New Rotors at 45k??

You don't suppose he bought the infamous "James Sykes Prius" with the well worn brakes? !

 

If you get into the habit of braking in neutral for two or three stops when getting close to home should help in two ways.

(1) It will clean the brakes of rust at least once a day.
(2) It will warm the brakes up making them dry off quickly when you park up causing less rust.

 

My 2006 Prius (now at 78,000 km ~ 48,500 miles), serviced at authorized dealer, has been recommended for front disc rotors replacement for the last 2 years or so.

I have always said no, because I never experienced noise or vibrations, and because of the cost of the rotors.
Brake pads have been replaced one time so far.

The people who ask me if I want to change the rotor are always non-mechanics, who don't really know about the problem in detail, and I don't get to speak to the mechanics. Few years ago, when I asked what was the matter with the rotors, the customer-service-woman said they were warped. Today, she tells me, no they are not warped, just scored (deep scratches). So I tell her to leave the rotors in.

One quirk I notice about the Prius (and some other mid-range Japanese cars) is that when moving off after being stationary for at least a day or two (esp. after rain), the wheels feel "stuck", so that some throttle is needed to break free, with a "clunk" sound. And after that, the brakes have a little bit of scraping feel for the first minute of braking. I don't know if this has something to do with the scoring of the rotors. I am located in the tropics, hot, humid whole year round.

 

Changing pads in less than 48,500 miles doesn't sound right at all, unless maybe you are super heavy on the brakes. Pads are reported to last 100,000 and even far longer because of regen braking. The rotor issue sounds like what others have reported as rust on the rotors from such light use, again because of regen braking. Some have mentioned sanding the rust off with the appropriate sandpaper or steel wool. Others have recommended getting away from traffic, and from a good spped putting in neutral and applying brakes briskly a few times to clean off the rotors. At the very least I would get another opinion or two.

 

Hi AaronA and SteveLee,
Thank you for your views.
I have attached a photo and a line diagram of the shape of the discs.
Both surfaces of both front discs are affected. Rear discs are normal.
Brake performance seems normal.

My driving style has always been very conservative and "eco". Urban roads, averaging 5.3 litres per 100 km (44 mpg) according to the MFD.

 

Pnerd: Looks pretty normal for a Prius. Nothing abnormal about the wear on the disc. Thats how they wear.
They don't wear to the edge so they leave a lip around the edge because thats where the discs end.
Looks like you never ever do any non regen braking. Go do some non regen braking and then take another photo of the discs.

And clunking is usually sign of struts wearing out. Especially if it clunks loud when braking upon backing up. Prius the struts are good for about 60,000 miles tops. But the brakes make alot of noise especially if the car is left outside and after it rains. A Pius never braked with no regen & always left outside is going to do alot of noises when it brakes and first moves and then first brakes. Lots of scraping till the top layer of rust is blown through.

 

You mean because that's where the *pads* end?
I have never seen this shape on any cars before.

Do you mean because of the rusty appearance? The car hasn't been driven for the past week, and it has been rainy.
By non-regen-braking, you mean I should get up to speed, shift into and N and brake? (Yeah, I never do this)
If I had done more friction braking, the wear on the disc would be more extreme, not less, right?

I see. not sure about this, I get the clunks when first moving off after leaving the car for many days. Feels like things had seized up with rust.

 

Ah yes...yes...and yes.

 

pnerd, when the disc get rusty this accelerates wear because the surface of the disc is eroded away by rust. This is rubbed off by the light pad contact and being a none smooth surface wears the pads faster and leaves a porous surface. When the discs are smooth and bright the surface is less porous resists rust better reducing disc and pad wear.

John (Briprius)

 

Rust never sleeps.

 

Judging from the lip at the outer edge, your brake disk thickness has gone down a fair bit. Pick up a micrometer and check thickness. The values AaronA posted for new and minimum thickness sound reasonable, see if you can verify. In a pinch a phone call to your dealership might get that info.

With a previous non-hybrid vehicle we had, the front pads didn't seem to be releasing properly, the hubs would feel warm after a drive, the car ate brake pads. The rotors also wore down to the min. thickness, and one eventually cracked.

 

Thanks AaronA and Mendel.
Forgot about this thread until I went thru the contents of my smartphone.
Here's a video I took, moving the camera around in an attempt to show the shape of the disc edge.

I don't have a micrometer.
I don't have clunking noise when going backwards and braking.
Only when first moving off after the car has sat for a few days, esp. rainy days.

 

Your rotor's looked like just like ours did right before I had them changed. The grey spots in them is rust that is embedded into the rotor. It is caused by the car sitting during the rainy days. The Clunk noise you hear when first starting off is the rust breaking loose so the rotor can move.

It seems with the regen brakes, the rotors don't get used a lot since the friction brakes only kick in around seven miles per hour and that is normally just before you stop. Only if you are in a panic stop or the ABS kick's in, almost all braking action on the Prius is done by regen. That is why the rust is common. Your situation is nothing new. About the only way around it is to do what other's have suggested. That being to throw the Prius in N around 40 or so and use the friction brakes to come to a complete stop. This will help to clean up the pads and rotors. Also, the rotors new are only a few mm over minimum so there is not much room if you want to remove them and have them turned.

Best of luck to you.

Ron

 

I'm thinking the pad are used more in day-to-day driving then we think. Maybe especially after startup, possibly because regen is suppressed during warmup? My reasoning:

After washing the car and letting it sit a while, for the first few blocks you drive brake application is very audible, due to surface rust on the rotors, and it seems like every time you apply brakes you hear their "song".

 

The minimum thickness for the front rotors is 20mm (0.78 inches) the new thickness is 22mm (0.86 inches).

Hope this gives some guidance.

John (Britprius)

 

The regen is not suppressed during warm up. I live near the top of a hill as you can possibly make out from my avatar, and often I see 8 green bars going down the hill with my foot off the throttle from a cold start.

The results are no different if the car is still hot no more no less charge. The only difference I see is when the car is cold I am lucky to see more than 25 mpg on the MFD when hot it reads 99.9 mpg and the ICE does not run.

John (Britprius)