Are the pads hanging over the outer edge of your disc? It could just be that your new disc has a slightly wider braking surface than the previous one. I've seen a few shimano setups where the entire pad is being used, but only about 80% of the disc surface.
The disc is the same model as before. So... unlikely.
The pads however have changed. I upgraded to a "better" 2quid more expensive version. I'll check where the disc sits and if it clears the upper edge of the pads.
Are the pads hanging over the outer edge of your disc? It could just be that your new disc has a slightly wider braking surface than the previous one. I've seen a few shimano setups where the entire pad is being used, but only about 80% of the disc surface.