Hello,

I have a "mysterioius picture" for a pair of rear brake shoes that I installed last week, I wonder if anyone can help me understand what the issue(s) would be. Here goes the story:

Last Friday, I installed a pair of brake shoes along with a new drum (both purchased from Murrays: shoes $25, drum $35 each) for the rear driver-side wheel. I did not have time to get to the passenger side before I had to get on to a long distance round trip (250 miles each direction). On my way out, I did not found anything particularly bad, but on my way back, my car shaked everytime I stepped on the brake.

After I got home, I took off the rear left tire and undid the drum, the following was what I found.


http://i7.photobucket.com/albums/y26...b/DSC04825.jpg

http://i7.photobucket.com/albums/y26...b/DSC04824.jpg

Bascally I saw this unusal wear pattern (as shown in the pictures) on both shoes! Can anybody explain to me what might have gone wrong? Thanks for your help!

Shay

 

that is caused by the brake shoes not being smooth from the manufacture make sure that everything is adjusted properly and then follow the recomended break in procedure. usaully that involves light brakeing for the first 5 miles or so. with lots of starts and stops. part of the problem could be that the left side was adjusted more than the other side so was working more. should only do brakes in pairs ie both front. both rears, unless fluid/ grease damaged the old ones when less than 50% worn.

if we aren't supposed to eat animals, why are they made out of meat?

 

Just a left-field thought here, but did you thoroughly clean the braking surface of the drum before installation? The new drums usually come with a rust preventive/preservative on them.

 

Speedwrench:

Are you saying that one need to go thro with the "break-in" procedure because the parts I purchased were NOT WELL MADE? I'm asking this because I'm thinking if I go to a brake service shop to have the job done, I would not be asked to go thro the tedious procedure you mentioned. Or are you suggesting that the shop people actually did it before they turn the vehicle back to me?

I understand your point of doing brakes in pair. But I've done it the sloppy way before (i.e. only changing one side) and did not experience the terrible vibration and revealed this strange wear pattern.

Would you mind sharing what what you mean by "make sure that everything is adjusted properly"? That is, what are the things to take care when you adjust brake?

the_tow_guy:

I did not thoroughly clean the inner surface of the new drum. Would you mind explain what should I do to "clean the surface"? Alternatively, do you think after this 500 mile I put in, it still make a difference that I do a surface cleaning?

Thanks.

Shay

 

no I am saying that the breaking in process is to seat the brake shoes to the drum, way back when i first got into auto maint we had a brake sander that was set to the drum size to shape the shoes for proper fit fast. I am sorry I should have mentioned the cleaning of the drum first, I just helped my son install new rotors and that was the first thing I made him do. I would suggest useing some 120 grit sand paper and lightly sanding those shoes now because they probably have rust preventive ground into the surface. when I talked about everything adjusted properly I ment the clearance between the shoe and the drum. there should be a slight amount of drag when you rotate the drum, the best way is with a dial type torque wrench to make sure each set of brakes has the same amount of travel. as you are adjusting the shoes either yourself or a helper should depress the brake pedal to help center and set the shoes to the drum while rotating the wheel and drum assembly. By the way the wheel should be mounted and tourqued to make sure the drum is properly seated when adjusting the brakes. I also completely bleed out the old fluid when replacing shoes or pads just because brake fluid is hydroscopic this helps cut down on corrosion inside the system. at this point if you pull the drum back off of the vehicle i probably would take it to a parts house and see if they would just skin the drum to make sure it is still round. don't let them do a full turning just skin it to check for trueness. if it is not true I would ask for a new drum due to manufacturing defect.

the steel that brake shoes are mounted on is thin and stamped out, the shoes are not usually perfect circle parts when new and need to take a set to the drum during a short break in process. also most of the time the steel is recyled and may be damaged during the cleaning cycle, or during storage so that it is not perfectly part of the circle it is designed to fit.

if we aren't supposed to eat animals why are they made out of meat?

 

Aerosol brake cleaner would have been good on the drums. I agree with Speed; I don't know that there would be any coating still on the drum. Probably wouldn't hurt to hit them with the cleaner anyway.

 

1. here's a totally left idea: warped drum. needs to be turned so that it mates with brake pads well. yes, not just front rotors warp, drums do so either.
2. speaks for itself:

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I, personally, simply go to a straight stretch of a local 2 laner, with very little traffic(and no cops) on it, bring it up to 50 and slow down to 10, 50 - slow down, 50- slow down. following same road, i get to a very stip downhill, over mile long. after i am done with 50/slowing to 10 part, i wait for no cars, get her up to about 50 mph, and let her roll down. then i just drag the brakes as long as i can. i know, it can boil the fluid. so far, done countless times, works every time.
result? if the rotor gets nice shiny bluish tint - it's broken in awright.

 

Gee I thought I answered that.