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If you look at the table below you'll notice that there is a huge difference between the number of teeth on sprockets 6 and 7. Less obvious is that the difference between 1 and 2, if expressed in percentage terms. Why does this matter?
If you look at the power curve on Shiftless Page you'll see that our goal is to pedal at a fairly constant rate. Too fast and we just produce spin, too slow and we work hard but don't get much out of it. Better to get it just right. There are two parts to "just right."
One part is our own ability to push the pedals, our strength and conditioning. Gordon Wilson seems to say that this is about 90 rpm. I can't go that fast, I guess I'm just a geezer. So I plod along at something slower where I am comfortable.
The second part is accomplished by gearing, sprockets and chains and all that. The Shiftless Page shows how I've calculated the ratios for my own bike; this helped me understand some of what was going on. Riding has helped with the rest, here's what I've learned.
Rear |
Teeth |
% Up |
1 |
13 |
|
2 |
15 |
15% |
3 |
17 |
13% |
4 |
19 |
12% |
5 |
21 |
11% |
6 |
24 |
14% |
7 |
34 |
42% |
I'm most effective if I can manage to stay in 2 through 6 except for extremes So,
- When it's mostly flat I stay on sprocket number 2 in front and only use cassette sprockets 1 and 7 in extreme and very temporary circumstances.
- If I can see that I'm mostly going to be heading uphill I use #1 in front. I avoid 6 and 7 in the rear because it puts the chain at a stressfull angle.
- If I can see that it's going to be downhill (Whoopeee!) I use #3 in front. I avoid 1 and 2 in the rear because... it puts the chain at a stressfull angle. surprise.
Oh, yeah, granularity. Refers to how fine the grains of sand are on the beach. In the ancient days of film photography "grainy" meant fuzzy, now we say pixelated. In biking fine granularity means a smaller difference between "gears." Early derailleur bikes were very difficult to shift correctly and many bikers, myself included, tended to find a gear that worked and leave it there. Now it's so easy that you can shift all the time. And you should.
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