Bicycle Mechanics - Changing cranksets

My ride is a late 80's Trek 560 road bike that I bought for triathlons. It's been hanging in my garage for about ten years. Six months ago I decided to use it to commute to work. Tuned it up and took off - so far - so good. What I don't like is lugging a laptop, lunch and clothes in a messenger bag PLUS the gearing is too high. I think I can live without panniers if I can change the gearing. I've got a 52/42 Suntour crank with a 6-speed 28/14 cassette. I've seen an ad for a 50/34 crank at Nashbar, but can't figure out if it would work on my bike. The ad says it works with "standard double derailleurs". Mine is a Suntour Cyclone (I told you it was old).
1. Will this crank work on my bike set up the way it is?
2. Will I need a new front derailleur?
3. If the answer to #2 is yes, should I also change the rear to match?
4. How do I know if this will work with my BB?
5. If it won't, how do I select a new BB that will work on my bike and the new crank?
6. At what point do I throw my hands up and spring for the new $1500 Cannondale touring bike that I want?

My ride is a late 80's Trek 560 road bike that I bought for triathlons. It's been hanging in my garage for about ten years. Six months ago I decided to use it to commute to work. Tuned it up and took off - so far - so good. What I don't like is lugging a laptop, lunch and clothes in a messenger bag PLUS the gearing is too high. I think I can live without panniers if I can change the gearing. I've got a 52/42 Suntour crank with a 6-speed 28/14 cassette. I've seen an ad for a 50/34 crank at Nashbar, but can't figure out if it would work on my bike. The ad says it works with "standard double derailleurs". Mine is a Suntour Cyclone (I told you it was old).
1. Will this crank work on my bike set up the way it is?
2. Will I need a new front derailleur?
3. If the answer to #2 is yes, should I also change the rear to match?
4. How do I know if this will work with my BB?
5. If it won't, how do I select a new BB that will work on my bike and the new crank?
6. At what point do I throw my hands up and spring for the new $1500 Cannondale touring bike that I want?It'll work but you need the BB to match it. Your BB is english thread with a 68mm shell width.Your derailers will work.Doing it yourself will require a crank puller,BB tools to get your old BB out and a tool to install the new BB. If your BCD is 130mm(76.4mm between adjacent bolt holes) you could stick a 38 ring on your crankset.

Thanks for the help. Your last statement intrigues me. What the heck is a BCD? It sounds like you're saying I could just change out my 42 for a 38 and avoid some hassle. Am I reading you correctly?

Thanks for the help. Your last statement intrigues me. What the heck is a BCD? It sounds like you're saying I could just change out my 42 for a 38 and avoid some hassle. Am I reading you correctly?Bolt Circle Diameter. Ring changes are easy,assuming they aren't riveted together,and yours likely aren't. Doing it requires matchng bolt pattern(yours is 5 hole), and BCD.Nashbar has inexpensive rings.

It'll work but you need the BB to match it. Your BB is english thread with a 68mm shell width.Your derailers will work.Doing it yourself will require a crank puller,BB tools to get your old BB out and a tool to install the new BB. If your BCD is 130mm(76.4mm between adjacent bolt holes) you could stick a 38 ring on your crankset.

I'd second what was previously said and add that you might want to replace the 28 tooth cog on the cassete with a 30 (most derailuers will handle it). Sheldon Brown (http://www.sheldonbrown.com/k7.html) has all kinds of information on how to do this as well as the cogs.

I'd suggest saving your money for that Cannondale (although I think the T800 is just as good as the T2000 for less money. I have a T800 and love it to death.)

Stuart Black
"Sticking my nose in for too long."

Bolt Circle Diameter. Ring changes are easy,assuming they aren't riveted together,and yours likely aren't. Doing it requires matchng bolt pattern(yours is 5 hole), and BCD.Nashbar has inexpensive rings.

Since it's hard to measure the bolt circle diameter directly with a 5 arm crank, measure the center-to-center distance of any two adjacent chainring bolts.

32.9mm = 56mm BCD
34.3mm = 58mm
43.5mm = 74mm
55.4mm = 94mm
64.7mm = 110mm
76.4mm = 130mm
79.5mm = 135mm
84.6mm = 144mm

The BCD is 144mm. I can't find a chainring smaller than 42 that will fit it. I have decided to take the plunge and replace the crank and BB.

Thanks for all the advice.