Rear Brake Clean and Adjust

[galaxee]

we hit 60k miles recently, so before we take our usual road trip, DH did the whole rear brake clean and adjust job on our prius. and i took pictures.

this job is something that can be done by someone who is fairly DIY competent. that is, a novice or anyone who thinks they might mess things up is strongly discouraged from trying this. there are several things that can go wrong in this process that could lead to problems either immediately or down the road.

that out of the way, here's what you do.

1. lift the car. safety first- use proper supports. remove the wheel.
2. remove the brake drum. chances are it will be tight. use two bolts to push it off as shown:





3. sandpaper the friction surface of the drum with aluminum oxide sandpaper- 80 grit wet or dry is what DH is using here. see how shiny that surface is? that's glazing. the glazing will be removed as well as brake dust. NEVER sand in the direction parts are moving. do not sand around the long surface, sand perpendicular to it. if you sand parallel to the long surface, you can score the surface, which you really do not want to do.



4. next up is the rest of the brake assembly. it is filthy.



rear shoes looking very good at 63k



but they are glazed.



7. shoes get sanded to remove glazing, too. again never sand in the direction of parts movement. always perpendicular to it. same reasons as for the drum.



now cleaned of glaze, will brake more efficiently.



8. and the rest of the cleaning part: brake parts cleaner removes brake dust built up all over the place



don't forget the drum



9. reassemble brake assembly. DH always makes sure to put the drum back on in exactly the same position as when he took it off. make sure it is all the way back on.
spin assembly, pull gently on parking brake cable and flex it to stop spinning. if it stops, then all is well.



10. adjust rear brakes.
this is trickier than what's been done so far.
where DH has the screwdriver in this picture, there is a rubber plug that reveals a hole through to the star adjuster screw.



start by finding the adjuster screw with your screwdriver. now that you know where it is, spin the drum. listen for any light drag. adjust one click forward. listen again for light drag. continue doing this until you hear a very slight drag sound. then stop making your adjustments.

some of you are probably wondering why you would want the brakes to drag slightly. remember this is an adjustment point, and the self-adjusters will readjust the shoes again when you step on the brake.

it has been about 30k since the last time DH did a clean and adjust on our prius. the left side was in fine adjustment, but the right side took eighteen clicks to adjust. those self adjusters aren't always perfect. i was getting a slight wobble (only on hard braking) as a result of this adjustment problem. now things are back to normal.

[hobbit]

If they weren't self-adjusting this whole time, perhaps the lead
screw on the star adjuster was gunked up and not being turned
by the adjuster arm?
.
It also helps to get a little grease onto the little nubs on
the backing plate that the sides of the shoes ride on, which
will not only make things quieter but also help them self-center.
The slight dragging on reassembly may simply be from the pair
of shoes shifted slightly front or back at the piston end. A
couple of solid braking events should straighten 'em right
up, though.
.
Thanks for more views on this! I've never actually used brake
cleaner like it's supposed to be; something about lots of nasty
solvents flying around didn't sit well with me and fortunately my
brake innards were always fairly clean to begin with.
.
Gotta do my own all-corners spring checkout real soon myself, too...
.
_H*

[tochatihu]

Great stuff Galaxee, especially the brake drum push-off bolt trick. Details on "proper supports" can be found here:

ABCD's Bridge Design Tips for Kids

Hobbit, those brakes aren't rusty. Dave Bassage' brakes were rusty. I don't know what the put on the roads in winter in West Virginia but it's quite fond of iron alloys.

[Vincent]

Great recommended service at 60,000 miles, which is when I had the cleaning/adjustment done. This was a cheap investment ($60 at dealer) that I'm sure will increase the life of my brakes.

[Aaron]

What size bolts did you use to get the rear drums off. I can't get mine off. I need to get those bolts!

[tochatihu]

Metric bolts. Size forgotten, but they are the same as the thing holding down your donut spare tire.

[Aaron]

I found it. It's 8mm x 1.25

[Aaron]

This was EXTREMELY easy to do as long you have the proper tools. I would put this on par with an oil change. Saved $80 by not going to the dealer and doing it myself. Use two 8mm x 1.25 bolts of any length to get the stubborn brake drum loose if a hammer won't loosen it.

For those who have done this:

Is it just me or do the rear brakes seem to adjust themselves when I start spinning the tire while the car is still on the jack? I adjusted the Star Wheel to where the shoes were putting enough pressure against the drum to feel some tight resistance. When I continued to spin and applied the Emergency Brake to test it, everthing loosened up a bit to the point where you could barely tell the shoes were touching the drum.

After watching How to Make Final Adjustments to Car Brakes: How to Adjust Brake Drums on Cars | eHow.com I learned that you should adjust for enough resistance that the tire should only be able to make one revolution when you spin it as hard as you can. This is the "pre-adjustment procedure" to fine-tune the adjustment. I'm not sure that this matters a whole lot because like I stated above, everything loosened up right away after a few spins to where there was little resistance.

[DaveinOlyWA]

post should be made part of knowledge base.

[Aaron]

Do Prius rear drums self-adjust when applying the parking brake or braking in reverse?