You said, wheel. Do you mean chuck or face plate, or pulley and/or collets? And I am not sure what you mean by outside. On the side of the headstock where you fasten the material to be turned, or on the other end?
If it is a pully, then it is probably loose. Depending on the age of the lathe and how much it has been used, the bearings could be worn out. Or bushings, if it has those.
Also, do you turn between centers? Do you put a lot of pressure on the turning tool when you work? If you do, you might want to check the wobble of the chuck, collet, faceplate or whatever you use. If there is no wobble, then you have at least eliminated that part.
None of these suggestions might be the cause, but it is a place to start.
Hope this helps.
Bonefish