Cast Iron Drum temperaure too high??

J

James G.

Senior Member
The temperature was in the mid 80s when I took a test drive with new rear cast iron drums installed. Gone for maybe 20 minutes driving around the neighbor hood, stop and go,and then a mile or so down the open road trying a couple of hard quick stops. Returning home I checked the temp and one was at 175F and the other 190F.
Is this normal for this kind of use on a 80F day drive? What would be considered too hot, overheating?
All comments/experiences welcomed.
Thanks,
Jim G.
 
I too went out over the weekend @ 80 degrees +/- ; don't know what kind of drums I have but the temperature of the lug nuts after a 10 mile drive was 85 to 90 degrees on all 4 wheels... I've got a '29 coup...
 
If they are more then hot to touch like burn your fingers, yes too hot. Warm would be ok on a short test drive. Generally heat comes from shoes dragging, parking or service and or lots of use. Try adjusting the brakes and see if that helps. Make sure the parking brake is fully released.
 
That is my thought too. That doesn't sound too hot to me. Check to make sure they are adjusted properly and drive it.
 
I agree with Patrick.

Jack up the front and spin the tires, you should just barely have a little bit of rubbing.

Then do the same with the rear.

Then road test. Slam on the brakes and make sure they stop straight and that you can lock up the tires. Drive around, go home and shoot the drums again.
 
When I first drove my car after installing new cast Iron drums the temperature was high like yours is. After several adjustments and a few miles, the temps came way down. Were your shoes arched to fit the new drums?
 
The temperature of the brake is a function of physics.


Conservation of energy:
Kinetic Energy = Thermal Energy


mv2/2 = Ffd

where m is mass, v is velocity, Ff is the frictional force and d is distance.
Thus Ff = mv2/2d which shows that increasing the mass and or velocity when braking increases the thermal energy (heat) in the brake drum.
 
Jim,
The temp gun is good for knowing which one is working the hardest .... but will at the initial break in be more than when they get settled in. Don't get too stuck on it. See how the skid track is on a good blacktop parking lot hard skid stop and how the front tracks. The wedges should have been adjusted first with brake rods disconnected and then rods adjusted as needed for equal wheel lock up on the rear and applicable lock up on the front left to right. From there test drive and tweak rods as needed. Once dialed/broke in the wedges can be brought up a click or two as needed.

I break them in pretty quick with a little constant pedal pressure at first to get things seated. I do a lot of brake jobs so have it down to a pretty streamlined process.


Once all is functioning and a little broke in your wheel temps should be pretty close.

Larry Shepard
 
Thanks Larry, sounds like too soon to really tell. Both

the rear wheels brake the same (new drums). I'll wait for "seating/brake-in and check the temps again. Coasting at slow speed is really good so shoe drag is hopefully minimum an brake-in shouldn't take long.
Again, thanks.
Jim G.
 
Brake drag is fairly common on the rear when the rear brakes are adjusted with the car on stands . The rear axle bearing races and rollers support the weight of the car . The rear bearing races are part of the rear axle housing and eventually wear on the bottom and will cause drag when the back wheels touch the ground or the shop floor . Wear on the long straight roller bearings and the bearing races in the hubs can also add to the drag that is caused by the weight on the rear bearings . When adjusting the rear brakes the drag caused by worn bearings can't be felt with the car on stands . I adjust the rear brakes with the wheels on the ground or shop floor . By pushing the car back and forth slightly when adjusting will allow a person to feel the drag and avoid tightening the rear brake adjustment too much . The front hubs use tapered bearings and should be adjusted with the front end on stands so that the wheels can be spun to feel the drag . People often have drag on the rear brakes because of the bearing design on the rear . Bearing wear on the rear rollers and hub and race wear causes drag when the weight of the car is put on the rear bearings . Even slight wear on the rear roller bearings and races will cause drag that can't be felt with the car on stands . This is usually the reason that the rear brake adjustment can feel good when the car is on stands but drag when the rear wheels are on the ground .
 
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