Focus Paralane: Garmin Rally XC200 Power Meter SPD Pedals

Recently I had the chance to test out a pair of Garmin Rally XC200 Power Meter SPD pedals. These are new power meter pedals from Garmin. What's cool about these pedals is the small size and the SPD compatibility.

Previous iterations of power meter pedals are usually rather large, and with a bulge at the pedal axle. For this version, Garmin has managed to shrink down all the electronics, such that it all fits inside the pedal axle! At the same time, the SPD platform is what I prefer, so that I can use it with my Shimano RX8 gravel shoes. 

I have previously been using one-sided crank based power meters, such as the 4iiii Dura-Ace or the 4iiii 105 versions. Being one-sided, it takes the power generated by the left leg, and multiplies it by two to give an estimate of your total power. This assumes that your power is equal on the left and right legs, which is usually not the case. If it is not equal, the total power will not be accurate. This is the case on the Focus Paralane, where the 4iiii 105 left crank arm is currently installed.

I decided to install the Garmin pedals on the Focus Paralane, since it is the bike I ride most often. Let's take a look and see how it compares to my existing pedals.

XTR M9120 Trail pedals, next to the Garmin Rally XC200. SPD mechanism looks similar.

The SPD centreline of the Garmin pedals look to be further away from the crank arm.

The Garmin pedals also look much thicker, which means a larger stack height.

Understandable due to the electronics packed inside the pedal axle.

Weight of XTR M9120 pedals is 393 grams, a bit more than the previous M9020 version.

Garmin Rally XC200 pedals weigh more, at 443 grams per pair. Not for weight weenies!

The Garmin pedals are 50 grams more than the XTR pedals, which I think is acceptable for a dual sided power meter.

After I removed the XTR pedals from the bike, I decided to do more comparisons before putting on the Garmin pedals.

Difference in stack height as seen from the different pedal axle height.

Pedal axle on the Garmin has a slightly longer thread, to fit more electronics inside.

SPD mechanism looks similar, although the Garmin version does not have a cage on the outside.

Another side view showing the different axle sizes and thickness.

Thickness of XTR pedal is 17.3 mm. (A bit different from this other post because of different measurement point.)

Garmin pedals are much thicker at 27.2 mm, nearly 10 mm more. 

This translates to an approximately 5 mm increase in stack height.

This 5 mm taller stack height means that the distance from the saddle to the pedals is effectively reduced by 5 mm. If you are sensitive to saddle height, you should adjust your saddle height upwards by about 5 mm. For most people I guess it won't make much of a difference.

Garmin pedal on the left has a closed pedal axle as it is packed with electronics inside. A size 15 pedal wrench is needed to install the Garmin pedal.

Garmin power meter pedal installed on the Dura-Ace R9200 crankset!

This means that there are actually two sets of power meters on this Focus Paralane. The Garmin Rally XC200 pedals and the 105 R7000 4iiii left crank arm power meter. I decided to deactivate the 4iiii power meter while testing this Garmin power meter pedals.

There are some useful metrics which you can get from the dual sided power meter. Other than giving a more accurate overall power output by measuring the left and right sides separately, it also gives some other interesting metrics.

One of those I found interesting is the left and right balance. It basically compares the power output of your left and right legs, to see which leg contributes more. It is common to have unequal outputs.

In my case as you will see below, my left leg is producing noticeably more power than my right leg. This is likely to be related to the imbalanced pedaling stroke between my left and right legs, as discovered during the bike fitting session at LOUE Bicycles.

Left leg producing more power than the right leg.

I'm not sure what's the correct way to read the left right balance. I can think of 3 ways to interpret this, all of which could be wrong though.

1) Left and right legs are both 4% away from an equal output of 50/50%.

2) Left leg is producing 8% more power than the right leg (54 - 46 = 8).

3) Left leg is producing 17% more power than the right side. My math goes like this:

Assume 100W of total power output, the left leg is contributing 54 watts, while the right leg 46 watts.

Difference is (54-46) / 46 x 100% = 17%

I'm inclined to believe that the correct calculation is case 3. If it is case 3, my left right imbalance is quite bad, but apparently this is not an unusual figure after doing some online research.

Another data from the picture above is the angle where the power phase starts. It seems that the right leg power phase starts earlier (3 degrees) and ends earlier (208 degrees), compared to the left leg where it starts and ends at 10 degrees and 221 degrees respectively. Left and right power phase total angle is 211 and 205 degrees respectively.

Moving on to other metrics below, the power meter pedals can also detect an offset in pedaling force relative to the centreline of the pedal, which is the SPD cleats. This can be useful to detect if you need a pedal shim to shift the pedal out slightly, or need a pedal with a longer axle.

Both left and right side indicate that the pedaling forces is slightly outwards by 5 and 6 mm.

The data shows that my pedaling force is slightly outwards of the centreline of the axle, but they are fairly equal between the left and right sides. Based on this, I could probably benefit from a pedal with a slightly longer axle, or a crankset with a slightly wider Q-factor. However, there are other schools of thought which states that a zero center offset doesn't mean it is the ideal condition.

In reality, it doesn't matter too much as I don't need to optimize it, since I am not after marginal gains for training or race. Sometimes data is good, but too much data can be confusing as well. I think what's most important is that pedaling feels natural and efficient, while also being pain-free.

I probably don't need a power meter to track all my rides, let alone a dual sided power meter such as this Garmin Rally XC200. However, it is good to at least try it, so that you can get some data to have an idea of what your cycling power and other pedaling metrics is like. If there are some problems with your pedaling stroke, this can probably detect it.