How to count teeth on rear sprocket ?? (serious question:) )

[coffeejo]

Keep your index finger of your left hand on tooth 1, while using the index finger of your right hand to count the others

That's my preferred method. Alternatively, clean each tooth as you count it.

 

[Profpointy]

Keep your index finger of your left hand on tooth 1, while using the index finger of your right hand to count the others

it's best to move the counting finger rather than keep finger still and turn the pedals

 

[SatNavSaysStraightOn]

look for the little number on the sprocket... 22T = 22 teeth... 11T = 11 teeth and so on

 

[fossyant]

Wipe the grime off one of the teeth...

Wot if there is no grime

 

[jowwy]

it's best to move the counting finger rather than keep finger still and turn the pedals

is the wheel not off the bike in this scenario - mine would be as not to get my fingers caught in said chainage

 

[coffeejo]

look for the little number on the sprocket... 22T = 22 teeth... 11T = 11 teeth and so on

See previous grime comments

 

[Profpointy]

for all the serious and not so serious suggestions the easy mistake is to forget if you counted the first tooth already or twice

 

[Cyclist33]

FFS.

Just count them. I mean, really.

Stu

 

[puffinbilly]

Keep your index finger of your left hand on tooth 1, while using the index finger of your right hand to count the others

This all wrong - here's what you need to do.
Keep your index finger of your right hand on tooth 1, while using the index finger of your left hand to count the others
.......perhaps it's just because I'm left handed.
Just been doing this over the last couple of days - looking to change cassette - from thinking the cassette was a 11-28 found it to be a 11-25 explains why some of the hills have been a bit of an effort.

 

[potsy]

You may need a friend to help, once you've used your fingers and toes to count to twenty you may have a few teeth left to count
Unless you are @hopless500 then you may be able to go up to 22

 

[ayceejay]

Dave: I take it you mean 'cassette' rather than just one 'sprocket'?

 

[fossyant]

You mean some of you don't know the number of teeth you have on every sprocket

13, 14, 15, 16, 17, 19, 21, 24

Am I weird

 

[winjim]

It's best to use an empirical approach. You will need a correctly calibrated bike computer with cadence measurement.

First, select the sprocket you wish to count. Find a nice flat straight piece of road, and ride your bike at a constant speed. Note the cadence. Now use the equation:
Speed(mph) = Gear(in) × Cadence (rpm) ÷ 336
to calculate your gear size in inches. Repeat this three or four times and take the average.

Now you will need to measure the diameter of your wheel in inches. Do this twice at right angles to ensure accuracy. Include the tyre inflated to the correct pressure. Now use this value, the gear inch value from earlier and assuming you know the number of teeth on your chainring, this equation:
Gear(in) = Wheel diam(in) × Chainring(teeth) ÷ Sprocket(teeth)
to calculate the number of teeth on your sprocket.

Repeat for each sprocket on the cassette.

 

[Yellow Saddle]

OK, try this method.
Count the teeth on the big chainring (CR)
Now have someone hold the bike's back wheel off the ground and turn the crank exactly one revolution. Count how many times the back wheel turns (R)
Calculate the number of cogs (yes, a tooth is called a cog) on the sprocket in question using this formula:

C (cogs) = CR divided by Revolutions of back wheel.

 

[Hugh Manatee]

Unless your friend is a time trail fan, they might need to take shoes and socks off and possibly take their trousers off too.