Thread: Gear Ratio
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Old 01-21-14 | 05:56 PM
  #12  
laserspeed
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Originally Posted by FBinNY
42/24 isn't going to cut it in hills for any but seriously strong riders. Buy yourself a wider range freewheel for starters, but even that may not be enough.

BTW- there's never a problem with a chain cut to Maximum length. Loop the 42/24 combination through the derailleur and take up slack until the idler cage moves off the dead stop. That's the longest chain length that will work in all gears, and will leave room for a larger freewheel later.
I sort of got the sense that this would be the case after perusing some bike recommendation threads (that a 42/24 gear ratio would be way too aggressive for me) but didn't have any point of reference since I haven't owned a bike in years. I like the flexibility permitted with this idea!


Originally Posted by cny-bikeman
The 28 tooth low is the minimum I would suggest you consider. There's no way to tell if that's sufficient, as "average shape" means little when it comes to cycling. The problem is that we don't know if your derailleur will handle the 28 tooth cog. It's not "clearance" but rather "capacity" that is the issue. You need to find out what model of derailleur you have, or at least take a picture (from the side, at the level of the derailleur). If the bike is friction shift then changing both derailleur and freewheel is still not that expensive, and you can go larger than 28 teeth. But even a 42/34 may not be low enough for "any hill" you may encounter.

I would not recommend any chainwheel upgrades without knowing more about the bike, as you may end up putting in much more money than is advisable.
This is the rear derailleur. According to this website, the max cog size permissible is one with 28T -- that answers the freewheel question. The bike has friction shifters but can switch to indexing by turning a little pin and uses this (1050) group set.


Originally Posted by Barrettscv
You might consider this http://store.velo-orange.com/index.p...et-34x48t.html

The smaller 34t inner chainring will provide a much greater improvement in climbing range (about 20%) than changing from a 24 to a 28 large cog on the freewheel (a 14% change). You existing derailleurs will work fine with this crankset.
Originally Posted by Bill Kapaun
Much better to spend $100 for a crank set (and maybe more for a new BB) than $15 for a freewheel!
http://www.amazon.com/Shimano-MF-TZ2.../dp/B003EQ71QI

Sarcasm off.
Originally Posted by Al1943
You can probably replace the 42 inner chainring with a 39 or 39 (assuming a 130 BCD), and also replace the freewheel with a 12-28 or similar. See sheldonbrown.com for how to measure BCD.
I measured the BCD to be 130 mm (77mm between two bolts c-c on a 5 bolt system). After hearing that a 42/28 ratio still might not cut it I am definitely interested in replacing the smaller chain ring but as Bill alluded to, price is definitely a factor. I do want a bike that is efficient but at the end of the day it is just for recreational rides so really it'll do its job just fine with any configuration really. If I can make it a bit easier on the cheap then I'll go for it. Thanks for all of the suggestions I've got some homework to do!

EDIT: I forgot to add that I have "Biopace" chain rings that are not perfectly circular. Would it be okay to keep the 52T Biopace chain ring and use a perfectly circular 39T (or other) chain ring?

Last edited by laserspeed; 01-21-14 at 06:00 PM.
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