Author Topic: Gearing for Audax Mk 3  (Read 3578 times)

philb

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Gearing for Audax Mk 3
« on: July 15, 2010, 03:37:21 am »
Hi All. I've been mulling over a problem with the gearing on my audax mk 3. I currently have a road groupset of triple crank 30-42-52 and a 12-27 rear casette. This is great with the bike unloaded and I use it as a roadbike for training rides. Im looking at using the bike for some touring duties and I think my current gearing will be too big. I've thought about getting a smaller crankset, but I don't want to change the unloaded nauture of the bike. Is there an easy fix for this? I currently run 175 mm cranks. Would 172.5 be better for loaded touring?

any thoughts would be apreciated before I waste my money.

Phil

geocycle

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Re: Gearing for Audax Mk 3
« Reply #1 on: July 15, 2010, 09:00:55 am »
I thought crank lenghth was more about comfort than gearing?  I guess there must be an effect on leverage but I would assume not a great one. How about changing the rear cassette to give a bigger range?  That would probably be the cheapest option and you wouldn't lose the smallest gear.
 

rualexander

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Re: Gearing for Audax Mk 3
« Reply #2 on: July 15, 2010, 09:05:36 am »
Shortening your cranks without changing the chainrings or cassette sprockets will actually effectively increase your gearing rather than lower it, you are shortening the lever through which you are applying the force.
The easiest and probably cheapest thing for you to do would be to change the cassette for something like 12-32 but only if you have a long cage mtb rear derailleur that will cope with it.
Otherwise you could change the chainrings, maybe change to 28-38-48 (although I personally would find that still too big for touring with much luggage). Your front derailleur should cope with that but may need to be lowered on the seat tube.

philb

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Re: Gearing for Audax Mk 3
« Reply #3 on: July 15, 2010, 11:24:31 pm »
Thanks for the replys. I thought changing the rear deralier to a long cage mtb one would give me the flexability to change between cassets, but I was concerned about the chain length. I might give it a try and post some feedback to others with the same problem.
Phil

skritikos

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Re: Gearing for Audax Mk 3
« Reply #4 on: July 16, 2010, 12:34:19 am »
Phil, visit this http://sheldonbrown.com/gears/ and experiment with as many configurations as you wish.


philb

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Re: Gearing for Audax Mk 3
« Reply #5 on: July 16, 2010, 07:57:59 am »
Thanks for the information.
Phil

mickeg

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Re: Gearing for Audax Mk 3
« Reply #6 on: July 17, 2010, 02:46:12 pm »
On my two touring bikes, I use a 52/42/24 front and 11/12/14/16/18/21/26/32 Sram eight speed rear.  That gives me one and a half step gearing with the outer (52t) and middle (42t) chainrings and several very low gears for climbing with the 24t granny chainring.

Changing from the 30t to a 24t chainring would give you lower gears at low cost.  The upshift from the 24t to 42t chainring is not very smooth, but I rarely use 24t chainring so it is not a common shift.  My front shifter is friction bar end shifter.

Yes, if you use a MTB cassette, you would likely need a long cage and a few more chain links.  My XT derailleur cage is not long enough to take up the slack when I use the 24t front and 11t or 12t rear, but I never use those gears anyway.

philb

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Re: Gearing for Audax Mk 3
« Reply #7 on: July 19, 2010, 02:59:23 am »
Thanks, it's hard to get one set of gears to do everything you want. I have a long cage derailer on my triple so i might try a few extra links