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Old 02-24-09, 10:50 AM   #1
wazzu1991
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Replacing a crankset on an old Trek

I wan to get rid of the oval crankset on my 1989 Trek. It has a 52/42 double. I'd like to go with a compact double if possible. Has anyone done this or have any suggestions. I am fine with the downtube shifters and the 7 speed cassette but I need lower gearing.
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Old 02-24-09, 12:52 PM   #2
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Check your current cranks. They might be drilled for a granny ring. My brother had a Trek from that era with oval rings (SR Ovaltech I think) and the crank was drilled for a granny but run as a double. You might need a longer bottom bracket axle to use as a triple, though. And depending on what you run, you may need a triple specific FD and/or a long cage RD.

Also measure the bolt hole distance. The crank is probably 130mm (~76.5mm between adjacent holes) but may be 110mm (~65mm). If 110mm, just get new rings (and adjust FD height).

Otherwise get the compact crank of your choice and bottom bracket to match, install, adjust FD height, and go.
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Old 02-24-09, 01:12 PM   #3
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You might be able to get that 42 down to a 39 on the current crank.
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Old 02-24-09, 01:47 PM   #4
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If its a 130 bcd crank you can go down to 38.
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Old 02-25-09, 02:15 AM   #5
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Originally Posted by wazzu1991 View Post
I wan to get rid of the oval crankset on my 1989 Trek. It has a 52/42 double. I'd like to go with a compact double if possible. Has anyone done this or have any suggestions. I am fine with the downtube shifters and the 7 speed cassette but I need lower gearing.

I have an '86 or '87 Trek 560. This was initially a Shimano 105 equipped bike, with the Biopace double cranks. It sat idle for years. When I started riding it again I did the swap you're considering. It worked out really well, and I'm very happy with the compact. I was able to use the existing FD and RD. I went with a SRAM Rival compact with new bottom bracket on sale at Performance.

Here's an example I just googled: http://www.amazon.com/Rival-Compact-Crankset-Bottom-Bracketdp/B0011ZGJ08

I find the big jump in front is perfect for the local terrain with undulating hills. Here's what it looks like.

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Old 02-25-09, 12:19 PM   #6
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Thanks for the help. Nice bike sunburst. Did you change the cassette and chain as well? If I remember right the hills around SF aren't that different from the one's I'm facing here near Seattle.
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Old 02-25-09, 10:32 PM   #7
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Thanks for the help. Nice bike sunburst. Did you change the cassette and chain as well? If I remember right the hills around SF aren't that different from the one's I'm facing here near Seattle.
I already had the max freewheel I could get on it, a 28tooth. I used the same chain but removed a link or two. I actually like the compact better than the triple that came on my new bike, and I find I can climb some serious hills with the 34/28 combination (and I'm 54!).
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Old 03-02-09, 11:36 PM   #8
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I talked to the guys at the local bike shop and we decided on a shimano r600. Should be an improvement.
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