I remember reading an old study about this. I can't find the link at it was an old PDF version. The online bike calculators don't seem to back this up. Maybe this was up a certain % grade. But for some reason I have remembered the 12lbs per 1mph rule. But I could be wrong. Not the first time.

Here was some interesting reading though: https://www.velonews.com/2012/05/bik...-matter_220429