Reducing mp3 filesizes after removing album art?

[nippywiffle]

Hi,
It was bothering me that itunes was unable to find album art for a lot of my mp3s, so I added album art myself (to the ID3 tags) on around 30 albums. The images were small.. only around 300x300 or so, just a few kb each. I actually used the free version of "TuneUp" to do this.

After I added this album art, and then sync'd with my iphone, the mp3 space usage on my phone went up by more than 1GB!!

First - I don't know why tiny image files would increase my mp3 file sizes so much. Even if the image was a huge 100k (which they weren't), that would only add up to around 30MB total.

Second - I now removed the album art from EVERY track in my library, using itunes, but it didn't reduce the mp3 files back to their original size. It's like the file is still expanded with 'whitespace'.

Does anyone know how I can reduce my mp3 files back to the size they were before the album art was added?

Also, has anyone else seen this issue, of adding album art, and it somehow taking up a huge amount more space on their iphone?

Thanks,
Dan