Originally Posted by
SJX426
Talk about what you are thinking wrt "upgrading the rear 'cog' set." What is the current spacing, 126? I would think you would want a full range of gears in Seattle, unless you are sticking to the flats. Flats in Seattle?! Queen Anne would be a challenge without two or three rings up front. guess
The 1984 Trek 510 was definitely 126 mm in the rear, from the factory.
I think SJX426 is right on the money, suggesting the OP really look at the gearing you'll need. Most of my riding has been Chicago, Ann Arbor MI, and Denver CO in order of hilliness. My Chicago gearing would never have worked for me for either of my other two cities, any case not once I was older than 25 or so!
A big single could cover a range maybe 44/11, maybe 4:1. A more standard one 32/11, just less than 3:1. A front triple can gt you 53/30, a ratio of (32/11)*(53/30) =5.14:1, you''d have over 25% more range, though the gears might not be the same. Anyway, keep an open mind!
Overall, I'd suggest don't try to make this bike your ideal concept bike. Just work within what it is and make it work right, then ride it a bunch! Some simple-seeming changes need changes to the frame, and this step can get complicated.