Originally Posted by
spclark
My venerable '72 MBGR came with 52/40 chainrings & 14/24 FW in back. It was perfectly fine when I lived and rode in Flatland (Illinois) until we moved up into SW WI late in 2013.
Or I should say until I started riding it again earlier this year, after a 12 year hiatus.
There are hills here. Some're HILLS. Even a few HILLS... it't ain't California or Colorado though so my question is:
With 120 OLD geometry in back, and a choice of cogs from 14t to 34t, what's a useful 2nd - 4th combo for recreational rides < 20 miles in length?
Classic 48/38/28 (or even 26) triple would fix the front. How much do you want to mess with the back? There were uniglide hubs that would fit 120mm, but you would buy yourself a lot more options if you stretch it to 126mm. You could keep the 5 speed at 126mm or jump to 6 speeds on the same uniglide hub. If you jump to 130mm, then you have access to a whole lot of more modern stuff.
My Trek 720 started as a 126mm spec bike, I bump it to 135mm so I could use mountain bike hubs. It is trivially easy to do (for you to hit 126mm or even 130mm). It is a matter of what you want and what you are willing to do. Even Dura Ace had an early 120mm Uniglide hub but you'll have a bear of a time finding it and the rings for it (it uses loose rings and spacers, the last ring screws on top holding everything in place).