Last week my coach and I were discussing a workout whereby I am supposed to cycle up Kings Mountain twice. I told him that my cadence is about 60-70 RPM usually, at which time he tells me about compact cranks.
Compact cranks are a crankset that have a smaller bolt pattern to allow smaller chain rings on the front. Basic mechanics says that using smaller front chain rings will allow more direct power transfers although at a higher cadence. And as Lance Armstrong always preaches, pedalling at a higher cadence is much better than burning your muscles out at a lower cadence.
I head out on my newly installed compact cranks. The feel is different as now the ratios favor a higher mechanical advantage for power transfer, although at the higher pedalling rate.
The first hill I encounter is a short 6 percent or so. I drop to a 34/25 and roll over it at 75 RPM. Not bad for 5 min out of the house. Normally, I am either grinding or out of my seat as it is only a stone’s throw away from my house and I’m barely warm.
As I move down Foothill Expressway, I find that my cadence is definitely higher for a given gear on the back. It also presents an interesting adaptation challenge as now I am shifting a bit more to compensate for my higher cadence. I also find I sit in a higher cadence a little longer because I am used to watching my speed and cadence together.
At the end of Foothill Expressway, there is a little steep climb up to Page Mill Road. It is probably a 5% grade or so. I downshift and make it up that hill at 85 RPM. Now I’m warm and going over a hill that normally requires me to stand and grind, even though it’s a short distance.
After that, it’s just a rolling ride to Woodside Road. There is yet another challenging, longer hill from Alameda de Las Pulgas to Canada Road. Again, I am about 10 RPM higher than normal, about 70-80 RPM. I cruise over the hump past Buck’s and onwards to Kings Mountain Road.
At Kings Mountain Road, I proceed up. My coach has asked me to do this twice and the day is warming up. I head up and on its very steep sections, I am about 70-75 RPM and on its flatter steep sections, I am about 75-80 RPM. As I spin up the hill, my HR is rising, as is the temperature. Some sections of Kings Mountain Road are fully in the sun, and as I pass through them, I am feeling the heat. About half way up, I start to crater because of the heat and the knowing sign is the drop in cadence to about 50 RPM, and general weakness through my legs. I grind the rest of the way up and decide to not the next climbing rep. Instead I continue down Skyline and 92.
One weird thing here is the competing climate. The very warm sun constantly beats back a chilling wind and in general, I do cool down. But I feel the energy has been sucked from my legs for sure. I recover as I blaze down 92 and hit Canada Road.
Here I am supposed to practice Ironman Race Pace. But it’s difficult because the heat has sucked my energy away. I proceed to spin and shift gears to maximize my speed relative to my energy level and while maintaining 90-95 RPM. On certain stretches, I do notice that my speed is higher, due to the higher mechanical advantage. I zip home and am glad to make it there. I run a quick 10 minute brick run and then I’m done.
Notes:
Need to take some time to adapt to the higher cadence pedalling. It is driving my HR higher to maintain the higher cadences. I need to shift more and be aware of the new power transfer ratios at each gear.
Definitely the compact cranks are great for hill climbing. Better spinning is going to allow me to get up and over hills without grinding and burning my legs. I am looking forward to getting used to them, especially prior to Ironman Austria.
Compact Cranks on my Bike
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