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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 10-25-10, 01:10 PM   #1
garlic_rice
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Changing gear ratio - chainring or cog?

Hey all,

I'm thinking of lowering my gear ratio for a couple reasons-
1) Moved boroughs, daily commute now involves a bridge.
2) Preparing for winter cycling, which i haven't really done before because
3) I'm a huge wuss (working on it).
4) My knees are telling me to.

I rode on the stock setup (42/17) for a year, which was fine but i found myself spinning out a bit going downhill and also when trying to pick up speed. I later upgraded to Eighthinch cranks and enjoyed 46/17 until now. Starting to think that the combination of change in commute and huge jump from 66 G/I to 72.4 G/I has something to do with the pain i'm feeling in my knees after an 8-mile commute.

A little more info about my riding habits:
-Bike is a 2009 Dawes MTA with minor upgrades. I am aware of how heavy/cheap it is, but i like it, ride the hell out of it, and will keep it as a winter beater once i get a new bike.
-Like i said before, Eighthinch cranks, 46t with 17t cog.
-Front brake, not really interested in skidzzzzz (bike's a little on the heavy side, as am I)
-Commute is Queens to Chelsea via Williamsburg bridge (not much of a climb, but then again, I'm not much of a cyclist)

So here's my question:
When it comes to lowering the gear ratio, what are the main differences between changing the cog or the chainring? Wear issues, dialing in an exact number of gear/inches, what should I look out for? Thinking of either 18t cog, or 44t chainring.

Or am I overlooking the obvious 'HTFU' option?

Thanks!

Last edited by garlic_rice; 10-25-10 at 01:27 PM.
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Old 10-25-10, 01:23 PM   #2
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Changing cogs will give you more of difference in gear inches. Changing chainrings results in more of a fine tuning. If 66 inches was too low and 72 was too high you should be aiming for something in the middle. If you run 42x16 that should put you at 69 inches. So I'd start by purchasing a 16t cog.
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Old 10-25-10, 01:43 PM   #3
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cogs are cheap.
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Old 10-25-10, 01:55 PM   #4
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http://software.bareknucklebrigade.c...it.applet.html

good to check skid patches too. 44 would keep you at 17 skid patches.. or going an 18 cog would give you 9.
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Old 10-25-10, 02:11 PM   #5
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http://software.bareknucklebrigade.c...it.applet.html

good to check skid patches too. 44 would keep you at 17 skid patches.. or going an 18 cog would give you 9.
He stated that he is not interested in skidding so skid patches are not relevant.
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Old 10-25-10, 02:17 PM   #6
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46x17 is a pretty reasonable gear ratio for a normally sized (not obese) person with healthy joints. I commonly ride up grades much steeper than any NY bridges with 49x16. Gearing down a few gear inches isn't really going to make those hills much easier, but it will further limit your speed and cause you to spin out more frequently, which is the reason you went to 46x17 in the first place. Its more likely your saddle is too low. Before wasting money on a new gear ratio, try raising your saddle incrementally a few mm at a time. Also, use your brake to stop and get into the habit of climbing out of the saddle. This will eleviate pressure on your knees and give you a power boost. Plus, the bridges are fun to attack.

Last edited by mihlbach; 10-25-10 at 02:20 PM.
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Old 10-25-10, 03:33 PM   #7
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How does crank length play into this equation?
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Old 10-25-10, 03:52 PM   #8
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Crank length doesn't have an affect on gear inches. Although shorter cranks are generally easier to spin, while a longer crank length will have more leverage to push a harder gear.
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Old 10-25-10, 04:12 PM   #9
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How does crank length play into this equation?

Crank length doesn't influence your gear inches, but they do influence your overall machanical advantage. Longer cranks give you more power, but force you to move your feet in larger circles, thus limiting your cadence. Shorter cranks give you less power, but you can sping faster. However, the tiny differences in crank lengths are so small, you are unlikely to notice a difference and certainly aren't going to make much of a difference to your overall power.
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Old 10-25-10, 05:46 PM   #10
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46x17 is a pretty reasonable gear ratio for a normally sized (not obese) person with healthy joints. I commonly ride up grades much steeper than any NY bridges with 49x16. Gearing down a few gear inches isn't really going to make those hills much easier, but it will further limit your speed and cause you to spin out more frequently, which is the reason you went to 46x17 in the first place. Its more likely your saddle is too low. Before wasting money on a new gear ratio, try raising your saddle incrementally a few mm at a time. Also, use your brake to stop and get into the habit of climbing out of the saddle. This will eleviate pressure on your knees and give you a power boost. Plus, the bridges are fun to attack.
+1 on checking the fit, not only saddle height but how far forward/back it sits.
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Old 10-25-10, 06:09 PM   #11
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Longer cranks give you more power, but force you to move your feet in larger circles, thus limiting your cadence. Shorter cranks give you less power, but you can sping faster.
power doesnt vary. torque and angular velocity do.
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Old 10-25-10, 07:05 PM   #12
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power doesnt vary. torque and angular velocity do.
Thanks Bill.
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Old 10-25-10, 10:33 PM   #13
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Come to think of it, it's been a while since I adjusted my saddle. Definitely could've sunk a millimeter or two.
Thanks for the advice all y'all! Will try saddle/height position for tomorrow's ride and report back.

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Old 10-25-10, 10:37 PM   #14
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power doesnt vary. torque and angular velocity do.
WOW WOW WOW WOW WOW....

STOP EVERYTHING...

adriano has been banned permanently, I for one, am upset.
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Old 10-25-10, 11:33 PM   #15
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WOW WOW WOW WOW WOW....

STOP EVERYTHING...

adriano has been banned permanently, I for one, am upset.
I noticed that as well. WhAA?A?AA?A?A?A?AAA??AA?!A??!?A!?A?
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