Brake drums

[old-tank]

I am replacing the brake shoes on my 55 Century and had the drums checked for turning. Seems that they are all 0.090 to 0.130 oversize now. The 55 service manual says that 0.060 oversize is the maximum allowable. The brake shop owner (in his 70's) says that the old drums could be turned up to 0.090 oversize. The car was stopping well before and even locked the wheels in a panic stop on my last road trip. I guess ignorance is bliss because now I am worried. Kanter has new drums at $135 a pop, but not including the hub for the front ones.

Does anyone have any info or opinions on over size drums and has anyone replaced the drum on a front hub?

Willie

[RocketDude]

.060 is the max allowed. However, when the machine shop I worked for got a drum over .060, we would turn it as far as the customer wanted it turned. we would simply write on the reciept, that it was over .060, and the customer was told it was oversized, and should be replaced. That took away our libility, and saved the poor customer from an expense he couldn't afford.

If it is an every day driver, I wouldn't reccomend going very much oversize. If your car is driven like mine, a couple of thousand miles a year, at most, it will never get the brakes hot enough to ever have a problem.

Turning it oversized means there is less metal to dissapate heat. How much heat can you generate going 20 MPH in a parade? If you have a car driven in parades, and not for daily driving, it shouldn't cause a problem. If you want perfect brakes, convert it to disc brakes..!!! However, drum brakes worked very well for many years, before disc brakes were invented....

As far as replacing a front drum, you have to press out the studs, replace the drum, press in the new studs, and swedge over the studs to hold the drums on the hub. Then it needs to be turned to make it round again.

[old-tank]

RocketDude

Thanks for your input. This is a Buick and there are no studs, the wheel is attached to the drum/hub by bolts. The drum is attached to the hub by rivets, one of which is a locating pin for the wheel. I can grind and/or drill out the rivets, but I wonder what to replace them with.

Willie

[KAD36]

Hey Willie - been awhile - hows things?

Brake drums - well, I'm a bit embarassed to say mine are .120 oversize in the front and .045 in the rear - in fact I just checked my record book in the car to be sure. Not ever having owned a car with "good" drum brakes, I'm not sure what to expect for "good" performance. I can tell you that on most typical to hard everyday stops they work just fine. At a typcial 30 - 45 mph and stand on the brakes for an around town panic stop because someone pops their car door open in front of you - yep I can lock them up and stand the car on its nose and avoid hitting something. The only time things get a bit sporty is at highway speeds of 65-70 mph or on long downhill runs if I have to really stop fast - forget it. Might as well floor it and try to go through it than try to stop. They heat up fast and fade away. But then again, I wouldn't know what to expect if they were up to par. I just know when I drive the car to be extra anticipatory and alert, don't ride the brakes. They've always been like that for 20 yrs so I suppose I'm used to it. If I were to start doing more X/C driving - I'd probably fix it.

I saw those new drums Kanter had - never thought you'd have to put the hub on them though. If you decide to go that route let us know what happens.

Hey - how did that 56 dynaflow ever work out? Who got the closest measurements?

Take it easy

[RocketDude]

You're really taxing my memory now, going back 40 years to installing new drums on mid '50's cars.

I remember the ones with rivets, and no studs. Plymouths used the bolt method, too, rather than studs!

You drill out the rivets, and don't worry about replacing them. mount the new drums on the hubs, and bolt the drums to the hub to hold them in place to turn them. the rivets were only to make manufacturing easier. Once on the car, the rivets serve no purpose. It would be a good idea to index the drum and hub, so they go on in the same location they were in on the lathe.

But, as I said earlier, and confirmed by the other posting, you can get away with an oversized drum. You would have to drive the car pretty hard to get it hot enough to have a problem. When ever driving an older car like these, I would hope everyone is driving extra defensively, anyway. No reason to be in a hurry, when you're out tooling in the toy..!

Unless your drums are really super bad, save the money to buy gas for it!!

[NTX5467]

Other than the "thinness" issue, as mentioned, the other issue is how much of the brake lining is actually contacting the drum itself. There is a certain "design diameter" to the brake linings themselves, just as there would be for the drums internal diameter. It would seem that as the drum's internal diameter enlarged, less and less of the brake lining material would contact it (little circle fitting against the inside of a larger circle) unless the shoes were arc ground to match the drum's internal diameter. Seems like some of the prior "name brand" brake linings used to say they were "oversized" (to compensate for the turning of the drum to a larger diameter of the drum, as necessary to get a smooth contact surface . . . and then matching the arc of the shoes to that internal drum diameter, while still having good lining amounts left)?

I understand that taking the customer's real-world use of the vehicle into consideration in whether or not you "replace" or "turn" a brake drum to an unrecommended oversize can be a good thing to do (the classic elderly owner that never drives over 30mph comes to mind, driving very carefully too), BUT considering that Willie "drives" his cars, it might be a different judgment call--with all due respect.

The way I look at it, brake drums and such are less expensive than bent sheet metal and bruises (and the fixing and healing of such!), in the grand scheme of things. I suspect, that at this point in time, any non-NOS brake drums will pretty much come from the same one or two factories, so shopping around for the best price and availability and such might be recommended. Considering suspected federal standards on brake drums/rotors "quality", I'd rather have a set "in size specs" from "anywhere" than have some which might be of questionable sizing and related stopping power. That's just the way I look at it.

Willie . . . your car, your money, your insurace, your judgment call.

Enjoy!

NTX5467

[RocketDude]

Good point on the fact that expensive brake drums are cheaper that replacing fenders, and getting a new family. I guess it all comes down to the person driving the car. he has to decide how it will be used, and how much money he wants to spend. At this point in time, we have all spent ten times what we originally planned to spend, so what's a few hundred more?

As far as how the shoe contacts the drum as the size increases, in the old days, you measured the drums, then used an arching machine to match the shoe exactly to the drum. I spent many years arching shoes, sucking in a snoot full of asbestos dust, before some genius came along and said that isn't a safe practice, and the arc machine was put out to pasture. After that, the shoe manfactures came out with "pre-arced" shoes. Pre arced probably meant they cut them to a happy medium.

[NTX5467]

And we found out, too, that you could take an air hose and blow out the drums (blowing air around the gap between the drum and backing plate) to clean the residual accumulation of brake lining dust and other "things" out. Doing just one drum, for the first time, would typically "dust" a whole shop up, putting "tasty" things in your mouth and nose as you inhaled (sans respirator!). But those brakes sure did stop better after that was done! I later did the same things with a water hose in the driveway . . . letting things settle out in the sewer system--worked just as good, provided you let things dry out first, but without the atmospheric additions that you tasted/smelled for days (it seemed). Now, the proper way is to take the drum off, position a plastic bag-lined pan under the exposed brake linings, then use a non-chlorinated brake clean to spray things down with, and finally dispose of the plastic bag and contents in a "approved manner"--wearing safety goggles should any stray sprays ricochet around. Sometimes, you might suspect (before you "knew better") you were doing things "wrong", but things sure did work great when you were through.

Enjoy!

NTX5467

[Guest DaveCorbin]

Dear Willie:

There's a shop in Dallas that has one of those old fashioned machines that matches the diameter of a turned drum and new brake shoes. Let me know if you need help.

Regards, Dave Corbin

[GMPARTSMAN]

NTX5467, you probably remember the "old" parts books listed a oversize brake lining for some applications. Pontiac comes to mind, I can't recall ever seeing one listed for a Chevrolet though.

In all the dealerships I worked at, I don't remember any that had the oversize linings in stock.

Anyway, on my personal vehicles, I would rather replace than use a drum (or rotor) that is machined in excess of the discard figure. I'm not a expert on braking systems, but I am concerned about heat dissipation, fading, and glazing of brake material. A couple of months ago, I replaced the front rotors on my wife's Aztek as the inner rotor surface was spalling, heat cracked and the pads were glazed over. And no sign that the calipers were binding or frozen pistons. This at 31,000 miles. I didn't have confidence in those rotors to reuse them even after machining. I personally do not take any chances with a safety item like brakes or suspension systems, if it's marginal or unknown, it gets tossed.

[old-tank]

Update: I finally got off my dead a** and braved 100* heat, wasps, scorpions and spiders and pulled 4 front wheels from 2 parts cars with wheels, drums/hubs as a unit (the brake shoes as usual were glued to the drums and leaving the wheel on gives me something to attach a chain to so I can pull it off with my truck). Anyhow after measuring I found one to be right on 12" (no oversize) and one at 0.060" oversize. That was good news until I detached the wheels and found that the one that was 12" was an aftermarket replacement drum that weighed only a fraction of the stock drums and had considerably less "meat". Bummer...I would try these lightweight drums if I had a pair. So now I will call Kanter tomorrow and see if they can provide a picture and weight of their drums. Right now I would rather go with up to 0.090" oversize stock drums than some lightweight units.

Willie

[old-tank]

Kanter will not provide a picture or weight of the drums. Now I have to add another name to the list of people who [censored] me off...

Anyhow it is back together, just used the best of what I had on hand: rears are 0.090 oversize and fronts are 0.060 oversize.

Willie

[RocketDude]

My personal, very experienced, opinion.... Mine, and mine alone...

That car is going to outlast you, with narry a problem with the brakes, as long as the rest of the brake system is 100%