Sprocket Size & It's Effects

[FrizzleFried]

OK... so my rudimentary math skills tell me that if I go from a 40 tooth sprocket to a 36 tooth sprocket, I am reducing the number of teeth by 4... or 10%...

I would then assume that at the same RPM my bike would be running 10% faster than it was prior... right?

I would then assume that I would lose about 10% of my torque across the board... no?

I suspect this may not work exactly right though as there is a front sprocket in play, but what do I know?!?

 

[Sidewinder Jerry]

OK... so my rudimentary math skills tell me that if I go from a 40 tooth sprocket to a 36 tooth sprocket, I am reducing the number of teeth by 4... or 10%...

I would then assume that at the same RPM my bike would be running 10% faster than it was prior... right?

I would then assume that I would lose about 10% of my torque across the board... no?

I suspect this may not work exactly right though as there is a front sprocket in play, but what do I know?!?

The basic thing to remember is a certain horse power can only move a certain weight at a certain max speed.

For instance on my shifter bike if I'm running 7000 rpm in a gear at wide open throttle on level ground and shift to a higher gear the rpm will drop to around 6000.

 

[weefek]

Not really, no.

Generally the bike will go whatever top speed due to whatever RPM your engine decides to run at. So going to a 36 tooth vs a 40 just means the same RPM results into a higher top end speed. However, this also increases the load on the engine (ie wind drag) so it doesn't end up mathematically perfect. Like @Sidewinder Jerry said.

Just google 'gear ratios'. Small tooth drive sprocket and large tooth wheel sprocket works the exactly same way.