Front brake noise

This is strange. I got my 750 Seca last fall and went through the whole bike... biggest problem was both front calipers were froze. I rebuilt them and changed both pistons... problem solved for the most part. A couple days ago was out riding with a friend and heard a weird evenly spaced pulsating scratching noise coming from the front. Stopped, put it up on the stand, spun the wheel and was able to isolate the source of the noise. There was a tiny dimple on the rotor, almost like a BB, and as it passed through the pucks it made this scratchy noise, and it was making a little metal. I pulled the caliper and everything seemed normal, not even a scratch line on the pad that was making the noise. I've put a few hundred miles on the bike since I rebuilt the calipers last fall with no problems. This just started happening over a time period of about a second... worked fine, then scratchy noise. I took my dremel and ground the little BB off the rotor and no more noise. The wheel does drag a little when I spin it though... not sure how much of that is normal with relatively new brakes. But WTF? How does a tiny dimple/BB suddenly appear on your rotor and start scratching the pad? And how much brake drag is acceptable on the front wheel? If I spin the wheel as hard as I can it might go around one time. Thanks for any input. Beautiful day today in Chicago. Hope you all enjoy it.

 

lube up the pins on the caliper with brake grease to make sure they move free.
drag will cause heat bad for fluid and seals.
did you rebuild the master cylinder? there is a tiny hole in there that lets fluid come back into mc
are your pads still in square? if not the pistons may bind some.
you could do a run out test on the disc to see if it is warped

Removed the hoey

I also think releasing the lever pulls back a small amount of brake fluid helping release the pads

 

A tiny dimple is weird, but if your brakes are dragging they're going to heat the rotor beyond what's it's able to deal with. This, because the dragging will keep the temperature up when you're not braking. Overtemp, you can get warping of the rotor. I suspect what happened is there was a impurity in the rotor steel there, closer to one side than the other, and excessive temps caused it to expand differently and push out. This is just a guess though.

They shouldn't drag that much. I'd suspect the MC needing some quality rebuilding with particular attention to the teensie tiny return hole inside.

My front will rotate 2-3 times on a gentle spin.

Question: After a ride, are both rotors the same temperature? Or is one noticably hotter than the other?



Edit: have you checked rotor runout? It's certainly likely that one (or both) are warped, and that would cause the extra drag as well.

 

Ummm....on my bikes, the pads squeeze tighter and tighter because I'm squeezing the lever tighter and tighter. That's' how hydraulic brakes work. When I release the pressure on the lever, the pressure releases from the caliper. You're not gonna gain or lose heat that fast.

 

Dimple on the rotor........I'd suspect one of two things....

1. Either a rock kicked up
2. It actually is a ding from a BB.....some punk kid probably thought he was being funny

 

yeah I thought that the heat/cooling was hoey when this person told me that he got pissed. at my comment