Old 02-21-10, 10:41 PM
Ovdabak, OR
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Location: Michigan
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Bikes: 2008 Mercier Corvus Steel, 2007 Trek 4300, ~1980 Takara Deluxe 12, 1985 Trek 620 (modernized)

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Originally Posted by richardtc View Post
I am interested in buying a bike from a friend. The only thing holding me back is it has a Shimano 105 39/53T Chainring.

I really need to minimally be using a 34/50 compact or a triple with a 30.

My question is, what are the costs associated with changing that out? I assume that it would involve a change of the 105 front derailleur to go triple. Can I simple change out the rings and not the cranks if I go for the double?

I know my friend will give me a deal, but I do need to consider the additional cost.


The cost depends on your bike and what you are prepared to settle for. Ideally, you should use a triple with a triple front derailleur and a compact with a compact front derailleur. You can certainly get away without doing that, but shifting between the smaller two rings on a triple can be compromised if you use a double derailleur. Cranksets and chainrings are two of the most overpriced bike components, in my opinion. The more cost-effective solution is to get a new cassette or freewheel. Unless you live near pretty hefty hills, a 39/27 gear ratio is usually enough. A new cassette will run $25-65 depending on how many speeds it is. New cranksets are well over $50 unless you get lucky.

That said, I live in Oregon and advocate for triples constantly. Too many of my friends avoid beautiful rides over hills because they saved a minimal amount of weight by going to a double.
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