FRONT DISK BRAKE PADS

The front pads are of the same design as any other car so can be changed by any good mechanic, but!!!! make sure the mechanic understands that the 12v battery must be disconnected before work begins. If this is not done the pistons may be pushed out of the calipers by the hydraulic brake pump starting up and pressurizing the system. This can happen at any time even with the fob well away from the vehicle, and opening the drivers door is almost guaranteed to set it off.

Rust on the rotors is fairly normal on the Prius but it does depend on the level of rust. If the rotors are smooth and flat but but are rust colored they should be fine, if they are grooved and uneven then have them ground or replaced.
After market rotors are much cheaper than OEM and the quality seems to be as good, and at that mileage I would replace rather than regrind.

90,000 miles is considered very early for a pad change on a Prius as often they will go to 200,000 miles plus, so I would have someone else check them out if you cannot do this yourself. New pads are 11mm thick minimum is 1mm. It is reasonable to expect a wear mileage rate of 15,000/20,000 miles per mm of pad thickness.

John.

 

My question is: Why can't they grind the rotor to remove the rust? Sounds like a sham to me. If they have the minimum thickness after turning the rotors, there should be no issue. Rotors can be turned if after turning they still retain a minimum thickness (the spec I don't know). You should really consider doing this yourself. It is one of the easiest repairs (even if you have to replace the rotors). Just make sure to disconnect the 12V battery as Brit says. I think many dealers and repair shops prey on peoples lack of knowledge concerning brakes.

 

New rotors on gen2 Prius are 23mm, minimum is 21mm so this is only 39/thousandth's of 1inch maximum of machining and wear per side. If rotors are machined down to close to 21mm and new pads fitted the pads will outlast the rotors meaning that at a later date the rotors and pads will have to be replaced again, witch is why I recommend replacing the rotors at the same time. The cost of machining compared to aftermarket new rotors is minimal.

By the way I forgot to mention in my first post, do not open the bleed valves to push the pistons in as this will through a brake fault code and bleeding of the system will be required. This can only realistically be done with Toyota Techstream software and suitable computer, this also applies if the pistons are pushed out of the calipers.

 

The minimum rotor thickness is normally the minimum allowable for machining, not the wear limit so they should be good for the life of the replacement pads if they cleaned up at 21mm during machining. Also, not all pits need to be machined away.

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Most dealer shops are parts swappers, not parts fixers so they probably aren't set up to grind rotors. That doesn't necessarily mean I disagree with your sham evaluation ​

 

In the UK the minimum thickness is just that. Rotors below minimum thickness will fail our MOT (yearly safety inspection) however this may be different in the US. The Toyota manual says to replace the rotors if they are at or below the minimum thickness.

It is quite common in the UK now with modern pad materials for the rotors to wear out before the pads on some vehicles (not the Prius).

 

We need a couple of close up pictures of your rotors to really make a valid recommendation. Rust may not be structural, only cosmetic.

I had to replace the rotors on my truck from rust, but that was mostly due to chunks starting to fall away. Some surface rust can be fixed by hitting the surface with a DA sander with about 80 grit. That may very well be all you need with the new brake pads. Sometimes new pads is all you need to get the surface rust off the rotors.

I've never had to turn rotors. They are cheap enough to replace, I never fooled with getting them turned. For a 2006 Prius, I see AAP has rotors from $38 to $73. Probably last the rest of the life of your car.

 

I don't have to worry about inspection in my state, but did verify that the shop manual for the GenIII also says to replace at or below the minimum thickness. US Toyota maintenance schedule calls for measuring the thickness at 30k mile service inspections.

However, since conservative Toyota has a 30k mile inspection interval, they are saying it's OK to put a car on the road at minimum rotor thickness knowing the car can be subject to hard brake usage for 30k miles before it is checked again. That 30k inspection spec is also likely a Toyota fleet wide spec that is good enough for Toyotas that wear brake discs much faster than a typical Prius does.

I would turn Toyota roads (within spec limits) before I would use $38 AAP (or any other chain store bottom of the line) rotors.

 

I got some cheap rotors for the CRX that worked well. When I went through it after I bought it I found the rotors to be below tolerance. Replaced all four corners rotor/pads/shoes/drums for next to nothing. Worked just fine. Of course, the CRX was an exercise in minimalism and cheap was the operational goal.

On all other vehicles, all other parts, I generally don't settle on the cheapest or the most expensive.

For our OP, at this time there's no telling if the brake shop is handing him a line or not. Brakes are an easy mark for upselling. I would dare say a great number of front brake jobs could get away with a new set of pads and nothing to the rotor. Surface rust will easily scare the uninitiated.

 

As long as the wear area where the pads contact the rotor is fairly smooth with no deep gouges or pieces missing I would only change the pads provided the rotors are not warped. On a Prius the rotors should be good for 200K+ miles.

 

You will know if the rotors are warped because you will feel a vibration in the steering wheel when you brake if you put the car in neutral first and coast so that you don't get regen and force the use of the disc brakes.

 

When you have your next service check how much pad material is left, if the minimum amount of material is above 2mm I would leave the pads as they are. Remember every mm is at least 15,000 miles.

 

For most of the cars I've had experience with, warpage of rotors is kind of a will-o-the-wisp. One would think that's what it is, but it isn't. I have no in-depth knowledge of the Prius-Specific braking system, but it seems too long a stretch to believe that anyone drove a Prius hard enough to warp the rotors.

For the largest percentage of autos that shuddering one feels when braking is merely a corrosion buildup in a couple of keys areas, or it has to do with deposits/no deposits on the rotor face caused by the pads and the atmosphere. This is largely non-Prius specific info, but some of it can be used with Prii.

Corrosion/rust can build up where the back of the wheel meets the rotor, and where the back of the rotor touches the suspension. At each tire rotation be careful to check the cleanliness of the back of the wheel and the contact points on the rotor. Wire brushing the worst away, sometimes some sandpaper, worst case might require a wire wheel on a 4.5" grinder. I use anti-seize over these contact points once they are cleaned.

The back of the rotor can be accesses when the brake calipers are removed. This can be done at pad changing time. It's only a couple of (tight!) bolts to remove most calipers. Hang the caliper out of the way with some wire so the brake line isn't stressed and remove the rotor. The back of the rotor gets the same cleaning treatment. It really doesn't take but .003" or less runout worth of corrosion to cause a vibration in the brake pedal. And this amount can be shared between the two faces.

For brakes where the front rotor contains bearings and races, it's a different story. I've not done any of those since my brand new 1986 Chevy 2wd truck, and I don't even remember why I was fooling around with them.

The brake pads themselves can cover an area of the rotor and keep them clean when atmospheric moisture can coat all the rest of the rotor in a tiny bit of rust. This small clean area can grab the pad differently each rotation and can be felt in the brake pedal as a pulsing.

As for the OP, at 15k miles or so a year I wouldn't think the rotors would have a problem with rust. On my truck that only sees maybe 2k miles, I get rust. If you're close to the shore and get sea spray, maybe. I don't know much about living near an ocean. Without seeing the OPs brakes, I can't be sure. But I DO believe there may be some monkey business going on and the OP needs to bone up on the web about what brakes are supposed to look like and what what brakes look like that aren't doing well.

Common rule of thumb for pads is to replace them when the material reaches the same thickness as the backing plate. There are some special considerations for Prii, but I have not yet changed pads our either of ours. If I wind up with a rotor that has a lot of deep ridges I simply replace it. I don't get them turned. A rotor should last through at least one pad change, and maybe another, before requiring replacement. I've never seen a rotor go replaceable-bad in only one set of pads. I'm sure some have somewhere, but nothing I've seen has.

 

What about rear brakes? Can those pads and rotors be done by any run of the mill mechanic?

Also, @Britprius what do you mean "before any work begins" does the auxiliary battery need to be disconnected if all that's happening is an inspection? Or just when the pads and rotors are being replaced?

My rotors are very rusty. It's been a michigan car i it's whole life (2009, 138K). I can't be certain, but just recently it looked like a lot of the rust has been removed from my front rotors. I have never put it in neutral and applied the brakes at 40mph as some have suggested so I don't know why they all of a sudden look like fresh metal. The rear rotors are completely covered in rust.

I bought the car at 128K and the toyota dealership that inspected it for me said the brakes were at 3.5mm (front and rear) and I should have them checked in another 10,000 miles. Then I drove to california and back and did A LOT of mountain passes. and I do mean a lot.

when I release the brakes after a cold start it also seems like they make more noise than they used to.

there is no squeeking at all.

Dealership want's $30 just to inspect them but I will almost certainly have the job done by a shop that will do the job cheaper. (after I confirm they are familiar with the procedure for disconnecting the aux battery of coarse).

Also, should I look for a certain type of brake pad?

Thanks everyone for your help.

 

If you've got an American market 2nd gen Prius, chances are the rear brakes are drum brakes. Strange that it's disk brakes, could it be a (3rd gen) 2010??

For pads (or shoes), I would stick with Toyota brand, just to be on the safe side. There's minimum thickness for rotors (and max inside diameter for drums I think). If either is not near these limits, they can be machined, though it might be more expedient to replace, depending on cost, how much is left. It is not mandatory to do anything: on past cars I've just slammed in new pads, with old rotors, everything was fine. Or just removing the rotors and "dressing" them with sandpaper might do the trick.

Particularly if the brakes have been neglected, on the disc brakes you you should pull out and lubricate the caliper slide pins. SilGlyde is one commonly available lube used.

The big issue with Prius brakes: any time the caliper is pulled off the rotor, or the drums pulled off, there's a chance of the system pressurizing, and pushing a piston right out. For this reason it's safest to disconnect the 12 volt negative lead before starting anything.

There's a second possible issue: if you for example push in a piston to accommodate new disc brake pads, then just reassemble everything, rehook up the 12 volt, start the car and drive, the first time you apply the brakes the car may detect excessive travel, throw codes. For that reason, when completing a brake job, it's good practice to pump the brake pedal multiple times before hooking up the 12 volt, basically so the car's none the wiser.

Just in case it'll come in handy, I'll attach 3rd gen info on brake maintenance.

 

did I say something about discs? I didn't know there was a difference. I thought discs/rotors/drums, were all the same thing but some people use different terms.

So If I reading correctly @Mendel Leisk , the 12 V battery should be disconnected even for an inspection?

 

Anytime it's possible for a piston to be "born", basically.

Discs (aka disks) and rotors are the same. Drums are a different beast.

 

Toyota very kindly checked my brakes at the last oil change. My front pads had 6mm left, rears, 4mm. I was told since this was 'borderline' and my rotors had some rust...that I should get the pads & rotors replaced then and there. Only $505.99 !
I have a 2004 with 110,000 miles. If you start out with 11mm of front brake pad, and they wear approx 20,000 mi per mm.....then mine are right on schedule. ....and..... at 20,000 mi per mm, I have 5 more mm left to reach 1 mm. That's 100,000 more miles.