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Drum brakes only wearing the front shoe?

Started by TJ Hopland, October 01, 2020, 10:02:02 PM

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TJ Hopland

Just trying to figure out why I have soft brakes and seem to be eating up the fronts on one of my rigs I figured it was time to inspect the rears.    Not that many miles or years since I did the axle seals and all new hardware and shoes.   Everything looks good but the font shoes appear to be about half gone while the rears look almost new.  Same thing both sides.

Springs and adjuster arms were all new.   They seem to be floating nice on the backing plates.  Short shoes in the front.  Adjusters are on the correct sides and turning in the correct direction. 

Ever seen that before?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

wrench

#1
Could be a combination of factors. The front shoes may wear a little faster than the rears due to physics, but you could have wheel cylinder sticking issue, sticking to the backplate issue, or parking brake cable adjustment issue or ?

When I was reading up on the drum brake replacement procedure on my 70 Eldorado, there was verbiage very specific about the yellow spring and the blue spring being in very specific locations, so maybe a quick review of the specific procedure for the vehicle may indicate a return spring assembly issue if a specific hardware orientation was / wasn’t followed on assembly.
1951 Series 62 Sedan
1969 Eldorado
1970 Eldorado (Triple Black w/power roof)
1958 Apache 3/4 ton 4x4
2005 F250
2014 FLHP
2014 SRX

TJ Hopland

Parking brake seems to work fine and nothing appears to be sticking.   Springs in this case are different enough physically that I don't see any way you could reasonably interchange them.   Now did the person at the factory that made my replacement springs know or care what the original specs were?

I wondered about one piston sticking but it would seem strange that it happened to the rear pistons on both sides.   Also isn't it the case that once you get any sort of brake pressure going while moving forward the rotation rotates the whole mess into the rear of the anchor pin anyway?   So if my back pistons were stuck that would only weaken my braking in reverse?     I think that is why trailers often just have a front piston,  most of the time you don't need trailer brakes for reverse and that makes them special so you can charge a lot more for parts.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

wrench

#3
I like to read up on any reference material that is available before I assemble stuff. I don’t assume things have been assembled properly before me, especially if I am troubleshooting something.

This forum is a great way to reach out for resources and other folk’s experiences putting things together.

If the drums and/or shoes are worn enough, the shoe can get hung up on the backing plate and drag. That’s why you use that doohickey caliper thing so you have an idea what’s going on inside the drum when it is installed. It’s also why you put strategic dabs of grease between the shoe and the backing plate to reduce friction.

https://www.ebay.com/itm/Vintage-K-D-Mfg-No-278-Brake-Resetting-Gauge-with-Thumbscrew-for-Adjusting-Drum-/392941763369

You could check that the wheel cylinders are not seized up.

Depends on the brake design, self energizing. Usually the front shoe takes more wear, but not extremely disproportionate.

https://en.m.wikipedia.org/wiki/Drum_brake
1951 Series 62 Sedan
1969 Eldorado
1970 Eldorado (Triple Black w/power roof)
1958 Apache 3/4 ton 4x4
2005 F250
2014 FLHP
2014 SRX

TJ Hopland

I have made the mistake of putting things back the way I found em too especially on my early days of dealing with drums.  Now I have done enough of them and they are all the same to a degree where it counts so I usually don't make too many dumb mistakes.    Other than seeing if I had something leaking again I wanted to double check that I had the short shoes up front and that the adjusters were turning the correct direction and they were.   

I did end up adjusting them quite a bit so I'm not sure if that caused it or was the result.   Also don't know why they were not self adjusting.   Getting out of my driveway takes at least 2 backup stops and then where I usually park this one takes at least one back up stop and maybe more depending on what else is in the way so its not like I never back up.  Maybe I just need to slam the brakes harder when backing up?   

I don't know whats up with my brake luck lately.   Got squeaky discs for the first time in my life on one rig and now drums that seem to be a mystery which has never happened to be before either at least after I give up and replace everything and get the stuff in the correct places. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

The Tassie Devil(le)

#5
What car are we looking at?

None of the cars in your list have front shoes, just pads.

With regard to the Primary and Secondary shoes, the primary gets applied initially, which in turn puts more pressure on the Secondary, which is held in place by the Anchor Bolt.

The front brakes will always wear out faster than the rears on any vehicle, as the rears do less actual work.   These brakes retard instead of locking up.

Virtually all they do is keep the car from losing control, as they stop the locking up, causing the rear to slide.  Oh, and operate the Parking Brake.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Dave Shepherd

Regarding the self adjusters, when backing up they will only reset once and adjust once, go forward then back to get another adjustment cycle and so on.

fishnjim

No info given; make, model, shoes, miles, - if these were new or relined shoes?   

Could just be your technique, but a pure guess without examination.   There's a bit of art here.   Adjust them first manually at install, don't just rely on the adjusters.    I usually test the adjusters on test drive.   Also where on the shoe it's wearing can give clues; top, middle, bottom where to look.   Inspect the backing plate for shoe rubbing/wear.   The shoe "grease" is special stuff and applied sparingly.   Supplied with shoes.
Quality of the shoe lining is also a big factor.   I usually opt for riveted over glued if available.   
Nothing mentioned about condition of the master/hydraulic system.   Could be crud in the lines, wheel cylinders, not bled properly, etc.   
I like to disassemble the adjusters, clean them, make sure they're "free" the whole length, then put a dab of graphite lubricant on the threads, work it in.   Same stuff used on the pins of disk.  Should be smooth, effortless.  They go in one way.   You don't want grease or any oily material that'll attract brake dust.   

TJ Hopland

Getting one of those drum calipers may not be a bad investment.   At first I was thinking that maybe someone before me had machined the heck out of the drums and that was part of the funny wear but looking at them there is a matching chamfer on both the inner and outter edge of the braking surface of the drum that looks factory but no way to know for sure without measuring.     

On this thing the front shoe looks to be worn pretty parallel with the backing plate.  The rear shoe looks almost un touched over most of its area but you can see has some wear at the ends at least compared to the plate.  Thinking about it now the wear is about where there is no material on the short one.    Guess next set of drums I do I will have to do a test fit of the shoes in the drum to see how and where they contact the drum.    Not worth the effort on this one to take it that far apart to just see plus I think they have worn in now.   It would have been interesting to see what they were like when new.

In the past assuming something with fairly easy to slide on and off drums I would just turn the adjuster by hand till the drum didn't want to slide on and then back it off till it did go on.    Would call it good then and put er all back together then do a couple dozen back and fourths in the driveway or parking lot and that seemed to get em adjusted.   

On the hard to get the drums off stuff like where they weigh a ton or have an integral hub was when I finally broke down and bought the 'spoons' to adjust them through the slots.  Also came in handy for trailers that are often integral hubs and not self adjusting.   On those I go till the drum locks up moving it by hand then off about 3 clicks.   

Manually adjusting them seems to have improved things for now so i will have to keep an eye on them and see what happens.   Pedal feels much better and the new fronts no longer smell hot after normal driving.  Poor things must have been doing all the work lately so that is why one caliper and piston just said 'im done and gonna stick right where I'm at'.  Both the piston and caliper were not moving without a massive amount of force.   I usually don't see both stuck at the same time on the same caliper unless its been something that sits a lot which this doesn't.   

Just not my month for brakes I guess.   At least for the most part I still have them so that's something I guess.   I rarely suffer blown lines in the summer,  that always happens in the winter so I end up laying on the cold ground with salt dripping in my face while doing the repair.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Dave Shepherd

When I worked for Cadillac  way back, we relined our own brake shoes and arc ground them to match the oversize if any. Today's replacement  shoes are of course not handled this way. White Post restoration asks for the drum measurements when relining the shoes for a customer, then they can accurately  contour the linings for full contact.