# teeth



## MGSuarez (Jan 27, 2003)

I remember being told a while back that 1 tooth in the front was equivalent to 3 on the rear cog?? Actually I dont remember the exact #s does anyone know?? thanks in advance.


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## Kerry Irons (Feb 25, 2002)

*Huh?*



MGSuarez said:


> I remember being told a while back that 1 tooth in the front was equivalent to 3 on the rear cog?? Actually I dont remember the exact #s does anyone know?? thanks in advance.


If you are talking gear ratios, you've pretty much got it backwards. The change in gear ratio is a percentage. Assuming a 53t chain ring, 3 teeth is 5.7% change. Assuming a 17t cog, 1 tooth is 5.9% change.


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## MGSuarez (Jan 27, 2003)

i guess what I am trying to figure out is which would be easier to pedal, less teeth on the front chainring or more teeth on the rear cog? Are they equivalent e.g. 1 less in the front = adding 1 tooth on the rear cog. 
thanks


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## MisterMo (May 31, 2004)

*I'll try........*



MGSuarez said:


> i guess what I am trying to figure out is which would be easier to pedal, less teeth on the front chainring or more teeth on the rear cog? Are they equivalent e.g. 1 less in the front = adding 1 tooth on the rear cog.
> thanks


In general: 
Less teeth (smaller ring) on the front =lower gear = easier pedaling
More teeth (bigger sprocket) on the rear = lower gear = easier pedaling
The opposites are true in both cases. Your 'easiest' gear on the bike is the combination of the smallest gear in the front and the largest in the back; the opposite extremes will give you the 'hardest' combination. You've probably doped this all out yourself.
Your question about equivalance is essentially moot since your front chainrings differ from one another by ten or more teeth. You can only shift the front by large increments whereas the difference from one rear sprocket to another is usually only one or two teeth.

Presuming your bike has, as many do, 2 or 3 front chainrings and 9 rear sprockets you have potentially 18 or 27different gear combinations. However, you will not have this many different ratios as in some instances differing gear combinations produce nearly the same ratio. This is OK since there some combinations which are hard on your chain & should not be used. In general one should avoid 'big-big' and 'little-little' combinations.


Count your teeth, pull out your calculator and make a chart. By the time you've finished you'll understand it perfectly. 
For each gear combination divide the number of front teeth (your input) by the number of rear teeth (the output). For example 52/12=4.33 In that gear combination 1 rotation of the pedals will turn the rear wheel 4.33 revolutions. That's flying right along but it's also a lot of work. In another example 30/25=1.2 That's not nearly as many wheel revs per pedal rev but it's also a lot less work. Doing the same math for all possible combinations should give you a good sense of the progression of the gear ratios and also the knowledge of which are duplicates.

Hope my explanation is not too confusing.


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## RodeRash (May 18, 2005)

*Did You Catch That ???*

Let's look at this by analogy. 

You have three times as many teeth/cogs on the front chain ring as on the rear sproket. Let's say you have 48 teeth on the front and 16 teeth on the rear. That means one revolution of the cranks will turn the rear wheel three revolutions. 48 divided by 16 equals 3. 

If you shift into a 32 tooth chainwheel, you lower your gear. 32 divided by 16 equals 2. Your rear wheel goes around twice instead of three times. 

Back on the 48 tooth chain ring, you shift into a 24 cog rear sprocket. 48 divided by 24 equals 2. You're in the same gear as 32 X 16. The wheel goes around twice for each revolution of the crank. 

24 tooth in the rear and 32 tooth on the chainring. 32 divided by 24 equals 1.33333. The wheel goes around one and a third times for each revolution of the crank. 

Gears are designated, or used to be designated, in "inches" -- You figure the diameter of the rear wheel in inches and multiply that by the number of times the wheel goes around with each turn of the crank. 

27" wheel, which is what they used to be before they went metric. 48 tooth chainwheel, 16 tooth rear cog. Wheel goes around three times each revolution of the crank. So, 3X 27" equals 81" gear. Sprint road gears run in the 88 to 100 something range. Climbing gears run around 50 inches, more or less. Level road gears run 75" more or less. 

It's basic math. Diameter of the wheel (Wd), times rear cog (rc) divided into the front sprocket (fs). 

G = Wd X (fs/rc) 

They used to provide "gear tables" to riders on a wallet sized card. 

Now that we have 700 cm wheels, I don't have a clue about gears. I'm still doing "inches."


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## MGSuarez (Jan 27, 2003)

*Ss*

Well I guess I left out an important fact. This is on a Single Speed. So what I want to know is running a 32 x 16 the same as a 34 x 18? So gear inches would be 52 - 49. So the 32x16 would be more difficult to pedal? So a change in front teeth is greater than a change in the rear?? A 34x17 would give the same gear inches but, would if be more difficult to pedal than the 32x16? Or would it feel the same?


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## wim (Feb 28, 2005)

*Interesting question.*

A gear made with more teeth is a little easier on the bike than the same gear made with fewer teeth. More teeth distributes torque over a larger number of teeth, meaning less stress on chain, chainwheel, cog and rear hub and, to a small degree, the frame. The downside of "more teeth" is possibly a longer chain, and a bit more weight because of the larger chainwheel and cog.

Easier to pedal? Interesting question. Years ago, a lot of track riders used a 92-inch gear for all events. For steady speed events like the pursuit, they'd make that gear out of something like a 51 front-15 rear. For sprint events, they'd make the same 92-inch gear out of a 48 front-14 rear. Some riders swore that there was a noticeable difference. They claimed the 92-inch gear made with more teeth was softer and easier to pedal round, while the same gear made with fewer teeth felt "harder" and made it easier to jump explosively. I never could feel much of a difference.


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## carioca (May 27, 2005)

RodeRash said:


> They used to provide "gear tables" to riders on a wallet sized card.


Nowadays you can make a handy dandy gear chart on a spreadsheet program, print it and tape it to your stem. A friend of mine who raced always had his gear chart taped on his stem during training rides. Whenever he changed the crank or the cassette he would print a new chart and tape it to the stem. After a while he pretty much memorized all his gear combos for whatever crank/cassette combination and stopped printing the charts... He would never have the chart there when he raced, however.


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## RodeRash (May 18, 2005)

carioca said:


> Nowadays you can make a handy dandy gear chart on a spreadsheet program, print it and tape it to your stem. A friend of mine who raced always had his gear chart taped on his stem during training rides. Whenever he changed the crank or the cassette he would print a new chart and tape it to the stem. After a while he pretty much memorized all his gear combos for whatever crank/cassette combination and stopped printing the charts... He would never have the chart there when he raced, however.



Let's see . . . On my "stem console" I have a cycle computer, a heart rate monitor and a spread sheet with LT and heart rate. I should add a spread sheet for my gears. Then I'd be looking at read outs, dials numbers and data all the time and would never see the road.

Gears -- on the rear casette (We used to call them clusters, back when they had five "clusts.") middle gears for level ground, smaller cogs for down hill, larger for climbing. I don't worry about "inches" or whatever we're designating gears in these days. I just ride the one that works for the road I'm on. 

"One gear makes you larger. And one gear makes you small. But the gears that mother gives you don't do anything at all. Ask Alice, when she's ten feet tall!" -- Jefferson Airplane.


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## wooden legs (Oct 20, 2003)

really easy simple awnser:

1 tooth in the rear is a much bigger change in gear than 1 tooth in the front.
There is never an exact ratio, like 2.6 teeth in the front = 1 tooth in the rear cause it's all percentages, i.e. a one tooth change from a 39 to a 40 is a bigger change in gear inches than a 53 to a 54.

my advice to simplify all of this is find an online gear inches calculator or chart, and run all the combinations through that, any ratio that comes out on the same gear inches is by definition the exact same gear.


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## MisterMo (May 31, 2004)

MGSuarez said:


> A 34x17 would give the same gear inches but, would if be more difficult to pedal than the 32x16? Or would it feel the same?


Equivalent gear inches = equivalent gear ratio (with the same wheel, of course). It should feel and be exactly the same.


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