Originally Posted by
mickey85
Hey all,
I have kind of an academic question...
Let's assume you have a bike with a given set of wheels, cranks, and tires. Is there any difference in gear ratios, if the gear inches stay close to the same? So, for instance, 40x15 and 48x18 are both 72 gear inches (or a gain ratio of 5.4). Is there any functional difference between the two setups as far as acceleration and braking ability?
If comparing two identical bikes, then effectively, no. A larger chainring/sprocket combination can reduce friction and technically make for a smoother more efficient drivetrain, by reducing the torque load on each individual tooth (spreading torque load out through larger number of teeth engaged) but the difference between these two combinations isn’t going to create any practical difference because they’re extremely similar in size. If you’re talking about a fixed gear setup and using the back-pedal ‘brake’, different size sprockets give varying number of contact patches on the tire. useful if you like to do skids, but otherwise inconsequential.