Judging from the variety we see on the Cimarron thread, it's certainly true that you can take a vintage MTB in a variety of directions. Here are some things I discovered in my process:
- The first decision I recommend you consider is what kind of handlebars you want. Handlebars have two important diameters: Grip, where the levers and shifters go, and Clamp, where the stem goes. Any stem with a 7/8" quill will fit this bike, but the clamp diameter varies according to whether you want to install road type drop bars or MTB style bars. Then, the brake levers and shifters will need to match the grip diameter. Basically, road style brake levers fit drop bars and flat levers without hoods fit MTB bars. I forget the exact diameter numbers, but you can find those numbers easily.
- The next decision should probably be whether you want a modern drivetrain or not. My Cimarron's rear dropouts were spaced at 128mm, to accommodate either rear hubs at 126mm or 130mm that were available at the time. A more recent standard is 135mm, and it's a relatively easy matter for a bike shop to spread ("cold set") the rear triangle to accommodate. If you stick with a vintage spacing, you'll either need to use a modern road hub, which is 130mm or a vintage MTB hub at 130. There aren't too many around of the latter. Very simply, the amount of space in the rear determines: 1) How potentially strong the wheel will be, and 2) How many sprockets you can fit. In the end, I decided to respace my Cimarron's rear dropouts to 135mm so I'd have a strong wheel with the option of modern parts in future, but I actually had my bike shop build wheels on vintage hubs at that width (135mm became standard for MTBs in the late 80s) because I like vintage parts. Note that you can basically use ANY derailleur with ANY rear spacing. You just set the limiter screws on the deraileur accordingly.
In my view, handlebars are mainly a utilitarian choice and also a matter of preference. e.g. How do you want to use this bike? What kind of bar do you prefer? The rear spacing matter is, in many ways, a factor of convenience -- availability of parts in future -- as well as aesthetic -- do you want to bike to still look basically vintage?
Cost is a factor, too. I've read this elsewhere on the forum, and I agree: it's not possible to build a bike for less that it would be to buy a whole bike. So, most people build their own bikes because they are very picky (that's me) or enjoy the process (that's also me). If you're not building wheels, installing a bottom bracket or headset, you only need standard tools to assemble a bike.
I may very well have chosen to ride my Cimarron with original parts except for the fact that it was spec'd with a Suntour freewheel. I wanted indexed shifting with my Shimano bar-end shifters, so that necessitated Shimano hubs.
Whichever way you go with your bike, you may enjoy the learning process! This particular build was a lot of fun for me, because I had to learn about a lot of bike-related things I didn't previously know. That's part of the process which I enjoy, and the folks on the forum have a LOT of knowledge to share!
Cheers,
Oliver Henderson