Design defect found on 05 aveo rear drums.

I have a 05 Aveo LS with 116k miles on it. For about a year now I have been having problems with my brakes. The pedal would go to the floor with very little stopping power. I keep getting the runaround from the dealor. Finally the dealor just said I need new brake pads on all 4 wheels. I did not trust them and took it to another local shopand they said I had 75% of my pads left the looked at the car and found the rear drums are not self adjusting themselves. They tested the auto adjuster and everything works fine. They found there is a design defect in the auto adjuster that keeps it from adjusting the drums. They don't know of a fix for it. So they just manually adjusted them. Guess I will have to get them adjusted manually every so often.

I've been wondering about this myself on my '04. I just bled the brakes and have new pads up front, but have a very "soft" pedal. Very little braking power until it nears the floor. I haven't had much of an issue, since the car is now a dedicated rallyX car... and any amount of left foot braking and the pedal turns to stone.

I never did the full proper adjustment procedure, and haven't had the chance to check it out. I did once bring it up at an inspection maybe 2 years ago, and they mentioned the adjuster... I ran in reverse to 15mph and stomped the brakes maybe 10 times and it seemed a little better. They attributed it to the lack of weight over the rear wheels and not having enough force to kick the adjuster over.

I'm still on the original shoes at 80k, and just noticed a squeak so I'll be pulling the drums in a week or so and see what I can figure out.

We might want to move this over to the technical forum.

Exo

did they mention what kind of adjuster it is? some require you to use the ebrake regularly, some "slip and lock" with the spreading of the pads, and others adjust really fast in reverse like exodus said..

Not sure if it helps you, but I think the proper "full adjustment" procedure is:

Completely loosen the parking brake at the lever, raise the rear and press the pedal until the adjuster no longer clicks (sounds like slip and lock...),

Raise the parking brake two clicks and tighten until the rear wheels are bound, lower the parking brake and check for drag.

Then do the 10 reverse runs (wtf both?).

Think this is also in the how-to section somewhere...

edit: I've also noticed that the parking brake adjustment definitely has a significant impact on pedal feel.

Quote:

---

Originally Posted by exodus0784

We might want to move this over to the technical forum.

---

Good idea - moved.

that procedure sounds like adjustment after a new pad install, BUT have to do all three of the adjustment actions does not sound right to me.

refer to service manual:
http://gm.ws123.net/EN/documents_200...en.html#T4E0BA

so it is a "slip and lock", but all the notices in the manual i can see several spots that could allow the failure.

the cylinder and adjustment rod are on the top, only the ebrake is on the bottom which means when the pads push on the drum only the top pushes out. The bottom only pushes out when the ebrake is applied. (cant stay out because the rod is on the top.) That design also creates the adjustment rod and nut as a pivot point, and the pivot point mores out with wear. but your not using the whole pad, not really, so wear would not be very significant overall.

It says several times to press the brakes until it stops clicking, And that the nut can not be tightened against the back of the rod. This would prevent it from adjusting at all. I would probably not put it against the rod as the procedure says, i would leave a thread showing..

well honestly i will upgrade to disk.

I have not looked at my o8 rears yet but it sound like it set up like the 76 set up almost. you tighten up the ajuster until it snug all most does not let the drum back on. Then you then you ajust the ajuster wheel from the backing plate side,( ovel blk rubber plug keep the drity out and water ) or back up quick and stomp the brakes two or three times.

Quote:

---

the cylinder and adjustment rod are on the top, only the ebrake is on the bottom which means when the pads push on the drum only the top pushes out. The bottom only pushes out when the ebrake is applied. (cant stay out because the rod is on the top.) That design also creates the adjustment rod and nut as a pivot point, and the pivot point mores out with wear. but your not using the whole pad, not really, so wear would not be very significant overall.

---

This is the norm for most drums it's sort of like a safety for people that drive with e-brake on. You will still have rear brakes if you do this a lot but your e-brake side will be tossed. If you use your e-brakes on when parking do not forget to take them off and keep them adjusted your rear brake side should be wore out before your e-brake side most times when your time to change the rear drum shoes.
One side or the other should have enough shoes to help stop you in a fast stop if needed. If not then they need replaced. I like to have then a little bit more than half wore out. But that just me.

Thanks for the info. My wife's 04 Aveo was having the same issues with the front pads being ok but low pedal and barely any stopping power. I did the reversing and stomping on the brakes method and now the car stops on a dime. This car was under-engineered in many ways. I can't believe there was no access hole in the back of the brake drum to adjust the rear brakes.

Under engineered would be if they did not they self adjust, you must have to must grime back there. they should naturally adjust out slowly as you back out of parking spots, use the ebrake, etc.

technically having drums is kinds of under engineered for these days, but if you wanted a feat of modern engineering, you would buy a corvette, mercedes, audi, etc. Not a aveo.

The "reverse fast, then stomp brakes" technique worked for my 2008 Aveo sedan. After a rear brake cylinder replacement, my brakes were weak and wouldn't bite, and the pedal would engage only about halfway down to the floor. This was after a thorough brake bleeding. After trying out the technique, the pedal engages early, and stopping power has returned. Many thanks.