Originally Posted by
Grand Bois
You can buy an 18 tooth Alfine cog for less than $10 on Amazon. That's about the same as switching to a 39 tooth ring, but cheaper.
That will make the gearing higher, not lower. The OP's current cog is a 19T. It would take a 21T cog to make the same change as going from a 42T to a 38T chainring. Will the Alfine accept a 21T or larger cog? If so, this is indeed the cheapest change.
Yes, switching chainrings is really as simple as removing the 5 bolts, replacing the ring and reinstalling the bolts. BTW, it's
bcd (bolt circle diameter) and, as you noted, a 38T ring is the smallest that will fit on a 130 mm bcd.
If you want to go smaller, you will have to replace your crank with one with a smaller bcd and the next common size down is 110 mm which will take down to a 33T chainring.