Bicycle Mechanics - New bottom bracket/crankset for Trek 1200??

Hey all,

I have a couple of quick questions regarding the bottom bracket and crankset for my old(ish) aluminum Trek 1200. I recently started developing a clank when pedaling. It sounds when I begin to put pressure on the drive side pedal. Upon removing the crank arm, I found that the square hole had become slightly rounded out and had begun to strip the spindle. I have a Shimano 105 crankset on there (FC 1051, 170mm) and I'm not sure what kind of bottom bracket. I assumed I'd have to replace both the bottom bracket and the whole crankset, but the mechanic told me that with replacing the crankset I'd have to replace the whole drive train. I bought the bike used ($200 on craigslist) and have put about 600 miles on it, so I'm a bit hesitant to spend more money fixing the bike than I did to buy it in the first place.

My questions are these:

1. Is there a cheaper alternative? For example, would it be feasible to replace just the crank arms and bottom bracket, but keep the chainrings so that I wouldn't need to futz with the entire drive train? (I don't need anything high end, just something to get me to work without a danger of the crank falling apart.)

2. Is this the sort of thing I should do myself? I don't have the tools, but I do enjoy getting greasy. I'm just not sure that it would be cost effective to buy the tools when I probably won't need them again for a while.

3. Does anyone know where I might found out what type/size bottom bracket would be required for my model bike? Or of any good resources I might use to find said parts and confirm their compatibility?

Thanks very much! And sorry for my longwinded thread!

your mechanic might just want money. even if your chain and cassette are shot, theres a good chance your chainrings are ok still. they take alot longer to trash, as they have more teeth to spread the load/wear over. you have a few options: one is, buy used cranks on ebay, the sellers are generally good about stating conditions of items. this will let you stick with a square taper bottom bracket, which again helps keep costs down. here's a link for an ebay 105 crank that looks ok, and i promise will go for under 30 bucks cause its old: http://cgi.ebay.com/Shimano-105-cranks-175mm-8-speed_W0QQitemZ250018322043QQihZ015QQcategoryZ56195QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
combine that with a new shimano bb, a un73 for 40 bucks, and you have it fixed under a 100 dollars. as for tools, you need an 8mm hex wrench, which are cheap, a crank puller, which i assume you have, if not, they are about 25 dollars, a bottom bracket cup removal tool, maybe 15 bucks, and a big crecent wrench to use that tool, which are expensive if you dont have one. channel locks might work... oh and in terms of bottom bracket sizing, i would say you'll need a 68 shell with a 111 or 107 spindle. maybe it take it to anouther shop and have them figure that you for you, after you get the new cranks. btw, if you buy the bb from whatever shop, they'll probally put it all together for you for less than all those tools cost, maybe 20 bucks, all told.

your mechanic might just want money. even if your chain and cassette are shot, theres a good chance your chainrings are ok still...........btw, if you buy the bb from whatever shop, they'll probally put it all together for you for less than all those tools cost, maybe 20 bucks, all told.

I think he's absolutely right. Your dealing with one of two things here, either a mechanic who's dying to take you for some cash, or a mechanic who has so little experience that he/she has never worked on anything that had downtube shifters. First, I would seriously consider looking at giving another shop your business of working on your bike. This should be a very simple and relatively inexpensive fix. Ebay is filled with "older" cranksets/bottom brackets which will go on your bike and with a slight front derailleur adjustment, you'll be on your way. If you have a caliper (preferably one with metric), just measure the width of the spindle to find the replacement size, considering you will be replacing the crank with a like model. Of course, I always promote doing your own work, if you simpley don't want to invest in the tools, again, find a more experienced mechanic to do the work. Good luck!

Great! Thanks for the advice. It seems like there are a bunch of usable cranksets on ebay. Just a couple follow-up questions:

1. Should I try to find a similar crankset and mount my current chainrings to it, or should I just install the whole new crankset, chainrings and all? I wonder because I have Biopace chainrings on there now and I'm not sure how compatible they are with other cranksets or whether new chainrings would mess up the chain or cassette.

2. As far as other cranksets go, what specifications should I look for to make sure it will fit? I currently have a Shimano 105 FC-1051 170mm. on there, which I can't find.

Thanks again for all your help!