New rotors after only 2 years?

Get a second opinion, as regenerative braking does the work, not the brakes, and the rust isn't on the wearing surface, have the pads measured and have the calipers adjusted and the pins greased, yes, Toyota is fleecing you, but do have them professionally checked and serviced yearly.
Have the fluid changes every three years.

 

Fairly relevant: disclose your (general) location.

Did your mechanic have previous experience with 3rd gen Prius rear brakes? It is imperative to assemble the rear brake with the caliper piston in a specific orientation, so that the spoke pattern on the piston face straddles the pin on back of pad (does the wagner pad even have this pin?). You also want to ensure the whole assembly is well seated thus. Other wise the piston may rotate when the parking brake is applied, ride up on the pin, and from there on you will have brake drag.

What did the rotor rust look like? See if you can talk to the mechanic. If it was uneven wear, and roughly 50% of the inner face of rotor completely rusty, that would be another clue to aforementioned improper assembly.

 

Here's what the inner rotor of mine looked like, 6 months after I opened up and reassemble the rear brakes, blissfully unaware of the need to align the pin with the piston:



I ended up replacing the pads, but the rotors I just steel wooled and reused. They still sounded terrible for about a week, but eventually back to normal. Here's a snapshot of how the piston should be oriented, to straddle the pin:



Failure to do this, the piston starts rotating (and screwing out in the process) and the pin on back of inner pads rides up on one of the spokes, causing drag and skewed brake pad pressure on the rotor. You get the rust per above, and the pad looks like this:



It's interesting too: if it were just environment, why are the front brakes ok. Bottom line, Toyota's 3rd gen rear brake design, with incorporated parking brake mechanism, is poor. Because it is unorthodox, requires diligent/specific care to avoid this situation.

I'll attach the Repair Manual Section on brakes:

 

See how the rear wheels spin when the car's up. Normal condition, there's a slight bit of noise/drag, but the wheel will easily free-spin a revolution or two.

 

why aren't you going back to your mechanic for a looks and discussion? it is possible that nothing is wrong, dealerships have all manner of ways to make money.

how many miles in those two years?

 

Second this. And how many miles (well km's) in total?

I'm still wondering too, if the Wagner pads were completely compliant, had the backing plate pin:



Addendum: Googling, it looks like Wagner pads do have the pin.

 

If you’re the type that is a DIYer, you would save so much money on this job. The rotors should last along time unless you’re in a cold snowy wet climate, which can rust and destroy your brakes quicker than summer places.

 

Does your car sit for extended periods? Usually, rusty rotors are due to non-use.

And yes, aftermarket rotors are generally of lower quality. They will tend not to last as long, and will rust more easily than OEM Toyota.

 

Replacement rotors are maybe not the expensive, but in my case, even though I'd messed up and they'd had uneven wear, a bit of steel wool, and 2~3 weeks down the road they were completely healed. As long as they're not out of true, and good thickness. See attachment for specs. You can check for yourself with dial gauge and micrometer.

If you're not going to DIY though, I think dealership will be reluctant to send you on your way with new pads but knackered rotors. Maybe just chalk it up to experience?

If you have an opportunity to jack up the back end beforehand though: it'd be real interesting to see how those rear wheels turn. Be safe, chock the fronts.

 

let's put it this way, two year rotors are extremely rare, in any climate, but anything is possible.
some have had trouble with the rear brakes because they don't get the same use as the front, and the caliper slide pins seize up.

 

If you are running ceramic brake pads, they will wear out rotors faster. I myself prefer semi-metallic pads, They stop the car faster without warm up and rotors tend to live longer. Brake pads and rotors can wear out faster depending of load/weight, hills, speed etc. The brake regeneration does a great job. 1st set of pads wore out in 120k on the 2010. I had to replace the rotors on my 2011 @ 297k because of rust and now it is on its 3rd set of pads with 309k.

 

extrapolating that to mean 1,500 - 2,500 miles per year. if that's the case, it would be surface rust like we all get, and dealer shenanigans involved. if more than that, i would question what kind of rotors the mechanic installed.

 

The rear drivers side rotor on out newly acquired Prius V (wagon) has a *severe* amount of rust on the rotor hub. Rotor friction surface is fine. Very strange as the other three have very little rust. Of course, I have no idea what the history of the vehicle is other than it was run in a fairly 'dirty' environment ( probably lots of dirt roads ). No history of any brake work either. Of course, that means nothing as the previous owner could have done their own maintenance, etc...Or maybe a dud rotor?

I went ahead and ordered a nice zinc-plated rotor/pad kit for all 4 wheels from R1 concepts ( I had noticed some of the modders have used this brand ). They look nice. Planning on installing them this spring/summer.