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Old 01-21-14, 02:03 AM   #1
laserspeed
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Gear Ratio

I am rebuilding an old road bike (new to me) and am about to put on a new chain. I was doing the calculation to see the length of chain needed and got to thinking maybe the current gear ratio is not right for me and I should address that before cutting down the chain. The chain rings are 52/42T and the 6-speed freewheel is 13-24T.

This is my first bike since I was a kid and got the bike to ride for recreation at a pretty leisurely pace. I'd like to use the bike in somewhat hilly (and scenic!) areas, am in my mid-twenties, and would consider myself to be in average shape. Is a 42:24 gear ratio low enough for any climb I'll ever face or should I opt for a different freewheel? Again, I'm not looking to power my way up any hills -- just want to make sure I'll be able to climb hills period.
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Old 01-21-14, 09:05 AM   #2
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I have a 52/42 on my '85 trek 460. I have ridden it with a 14-23 and a 12-28 7 speed cassette out back (newer wheels & hubs). The 12-28 is much better.
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Old 01-21-14, 02:48 PM   #3
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I have a 52/42 on my '85 trek 460. I have ridden it with a 14-23 and a 12-28 7 speed cassette out back (newer wheels & hubs). The 12-28 is much better.
Did you have any trouble with the 12-28T freewheel and the rear derailleur or was there adequate clearance? What group set did you replace the freewheel on? Thanks!
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Old 01-21-14, 03:00 PM   #4
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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.
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Old 01-21-14, 03:31 PM   #5
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I'm going to move this to the Mechanics Forum where it will find a larger pool of mechanical experts.
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Old 01-21-14, 03:37 PM   #6
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Quote:
Originally Posted by Barrettscv View Post
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.
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.
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Old 01-21-14, 03:46 PM   #7
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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.
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Old 01-21-14, 03:49 PM   #8
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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.
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Old 01-21-14, 03:51 PM   #9
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Quote:
Originally Posted by Bill Kapaun View Post
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.
Price is not the only issue, it may not be a primary issue. The larger cog size will also create bigger jumps between cogs and some rear derailleurs can't fit a 28t cog.

The owner needs to know his options.
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Old 01-21-14, 03:57 PM   #10
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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.
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Old 01-21-14, 03:59 PM   #11
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Originally Posted by laserspeed View Post
Did you have any trouble with the 12-28T freewheel and the rear derailleur or was there adequate clearance? What group set did you replace the freewheel on? Thanks!
Suntour Cyclone II derailleurs. No issues. It will be better than what you have and a 14-28 costs about $15. A good place to start.
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Old 01-21-14, 05:56 PM   #12
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Originally Posted by FBinNY View Post
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!


Quote:
Originally Posted by cny-bikeman View Post
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.


Quote:
Originally Posted by Barrettscv View Post
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.
Quote:
Originally Posted by Bill Kapaun View Post
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.
Quote:
Originally Posted by Al1943 View Post
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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