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Old 12-24-2017, 01:07 AM   #1
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Default Drum Brake Adjustment

I just installed new wheel cylinders in my new-to-me trailer. It's a single axle with surge brake system built in 2005. Brake cylinders were frozen solid with heavy layer of gunk.
Installation of new cylinders went fine. Got them installed and believe I have bled all of the air out of the brake system.
When testing the new cylinders, they extend the plunger about one quarter to one half inch when the tongue actuator is fully depressed. My question; is this amount of travel normal? I don't know what "right" looks like. I was expecting the plunger to extend more.
Also, after fully depressing the tongue actuator and releasing it, the actuator only rebounds about half way. It looks like the actuator has about an inch and a half of full travel, but only rebounds about three quarter inch when I release pressure. I have pumped the brakes and they get firmer, but still slight plunger movement and short actuator rebound.
Your suggestions are questions are welcome. thank you, Randy
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Old 12-24-2017, 04:34 AM   #2
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Drum breaks on autos have a star wheel adjuster at the bottom that you turn out so that the drum just fits over the break shoes. They auto adjust when backing and breaking as the break linings wear.

The cylinder will retract just enough to remove pressure of the shoes this way there is minimal travel when engaged again.
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Old 12-24-2017, 01:01 PM   #3
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Thanks for the reply. I have a star wheel adjuster, and the uni-servo wheel cylinders. I don't think this type adjusts automatically when you back up, but I'm not sure (at least nothing in the manual about this). I plan to lengthen the star wheel rod until I get a slight amount of brake shoe rub.
Do you think I should troubleshoot the tongue actuator to see why it doesn't fully rebound? I wasn't sure if this was normal, or the sign of a bad spring.
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Old 12-24-2017, 02:10 PM   #4
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While I have owned a surge brake trailer I never had to work on the actuator. Are you manually activating it or using your tow truck? If the latter and itís not fully retracting then I would think there is an issue.
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Old 12-24-2017, 09:54 PM   #5
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Trailer brakes are different than cars. They do not auto adjust as the brakes are not applied when you back up and come to a stop.
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Old 12-25-2017, 04:42 PM   #6
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Thanks for the clarification Phillbo, that makes sense. Manual for the brakes only talks about adjusting with the star wheel.
Mike, I've been manually depressing the actuator using a board as a lever. I can pull the actuator all the way out to full travel by hand. I was assuming the actuator should extend fully when unloaded. I thought the brake shock might be bad.
Unless I get any new suggestions, I'm going to put the drums back on, adjust the brakes with the star wheel, then call the job complete.
Thank you for your inputs.
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Old 12-25-2017, 04:51 PM   #7
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Letís us know the results.
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Old 12-25-2017, 09:12 PM   #8
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I've never had a trailer where the actuator extended completely on it's own. I always feel a little clunk as I start off after coming to a stop. It's typical.
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