Bicycle Mechanics - XT rear derailleur problem

Hi, I have a problem with my brand new rear derailleur. The chain rubbing on the left side of the long cage when I have my gears on the biggest chainring and the 2 biggest cassette cog. My setup is a 7 speed with a XTR crankset, XTR front derailleur and mega 9 XT rear derailleur. I was thinking about putting spacers in the pulley screw to make the cage more wider but if there is a way to fix it without any modification, I be more than happy to try it. Any idea guys?

PS: I was thinking that the problem is my chain. Because the XT derailleur is made for 9 speed, I figure that a 9 speed chain is more narrow than the 7 speed chain. Reason why it is rubbing against the cage.

Thanks

What chain are you running? Although you are crosschaining that shouldn't be a problem. Chain isn't too short is it?

Im running on a 7-8 speed chain. Just edit my first post and added that in. I thought it was that causing the problem but not too sure.

Thanks

Im running on a 7-8 speed chain. Just edit my first post and added that in. I thought it was that causing the problem but not too sure.

Thanks

It shouldn't be a problem because I run a Sram 8 speed chain through my 9 speed XT derailleur as well. Are you sure your chain isn't too short? Derailleur hanger not bent?

I'm pretty sure that its not because the chain is too short. I can see and hear it rub against the cage. When i loosen the pulleys screw 1/4 of a turn, the noise of it rubbing goes down. Only thing is that i dont know if it's safe to loosen the screw. I figure that if i put a spacer it will help. What do you think about putting a spacer in to widen the cage?

Your hanger might be bent. Have you crashed hard lately? You could try pulling it out a bit or buy a new one from the manufacturer.

No, the hanger is not bent, I am 100% sure of that. It is a brand new derailleur and I checked, the alignment of the hanger is straight. I thought it might be the pulley or hanger problem because the faster I peddle, the higher frequency of noise i hear. The noise doesnt really get louder but it click more faster. Now that i checked my bike more, I think Fixer might be right about the chain is too short. The chain gets pretty tight when im at the biggest cog and biggest chainring. Although, when loosen the pulleys screw quarter of a turn , the noise gets lower. I dont think its a good idea to loosen the screw tho but it seem to help my problem. Any idea guys?

Thanks