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compact crank benefit(4 posts)

compact crank benefitmarcoxxx
Aug 4, 2003 4:19 AM
i wonder if using a compact 50/36 for example, would you lose too much gearing or not? if you are not racing, like to sit and spin, and need the extra advantage for the local climbs, it looks good to me. seems like a good alternative to a triple setup and with less weight too.

marc
re: compact crank benefitSteve Bailey
Aug 4, 2003 5:40 AM
Best you do a gear chart to figure out what you currently use in your existing setup.

http://www.sheldonbrown.com/gears/

Next time you're out riding, pay attention to what gear combo's you use most. Then think about how often you use the big ring/small cog, or the reverse (do you live in Vermont ?), etc...

Then chart it out on Sheldon's gear chart and start playing with the options with a 110 BCD double crank. You may like what you find, or you may not need to change a thing.

It's not going to give you the range of a triple, though Shimano's triple offers mediocre range, with at best, 18 useful and non-repeating gears with a 30/42/52 crank and a 13-23 9spd. cassette. Still, a triple with a 30 small ring on a stock Shimano road triple and a 23 cog gets you a 35 inch low gear, which is better then a 42 inch with a 34 small ring on a 110 BCD double and the 23 cog. The advantage to the triple is that you get the "range" from the triple which then allows you to run a tighter cluster on the cogset. This is an advantage if you ride rollers and/or flat terrain a good bit of the time and only need the small ring occasionally for some long steep hills.

There has been enough written on the internet about the lousy gearing choices from Shimano to fill a book, including how the high gear is way too tall for the avg. recreational rider. That said, sometimes you're better off with what you have, then plunking down the cash for a new crank, rings, bottom bracket, and possibly a cassette. Remember that if you're using Shimano STI you will need a ramped/pinned big ring and they ain't cheap - $50 or so. It gets expensive fast.

Note also that the term "compact" has refered (in the past) to the 94/58 5 bolt cranks, that are (or were) the standard mountain bike crank. The stuff you now see in the press, such as the FSA crank used by Tyler is a 110 BCD crank, which is the older mountain bike BCD standard (with a 74 for the 3rd ring).

SB
thanks..excellent!! (nm)marcoxxx
Aug 4, 2003 6:30 AM
nm
re: compact crank benefitLC
Aug 4, 2003 9:55 AM
53 vs 50 is about the same as 1 tooth on the rear cog. If about all you can push is 53x13 then 50x12 will be fine.

39 vs 36 is about the same as 2 teeth on the rear. If you have a 27 cog but wish you had a 29 then this would be a good way to go.