Saturday, August 31, 2013

Cranky Musings

Egg shaped works here.
I have heard a couple of things over the years about certain components. I tend to think about claims and then if I think it is interesting enough, I'll play around with stuff to see if I can verify the claims for myself.

Egg Shaped: One of these things I've heard and have been playing with is the concept of ovalized chain rings. The claim goes something like this: The oval is aligned in such a way that when you reach a "dead spot" in your pedal stroke the oval is in the "squished" position and makes getting through that dead spot easier. Then when you reach the power section of your stroke, the oval is at the widest part where your leg power can turn the gear over. Well, something like that anyway.... 

So I got a BioPace ring, a 42T from a seven speed crank, and took it home and then analyzed the Rotor site , which pointed me to how I could align the BioPace ring to best mimic what the Rotor chain ring does. Mounted that ring up, and went riding. (Never mind that it is on a 10 speed drive train. It works fine...)

Okay, so after six months of riding, what do I think? I think there is something to this, if you are more of a power cranker/masher. It does allow you to have momentum in the dead parts of your stroke, and keeps the speed up when you are cranking up a climb, instead of loosing it when you ultimately slow down at each point where your dead stroke is. (Or "deader stroke", if you will! "Anti-power stroke, perhaps?...whatever...) If you are a spinner, I don't know if there is as much of an effect, but it probably also helps you there. I tend to be a slower grinder in cadence on gravel roads, so I think, (for me anyway), this ovalized chain ring thing has merits.

"Spin Cycle" works here.
Short Arms: Years ago, I heard the original pocket of 29"er freaks in Grand Junction, Colorado were all about using 170mm cranks. Said it was better for the big wheels, but I have never really had anyone tell me exactly why. (And I've asked the folks that were at "ground zero" in this area, and they just said, "try it, it works!")

Well, ever since 2007 I have been using a 170mm crank on the OS Bikes Blackbuck. No other crank has ever been on this bike. I have several other bikes that are single speeds with anything from 175mm to 180mm cranks on them , and all are 29"ers.

So, does it "just work"? The answer is "yes" if you like to spin a bit higher cadence. Much like the rotor-esque BioPace chain ring, the shorter arms seem to allow for less "dead stroke" rotation when you are grinding out a climb in a slower cadence, plus you can maintain momentum going up off road/single track climbs better with a spinning cadence. At least I feel this. Now keep in mind, this is all for off road, trail riding, not on pavement or gravel. There the "spin cycle" about drives me nuts, although I must say it has made me a better spinner whenever I spend time on the Blackbuck commuting or using it on gravel.

So, there are my personal thoughts on how those controversial things work for me. I suspect that there are several others who feel at 180° odds with what I've just written, but I believe there is something to the claims. I've felt it, compared it, and it is repeatable. Maybe I need to invest in a power metering device to get into this deeper.

Naw....what am I thinking! I just need to go ride and have some fun already!


Jon said...

I use a 165 crank on my 29er hard tail, and it works fine. I don't feel any quantifiable difference between it and a 175, but I enjoy a bit more ground clearance in the rough stuff.

Brian said...

Coming off of double knee surgeries, I switched both my mountain and cranks to 172.5s to make it easier to spin. Over the past couple years, I've regained most, if not all of the strength I had pre-surgery, and have been climbing out of the saddle more frequently on both bikes. I recently switched both cranks back to 175s, and felt a noticeable difference in my average cadence (slower) as well as more speed retained when climbing out of the saddle. It's all a tradeoff depending on strength and riding style, in my opinion, but I think you're spot on in your observations.