Which Bike gear is faster? 39/14 or 25/9?

Bryan M · 01-12-2008, 03:49 AM

I installed a 25 sprocket to a 14 freewheel.
But now all i do is accelerate to like 13 MPH
Im going to spend another $80 on a new cassete with 9T.

Which should i go with, buying new gears which are 25/9
or reverting to 39/14.

Can you guys please tell me the FASTEST ratio?
Thanks

Rusty · 01-12-2008, 03:50 AM

39/14 and 25/9 are pretty much the same ratio. 2.78 for the 39/14 and 2.77 for the 25/9, so for all intents and purposes, they are identical. 20 inch wheels=55.5 gear inches, 24 inch wheels=66.72 gear inches, 26 inch wheels=72.28 gear inches, etc. Stick with the bigger sprocket/freewheel combo. More teeth=stronger, lasts longer.

onlyme Mr G · 01-12-2008, 03:57 AM

It seems Rusty has done some calculations with ratios, which I wasn't even going to look at.

If the ratios are the same, then stick to a larger chainring, the bike will roll much better and wears better too!

.