Originally Posted by grolby
Shimano spacing for 7-speed systems: 5.0 mm.
Shimano spacing for 8-speed systems: 4.8 mm.
You should be able to get away with indexing 8-speed bar end shifters on a seven-speed freewheel or cassette. This is what I'm planning to do with the 8-speed shifters that I just bought.
Update: This is indeed possible. I've only taken the bicycle on a short spin, so I can't report on it long-term. It does seem less than optimal - I haven't figured out how to get the indexing adjusted well enough to prevent some roughness in at least one gear. However, it doesn't seem to be actually jumping out of gear, and it is smooth in most of them. Any tips on adjusting the indexing to get it to work smoothly for all gears?