Hot brake expansion action...

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#1 Post by **yoda731** » Tue May 23, 2006 4:07 pm

I adjusted the play on the brake pedal a few weeks ago. On the CX500, this is easily done with a thumbscrew to the left of the back wheel, which is at the end of a spring-loaded rod that goes to the pedal. I turned it in slightly, to get the pedal into the factory recommended free-play range. I did the adjustment with the bike "cold," not thinking it could make a difference.

Come to learn...

Once the brake drum (rear drum brakes) heats up, its heating up the nut-spring-rod assembly enough to apparently cause some expansion, enough that when the newly tightened brake assembly heated up, the combination of the pieces heating actually was applying the brakes constantly (be it ever so slightly). I pulled in my garage last night, and realized that the bike was "braking" to a stop in neutral without me applying the brake! Parked the bike, put it on the center-stand, tried to spin the back wheel with my hand and it barely budged. Tried to back off the thumbscrew, and it wouldn't budge (and it was HOT). So, I grabbed the right size open-end wrench and backed off the thumbscrew just enough to let the wheel spin, even with the brake hot.

Took her out tonight, kept stopping every 20 minutes for the first hour and checking the rear brake play. Seems fine now. And it rode so much better. I had been feeling that slight pull on the back end without being able to tell what it was.

So, after low-siding and feeling paranoid that something wasn't right...turns out that something wasn't right.

OK. Its safe to laught at me now.

I am making some silly mistakes, but damn I've having a good time!

And I just hit 700 miles on the bike as of tonight...

Peace, thanks as always,
JC

TechTMW · #2 Post by **TechTMW** » Tue May 23, 2006 6:05 pm

Good thing you noticed that ... single-action drum brakes can self-actuate if they get hot and expand (Locking up on their own when you are cruising)

#3 Post by **yoda731** » Wed May 24, 2006 3:11 am

TechTMW wrote:Good thing you noticed that ... single-action drum brakes can self-actuate if they get hot and expand (Locking up on their own when you are cruising)

Yes, I think it was contributing to some drag I had been feeling on the back end for a few of my rides. It felt like the back wheel was vibrating slightly at speed, which (as you can imagine) was unpleasant.

Lesson learned. I'll periodically check that after a ride, to make sure she is all free and clear back there.