I have an old (circa 1991) Trek 950 mountain bike that I'm using as a city bike. In addition to being a grocery getter, I use it to pull a Burley Piccolo trailerbike. It's getting kind of tatty and I either need to upgrade a few things or replace it. The rims are all scarred up from dirt riding, so it makes a lot of noise when braking. And while it still shifts well, I really think the crank and freewheel (yep, it's still got a freewheel) are worn and need to be replaced. Also, the padding on the saddle is just about gone. So, I'd be looking at needing all this:
Wheels ($100 closeout at Performance)
Crank ($40 closeout at Nashbar)
Cassette ($25 at Performance, includes chain)
Probably should replace the bottom bracket while I'm at it ($25)
Add all that up, and it equals the price of a new Trek 820. And that's assuming nothing goes wrong during the rebuild. Now, there are certain things the old bike has going for it - while the brakes and derailer are old, they're probably still better than the ones on a new cheap bike. Also, the closeout wheels I'd be buying are also probably way better than the ones on a new cheapie. And, the old bike has great karma, and it's kind of scratched up from dirt riding, which means I don't have to worry about a few more dings. The other problem with new cheap bikes is that they all come with a suspension fork, which I'd rather not have for pulling the trailercycle. The roads here are smooth but it's hilly, and besides I don't need another variable when pulling a 5 year old stoker. The problem with the old bike is what if something happens to the shifters? Then I'm stuck replacing them, and probably the brakes and possibly the derailers.
I do have another bike available, it's an even older (1984) Trek 610 sport road bike. For pulling the trailercycle, I really like the MTB on city tires that I now have. I'd like to get a new road bike at some time, as I miss the indexed shifting and I'd like a lower gear on the hills. That's not likely to happen until next year, and I'm leaning towards getting a more upright drop bar bike like a Trek Pilot or Cannondale Synapse Sport, which I wouldn't want to use for pulling a trailercycle. The youngest child in our family is five, so we probably have about four more seasons with the trailercycle. After that, I'd still use the city bike for going to the store and for noodling around the neighborhood with the kids.
So, which way would you go?