tristen

Say for the purposes of discussion you have two different pairs of chainrings/cogs intended for use on exactly the same bike.

The first chainring and cog combination works out to be say 75 gear inches (on that bike)

The second chainring and cog combination have different numbers of teeth but also works out to be 75 gear inches (on the same bike)

so let's say for example the first chainring has less teeth than the second chainring and, unless i've been at my crack pipe (like again), that must mean that the first cog has more teeth than the second cog.

If both work out to be 75 gear inches, is there a difference in your ride?

this ultimately leads me to ask: if you want a different gear ratio, does it really matter whether you achieve it by altering the chainring size or by altering the cog size?

Squirrelli

In a nut shell, you'll feel a slight difference if the frames are different.

The difference is not in the drive train itself but more on the frame's geometry, tires, rear wheel, frame material/stiffness and crank length. If the X bike is of a stiffer material and have shorter chain stays, the acceleration should be theoratically be faster than the Y frame with a longer chain stays and things like that.

If the both of the bikes are spec'd exactly the same, then you won't even notice.

prathmann

Put down the crack pipe - if the first bike has a smaller chainring then it must also have a smaller cog to end up with the same effective gearing.

Using larger rings & cogs will add a little weight for those components and also for the extra chain links required. But it'll result in better longevity and marginally less friction in the drivetrain. It may also feel a little smoother if the alternative smaller cog is really small. For reasonable size components the differences will be very minor. Off road the smaller chainring would have an advantage in increased ground clearance.

tristen

yes (throws away crack pipe in sudden fright)

greyghost_6

I would also say that it wouldn't make much difference. For instance I ride a 53/38 in front and a 12-27 in back. Without doing the math, someone could get a similar gear ratio using a compact crank 50/34 or what have you, and a 11-23 in the back. You could argue that the compact+11-23 weighs less, but wears out sooner since the chain will have more contact with all the teeth more.

Corwings

https://sheldonbrown.com/fixed.html#gearing

There is a section of pros/cons for big/small.

CaptainCool

Last section of this page: https://surlybikes.com/blog/spew/spew...d_gearing_101/

tristen

cheers all, appreciate it.