Just saw his chart, I'd take it with a pinch of salt TBH.
Old MTB rims are usually 17-18mm internal, it's only recently that MTB have 21-23mm internal width as normal.
I'd says this is much more accurate (althought you can go one smaller like 23mm on 17mm internal);
By Old I would guess you'd mean 90s; in the 80s they were still pretty wide.
@withered_preacher started
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Just saw his chart, I'd take it with a pinch of salt TBH.
Old MTB rims are usually 17-18mm internal, it's only recently that MTB have 21-23mm internal width as normal.
I'd says this is much more accurate (althought you can go one smaller like 23mm on 17mm internal);