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We had a beautiful hilly and windy ride today that mostly followed the length of Loch Ness.
Which leads me to the question, does gearing on a bicycle really matter? You betcha. Some may question whether I am qualified to discuss anything physics-related, as evidenced by this thoughtful note that a friend wrote in my high school yearbook:
Let me take a shot at this anyway since I want to attempt to make a point. Most bikes have two “chain rings” on the front by the pedals, called a crank:
The size of a chain ring is defined by the number of “teeth”. A standard crank has 52 teeth on the larger chain ring and 36 on the smaller. “Compact cranks” are also popular and are 50/34.
Then there is the rear “cassette” which has between 10 and 12 rings or “sprockets”. The smallest usually has 11 teeth and the largest sprocket on a standard cassette has 28.
What does this have to do with physics? To propel a bike forward, the power supplied by pedaling is transferred to the chain and then to the rear wheel. If you are in a front ring with 50 teeth and a back sprocket with 25 teeth, for every revolution of your pedals the back sprocket fixed to the rear wheel will rotate twice,
A cyclist tries to spin (called “cadence”) at the same rate regardless of the terrain and adjust the gearing to compensate. You will go at a slower speed up a hill in an easier gear combination, but to spin at your “flat road” cadence, you will more than likely need to use the smaller chain ring in the front and a larger back sprocket. Using a 34 in the front and a 28 in the back, every revolution of your pedals only rotates the back wheel a little more than one time. If you think you can ride up a mountain road in a 52 front and 11 rear, that will happen right after you beat Lebron James in a game of one-on-one — in your dreams.
I know what many of you are thinking — this is a misguided musing by a physics class truant. Well, since 2008 I have used a Garmin cycling computer that has tracked a number of data points for each ride I have taken. And it ain’t a pretty picture. I am slowing down and am less powerful.
The fewer teeth in the front chain ring, and the larger the back sprocket, the easier it is to go up hills. Until I was about 50, I had a 52/36 in the front with an 11/28 in the back. My easiest combination for steep hills was a 36 front and a 28 in the back. I then went down to a 50/34 in the front and eventually to a 11/32 in the back. This year I changed my back to an 11/34 so that my easiest combination is 34 in the front and 34 in the back.
Serious riders will snicker at my rear 34 (including a certain woman who shares my last name and calls it my “wussy 34”). But I’m still out here spinning due to the wonders of physics with better gearing. Yes, slower than I used to be, but still able to enjoy the sport I love. So no excuses for any of you — just find the right gear combination and get out here.
And there was a lot to enjoy today. Here are a few pictures on our ride from Inverness to Fort Augustus:
After our ride, we took a boat tour on Loch Ness and the highlight of the day was catching a glimpse of Nessie:
After all these years it is about time you understoof physics relaton to physical, your dad would be proud(er). Althought I appreciated the lesson I appreciayted the photos a bit more, especially he one of Nessie portraid as a swimming double humped camel. Will you get into the "gear" you will be wearing in future posts? I have yet to find someone gaining life's experiences and getting younger in the process so onwards with the peddaling and recounting the days ahead. If you can catch up to her say hi to Mary!
As a mechanical engineer, about 1/2 way through the blog I said; "Wait a minute, why am I reading a physics post from a physics cutting lawyer??"
But, I continued anyway.
The trend (started by a Texan named Lance) is to spin much more than in days of yore.
If you caught the highlights from the final stage of Le Tour, you would have seen a close up of the rear cassette of a couple of bikes.
Granted, there was a hill involved in that time trial. Still, the size of the inner cog surprised me enough to take note.
So, gearing has morphed along with tire width and tire pressure.
That said, you are still "Wussy 34" to me…
When I moved to CT, I immediately ditched my 11/28 for an 11/30. There is no shame in physics!
I used to ride a custom built 10/23 cog on my disk wheel for flat courses... but that's a whole other thing! Enjoy the trip!
Sign of a great lawyer is being able to break down complex concepts for the lay person. Really enjoyed reading this. Thanks, Jon! I was going to try to re-brand the word “wussy” the same way Charlie XCX did with “Kamala IS Brat,” but “Jon IS Wussy”does’t have the same catchy flow. :)
nessi made me laugh