What would cause uneven brake SHOE wear?

[R18Civic]

I have inspection due this month and decided to check my driver side brakes on my 2012 Honda Civic that was gifted to me in March.

Pads are just fine but the rear shoes are looking iffy. The rearmost shoe has wore evenly and I would say the material is as thick as a penny, but the front shoe is thickest at the top and very thin along the bottom of the shoe. I didn't snap any pics and will be changing the shoes, drums and hardware this weekend but I'm curious what caused the uneven wear.

Thanks in advance.

 

[doitmyself]

It's somewhat normal and is caused by how the shoes expand at the top only and then how they grab onto the drum. The servo action results in the rear shoe pushing the front leading shoe harder against the drum (moving forward). It does seem to me that I see different wear patterns, so maybe the actual design is different between manufacturers? Some suggest that a sticking wheel cylinder bore or backing plate causes it, or maybe adjustment too loose. My Patriot brakes wear more on the front/leading bottom, like you explain above.
Random internet pic with top leading wear:

 

[R18Civic]

Looks very similar, however mine was thick up top and thin at the bottom of the shoe. Good to hear it's a normal wear pattern.

I've never done drum brakes before and know very little about them other than operation, good thing I've got help from someone a bit more experienced than me. Good news is the person who gave me the car also supplied Wagner Drums and Bosch shoes so I've got good replacement parts going back into the car.

 

[Trav]

I have inspection due this month and decided to check my driver side brakes on my 2012 Honda Civic that was gifted to me in March.

Pads are just fine but the rear shoes are looking iffy. The rearmost shoe has wore evenly and I would say the material is as thick as a penny, but the front shoe is thickest at the top and very thin along the bottom of the shoe. I didn't snap any pics and will be changing the shoes, drums and hardware this weekend but I'm curious what caused the uneven wear.

Thanks in advance.

Don't forget short shoe to the front and do not mix up the adjusters. The wear is normal.

 

[R18Civic]

Don't forget short shoe to the front and do not mix up the adjusters. The wear is normal.

Yeah I'm making it a point to take pictures before we start tearing in apart so everything goes back together properly.

EDIT: And thank you Trav, Between you and ClineBarger I don't know what us amateurs would do. Saved me from making a very simple set of mistakes.

 

[Chris142]

Don't forget short shoe to the front and do not mix up the adjusters. The wear is normal.

This. The front shoe is the primary shoe and does most of the braking.

 

[doitmyself]

Also be very careful not to overextend the wheel cylinder piston, causing fluid to shoot out and/or possible cylinder damage (piston, seal, etc.). Over extension can happen when you are re-installing the springs and the entire assembly shifts too far in one direction. It can also happen if you step on the brake pedal with the drums off. There are excellent YouTube videos showing how to secure the assembly so it does not over extend.

Also, I learned that during adjustment, it is good to pull on the emergency brake (drum on) between star wheel adjustments to center the shoes. Is this a common practice for you pros?? And.......... if adjusted "close enough", shouldn't the self adjust mechanism get them to the finish line/proper adjustment?

 

[Escape08]

Brake shoe and other mechanisms inside drum not properly installed to begin with.

 

[doitmyself]

Brake shoe and other mechanisms inside drum not properly installed to begin with.

Mine did this from the factory. I checked them every other tire rotation for wear.

 

[Escape08]

Mine did this from the factory. I checked them every other tire rotation for wear.

Looking at the picture you've provided, I suspect the pistons on the brake wheel cylinder are forced further to the right. That is why when the brakes are applied too much force applied on the piston on the right shoe and less force to the left shoe resulting uneven wear. I would change the brake wheel cylinder and the shoes. It is not expensive at all. Auto chain stores do offer lifetime warranty for both shoes & cylinder..

 

[eljefino]

It's good you're getting new drums. It will help you not having a ridge to deal with, and all measurements will be spot on. If the drum grows with wear then the new shoes won't fit perfectly, will wear to the drum, and offer poor braking in the interim.

It is good to recenter shoes while adjusting them, with the parking and or service brake. You'll get things close while being able to R&R the drum, but there's a little more tightening possible with the drum on. I'd set it a few clicks loose, drive around, break things in for a week, then revisit the adjustment, myself.

 

[2010Civic]

It's pretty rare for brake pads or shoes to wear perfectly even. Replace them and don't worry.