I've noticed that the new part that I got from Auto Ricambi looks quite different from the old one. Here's a comparison picture:

Aside from the fact that the old bearing is missing the rubber and the balls, notice how the outer metal rim appears to be thicker on the old bearing, whereas the inner part is much thinner (same inner diameter).
Still, I'm not doubting that this is the correct size, I'm just having trouble sliding the new one on. I've thought about sanding the shaft down just a little bit, and I've tried lubricating it, but I'm opening my ears to other suggestions. Is sanding a bad idea?