Online Bike Coach

Where Cyclists and Triathletes get Faster/Stronger/Leaner/Sooner

Rotor Optimal Chainring Position (OCP) – Flatter Terrain

The Rotor Optimal Chainring Position (OCP) – Use the Mechanical Advantage

Lake Pueblo State Park Singletrack
Lake Pueblo State Park has miles of open, flowy singletrack that is accessible almost year round. It is not heavily trafficked, and often, I was the only cyclist out there.

I’ve been a big fan of the Rotor Optimal Chainring Position App ever since it came out in, what, 2012? One of the FIRST people affiliated with the original ROTOR bike and crank system was named Andre, and he lived in Dallas. We rode past his house literally hundreds of times.

Later, one of the last great brand representatives, a guy named Howie, introduced me to the founder of Rotor Components, and we were able to discuss their product and goals in broken Spanish via WhatsApp. Later, Howie sold his practice to Kervin Quinones, and Rotor has a separate office in Salt Lake City, Utah.

But it’s the Concept of Optimal Chainring Position (OCP) that I’ve studied, and then applied, to all of my bikes since 2003. I even wrote a chapter about Moment and Crank Torque in my now completely outdated book (which is still available on Amazon).

The TL:DR? It works. It’s not a gimmick. The gains are small, but they do add up. The more pronounced the slope, the more the Optimal Chainring Position (OCP) works. But you have to know what you’re doing, and it’s definitely terrain-specific.

Optimal Chainring Position (OCP) in the Sierras vs. Optimal Chainring Position (OCP) in the High Prairie

When I was riding my mountain bike in the Sierras in Reno, I used the Rotor App to determine OCP, and it DEFINITELY made a difference. I liken riding with an ovalized chainring to ‘hacksawing’ up the hill. You can ‘feel’ the power jump with each pedal stroke, and then feel it sort of ‘hang’ in the area where the ring radius is lowest. This is intentional. The gains are measured in millimeters per revolution, and it adds up to MAYBE 3 links of a chain over the course of a complete chain revolution. But those millimeters, those centimeters, add up. And again, the steeper the terrain, the more you feel that lever-action working. After several rides over the years in Reno and on Peavine Mountain, I ended up riding in Position 1, to tackle the steep terrain.

It’s COMPLETELY DIFFERENT on flat terrain!

Riding in Pueblo was a different experience. the ‘climbs’ were maybe 1-2 minutes. They were POWER climbs. Trails were flowy and there were times there when I was working on smooth power output while letting the suspension soak up the smaller bumps and terrain. There were areas where power was necessary, however, in 2-5 second spurts. This became the norm, and I used Garmin’s Strava Segment Chaser to gauge myself against previous, faster cyclists. While I never caught the leaders, I definitely was able to use the ShockWiz technology to optimize my suspension setup, and use the Rotor Optimal Chainring Position in a different setting, to get just a wee bit more power out of every turn. It was a VERY anaerobic demand. Getting a few extra watts and a few extra centimeters out of every 30 meter section of twisty singletrack, made a difference.

Rotor Torque 360 App OCP Position 4 torque curve
This is a screen capture of the Rotor Torque 360 Visual Overview. Depending on what model of Rotor Power Meter you purchase, you can see Left/Right balance, Instant Power, Instant Cadence, Heart Rate if you choose (this could be useful when looking at Optimal Chainring Position on longer climbs), ‘OCA’ – Optimal Chainring ANGLE in instant values, and the all-important ‘OCP’, which shows you which chainring position might be optimal both instantly and over time. Finally, you get a BEAUTIFUL torque curve. The larger loop is the power curve part of the crank revolution. The smaller loop is the ‘drag’ from the trailing leg. Finally, the Green Arrow is a visual image of the ‘OCA’. In this case, it’s JUST BELOW 90 degrees.

 

Now, you can refer to my book or maybe you can still find a long-lost blog post about it in the internet archives, but the gist of the discussion goes like this:

Archimedes And His Simple Machines Work Better With Optimal Chainring Position (OCP)!

A crank is nothing more than a simple lever.

A crowbar is a crank and a crank is nothing more than a lever.
Repeat this 180 times per minute, and you might actually get somewhere….

It uses MOMENT at the 3 o’clock position to ‘pull’ on the chain, which touches the chainring at the 12 o’clock position. Think of it like a crowbar. You can make the lever action easier if you lengthen the crank (not recommended), or you can increase the radius from the center of the bottom bracket, to the area where the chain touches the chainring. It gets a little more complicated when you add inertia. Legs show the most power between 2 and 5 o’clock. When you’re not thinking about it, peak power usually occurs at the 4 o’clock position.

Hence, look at the arrow three images above. The arrow is at 98 degrees, or just past 3 o’clock. If a crank were, say 170 mm, at that exact position, it’s only 155mm. The MOMENT has shrunk, but the POWER and INERTIA have both grown. Place the Rotor Oval Chainring Optimal Chainring Position at ‘4’, and VOILA! A 6-9% boost in power AT THAT ‘MOMENT’ in each revolution!

Optimal Chainring Position (OCP) – SLOPE vs FLAT

On Peavine Mountain, with regular climbs in the 8-15% range for minutes on end, The Rotor Optimal Chainring Position (OCP) continuously recommended OCP 1. However, at Pueblo State Park, with all the punchy terrain and twisty singletrack, it frequently recommended OCP 4. Here’s a summary view of a short segment.

Rotor Torque 360 App OCP Position 4
I took this screenshot about 25seconds into a 20 minute effort on singletrack.

Notice that The Rotor Optimal Chainring Position (OCP) shows “Position 4”, while the Optimal Crank Angle shows ’95 Degrees’.

CONCLUSION

I performed this test about 3 times, before I made the change. The values for The Rotor Optimal Chainring Position (OCP) were consistent between Positions 3 and 4. Now, on my road bike, which is now 10 years old, the sprints and power climbs in the big ring kept me in Position 4. It feels comfortable on the road bike, so I pulled the ring, and placed it in Position 4 for the mountain bike.

I can’t say that this one change made all the difference, but I can say that it didn’t hurt. Look at the October 8, 2022 result, and look at the next several dates after that.

Strava Segment Pueblo State Park Northbound
Increased Power, Decreased Time. I’ve used Rotor products since about 2000, and I still think that they offer concrete marginal gains. You just have to know how to apply the information it provides!

Familiarity, plus power and fitness, plus perpetual tweaking of the Suspension system via the ShockWiz, made me faster. And Fast, is FUN!

Now that I live in Sacramento (long story for another time), I’ll probably go through the exact same thing, over 20 rides or so, and see where the Rotor Optimal Chainring Position (OCP) recommends I place my chainring. I don’t know if I’ll ever race again, but I’m having a blast learning and sharing the benefits I can witness myself in these technologies.

Thanks for reading, don’t forget to comment, and as always…

ENJOY THE RIDE!

 

 

Setting The Q Ring Position Based On Rotor InPower Ride Data

Rotor InPower Cranks Provide Crucial Insight

Rotor InPower OCP 1
Rotor Q Rings help make small improvements to power with every pedal stroke, but it’s on sections where terrain is steep, and traction is necessary, that they make the biggest difference.

I’ve been using Rotor products since at least 2000, when the RSX Cranks first became available. I have been a student of the original concept, and I use Q rings on all of my bikes these days. In 2012 or thereabouts, Rotor began building their own power meters. Specifically, they did it with the intention of providing data for the Optimal Chainring Position. Optimal Chainring Position, or OCP, looks at a rider’s power curve and helps determine where exactly the Q ring should be located.

Why is this important? Well, the Q ring acts like a crowbar, using something called “Moment“. This is a term in Physics. A bicycle crank at 12 o’clock has no moment. I bicycle crank at 6 o’clock has no moment. But a bicycle crank at 3 o’clock has a moment equal to the radius of the crank. In my case, that is 165mm. When the Rotor InPower software takes into account Moment plus Inertia, it allows Physics to provide an edge in the power output. For road cycling on flat terrain, I usually ride at OCP 4 or even 5. Until this week, I rode the mountain bike at OCP position 3.

What Changed

Rotor has software for their InPower and 2InPower cranks, as well as their most recent power meters, that runs as an app on a cell phone. I used this app in real time, as I rode up my favorite trail. While I had figured that OCP 3 was optimal, what I realized over the course of the climb was that the steeper the terrain, the more the Rotor software wanted me in OCP 1 or even 2! I was surprised by this revelation, but in review, it makes sense. When a cyclist is climbing, the “Moment” is still optimal at 3 o’clock. However, inertia is altered due to gravity, friction, and cadence. Placing the OCP at 1 brings that ‘Crowbar’ effect back.

I made two videos connected to this post. The first is pre-ride, when I was making my change to the crank and chainring. The second is post-ride analysis. I felt the change in torque IMMEDIATELY, and while I am not nearly as fit as I was two years ago, I am excited about the change, and hope to duplicate the lesson on my road bike in the near future.

Rotor has SCIENCE to Back Up Their Claims

While I’m not a qualified scientist, I do count myself as a certain Mad Scientist. That is, I rely on PhD’s and MD’s and DO’s to perform the studies that prove or disprove what I’ve ‘seen’ over the decades that I’ve been coaching. One of my absolute favorite scientists on Q Rings, who is also a highly skilled athlete and racer, is Dr. Christie O’Hara. Here is a short link to an article about her studies with Q Rings. She’s moved on from Rotor to other ventures in Academia, but her work stands and is seminal to the theory. The gains are small, but consistent, and in a sport where small gains are critical, Q rings in the Optimal Chainring Position can make a difference for any road or mountain bike cyclist.

Enjoy the videos and don’t hesitate to leave some feedback. I’m enjoying the process and as always, ENJOY THE RIDE!