Changed to a single chainring and now the chain slips off
I upgraded to some aluminum cranks and decided to just use a single 50 tooth used chainring. There are 6 gears in the back. The chain tends to slip off the front when I'm in the smallest or second smallest gear in the rear.
The chain is well aligned with the middle of the cassette. The chain is stretched by about 1/16", so I don't think that's enough to be the problem. The chainring is not very worn at all.
So, the only reason for the chain slipping off that I can think of is that there is slack in the chain. Does that make any sense?
I've heard that when mountain bikers convert to a single chainring they usually put a guard on the inside and outside to stop the chain from coming off, but is this necessary when I'm just riding on roads? Should I just put the front derailleur back on to keep the chain in check?