Brake Drum Removal, Inspection,
first published 2/09/R. Kwas revisions on-going
Preferred and Approved Puller Designs
Preparing for Normal Drum Removal
Removing a Difficult One
Reinstallation of Brake Drum
Guideline for Tightening Drumnut
An Inadequately Tightened Drumnut
Drums(1) do not rust or seize or "freeze up" onto axle shafts
(2) as a rule(!), the Drum hub is
aligned by a taper and actually stretched onto axle as the 1 1/4"
securing nut (4) is torqued (thread is 7/8" x 14TPI) , and this arrangement gives a
tremendous multiplying advantage to the force
applied by the nut, to secure the Drum...as well it should! The unified
assembly of Axle and Drum, are the
driven link between axle and the road, which needs to transfer drive power.
Since no tightening torque spec is given for the castellated nut (as far as I've
ever seen), a wide range of torques and resulting stretch and retention forces can
result, and be encountered at next brake service, because the final position of the nut needs to be tightened until it
aligns with the cotter pin holes, so final torque is dependent on the judgment
and attitude of the guy operating the wrench!
Separating Drums from tapered axle against this substantial unifying force requires the application of an even higher counterforce, and while removal can be one of the most distressing and stressing procedures which must be periodically performed in normal servicing, it doesn't need to be!
Exploded Diagram of the (sometimes) Demon Brake Drum.
Preferred and Approved Puller Designs: Drums are often difficult to remove and high, to sometimes, extreme levels of force are necessary to successfully separate the Drum and axle. With these levels of force required, it stands to reason that it be correctly applied only! Misapplied extreme force will damage or break things, instead of separating the components! Vintage Volvo Brake Job Rule No 1:
To remove Brakedrum, use a Drum puller of the approved designs ONLY!
Not using an approved puller will result in failure to remove drum AND/OR damage to drum and/or lug-studs to the extent that the Drum is rendered into scrap and will need to be replaced...and all this before Drum has even been removed!!!
Picture of the (one of the) preferred and approved puller designs. Dogbone striking wrench takes the abuse,
instead of your most favorite (and expensive) 1/2" drive breaker bar. Yes, it only connects to 3 of the 5 wheel studs, which makes it necessary to double-check and assure concentric alignment, because with only three wings, it is not automatic, but that is typical. 5 wings would naturally be even better, especially when dealing with a difficult Drum requiring maximum force.
Picture of a puller design which will not work (as it simply hooks over the Drum edge, and will NEVER allow the positive transfer of the huge forces required normally, to say nothing of the incredible forces necessary on a difficult Drum!). This type of puller is most definitely not approved, and it will quite likely damage drum or itself.
Do not use or allow other parties working on vehicle, to use this type of puller...EVER!
Horror stories of cracked drums edges (wrong, edge type puller used), bent lug-studs (wrong puller or correct puller, but misaligned!), wasted axle end or threads (nut not put back on to reinforce axle shaft when extreme force was necessary) and having to cut the drum off with cut-off grinders or oxy-acetylene torches, when everything failed, abound! Just for fun, I asked for stories on the Brickboard Link: http://www.brickboard.com/RWD/volvo/1330565/120-130/demon_brake_drum_removalseek_stories_removal.html ...responses ranged from pretty funny to informative.
Significant force is always necessary (even when Anti-Seize (AS) was been applied to tapered axle shaft during last time drum as assembled), high force is sometimes necessary (no AS was applied to shaft at last reassembly), or extreme force and time under high tension load (no AS was applied AND nut was overtorqued by a primate mechanic...maybe even with an air-wrench!).
Picture of a homemade puller also of an approved design puller (nice job!). It uses the same principle of attaching to the lugs, and is even nicer in that it is just about impossible to misalign. Picture used with permission, thanks and credit to Martin "Mcoldie" of the Volvoniacs Forum.
Impact is your friend (aka: Shock and Awe at Work in the Garage!): Many pullers also make use of the advantage which impact brings with it. After mounting the puller and making it a solid, concentrically aligned part of the drum, a threaded center shaft pushes against the axle (straight and concentrically!). This center shaft has a striking wrench intended to receive blows from a hammer and transfer these as huge pulses of torque onto the nut, which translate into mega pulling pulses on drum. Usually this brings the desired separation pop. Alternately, an air-wrench can be used on this to supply an irresistible force necessary, plus impact!.
A result of shock and awe in the garage gone wrong. Ouch!
Time under tension: Sometimes, in extreme cases, or in cases when air-tools are not available, or when after a session of whacking the striking-wrench, it just feels like the striking wrench is totally solid when it is struck such that nothing seems to move, a rest is called for...a rest for the mechanic, and a rest for the joint. Often if left over night, under the continuous substantial tension of the puller, temperature variations are enough to explosively separate the drum with an impressive sounding report, not to be confused with “shots fired”!! The quick release of all of that pent up force has also been known to be able to send the puller/drum assembly across the garage, if nut has not been turned around after loosening, and loosely applied back onto the axle shaft. To avoid damage to other garage inhabitants, human or otherwise, a heavy rag draped over the preloaded assembly when one leaves it for the night is a real good idea anyway!
Preparing for Normal Drum Removal: While corner is still on the ground, and tire contact with ground keeps wheels from spinning, remove hubcap for access. Break the initial hold of lug nuts, so that they can more easily be fully removed once corner is in the air.. Remove cotter-pin and loosen nut (1 1/4”) only. Lift and support corner of vehicle securely, remove wheels and drum securing nut rest of the way, replace nut back on axle, turned around, with castellation first, to reinforce axle shaft end. With gearbox in neutral, Emergency Brake not engaged, and manual adjustor backed of if possible**),. install a puller of the approved designs, and apply irresistible pulling force correctly with it, until it separates from axle.
Removing a Difficult One: In the worst cases, preload puller to the maximum pulling force you dare, and leave over night (after first spraying some penetrating solvent like Croil, Liquid Wrench, PB Blaster WD-40(listed alphabetically) onto the drum-hub and axle joint) ...if drum hasn’t separated on its own (often with an explosive report) by the next day, heating the hub with a torch to add some thermal expansion to the mix will likely get the job done. Draping a rag over the assembly will contain the assembly and dampen some of the mechanical violence when it finally does “let go”...so will putting the castellated nut back on (which is highly recommended anyway as it reinforces the end of the axle shaft from the serious forces which will be applied...compressed threads on axle shaft-ends are not unheard-of!), replacing the nut will also prevent the drum/puller assembly from possibly launching itself across the garage and paying a high-speed visit to the wife’s new car!.
** The manual adjustors adjust the rest position separation spacing of the brake shoes. IF these are free and clear to operate (meaning the reader has either new ones - great - or has previously freed and lubed them well with AS per my recommendations), then they should be backed off to the end when they can’t turn anymore counter clockwise, before attempting drum pulling. It should be noted that adjustors DO NOT influence the force required in initially breaking the axle/drum hub bond, because this force is strictly determined by the hub-stretch, but they do make a big difference in removing the drum once the initial hold has been broken, because the shoes don’t have to clear the wear lip. I do also recommend removal of Wear Lip once everything is apart...and why if someone has seen the advantage to rebuilding the adjustors with anti-seize, but hasn’t also heeded the advice to apply it to the axle taper, or grind away a significant Wear Lip, would be beyond me...
Once the Demon Drum has separated from the Axle: [These are some recommended steps which are in addition to any brake inspection or service which the drum needed to be removed for in the first place.]
Inspecting Drum: Once a drum is removed (and your blood pressure has
returned back to normal) it can be measured to see how much it has worn, and
what its inner diameter (ID) is. If you don’t own a 9 to 10” inside micrometer,
I have designed a handy template which can be printed, applied to a cardboard
backing, cut out, and used to measure the ID effectively. Accuracy to one
thousands of an inch is just not necessary.
PLACEHOLDER: LINK to 9-10” inside Micrometer. Coming...so's Christmas...in the meantime, here is a graphic to give an idea of the measurement. Be careful to not be fooled by the Wear Lip...measure inside of the Wearlip (see below!).
Measuring Drum ID. Don't be fooled by the Wear-Lip! See Below!
Drums with excessively worn IDs should be replaced as they are at risk of failing by cracking (not so good for braking!), and they also require the wheel cylinders and shoes to be separated beyond their designed normal working dimension range.
Friction Area Condition: Some circular grooves are always present. So what! Do not unnecessarily machine drums! Even the most terrible wear-groove is no reason to remove material in the writer's opinion...Note: The metal you machine off today will require you to replace the Drum that much sooner tomorrow!
Wear Lip: I recommend grinding off the wear-lip which is formed because the shoes don’t make contact right out to the Drum edge...this will make disassembly and reassembly easier as shoes don’t need to be compressed for Wear Lip to clear drum edge when replacing Drum...then again, adjustor should be backed off when new shoes have been installed so this shouldn’t be an issue on reassembly. But repeating: This lip has ZERO to do with why a puller is required break the Drum/axle bond!
Condition of Seal Contact Area: Inspect the contact area and if necessary, use a mild abrasive (Scotchbrite pad or similar) to clean away surface rust which will abrade felt seal rapidly. If key has been installed wrong (taper not first or not towards axle) it WILL cause damage in the form of a split with displacement in this seal contacting area, continuing from keyway in hub. This will hurt the seal felt also.
PLACEHOLDER FOR PIC
Reinstallation of Brake Drum: My normal reassembly practice is apply a very light film of graphite containing AS to the tapered axle shaft*, then place drum on shaft (which has previously been turned such that keyslot is at about a 12 o’clock position), then rotate drum with respect to shaft until its keyslot aligns with that of shaft, install key (insert tapered end first and with taper toward axle) by tapping in until it is just below flush with washer and nut bearing surface, then installing washer and spinning on nut until hand tight. Perform these steps with vehicle in gear to prevent axle rotation, snug nut, but do not bring to final torque. Proceed with shoe and Emergency Brake adjustments, and leave final torqueing of axle nut for when wheel is back on and that corner is back on the ground to prevent turning. Some judgment is called for here...since the nut is castellated and a cotter pin should safety the nut, I generally tighten the nut (after it has been first snugged) to the next clear alignment position with a 1/2” drive and 1 1/4” socket (two holes are available in shaft, one at the key-slot, and one 90 degrees to that...which results in manageable angular increments of 30 deg). In the worst case, if it just “feels” like the nut needs to be tightened too much in order to get to an alignment position the washer can be thinned slightly by grinding on a flat plate with emery cloth...but this is typically not necessary!
* How does AS work specific to axle-to-drum hub joint? Using anti-seize on the tapered axle to drum hub interface will still allow the alignment and stretching which assures proper unification of the parts and safe function as designed and intended, but the film, containing the stratified graphite particles which easily shear apart, serves as a release agent which never allows the astronomical coefficient of friction which occurs when it is not present. It is this coefficient of friction which the puller must overcome to release drum.
Guidelines for Tightening Drumnut: Although no Torque is given for the Axle Nut, a guideline is to tighten Nut to 80-100 Ft-Lbs, then continue tightening until an alignment opportunity for the Cotter Pin occurs. Beware, some Axle shafts have a single hole, some two at 90Degs to each other...that gives alignment opportunities in 30Deg increments which works out well.
Tighten the Drumnut Adequately, or else! See: An Inadequately Tightened Drumnut
Comments are welcome!
Additional Brakedrum Notes:
[From the Torque-it-until-it-breaks,-then-back-off-a-half-a-turn Dept.] In response to a post...I disagree that greasing the axle taper causes the hub to split...it's grease in combination with excessive torque on the hubnut imparting irresistible splitting force to the hub which causes breakage! ...I mean what do you expect it to do?...it has no place to go...it MUST split if you keep tightening the nut (reminds me of splitting pipes with freezing water in January...somethin's gotta give!)! With the force multiplying which is taking place due to 1. Nut thread pitch, and 2. Taper (I’ll call it Effective Inclined Plane Angle) - (and presuming a halfway lubed system, so friction is not a huge factor), applying a torque of 100ft/lbs to the hubnut translates into thousands of lbs of force trying to split the hub wide open!...and it will obviously do this at the stress riser presented by the keyway.
My suggested procedure for refitting the brakedrum: Rotate the axle shaft such that the keyslot is at the 12 o'clock position. Apply a light film of anti-seize to a clean axle taper, and place drum (whose matching inner taper has also been cleaned), without key, onto axle. Rotate drum as you seat it on the axle taper watching for out of round effects as it is rotated, and finally stop when keyslots line up. Install key, also prepped with light film of AS, and insert beveled surface first and toward axle. Tap into position until end of key is just under washer surface of drum. Install washer and castellated nut, and torque the hubnut to around 50 ft./lbs. (no torque is specified). Then, continue torquing to the next available securing pin alignment opportunity, and finish by installing securing pin. …and visit a fitness club and punch around some dead weights, or maybe the backyard and split a cord of lumber to expend your excess energy, so you expend a little less on your poor car torquing that nut on like an animal!
I believe from my experience, that there is a significant difference and advantage to be realized in using anti-seize over grease on the taper. Grease, because it is not a solid, gets displaced until the hub and axle are making contact. Add to that, the substantial mechanical advantage that the wheelnut has to tighten the two together until the drum literally stretches over the tapered axle (and not so much as to split it!). At that point any grease has most certainly been displaced and intimate metal to metal contact exists (and this is required to assure concentric alignment of the two!).
The condition resulting when using (the thinnest film of) anti-seize is similar but with an important difference. The grease component certainly also gets displaced, BUT the miniscule particulate graphite cannot...think of that stubborn silver film which gets all over seemingly everything when using it. It therefore remains between the hub and axle at a microscopic scale, still allowing the and given graphite's layered crystalline structure, and these particles are all too happy to be sheared apart, when the puller applies this force, to allow the two parts to separate.
Add to Ser Notes: Impact works to your advantage...use an air-powered ratchet on the drum puller...the repeated impacts are just what is called for to remove a stubborn drum!
I recently ran across this...he uses what appears to be a homemade puller of an approved design, and I actually enjoy listening to the kind of melodic step-by-step explanation in Swedish!
(Time-stamps) Key points to note:
0:53 Adjustor tool options (see also: Manual Adjustor Tool)
1:50 Loosening Adjustor (if possible)
3:00 Preparing for installing Puller
5:44 Replacement of Drumnut (surface flush with Shaftend!)
8:38 Installing Puller
9:12 Application of Steady and Impact pulling force
10:40 Removal of Drum
11:09 Pointing out Trailing and Leading (11:17) Brake shoes (there is a difference!)
Another video for a jeep drum removal is applicable to vintage Volvos also: https://www.youtube.com/watch?v=PQQvFK4B6pY ..it shows all of the important steps (except for replacing the castellated nut loosely), and he has a pretty easy time of it...(I expect he loosened it before they filmed the video).
Link to VOC Thread: Seized brake drum http://www.volvoforums.org.uk/showthread.php?t=256050
An extended discussion about removing an absolutely miserable Drum, with good details presented. Short of "nuking it from orbit ...it's the only way to be sure" [Ripley, Aliens], any non-damaging method will do!
Drums "freezing up" (Excerpt from an e-mail exchange with Brian H.):
...given that I know you like anti-seize, that the above site sells a very high heat ceramic version of Permatex anti-seize. I never see this product in XXXXXX, and have only known about it for a year or so. I thought this would be THE product to use on a rear axle when re assembling a brake drum on a 122. - The drums that annually freeze up.
My response: I must be nit-picky here...Drums do not "freeze up"...this is incorrect terminology used by someone who should know better... Reiterating: Drum hub must be stretched over tapered axle for a positive, bidirectional, concentric, high-power-capable coupling, and this is done through the very high forces generated when tightening Drum Nut...so separating the two requires equally high levels of properly applied force...there is nothing wrong or improper about this...only when the required forces are applied wrong and not according to the well documented procedures and techniques do problems occur!
..."ceramic version of Permatex anti-seize" ...again, I prefer Graphite filled greases for the shear properties because of the structure of the graphite molecule...it works well to make this otherwise stressful procedure a lot simpler and less painful, so I have no reason to want to replace it with another material...but I'd be happy to take a look at a link...
The Other Hand of the Coin...An Inadequately Tightened Drumnut: This is also bad...to say nothing of the Cumulative Cyclic Stress happening at the joint!
Discovering rust when removing a rear Hubcap means Drumnut was not tightened adequately to stretch Drumhub onto Axleshaft!
Source: Swedespeed Forum Link: http://forums.swedespeed.com/showthread.php?123266-I-guess-I-ll-be-posting-in-here-more-often
Drum Removal discussion with some good info, but also some not so good info, and after reading this article, the reader should know which is which! http://barnfinds.com/122-project-update-brake-job-halted/
External material sources are attributed. Otherwise, this article is Copyright © 2001-2017. Ronald Kwas. The term Volvo is used here for reference only. I am not affiliated with Volvo…although I do also Roll….or Permatex/Loktite When did jungles become rainforests? When did Personnel become HR? I have used the procedures presented here in practice many times myself but they are presented strictly as a guide to be used in conjunction with normal, cautious, shop practice...your results may vary...and you are responsible for your own actions and knuckles! It’s a car, not a phone-booth! If you lived here, you’d be home by now, blah, blah, blah…
You are welcome to use this article and its contents for non-commercial purposes. But if you copy and republish it, whole or in part, without giving credit to the author, or linking back to the Sw-Em site as the source, you’re just a lazy, scum sucking plagiarist! Go work for the Washington Post or something!