April 22, 2014
After biking the Ironman Wisconsin bike course and dealing with those hills, I thought it might be time to understand my own gearing better. And I said I would post more about gears soon – so here you go! This won’t be the most exciting post you’ll read, but I’ll try to keep it from being too boring.
First, watch the video below – it’s pretty much the best video explanation of gearing that I’ve ever seen. (You will probably have to go to the actual website, or, if it doesn’t play, search You Tube for “Bicycle Gears Explained” and it should be the first or second video that pops up, by Terrycycles). It’s fairly short and tolerable, I promise!
Ok, so you watched the video, right? Well, let’s recap just in case you didn’t even though I’m sure you did. Back when bikes were first created they looked like this:
The pedals in the old bikes before gears were attached right to the wheel, for a 1:1 gear ratio – one turn of the pedals = 1 turn of the wheels. Thus, the size (or diameter) of the wheel mattered, as a bigger wheel was harder to turn over, and this is known as wheel inches.
Alright, I’m going to take my best crack at interpreting “low” and “high” gears, based on this. The introduction of gears allows you to change how hard you need to work to push the pedals, much like if you could swap out the front wheel with different size wheels, with the “inches” corresponding to the size of the gears. Basically, a big wheel = many inches = big gear = harder to pedal, and a small wheel = fewer inches = lower gear = easier to pedal. So, Low gears are better when it’s harder to turn the wheel over – when you’re going uphill and you want it to be easier to turn the pedals – and high gears are better when it’s easy to turn the wheel over and you want it to be harder to turn the pedals – going downhill. Another, maybe easier, way to remember it is taken from Mr. Bike: “low = slow, high = spry (fast).
The next thing she does in the video is talk about how to determine what gear ratios and inches you have on your own bike. So I did this with my tri bike, Delores. Delores is a double, meaning I have two large chainrings in the front. She has a 52 tooth large ring and a 35 tooth smaller ring up there. In the back I have a 10 speed cassette, meaning I have 10 different cogs each with their own number of teeth. The number of teeth from smallest to largest is: 12, 13, 14, 15, 16, 17, 19, 21, 23, 25.
Now that I have that info…on to Sheldon Brown’s Bicycle Gear Calculator! I’ve used his website for many years for other things so I was already aware of this website. For a little background – Sheldon Brown was an amazing bicycle mechanic of Harris Cyclery in Massachusetts who published a huge website where you could geek out on just about any piece of bike hardware that you wanted. Sheldon passed away in 2008, but his shop and avid fans keep his page updated. And he has a calculator for determining your gear ratios on it, which you saw on the video. If you plug my details in to the calculator, you get the following table:
Following Shimano’s recommendation as noted in the video, I crossed out the gear combinations they do not want you to use with a 10-speed to reduce rubbing and stress on derailleurs, and I got this table:
So you can see – assuming I did this all correctly – I have only have two gear combinations that really overlap. I also have an amazing amount of variety of gear inches available to me. I guess I knew this intuitively, since I was gearing by feel mostly before this. Of course, I probably still will – it’s not like I’m going to be calculating anything fancy while trying to cycle up or down a hill. But it’s neat to see and may still make me a better cyclist as I feel more confident about which of my two chainrings to be on to get the high or low gear I’m seeking. Totally worth the time to do this.
Hope you had a good Easter and have some candy for me!