Author Topic: Testing brake caliper function  (Read 157 times)

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Offline Odin

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Testing brake caliper function
« on: January 12, 2018, 02:49:40 PM »
I noticed that the rear disc on my Eglide (with ABS) was very hot to the touch on my last ride of the season, much hotter than I thought it should be. When I was doing the winter-once-over recently I found that the outer edge of the rear brake rotor and part of the disc face had turned an amber or gold color. Both pads seem to be evenly worn with about 1.5 millimeters or .006" thickness left. I suspect the gold color is due to excessive heat. The only heavy braking came with a panic stop earlier in the year that resulted in a minor (low damage) rear-end collision last summer.

So I have a couple of questions. What would cause the excessive heat? Pads dragging on the rotor would seem to be one reason. What would cause the pads to drag? I realize that there is some rotor pad contact in normal circumstances.

How could I test for stuck pistons in the caliper. Would a slight push on the brake pedal work to see if they move. This makes me a bit nervous since I don't want to push the pistons out of the caliper. I'm a bit out of my depth here and would be grateful for any help.



Offline Panzer

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Re: Testing brake caliper function
« Reply #1 on: January 12, 2018, 04:24:46 PM »
You didn't say if the brakes are apart or still assembled.
Assuming that the bike hasn't been pulled apart, I'd jack up the rear and spin the wheel in forward rotation and see if you have excessive drag.
If so, gently pry the pads into the calipers with a screwdriver.
If free-er doing that, hit the brake pedal and repeat spinning the wheel.......more drag, or slightly bound up?
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Offline bensfatboy

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Re: Testing brake caliper function
« Reply #2 on: January 12, 2018, 05:42:29 PM »
Had the same problem on rear of 2012 Fatboy after changing out the brake pads and bleeding the brakes.  Bad drag on the rear brake rotor making it hotter than hell.  Ended up replacing the seals in the caliper along with the pistons and problem was solved.

Offline Odin

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Re: Testing brake caliper function
« Reply #3 on: January 12, 2018, 07:40:51 PM »
"You didn't say if the brakes are apart or still assembled."

I had to remove the rear wheel for some work last week. The caliper is still connected to the brake line but is isolated from the rotor.
I should also have mentioned that I also had the dealer replace the brake fluid last fall before I noticed the hot rotor.
« Last Edit: January 12, 2018, 07:47:27 PM by Odin »

Offline HARRLY

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Re: Testing brake caliper function
« Reply #4 on: January 13, 2018, 03:48:30 AM »
Also check the spec on the rotor. When they get thinner, they have trouble dissipating the heat.