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Discussion Starter · #1 ·
I was considering going from a compact (50/34) crankset to a double (53/39) crankset. The owner of my LBS told me that making this change is a pretty big jump. I became hesitant and began second guessing myself. Im 21, 155lbs and have been cycling for about a year and a half now. I have been playing football for about 14 years so the leg strenght isnt much of a problem, I was just thinking of taking my cycling to the next level. So please, your opinion is much appreciated, I hope you all are enjoying the season and surpassing all your goals for the summer. thanks in advance I really appreciate the help.:)
 

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Going up a hill, pedaling at 80 rpm in your lowest gear:

39: 9.8mph 34: 8.5mph, assuming you have a 12-25 cassette

39: 10.6 mph 34: 9.2mph, if you have a 11-23 cassette

The real question is, are you ever really glad you have your granny gear? If so, you prolly won't like the standard. If not, you'll probably be ok.
 

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You can easily gauge what the different gearing will be like on your current bike. Going from a 34 to a 39 as your smallest chainring is about equivalent to a change of 4-5 teeth on your rear cassette with your current chainring. If your largest cog in back has 27 teeth, climbing with a 39 chainring on that cog will be about the same as climbing with a 23 tooth cog in back with your 34 -- maybe two gear shifts from your easiest gear. If you like the feel of that for your hardest climbs, you should be good to go.

You can easily calculate the actual gear comparisons:

39/(# teeth in largest rear cog) = new easiest gear ratio ~ 34/(# teeth in 3rd (or 4th?) largest cog)
 

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PdxMark said:
You can easily gauge what the different gearing will be like on your current bike. Going from a 34 to a 39 as your smallest chainring is about equivalent to a change of 4-5 teeth on your rear cassette with your current chainring. If your largest cog in back has 27 teeth, climbing with a 39 chainring on that cog will be about the same as climbing with a 23 tooth cog in back with your 34 -- maybe two gear shifts from your easiest gear. If you like the feel of that for your hardest climbs, you should be good to go.

You can easily calculate the actual gear comparisons:

39/(# teeth in largest rear cog) = new easiest gear ratio ~ 34/(# teeth in 3rd (or 4th?) largest cog)
Uhhh... Since the cogs are (roughly) half the size of the rings, the differences are roughly half as much. So a 34/13 is about the same as a 39/15. It gets close to 3 teeth at the big end.

An easy way to visualize the diff is to use Sheldon's calculator, and put 34 and 39 (or 50 and 52 if that's the end you worry about) in for the chainrings.

http://www.sheldonbrown.com/gears/
 

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Look, I am 45, 6'1" and about 205, I recently made the switch from a compact to a full size double. It was tough for a couple of weeks until I got used to it but now I love it.

Of course I don't live in Boulder, but I don't live in Florida either.

Also running 12-25
 

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Discussion Starter · #7 ·
B15serv said:
Id do it, in fact I did it myself. After two weeks youll be used to it and glad you made the change. Also what cassette are you using? Im running a double crankset 39/53 with a 12-25 cassette.
I am also running a 12-25 cassette, thats what I wanted to hear. thank you.
:thumbsup:
 
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