# Bicycle Gear ratios...do different gears (same resultant ratio) drive differently?

On a multi-speed bike, when you change gears to a setting that feels comfortable, will you feel a difference if you switch to a different combination of front/rear gears that result in the same ratio?

Let me illustrate it with this terrible bike setup:

If I had a 4 speed bike (2 gears on the chain-ring and 2 on the cluster) that had 3 resulting gear ratios, would I feel a difference between the 2 matching ratios? I’ll suggest ratios of 4:1 (big front, small back), 2:1 (big front, big back), 2:1 (small front, small back) and 1:1 (small front, big back).

There would be a slight differnce as the chain will fold and unfold less with bigger gears, and the tension on the chain will be different.
But I’m guessing thie diffrence would be minimal.

even easier test: fromt has 20 and 30 teeth and so does the rear.
I’m guessing 30:30 and 20:20 will fell about the same.

Brian

With the same gear ratios, however obtained, the pedalling effort remains the same. It make no-never=mind.

Perhaps I should ask if the effort will be any different.

The ratios will be the same, but will the effort required to pedal be different? The result would still be the same…taking 1 full revolution of the pedals to create 2 revolutions of the wheels.

very elementary lesson in calculating gear ratios:(in case you dont know)
Take the number of teeth on the front sprocket, divide it by the number of teeth on the rear, and multiply by the diameter of your wheels

the number of the gear is the number of inches you will move forward with a single revolution of the pedals. So a gear of 86 will take twice as much muscle power as a gear of 43. It doesnt matter which specific front and rear sprockets you use: what matters is the final number

.

No difference for an ideal bike. However, different gear combinations will have different chain angles (relative to the gears). Greater angles as the chain comes off the gear (instead of staying in the plane of the gear) will cause more wear of the gear teeth; in extreme cases the derailleurs might have a hard time keeping the desired gear settings (and, of course, if the chain is slipping or popping then the bike will be harder to ride).

Strictly speaking, if you’re talking gear ratio, you don’t need to multiply by tire diameter. And that number (the gear inches) is not the distance you will travel (development); you need to multiply by pi. Gear inches is a reference to the days of the penny farthing - the gear inches is the equivalent tire size (which would have been fixed on the old bikes) that results from using that gear combination.

And a doubling of the development doesn’t require ‘twice as much muscle power’ to travel; even with the same power input, the torque will change - that’s too much of a simplification.

In an ideal case, only the ratio matters. If two different gear combinations give you the same ratio, the effort to maintain a given speed would be the same.

In a real-life bicycle, there are slight differences:
[ul]
[li]The rear derailleur has a spring-loaded mechanism to take up chain slack, but it has limited capacity to do so. If you use the largest front gear and largest rear gear, the derailleur will be at its limit, and it may not work very smoothly. With the smallest/smallest combination the chain may be so loose that it bounces around.[/li][li]The largest front gear is on the right, and the largest rear gear is on the left. So a large/large or small/small combination will cause the chain to be slanted, which reduces efficiency.[/li][li]There is some experimental results that say for a given gear ratio, smaller gears are more efficient. (Sorry, no cite right now, I’ll dig it up later.) Possible explanation is that chain vibration is a major source of energy loss, so the higher the chain tension, the smaller the loss. And for a given bike speed and power, smaller gears results in higher chain tension.[/li][/ul]

After ruminating on the above…

So the concensus seems to be that it is the ratio that dictates the effort. I think one would be able to feel the differences in the mechanics of the system (a la SCR4) and be able to distinguish those factors.

I apologize now for the following question (it being 20 years since my last physics course).

Does the torque you are applying to the crank arm (small vs large ring) make a difference to the power that is transmitted to the wheel, or does the rear gear negate the difference?

I should have mentioned that the “real-world” factors are on the order of 1%. Possibly measurable, but not something you can feel.

Are you asking whether the efficiency depends on applied torque? In an ideal case, no. In real life: again, possibly a measurable difference, but not noticeable.