In reply to malk:
Spin wheel as it is and note the distance from disc-side chainstay to rim and chainstay to tyre at several points around the rim. Assuming that's even, then the wheel is at least straight.
Now, take wheel out of bike, turn it over and drop it back in the frame* - check the clearances again**.
If it is a bigger gap on the rim, then the wheel is incorrectly dished. It's also possible the tyre is incorrectly seated.
* you'll obviously need to make sure the chain and mech are out of the way and that the cassette doesn't catch the brake caliper - best to take both off, if you have the tools.
** Wheel QR/whatever needs to be tight on both measurements, or it'll skew the results.
Even easier, pop it down to your LBS - they'll drop it in their jig and tell you immediately if it's dished right.
Post edited at 13:36