I ride a 2009 trek road bike with disc brakes and once and awhile the rear rotor will rub initially on my ride then after using brakes i'll lose the sound is this a normal thing? While at ubi class i installed new cables and adjusted pads rotor clean etc.
I would take it back to the shop and have them to look at it.Is the disc lose? or it could be the wheel is a little out of true. Hope this helps.
My dad always told me a Sledge a matic can fix any thing.
So when you put it on your stand and spin the wheel does it rub then? If you eye it can you see where its hitting? You might just need to back out the caliper 1/8 of a turn.
Also one thing I've experienced. Once the bike is on the ground, completely loosen the quick release then re-tighten it. I have had a few times where the wheel was not completely in the dropouts when it was put on the bike. The weight of the bike will set the wheel correctly, if that is an issue.
Hopefully one of these things will solve your issue.
Could it be something in the Hydraulics, like a small foreign object tiny pebble etc? I do have a bike which I have not yet got to this winter but soon hopefully that has disc brakes. There is also an article here which may shed a little light but no guarantee...
http://www.parktool.com/repair/readhowto.asp?id=125
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
Awesome, Glad I could help.