Prius rear disc brake pads?

You need to remove the wheel for closer inspection. It all depends on your tolerance for trouble.

High tolerance: wait for it to be metal to metal.
Medium tolerance: wait for the wear indicators to start squealing
Low tolerance: if the thickness of the material is less than the thickness of the backing plate.

See Hobbit's picture of front pads for material thickness vs. backing plate.
http://techno-fandom.org/~hobbit/cars/brkjob/40meat.jpg

 

Yep. US Gen 2s come with rear drums.

 

The rear pads when new have 9mm of pad material, the fronts have 11mm. The rears do wear slower than the fronts.

I have just replaced my front and rear discs due to rust at 81000miles, the front pads had about 4mm left so I replaced those. The rears still had 7mm but the surface was uneven, so I put them on a surface grinder and took them down to 6.5mm and refitted to the new discs (cheap skate).

To measure my pads on the car I use the tail end of a vernier calliper then subtract 4mm for the pad back plate,

 

Forgot to mention the rear pads have noise makers on all four pads that operate at about 1mm of pad left.

The discs themselves new are 9mm thick rear, 23mm thick front (vented).

 

That's not being cheap, its being non wasteful which is mainly what driving a Prius is all about. Its funny that for almost a century the auto industry has been "turning" old rotors to mate with new pads and now you "turned" your brake pads to mate with a new set of rotors. I'm at 50K miles and am about to lube my caliper slides and clean/adjust rear drums, the car is 8 years old so I know the rotors are going to be rusted really bad since I never used the hydraulic brakes so I'd like to replace them w/o replacing the pads.

I only recently started using your "under 50mph neutral braking" trick to knock the rust off the rotors, but that doesn't change the fact that the rotors rust from the inside out since our only options in the auto industry are iron or outrageously expensive carbon ceramic discs.

My hobby is woodworking so if I want to flatten a peace of wood I use a planer, so I had never heard of a surface grinder, I googled it and it looks like a giant peace of equipment found in a machine shop. So who would be able to "turn" my pads which I'm guessing have around 8mm left?

I think what a brake shop uses to turn rotors would not be designed to turn pads. Another option would be to go to a deserted roads, go up to 50mph and neutral brake one or two dozen times, would that work or are there negative ramifications for doing this?

 

The pads wear so little on the Prius you Would have to run without regen braking for a 1000miles to bed them in.

A method that works well with a bit of care is to rub the pads flat on a belt sander then check with a strait edge across the pad to check how flat it is. A slight curve end to end does not matter to much but across the pad should be as flat as possible to rub all the way across the surface of the disc.

As I have said in the past I have access to an engineering workshop that makes life easy and less expensive.

 

cnschult if you are into woodwork try this to clean up your brake pads.

If you have a circular saw, "the type where you bring the blade down onto a piece of timber to cut it to length" set the cut as square as you can (not to critical) and cut a piece of 2"x3" or larger mark top and front.

Fasten a disc pad to the cut end of the timber with countersunk screws and washers on the metal ears of the pad.

Put the timber back on the saw and just skimming the end of the pad slowly bring the saw down (the pads are quite soft and will not hurt the saw blade), check to see if you have removed enough pad material to get a flat surface. You will be amazed the pad will look brand new.

This rely does work I have used this method several times.

 

On a Prius the rear pads wear faster, the front ones don't get much work to do (unless you do a lot of 'spirited driving') as most of the 'breaking' is done via recuperation so the front pads actually don't have to bite until your speed is very low.

 

The rear pads are only in use when the front pads are in use and since the brake bias is to the front the front pads wear faster. why would Toyota fit smaller and thinner pads on the rear of the Prius if they wear faster.

I have just change the discs front and rear on my car because of rust at 80,000miles and the front pads were down to 4mm from 11mm new a loss of 7mm, the rear pads I reused because they were only down to 7mm from 9mm new a loss of only 2mm in the same 80,000miles. These figures are very close to Uart's figures of 7mm of rear pad left at 150,000km (93,000miles).

 

Are you sure about that? I really doubt that when I step on the brake pedal only the front wheels are slowed down and the rear wheels can push the car forward. I agree that due to the weight shift forward the majority of the work is done on the front wheels but to keep the car stable also the rear wheels have to slow down. And as there is no generator on the rear axle, the brake pads have to do that job.

 

From gen2 Prius on only the front wheels are retarded when normal braking is done, if slippage is detected on any wheel regen braking is cancelled and the disc brakes on all four wheels take over, this is also the case below 7MPH I believe on the first generation Prius things were different but I have no knowledge of what those differences are.

Under vehicle stability control (VSC) situations the cars computer system takes over and this can apply braking to any single wheel or combination of wheels to maintain vehicle control.

 

Hydraulic brakes are not engaged for light braking. It is all regen.

The hydraulic brakes a complex. Caliper pressures are controlled individually. It is not clear to me if the rear brakes work harder than the fronts at higher speeds when regen is saturated and hydraulic brakes are required. However, I do not believe it is possible to have the rear calipers activated and the front calipers not activated.

 

Seilerts thanks for your take on the situation and in my rather long explanation this is what I was trying to convey.

I wondered about the situation at max regen if the car switched completely to hydraulic brakes or a combination of both systems.

 

Allthough I still find it hard to believe I guess there are two opinions against one so I take your word for it.