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Discussion Starter · #1 ·
Recently I've noticed my bike making a repetitive brushing noise whenever I drive past a surface that can bounce sound back at me; Jersey barriers, other cars, etc.

I figured it was the rear brake when I was lubing my chain -- when I spin the rear wheel with it up on a paddock stand, I hear the same noise. I looked at the rear rotor and saw a skipping wear pattern. Here's a picture to show what I mean (see how every few inches there's a shinier spot on the part where the pads touch the rotor -- the same effect happens on the opposite side of the rotor in the same spots):

Tire Auto part Disc brake Automotive tire Wheel

What do you guys think? My bike's a 2015 with about 1800 miles on it. Should just bleed my rear brakes as a workaround, or is this a warped rotor issue that could cause me headaches in the future?
 

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Take what I say here with a grain of salt as brakes on a bike or certainly not my forte; I'd determine what the ultimate cause for that is, fix it then see if the rotor could be turned on a lathe to even out the high spots. I'm not even sure if you can turn a motorcycle rotor though. I will say I here the same rubbing when turning the wheel on a rear stand, but my rotor is evenly worn.

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I've had good luck at simply wet-sanding the rotor with it on the bike. Use 400 wet paper, do small circular strokes, and do both sides as the bike is on the stand. Use a damp cloth to clean the rotor off as you slowly turn during sanding. This will help with your pads breaking in. Always worked for me. Turning rotors removes too much material, and not even sure you can do motorcycle rotors anyway.

Also, I see dirt and corrosion on your bike...is the caliper still capable of free-floating, and does the rear brake release ok after pushing on the control?
 

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Discussion Starter · #4 ·
Thanks for the feedback guys.

The caliper does not free-float -- it makes that same rubbing noise when there's no brake pressure being applied, and now that I take a second look at that picture, yeah, the wheels and swingarm are looking a bit dirty/corroded. Seems like a good excuse to go out and give her some pampering after she got rained on last week. I've read on other forums that having a little bit of contact on the rear brake isn't necessarily a bad thing, although the service manual says there shouldn't be any (page 3-13). Maybe worth bleeding the rear brake? And then wet sanding if it's still making contact?
 

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The caliper does not free-float -- it makes that same rubbing noise when there's no brake pressure being applied
First of all, I have found that calipers always have a slight drag when the brakes are not being applied. Every bike I've had, every car, every truck, etc. Not much drag, but if you're going by sound, you will always hear drag. And it will never be pure or constant throughout the turn or rotation of the wheel. That's normal

Second, since I don't have an FZ09 yet, does your rear caliper have pistons on both sides...right and left, or only one? If only one, then the caliper much free float, which means it moves left and right on slider pins. That way both pads (right and left side) can squeeze the rotor. If it has dual sided pistons, then both pads move with brake pressure and the caliper stays put. You really may not have any issue...I would cleanly wet sand the rotor, remove all the scuffs on the rotor and let it start over. Make sure you use a circular pattern while sanding...no back and forth...circular only. Also, examine the caliper and determine how it should work, and thus ensure proper movement of either both pads or the caliper.
 

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Pull your pads and take a look at them before you do anything.
 
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Something caused uneven wear on your pads. I would sand rotor as describer earlier, remove the pads, and clean up the piston with brake cleaner, then replace the pads at the very least. Personally I would remove the piston with my compressor and a shop towel, complete dis-assembly required. Check for spots on the piston, replace the seal, reassemble, reconnect the banjo bolt, and bleed the line.
 

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Something caused uneven wear on your pads. I would sand rotor as describer earlier, remove the pads, and clean up the piston with brake cleaner, then replace the pads at the very least. Personally I would remove the piston with my compressor and a shop towel, complete dis-assembly required. Check for spots on the piston, replace the seal, reassemble, reconnect the banjo bolt, and bleed the line.
That is a bit of overkill BUT, there is nothing wrong with being extra cautious since we are talking about a primary safety system: brakes.

To the OP, one other thing I suggest is to look at your riding position. I was teaching a class this weekend. One student has been riding 4-5 years on a couple of different bikes. I noticed his brake light was on a lot. So I checked his feet: he was resting his toes of his right foot on the rear brake lever and just riding around my range (220' X 120') at 15 mph had the rear rotor very hot.

Maybe you are inadvertently riding around pushing on the rear brake.

The spots you see are hotshots where the brake rotor has gotten too hot. Used to see this a lot back in the 80s when the stock stainless brake rotors would over heat on a lot of bikes.

The solution is to pull your foot back so the balls of your feet are on the pegs so that your right toes are not resting on the rear brake lever and your left toes are no resting on or under the shifter.

You shift your foot forward to operate the shifter/brake and then shift back when not operating the shifter/brake. This prevents inadvertent shifting or braking that might happen when you hit a bump or something like that.


Putting the balls of your feet on the pegs also give you more control and connects you to the bike better.
 
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It is not overkill if you live in Massachusetts and corrosion is invading the piston. Take a good look at his picture. A locked up piston will cause a crash. I won't buy northern cars and sell them in the south because of the extensive corrosion on the brake calipers and everything underneath.
 

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Discussion Starter · #12 ·
I took my rear brake caliper assembly off and sprayed brake cleaner on the pads and around the caliper. The brake pads had some weird pitting on the top edge, but other than that I feel like nothing looked particularly corroded or dirty. I put some sil-glyde brake lubricant on the retaining pin (not sure what it's called) as well as on the two main bolts before putting it all back together. After putting it all back together (same pads), I could still hear rubbing when spinning the wheel on the stand, and can still hear some noise coming from the bike when I pass a wall/barrier. It sounds different though, so I think I must have had some effect. Maybe the rubbing is normal?

Screw Geology Soil Auto part Wheel Vehicle Hand Table Auto part Brake Auto part Brake

EDIT: Sorry for the bizarre photo orientation, not sure how to fix.
 

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brake pads will drag a bit, so hearing a swishing sound when spinning the wheel on a stand is normal. can you take a video with clear sound? it won't be loud enough to hear when you're riding through a tunnel though - you're probably hearing something else.

if braking isn't affected, i wouldn't sweat it too much.
 
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