spokes. If it's rusty, step on the accellerator and the brake at the same time and scrape off the rust. I've noticed this myself, and taken corrective action, several times.

If you're ever in the Portland area, check out the meet up group in my sig.

 

<div class='quotetop'>QUOTE(Bill Merchant @ Apr 18 2007, 03:24 AM) [snapback]425188[/snapback]</div>

I have the same issue (Not too sure if it is really an issue). 2005 Silver Toyota Prius. 16,000 miles. Northeast PA. It has been cold and damp lately and I am thinking that is why they are GRABBING. Sometimes when they grab it almost jerks me forward into the dash. Oh well. It may be just the weather. It is going to warm up this weekend so I am going to have to see if that has a major effect of the grabbing.

 

i am having the same issue. It is almost comical in the morning when I make my first stop, i jerk forward. since my first stop is at a light by starbucks it seems to cause a scene. Has anyone been able to rid the issue?

 

+1

Try this several times before you look for another problem.

Tom

 

I, too have a '05 Prius and have loved it. However, when it was about a year old, I started experencing the brakes grabbing when coming to a full stop. When I took the car in for service, they said nothing was wrong with the brakes I took it in about 4 months later specifically because of the grabbing brakes, went to a test drive with the service man and he said "nothing wrong, your brakes are working fine": What I then realised was that they only grabbed when it had been raining. I asked the mechanic to check the brakes after throwing some water on the car. When I returned for my car they said I had to have all the rotors replaced at the cost of over $800.00.The front ones were "pitted and badly rusty". the back rotors were badly damaged because I must have been driving "two-footed" or with the parking brakes on. As I have been driving for over 40 years, I felt a bit insulted at both those suggestions. When I asked about the reason for the front brakes corroding, they said I must have left the car standing for long periods or parked it in salty air. (I live in a city and use my car almost every day). By the way, I have 80% left on my brake pads, and I tend to use the "B" for slowing down to save my brakes(ironically). I think everyone driving a Prius should have their service people check the state of their rotors. There is no reason why mine have all corroded. What is the normal life expectancy of rotors? Is this a safety issue? I'd like some answers from Toyota. Now I am reading about other peoples problems and the question of moisture getting into the brake linings. Surely this isn't normal wear-and-tear?!

 

I have a theory on this. My first Prius was an early 2005. The brakes never were grabby, but in the rain they were like typical brakes, they took a short period to begin to work because of the water film on them. On normal cars this isn't much of a problem because the brakes tend to work much more often and drag slightly on the rotors which helps keep water off the rotors. On the Prius the pads don't drag on the rotors as much, and the pads don't touch until you transition below 8 mph. So, when stopping in the rain the car would lose braking momentarily when switching to friction brakes because of the wet rotors.

My theory is that because of this problem, sometime in late 2005 Toyota switched to a more aggressive brake pad formulation. This pad works better in the rain, but on cold or wet rotors tends to have more "stiction" than the old pads. This manifests itself in the feeling of grabby brakes at low speeds. On my newer Prius, I have this grabby brake problem as described by the original poster whenever wet or cold, however the car's friction brakes work better in the rain.

I think the reason that you can temporarily solve the problem with several hard stops in Neutral is that you are heating up the pads and rotors. The next time you drive the car with cold rotors the problem is back. At least that's been my experience.

I don't have any hard data to back up this theory. One way to test this would be to change to a different formulation brake pad and see if the problem goes away. Of course, since the pads take so long to wear out most of us will never need to change pads.

 

Your theory, at least part of it, is bogus. Only in wet and only a slow, controlled stop does this occur during THE LAST FEW FEET of the stop. By that time, the rotors are free of most moisture. This is a frustrating and annoying problem in my Prius as well. In addition to the headlights turning off on their own independently, this brake thing is a bummer. Toyota quality is going down hill.

 

No, they're not. In a slow, controlled stop the rotors are completely unused until you get below 7mph. Above that point regeneration is doing all the work. The pads haven't even touched the rotors yet. That's why the brake pad life on a Prius is so ridiculously high.

How long does it take to stop from 7mph? A couple of seconds? 7mph is 3.12 metres per second, and you're decelerating so say you cover two metres/six feet to come to a halt. The rolling circumference of the tyre is 1,950mm, so the friction brakes are used for maybe one revolution total. It's no wonder they stick. They're completely cold.

 

Same problem here. It reminds me to scrape of the rust every few months. It's never been perfect, but much better. I'd like to see a TSB on this or at very least a strong instruction in the manuals.

 

Excellent analysis, sir! This makes it clear why the only sure way to avoid grabbing is to modulate the application of brake pedal, easing off just as or before grabbing begins. One can learn this so that it becomes unconscious.

 

Not that I want to be a me too post, but my 2001 Prius just recently started doing this. It has always had touchy brakes, but in the last 3 months (start of rainy season) it is a LOT more touchy. Took it to a brake shop - and they told me my brakes were fine - only 10% wear. They did not mention rust. I was about to take it to the dealer, but sounds like I don't need to?

 

I have 04 Prius w/ 72K miles. I thought I needed new front brake pads (especially after a service check at PepBoys last Summer indicated I had about 10K left). I heard some noise so I bought some pads and took the wheel/calipers off. There was more than 1/4" of pad left from the clip! Based on wear and what's left I have another 70K left! Is this normal?

 

Mike your explanation covers the symptoms I've experienced in a 2005 Prius. The "grabbing" only seems to occur in wet weather. I've found it possible to eliminate the grabbing the takes place in the last few feet of a stop by exercising a lot of very gentle control of the brake pedal, its is more like trying to anticipate when the brakes might grab and then easing up on the brake pedal. Thanks for the insight.

 

Good info here. I will try "cleaning" my rotors by stopping in neutral a couple of times, since 95% of my braking is done gently with regen.

Judging by some of the responses here, it looks like a few Prius owners have no idea that the pads and rotors don't get used during most braking events, except for the last bit as show in the graph below, hydraulic force being the pads and rotors in use:

 

Thanks for the ideas about the brake grabbing after wet weather. I have a 2005 that started the grabbing recently. I will experiment with the stopping in 'N' at the start of trips. Makes a lot of sense...even though it takes some time for an old brain to get used to the regen vs friction braking phenom.

 

Yes, my 2004 Prius is at 193.5k miles and the original front brake pads are at 50% worn. While your calipers are off, lubricate the slide pins.

JeffD