Joined: Jan 2009
Posts: 44,135
Likes: 6,350
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
If you use the SAE wrenches on bikes, it will be very rare, like once a year.
The difference is that metric wrenches are size 8mm, 9mm, 10mm, etc, and SAE wrenches are 1/4", 5/16", 3/8" etc, and the wrong wrenches won't fit your nuts.