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pedaddler
06-23-2004, 08:00 AM
Help! I have a double chainring on my bike and am finding out that i should have a triple. I am hoping that in all of this forum's collective wisdom that there is someone with an idea about a reasonable solution without changing the whole drivetrain deal. any ideas, oh women of great wisdom?

ChainsOflove
06-29-2004, 12:20 PM
Wow, I just did this conversion this weekend! Its def. a good thing. My LBS says he thinks everyone should have triples.

My prob was it was wicked expensive becuase I have Campy Centaur and the parts were $400!!!

But I can prob sell the old set.

I did it becuase I was just not riding the bike enough, and that was getting me very depressed.

pedaddler
06-29-2004, 05:23 PM
yeah... that "wicked expensive" thing is what i was hoping to avoid. i use shimano so it probably won't help to ask which parts you had to switch out. but enjoy! i'll keep pushing big gears until i can figure it out. thanks and let us know how the triple works for you.

Adventure Girl
06-29-2004, 06:21 PM
Originally posted by pedaddler
is someone with an idea about a reasonable solution without changing the whole drivetrain deal. any ideas, oh women of great wisdom?
If you're doing it just get a lower gear you might consider changing your cassette instead. Ask the LBS people what they recommend. If they say it can't be done, ask another shop. You might have to change the rear derailleur, but that will probably be less expensive than changing to the triple. They do it at my LBS all the time when people buy bikes with doubles, then later decide they want a triple.

In rough numbers:
Double 53/39, 12/25 cassette, lowest gear is 42.1 gear inches.
Double 53/39, 11/34 cassette, lowest gear is 31.0 gear inches.
Triple 52/42/30, 12/25 cassette, lowest gear is 32.4 gear inches.

The combination with the lowest gear inches will be the lowest gear. So you can see that in this example, the double with the 11/34 is actually geared lower than a triple with the 12/25.

I know this is a bunch of tech-talk mumbo jumbo... Here's a sight that explains it pretty well. http://www.sheldonbrown.com/gears/ I hope it helps.

emily_in_nc
06-30-2004, 09:34 AM
I'm wondering if you could try a compact double? That's what I have on the bike I got early this spring, and it's actually got a lower gear than the triple on my old bike, and weighs less to boot! I have an FSA compact double with 50-34 chainrings. Most "regular" doubles have 53-39 chainrings, so going from a 39 to a 34 in front helps! You can plug the chainring and cogset sizes into Sheldon Brown's gear inch calculator to see what it will give you - it depends on your wheel size and largest cog in back as well. I have smaller wheels (650C) and a large cog in back (13-29 Campy) so end up with a low gear in the 28-29" range. I haven't had any problems climbing even major hills with that. My Terry bike had a standard Ultegra triple in front (30-42-52) and a 12-27 in the back, still a nice large cog, but even in the granny, I only had a low gear of 30".

To change to a compact double, you'll likely require a bottom bracket change but not a front derailleur change, and shifting is simpler than with a triple in front and will be what you're used to now. Inquire at your LBS for details if you're interested.

Emily

pedaddler
06-30-2004, 03:33 PM
thank you both so much for the information. i feel much better about going into the lbs with the great help you've provided. thank you.