Gears on a bike

[FlyingCyclist]

Can someone please explain to me how do you tell how many one has?

 

[TissoT]

Example : 10 number of cogs on the back wheel.. ..2 no of chain rings on the front = 20 .....and so on ..

 

[Rickshaw Phil]

^^^^ What @tissot said.

I'll just add that in the real world (as opposed to the marketing guff) it's not practical to use all of the gears you theoretically have. Quite a few of the gears overlap on a bike with a double or triple chainring set-up and there are some gears you should actively avoid using (big chainring to big sprocket and small chainring to small sprocket) as they can wear the chain excessively.

 

[MikeG]

@Nigelnaturist , you do realise that this is the Beginners section? A table of gear ratios isn't really going to help a person who is asking how many gears a bike has got.

 

[ianrauk]

Mike it was to show that overlapping gears is no bad thing, and to dismiss the idea that a 30th inner ring is only for climbing, I couldn't word it in such a way as to make it clear, but if you deem it inappropriate I will delete it.
I appreciate its a beginners section, I understood this lot when I started cycling, just not quite how it all worked together in practise.

I can see were Mike is coming from Nige.
After god knows how many years, miles and gear changes I have done over the years I don't even understand that chart.

 

[Newman8]

I go with Phil totally:
In practical terms, 10 on the rear & 2 on the front = 11 (approx!) not 20... That is just marketing talk.
Going up in the gears - at some point roughly in the middle of your rear cassette you will change to your outer front chainring & the opposite coming back down. It doesn't always have to be the same cog. It's just a progression that seems right at the time.
Plus: It keeps a straighter line on your chain to stop it rubbing on your front mech or stretching your rear mech - especially in a big/big combo which could break your rear mech if there's not enough slack in the chain.