Last weekend in the Flatbike shop, we had two gearing-related discussions with potential customers:
- One caller wanted to know the teeth numbers for sprockets on the rear cassettes of various CHANGE models, to better assess gearing combinations of two bikes for touring potential.
- The other understood what the rear derailleur was for, but was unclear on the purpose and usage of the front derailleur.
Those two perspectives are essentially the end zones of a very wide cycling market, ranging from technical experts to those just learning the nuances of mechanical advantage. How do we make sure both have an excellent cycling experience?
Mechanical advantage 101
First, we make physics as simple as a stick or a gear.
Sometimes you are dealing with something hard and want to apply lots of force, so you have a lot of motion that moves something else just a little bit. That’s equally true with a long crowbar handle lifting something heavy and a spinning small gear turning a big wheel slowly uphill.
Or, sometimes you want to apply a little force and move fast. That’s equally true with a quick wrist flick throwing a ball a long way and a large gear spinning a small gear (with a wheel on it) a long way.
Gearing 101 (applied mechanical advantage)
Small turning large: If you want uphill gearing, then you can get that on your rear derailleur by aiming for the largest gear you can find when shifting with your right thumb. Press the big lever once per gear.
Still not easy to climb a steep hill? You can get even more mechanical advantage by making your front gear (called the chain ring) smaller, because you’re still trying for small turning large. That requires shifting with your left hand on the small lever, with your index finger.
Large turning small: For downhill gearing, reverse it. You’re looking for small in the rear (with your right hand) and large in the front (with your left hand).
Gearing 201 (gearing ratios)
So how does one bike’s gearing apply to another? It’s not the number of gears that’s important, but the range of gearing ratios.
When we place the tooth counts in a table, then we can see how many times the wheel goes around for each pedal revolution. This is called the gear ratio. Here are the gear ratio tables for three different CHANGE models. (NOTE: You might need to double click on a table to enlarge it for viewing).
That’s a lot of numbers. What does it tell us?
First, for all-around gearing range, the CHANGE 702 commuter bike leads the way. At the high end, your wheel is turning 4.5 times per pedal revolution; at the low end up a hill, just 0.9 revolutions.
The CHANGE 611 rugged hybrid has the next highest range, reaching up to 4 wheel spins per pedal revolution and even below the CHANGE 612 mountain bike at 0.6 on climbs.
And for overall most climbing gears, the CHANGE 612 offers the most choices.
Gearing 202 (what not to do)
Finally, note that the tables have some greyed-out gears. Today’s derailleurs are impressively engineered for maximum range, but some unnecessary combinations put more stress on the system than others. The greyed out combinations do this:
The best general plan is to ride mostly in the middle chain ring (front gear) and stretch up or down to a smaller or larger chain ring when you need to go faster or climb a steeper hill.
Gears for different uses. Optimal combinations. Awkward combinations. It’s a lot to remember!
The important thing to remember is, your bike has the ability to make any ride easier on your legs, just by making some small gear adjustments as you ride. And who doesn’t want biking made easier?