I have a Trek Elance 330 from the 80s and love it! However, I find myself needing something that can handle fire roads (gravel jeep paths) and am wondering if it is worth the effort. Also, if it would result in an effective ride. I am fine with the higher center of gravity, won't be doing any rock hopping, and won't be buying a new bike. Has anyone converted their steel frame? What experience can you share? Thanks! :)
I've done a conversion on an old steel Schwinn, and these look similar. I'm not sure how in-depth you want to go, but at the most basic level you only have to worry about two issues:
Tire Clearance The most popular size of cyclocross tire is 700x32. You may find that a knobby cyclocross tire will fit between your fork, but not clear the bottom bracket or chainstays in the rear triangle or vice versa. If you have a tire clearance issue with the rear triangle I would abandon hope right then. If the rear is fine but the front is tight, you can consider a new fork.
Brake clearance The brakes on that bike may not have arms that are wide enough or long enough to properly place the pads on the rim without touching the tire. IF that's the case you can check a touring source like Rivendell for brakes with longer, curvy arms.
Note: If the bike came with 27 inch rims, you may have a hard time finding tires and your clearance issues may be even tighter. If that's the case you can look at switching to 700 wheels, but you may find on an older bike that it expects a narrower hub. With a steel frame you can consider carefully bending the forks.
Is it worth it? Well - to me it's worth it if you will ride it. Start with the tires - that's the cheapest first step. Move on to brakes and fork only if you have to.
On first thought, I would say NO due to the lack of cantilever brake mounts. Caliper brakes which come on this bike limit tire choice a lot. But if you don't plan to do traditional cross racing and are just looking to ride this bike on fire roads and gravel paths, then I think you can make it work fine. The issues you'd have in a cross race would be dealing with a buildup of mud and leaves between your tire and brake / fork and it may be harder to get traction on loose ground, mud, and sand.
However, this bike originally shipped with 700x28c tires, so you may be able to bump up the tire size a little bit. You may want to try some 700x30c tires like Michelin Mud Cross tires. Even if you can't get bigger tires squeezed in there, I take my road bike with 700x28 tires on this kind of terrain all the time, so just go with the biggest thing you can fit. You'll enjoy the ride a lot more on fat tires.
You could also consider throwing on some Tektro R539 brakes which should clear 32c tires if your current brakes don't. This is what ships on the All-city Mr. Pink which claims 32c clearance.
Here's a great link to a vintage trek catalog with the orignal specs for the bike: