Strange Rear wheel noise

I have purchased a MTB a month ago and recently I started hearing this strange noise when riding. It comes from the rear wheel and when I apply the brakes slightly the noise stops. It comes on and off with the wheel rotation (as if something is stuck to the wheel somewhere) and sounds like a scratching noise.. The problem is that once I get off the bike, the noise stops. I have got Shimano Deore Hydraulic Disk Brakes (BR-M525). I removed the brake pads, cleaned them and re-aligned them but no to avail. In addition, after riding for an hour or so, the noise becomes really loud, like something is being badly scratched. But yet again it disappears once I get off the bike. Anyone have a clue what this could be. Its driving me crazy and I do not want to be doing further damage somewhere else by riding it further.

 

Is the rotor true?

 

Hello there; When you say that you have re-aligned them; do you mean the pads or the calipers? Like the other message states, it could be a warped rotor rubbing on the pad as the wheel/rotor passes that warped spot. When you spin the wheel on the bike, have a look down at the gap of the caliper(where the rotor goes into) to see if you can see the rotor's warp. If so, carefully locate the spot where the warp is then using a prying tool of choice(softer than your rotor-screwdriver handle/plastic tool?) try and straighten it. Go small and gentle and try many times until it gets true as possible. The other thing you might try is to take the pads out and have a close look on both pads to see if there is any "debris" lodged in the pad material. If so, cafefully pick it out with a safety pin. Don't use any solvents for cleaning the pads. Use emery cloth-type sandpaper on a flat surface. If needed, re-align the calipers with the rear wheel properly in their dropouts with the brake applied. Tighten the bolts gently back and forth between the two mounting bolts until the get tighter and tighter. Try also to see if the seatstay "deflects" when you sit on your bike. Straddle your bike then watch the gap in the caliper/rotor to see if the gap "moves" one way or the other when you sit on your bike. If so, that would indicate that your seatstay is "deflecting" when weight is applied to the seat. Carefully check all welds and tubing for possible damage. Hopefully you won't find anything. The last thing you might try is to take the rear wheel off and spin them holding both axles in your hands and see if you can feel anything in the axle(eg.-grinding, repetition of binding or any large amount of bearing play). Try it again after by holding the rear cassette still with one hand to see if the results are any different. If you don't have any success with that; chances are that it would be brake related. Good luck and let me know of any findings. Regards, John.

 

Do you have a spoke protector on your rear wheel? I had a noise like that on my roadie when I rode. I only heard the noise when I was on the bike. I took off the rear wheel and cut the spoke protector off and the noise was gone. Now my bike is as quiet as it should be. I hope it is that simple for you.

Good Luck,

Brian

 

This might be your answer ,when the shimano pads wear they slip lower in the caliper housing,causing the top of the rotor to rub on those leaf springs holding the pads in place.remove calipers main fixing bolts bolts ,add in two washers ,one each side to lift the assembly slightlly.I use stainless washers. replace bolts realiggn and tighten.
Hope this helps.