Yup. The tilt of landing gear bogies usually has alot to do with how it fits in the wheel well.
And A321 is much lighter than the B757, thus it only needs two wheels on its mains instead of four. As a general rule, the more wheels you have, the heavier a plane is. Weight limits at airports are per tire. So if you are very heavy, all you need do is put on lots of wheels so as to distribute the weight over a larger area, thus reducing the weight at any given point. This is the same principle as laying on a bed of nails. If you lay on one nail, it impales you. However, the more nails you lay on, the less pressure each individual nail applies on you skin, eventually reaching the point where they won't even puncture the skin.
Get it? Good.