How I think about setting up gearing
Hi All - I wanted to share how I think about my bike gearing setup. I am interested in how other people think about it.
I have Dura Ace DI2 on my bike. That came as an 11-speed with 11-28 cassette and 53-39 chain rings. I race IMMT with the out of the box setup last year and spiked my power much more than I had hoped to (VI 1.07). Heading into IMCoz, I was looking for a setup that would allow me to ride through the wind staying aero with a constant cadence and shifting to control power.
I created the chart (below) in order to see which speeds I would be riding and ended up with the setup on the left-hand side of the chart. This gave me compact chain rings and a 12-25 cassette – essentially 1 tooth different between nearly all the gears I would be riding. It worked out very well. I had VI < 1.02 on a day with winds exceeding 25 mph on the back side of the island.
Heading into Raleigh 70.3, I looked at my race last year. Specifically, I looked at the histogram of speeds that I achieved on the course. Although a portion of the course id different this year, it is essentially the same bike race.
The chart shows that I had a gap between my 15t and 17t gears on the cassette. Cumulatively, I spent over 27% of my time last year at speeds between 21 and 26 mph. This year I am opting for a 12-28 cassette that drops the 11t gear, one that spins out at about 35 mph / 100 rpm (only a couple % of the time using it) and adding a 12t gear that looks like I will spend nearly 13% of the ride using.
In any case – Let’s see how it works!
Comments
I used Mike Sherman's Bicycle Gear Calculator to get the speeds / rollouts. I'm checking the App out - it looks pretty cool.
I tried to d a couple things in addition to the rollouts to figure out what is best for me. First was to organize the rows by similar speeds so that I could understand where the gears overlapped. My setup will let me cross chain from big chain ring to big cassette, but I lose the last gear or two when I try going from little chain ring to little cassette, so I high lighted those.
Next, I pulled the speed histogram data from Golden Cheetah. I just did this manually over my ride on Raleigh 70.3 last year (since that is the ride I am planning right now), but it would be interesting to see speeds over several rides on similar courses. Intuitively I know that I didn't spend much time in my 11t gear, and the time I do spend in that gear gets spun out pretty quickly. Likewise, intuitively I knew that I was spending a lot of time around 21-23 mph.
I was pretty surprised to see that I had 27% at the latter speeds vs a couple percent at the former. Dropping the 11t and adding a 16t so that I had a third gear in this range is a no brainer.
The rollout / gear ratio apps show me the speeds for the gears, but they don't make that correlation of what gears I'm actually using.
I've read that the new Garmin combined with the DI2 can potentially keep stats about which gears are being used? This would be really helpful to figure out how to build a gear set for a course.
At the end of the day - if I am going to carry the weight, I want it to be useful!
Clearly you are a details kind of guy. I think that chart makes the data a lot more intuitive to understand.
It makes me want to look more closely at what i am racing but I think I will just have to use this as a "data collection" race since I don't want to change anything this late in the game.
Look forward to seeing you at the race.
R2