Did I fry my hubs?

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jcwren

jcwren

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I'm rebuilding the drum brakes on my '71 Dart. Hubs don't seem to be available, so I pressed the studs out of the old drums, cleaned up the hubs, and painted them with a high temperature paint. Curing it requires 250F for 30 minutes, cool down, 400F for 30 minutes, cool down, then 600F for 30 minutes.

I have a shop oven I did this in, and the unpainted surfaces now have a slight blue tint consistent with steel being heated to 600F. I figured curing them at those temperature should be OK considering how hot brakes can get.

But now I'm not sure if I may have damaged the hubs or not from a metallurgical standpoint. Opinions?

Thanks,
--jc
 
My rubbing rear drum was getting to 250 degrees. Normal, after fixed, is around 125. The new drums I had before this warped from the rubbing heat. The parking brake cable caused the drag.
 
Can't get them hot enough in a home oven to hurt them.
Install new races and bearings.
Now if you just re install drums with out new studs and having them pressed back into the hub as per the factory service manual, you will probably have vibrations. Great excuse to do a factory disc brake upgrade now.
 
MoparLeo said:
Can't get them hot enough in a home oven to hurt them.
Install new races and bearings.
Now if you just re install drums with out new studs and having them pressed back into the hub as per the factory service manual, you will probably have vibrations. Great excuse to do a factory disc brake upgrade now.
Click to expand...

I'm using new studs, but I can't swedge them (or swage, take your pick. That's a controversial topic). I think I'm going to countersink a hole in the drums and drill and tap a hole in the hub in two places, and use 1/4-20 100 degree angle head screws, like you see on a lot of disc brake rotors. I'm thinking these didn't have original studs as they're all RH threads, and they look like they had a very small tack weld instead of the swedge I've seen pictures of.

Disc brake upgrade is out for the moment. I need to get this thing rolling around again so I can work on it, and I've already got $300 invested in new drums, shoes, bearings, brake cylinders and hoses, and hardware kits for all four wheels.
 
Just beware of not swaging them back on. Many will tell you "I never had a problem." The factory didn't do things for no reason. It was the way things were done 50 years ago.I stared out in automotive repair in the early 70's when every thing had drum brakes. Retired in 2007 as a store manager for one of the world's largest tire/automotive companies. Many thousands of brake services in my stores and personally in that time. Seen a lot of changes in cars and tires in that period of time.
Modern brake systems, machining and designs have moved on but you are not do a modern brake service. Modern drums and rotors are centric to the center register of the hub/axle. The extra hole in modern rotors is threaded for 2 reasons. # 1 was to hold the rotor to he hub/axle during factory assembly before the calipers are installed.
#2 they are used to help remove rotors that have gotten corroded/ rusty and are a way to press the rotor back off.
The factory used to use a spring clip over 1 stud on the rear drums to keep the drums from falling off during the factory assembly when it would be flipped over before the wheels were installed. They served no purpose after the car was assembled and the wheels were installed. Strictly for factory assembly reasons.
Use your service manual. Use a torque wrench. 55lbs with 7/16" studs. 65 lbs.1/2" studs.Service Manuals – MyMopar
 
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Found this.

Screenshot_20211218-161804.png


I think your hubs are ok.

I would not wory about swedging drums on to the hubs. All drum brakes I have worked on were not swedged or tacked on (tack weld I would not do as that does change metelergy locally and could start a stress point.)
 
MoparLeo said:
Just beware of not swaging them back on. Many will tell you "I never had a problem." The factory didn't do things for no reason. It was the way things were done 50 years ago.I stared out in automotive repair in the early 70's when every thing had drum brakes. Retired in 2007 as a store manager for one of the world's largest tire/automotive companies. Many thousands of brake services in my stores and personally in that time. Seen a lot of changes in cars and tires in that period of time.
Modern brake systems, machining and designs have moved on but you are not do a modern brake service. Modern drums and rotors are centric to the center register of the hub/axle. The extra hole in modern rotors is threaded for 2 reasons. # 1 was to hold the rotor to he hub/axle during factory assembly before the calipers are installed.
#2 they are used to help remove rotors that have gotten corroded/ rusty and are a way to press the rotor back off.
The factory used to use a spring clip over 1 stud on the rear drums to keep the drums from falling off during the factory assembly when it would be flipped over before the wheels were installed. They served no purpose after the car was assembled and the wheels were installed. Strictly for factory assembly reasons.
Use your service manual. Use a torque wrench. 65lbs with 7/16" studs.
Service Manuals – MyMopar
Click to expand...

I'm a big believer in torque wrenches. The whole "ugga dugga" thing really annoys the hell out of me. As does not being able to find torque specs for bolts.

I agree with you about the factory didn't do things for no reason, but I think I'll be OK without swedging them. The knurling on the studs that were originally in there didn't touch the holes in the drum. The knurling on the replacement studs (Dorman 610-096) actually sticks out past the drum by about 1/8" or so, and they wouldn't just drop in to the new drums. I believe the drum hole is undersized enough that the knurling is solidly engaging, and with the 5 studs, the drum will be stable. If I feel any vibration in braking, that'll be one of the first things I check. The screw won't work anyway, the drums are too thin for that.

I spent about 2 hours on the phone trying to find a machine shop that could de-swedge (before I found out I could just press them out) and re-swedge, and none of the 12 shops I talked to still had the tools to do it. Most of them didn't even want to mess with knocking out and pressing in the new races, citing costs. Nothing in recent memory uses a hub on the drum (as opposed to drum on hub), and most of the time it's cheaper to just buy a new drum rather than resurfacing it. And the one machine shop I thought I could count on just got bought by NAPA, and was shutting them down.
 
Dana67Dart said:
Found this.

View attachment 1715838882

I think your hubs are ok.

I would not wory about swedging drums on to the hubs. All drum brakes I have worked on were not swedged or tacked on (tack weld I would not do as that does change metelergy locally and could start a stress point.)
Click to expand...

I know the drums are cast iron, but are the hubs? Good point on the tack welding. I'll skip that.
 
Nothing controversial about it. I can tell you this. If you didn't cut the swedges off the old studs, you likely ruined the hub. But you didn't ruin it in the oven.
 
Most High temp paint says 1200 degrees. Put them back in the oven until they turn bright red then repaint them.

My wife cooks the same way. You know to head for the kitchen table when the smoke alarm goes off.
 
I’ve installed wheel studs in street cars and race cars using nothing more than a BFH and never had an issue. We removed the wheels from the race car after every race so over one hundred times over the course of 3 years without an issue. That’s almost a one hundred times more than a normal street car. The key is to get the correct stud and make sure that the splines are lined up.
 
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