Wheel spacing?

Do you mean that the hub has a gap on one side when you put it in?

If so, there are a few different hub spacings in use. 135mm (MTB) and 130mm (road) are the more common. You need to make sure you have the right one for the application.

Or does the rim and tyre sit off centre when the hub is tight within the dropouts?

If so then check your chainstays are actually the same left and right (they can have different sections). If it is definitely off centre then either the wheel is out of dish or the frame is out of dish or both. Get someone at the shop to check the wheel.

Wheels and even frames can sometimes be out of alignment. Dishing the wheel to the frame is the best option.

Deathcycle said:

I just replaced my rear wheel with a new one and now that I've already thrown the old one away(trust me it was trashed)I notice that it sits closer to one chainstay than the other.Is that normal?

No, it is not normal for the wheel to be off-centered ...

Does your frame have vertical or horizontal dropouts?

Presuming that you have seated the wheel properly in the dropouts, then ...
[INDENT]Take the wheel out of the frame ...

remove the cassette, for a moment,

and mount the wheel in backwards with the freehub side of the wheel on the non-driveside of the frame & see if the wheel has shifted to being closer to the other stay.

If so, then the wheel needs to be redished.
[/INDENT]If not, then you probably didn't seat the wheel properly the first time OR your frame was bent at some point in time & your old wheel was dished to seat "properly" in the frame.

Thanks guys! I redished the wheel and fixed the problem.

Deathcycle said:

Thanks guys! I redished the wheel and fixed the problem.

What's pitiful is that it's a new wheel(brand new?) and needed to be dished.