this is what happens when you use cheapo brake shoes - you abrade the inside of the drum, create a lip, and end up having to cut the drum off because the lip will no longer fit past the self-adjusting shoes...
this from a honda civic. use of oem honda shoes sees drums lipless after 300k+ miles. this drum has
That sucks, but why cut the drum instead of backing off the shoe adjustment? SOP in the rust belt where that lip is going to form anyway, if not by abrasion of the friction surface then by rust on the unswept area.
nate
Exactly. It's common to simply deploy a spoon to back-off the star wheel while holding the contacting self adjuster plate out of the way with a screwdriver. A similar issue can result with the lip that develops on a rotor and caliper pad situation, but neither is any type of problem for an experienced mechanic.
Nate Nagel wrote in news: snipped-for-privacy@news1.newsguy.com:
Living in the Rust Belt all my life, I can attest to the universal formation of a rust-lip on the unswept area of the drum. It is routine to need to back the shoes off before drum removal is possible.
Once the drum is off, you place the drum on the ground open-end up, and secure it beween your feet. Then you use a small grinder with a bullet- or conical-shaped tip to swipe off the rust ridge. You try and cut it back a bit more than necessary so the ridge has more space to grow before it starts to trap the shoes again.
I'm OCD, last time I had the drums off the Heep I ran them through the electrolytic derusting tank (as I would for diff covers or any other undercar bits removed during maintenance/repair) to get ALL of the nasty scaly rust off of them, and then painted them with some caliper paint. So nice to be able to work on it again without the massive flakes of rust falling off. If I ever replace the drums I will paint the new ones before installation for the same reason. (when I had to replace the rotors, I used the Centric premium rotors with the e-coating, they look very nice, we'll see how they hold up long term, but they've already been on over a year and still look good)
As an aside, I'm assuming there's a reason but I don't know it - why do brake drums seem to develop rust so much more dramatically than any other under-car bits? Is it the metallurgy of the iron used? Or the heat from braking? Or a combination of both?
nate
-----
- gpsman
then you're not an "experienced" mechanic because if you were, you'd know that the civic's star wheel is not accessible unless the drum is already removed. the only concession you get from honda on this is backing off the parking brake*, and using /their/ brake shoes which don't abrade the drum.
go to a junk yard. every civic you'll see with drums removed is missing the retainer pins because they're the first thing that gets broken if you try to pull the drum off with brute force and it's what people need to replace the most frequently.
no, you have asperger's.
it's a tiny little of one, a whole lot of the other. gray iron [that used for brakes] is full of graphite flakes. that sets up localized electrode potentials between the iron and graphite in the presence of water. heat helps, but brakes are hot such a small proportion of a vehicles lifetime, and of course, heat evaporates moisture, that it's mostly irrelevant.
dude, if the lip has grown to the extent you see here, the internal diameter of the drum is already way out of spec. [and that's important because the new shoes you fit are ground on the assumption that the drums are within a certain radius. if you're outside that, your brakes will take too long to wear in and be unsafe for that duration.] you need to measure the internal diameter /before/ going to all that effort next time.
"correct" sop in this instance is to use the correct shoes in the first place then you don't have this problem. that's the whole point of this post. not relevant to those dealing with detroit's output of course, but hey.
I'm a very experienced mechanic, just not encumbered by such low self esteem that I'm only familiar with wasting my time solely on cheap vehicles that don't provide adjustment slots in backing plates and require proprietary brake shoes.
Wait, what? That's complete garbage. I thought Japanese cars were supposed to be well-engineered?
The only drum brakes I've ever touched that didn't have an adjustment slot in the backing plate were VW rear drums, which used a drop-wedge type adjuster and could be released by putting a screwdriver through one of the lug bolt holes. Never have I worked on a vehicle that didn't have a provision for releasing the rear shoe adjustment for drum removal (although a few have required RTFM as the methods used are sometimes non-intuitive; see VW above.)
This has to cause issues in states that have an annual safety inspection... I'd be tempted to drill a strategically placed hole in the backing plate if there is in fact nowhere to release the adjuster.
nate
True only if the lip is due to wear, not to rust buildup.
Back in the day, you could have your new shoes "arc ground" to minimize wearing-in time. Far more important in the days when front drums were the rule not the exception. I wouldn't know how to find a shop these days that still has both the equipment to arc grind shoes and someone on staff who knows how to operate it.
nate
Correction - I forgot about the old Studebaker non-self-energizing drums used on trucks (why?) cars w/ disc front brakes (so as not to require a prop valve) and very old (pre-1955, I think) passenger cars which used an eccentric on each shoe to adjust. But they were still able to be released externally with only a couple hand tools for drum removal when a lip was present.
nate
oem materials are excellent and don't give maintenance problems. it's not entirely unreasonable to design for the materials intended to be used and not for cheapo aftermarket crap.
non-intuitive??? you have to be kidding.
you can't "drill a hole in the backing plate" in this instance because there's no gap between the slave cylinder and the axle stub - and that's /ignoring/ the suspension arm. assuming of course that you can access and hold off the adjuster ratchet from the same hole.
this is not some p.o.s. where there's no camber control.
you could conceivably drill through the front of the drum without collateral damage since the hub underneath has holes in it, but then you'd still need to replace the drum [if you weren't a hack] since it would now be unbalanced and not be weather sealed.
did you not look at the link to the pic i carefully posted for you? [rhetorical]
why the f*ck would you bother when you can not have the problem in the first place by simply not cheaping out on the shoes you use???
I did - *your* situation appears to be due to wear, but a lip that size is perfectly possible - and maybe even likely (I've certainly seen it) - due to rust on a car operated in the rust belt. So simply stating "don't use cheap shoes" does not solve that problem.
You've never had a drum turned? And other vehicles use drums besides Hondas you know.
Clearly once upon a time this was a concern, and arguably "standard" friction linings were better back then than they are today due to asbestos content. Turning drums, relining or exchanging shoes, and then arcing the new friction material to fit was standard practice. I will say that good discs are much easier to make work well than a 50 year old set of drums, no matter how good the drum setup is (I've worked on/driven some cars with 4-wheel drum brakes that result in fairly acceptable performance even by modern standards.)
nate
So what you're saying is that OEM honda shoes cause zero or near zero wear to the drums. Thus softer compounds than the aftermarket shoes in question. However that relative hardness or softness has nothing to do with shoes being cheap or not. The aftermarket shoes could provide improved braking performance at the expense of drum wear while being anything but cheap.
Furthermore, if this were a design from a manufacturer you disliked you'd be ranting about it instead. It's a cost cutting design that just happens to make drums last longer in environments without road salt by reducing braking performance.
Nate Nagel wrote in news: snipped-for-privacy@news3.newsguy.com:
I did a Chev Corsica once where the owner had let the shoes go down to the steel. Way, WAY down to the steel. So far down that the shoes' backings had ground themselves into the drums such that drum removal was impossible.
Was I able to find ANY way into those drums so I could back off the shoes? No. No slot in the rear of the drums, nothing I could see at the front; nothing. No manual, of course, just the car. I ended up grinding off the hold-down-pin heads so I could lever the drum away from the backing plate enough to be able to turn the star-wheel and unhook the drum from the shoes. The rest of the job went smoothly.
Add the sliding adjusters used on the early vegas. Those had two tabs that slid to adjust. In theory they could be released but in reality they were usually so full of rust that they wouldn't push in.
I don't know of any modern drum design that doesn't either have the adjuster slot open OR as a knock out provision in the plate.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.