So what's so important about power? Do you really need a power meter? Do you really need a two sided power meter?
The answers are simple. Do you really need a power meter? No! Do you really need a 2 sided power meter? No! However, if you want to take your cycling to the next level, if you want to get everything out of your pedal stroke, or make cycling more enjoyable, then... YES!
First, lets talk power meters. There are 3 types of power meters out there. There are one sided power meters like Stages, single sided Garmin Vector Pedal or Power Tap Pedals. All of these power meters will run you around $600. Then there are Power Meters built into the crankset or bottom bracket spindle. These options will cost you $1000 or more. Lastly, there are the true 2 sided power meters. Garmin, Power Tap, and now SRM / Look pedals that have power meters in both pedals. These options will run you about the same as the crank option, costing $1000 or more.
Most of these power meters are stuck to the bike. Stages puts their power meters into the left crank arm. The Crankset power meter option is ordered specifically for your bike. Nowadays, there are so many different bottom brackets, spindle sizes, diameters, lengths, that if you ever sell your bike for an upgrade, the power meter would have to be sold with the bike, and a new power meter purchased for the new bike. That puts you out a ton of cash.
With the pedal option power meters, you can always pull them off the bike and transfer them from bike to bike. Even if you take a vacation where you are going to be renting a bicycle, you can take your power meter pedals with you. This becomes a single time purchase.
Now lets look at the single side vs. the double side power options. With single side power, all you get to see is power. The problem with just looking at power is that it does not tell you much. As a Bicycle Shop Owner, and avid ultra endurance cyclist, and bicycle fitter, I have come to find the importance of efficiency in the pedal stroke. This is where a single sided power meter falls short. When looking at single sided power, all you see is how much power you are putting to the pedals. This does not tell you how much power is driving the bike forward (we will get into this aspect below.) With double sided power, you can see how much you are pushing with your quads, but you can also see how much you are sweeping and lifting the leg on the back side of the power stroke, 5 o'clock to 12 o'clock. This is the most important part of your pedal stroke, and effects your bike fit dramatically.
Efficiency Pedaling on the bike is defined as how much of the power from your quads drives you forward, verses how much of the power from one quad is lifting the other leg. When one leg is pushing down, the other leg is coming up the back side of the pedal stroke. A 100% efficient pedal stoke (which we will never achieve) means that you are using the smaller muscles in your feet and legs to lift that leg on the back side of the pedal stroke without needing any power from the quads. That way, 100% of the power from your quads propels the bicycle forward, and all the smaller muscles in your pedal stroke lift your leg 100% on the back side of the pedal stroke.
This is where a single sided power meter falls short. It can't tell you anything about the metrics of your pedal stroke, only power. When using the Garmin Vector 3 pedals, they have pedal stroke dynamics that tell you a ton. Here is how:
Torque Effectiveness (TE)- this tells you how efficient your pedal stroke is over the entire 360 degs of your pedal stroke. It is broken down to both left TE, and right TE. Since the power meters are separate, it gives you this value of how much you are lifting your leg on the back side of the power stroke, and how much power from your quads is going forward. 100% means you are lifting your leg completely on the back side of the pedal stroke, and 100% of the power from your quads is propelling you forward.
Power Phase - This tells you where forward power is being applied to the pedals, and where this power ends for each leg. It gives you an angle from 360 degs (Top Dead Center) all the way around and back to 360 degs. For a regular cyclist, power phase usually starts around 15 degs (1 o'clock,) and ends around 180 degs (6 o'clock or Bottom Dead Center.) These values are displayed on the Garmin unit just as degrees. For the example above, the Garmin unit would read (15/180) in real time. The object is to start your power as far behind 360 degs as possible, and end as close to 270 degs as possible.
PCO - Pedal Center Offset - This metric looks at the center line of your pedal, fore and aft, and tells you where on the pedal you are applying pressure. The reason this is important is that you want to apply pressure on the pedal directly down the centerline. If you are outside center, or inside center, you will be applying adverse pressure to your foot, knee, and even hip. This metric can help you adjust your fit to find the most comfortable and efficient pedal stroke possible. For example, if you are pedaling 10 mm outside the centerline (+10) then you might try moving your cleat outside on the bottom of the shoe to bring your foot back to center. If this does not fix the problem, or feels painful anywhere, then move the cleat back, and shim the outside of your cleat to rotate the foot at the ankle to a more neutral position. You can continue to play with this metric and compare to your efficiency and power phase.
Here is an example of what the data looks like in Garmin Connect, or https://connect.garmin.com This is looking at my best 40 minutes climbing a local climb, Geiger Grade. When looking at my Power Phase, I start my left foot power at 348 degs, and finish at 209 degs. On the right, I start at 336 degs, and finish at 221 degs. I am slightly right leg dominant, and I am fairly close to center on my Pedal Center Offset. This entire 40 minutes had an average power of 274 watts. On a different page of data, my Torque Effectiveness for this 40 minutes was 88% left, and 88% right. I spent 3 minutes 41 seconds out of the saddle. Riding out of the saddle helps the body with blood flow, but lowers your Torque Effectiveness.
Now for the fun part. I do dynamic bicycle fits at Great Basin Bicycles for $80. This usually takes an hour, and I show you how to pedal differently to increase your efficiency. This is all done using software from CompuTrainer called Spin Scan. This program draws a graphic representation of your pedal stroke, and changes in real time as you use different muscles. Then you get to see what efficiency looks like, and what efficiency feels like at the same time. This is called immediate Bio-Feedback.
Now you can take this data with you, and take your cycling to the next level. You can rent Garmin Vector 3 Pedals and a Garmin 810 from Great Basin Bicycles. This will allow you to use the pedals and the (or your) Garmin and watch your pedal stroke real time on the bike.
Once you return to the shop, we will download the data to Garmin Connect, and analyze your pedal stoke, looking for what you're doing right, and what you can do better. All for ONLY $80.
This is a 3 day rental, usually Friday, Saturday, and Sunday. You will have to return the pedals/Garmin on Monday morning. Or you for the same $80, you can rent them midday Monday, and return them Friday morning for a free extra day.