Power Meter Choices Part II: Installation, Set-up, and other things that bring you to tears.

This the second in my little series about power meters and how I choose the one I did. This second part focuses on that happens after you get the nice shiny new box and starting the installation, setup and calibration process.

SRM
First up again is SRM...because well it’s the brand I have owned the longest and am the most familiar with. I would like to say I have had no experience with the new wireless version, but I imagine it would be similar to setting up a Quarq (See below).

Installation
Setting up a wired SRM involves two main parts. The installation of the crank it’s self and the routing of the cabling for the head unit.
Installing the crank is about a 10 minute process depending on whether you have the correct BB in the frame..... if not double it. At this point you can choose to install the crank sensor. Depending on which wiring kit sits behind the crank on the chain stay or if you have the more modern version is mounted using the bolt for the BB cable guide.
From here the job becomes a bit more time consuming if you want it done correctly the first time. Running the cable up the down tube and around the front brake cable so that you have a nice tidy set of wiring takes another 20-30 minutes and can be quite frustrating. I have used various methods including insulation tape and cable ties to get everything in place. One of the key things to watch is that there is enough length around the head tube area so that if the handlebars are turned 90° you do not snap the speed or sensor cable (been there done that $90 lesson).
The final step is mounting the head unit clamp and putting the unit on. I rate the SRM head unit as having the second best fixing method. I have broken a head unit before when a taxi in Sydney decided to open a door on me and snapped it from the mount. Given their position they can be damaged in an accident if something manages to get between your bars.

Trouble Shooting
I have had to trouble shoot SRM installations before and they are a bit more involved due to the number of potential sources of error. Sensor placement near the crank, faulty wiring kits, and batteries are the biggest causes of failure to get a signal from the cranks. The latter two are the expensive ones to fix as they require a new wiring kit or the crank to go off for a week to Kinetic to have the battery replaced.

Calibration
As I have mentioned previously SRM are the only power meter which a user can change the calibration on. I advise anyone that purchases one to check the calibration as the slope from SRM themselves is known to somewhat suspect. When I had two I would calibrate them once a month as it would only take about ½ hour and therefore I knew my data was always accurate.
The 0 offset for a SRM is set by pressing a combination of buttons back pedalling once, waiting for the numbers to settle then hitting enter. SRM’s seem to be more temperature sensitive than powertaps due to the way that power is measured with strain gauges. This means having to potentially reset this value a couple of times in a 5 hour ride if the weather is changeable.

Powertap
I have owned my powertap now for about 18 months and is the second oldest system I have experience with.

Installation
Depending on where you purchase yours from the system either comes built up in a wheel or as a hub which you have to have built up. The second option gives you more freedom of choice for rims and also it means that the freight costs are less due to smaller size of the box.
I had dramas with mine due to the LBS and my choice of spokes I used to get the wheel built up with. In summary it took over a year for the local distributor to admit that the spokes used on my wheel were a bad batch and replace them.
This issue aside getting the wheel, throwing a tire on and mounting the head unit up are as simple as it gets.
The Little Yellow Computer (LYC) is the most secure of all the head units I have tried due to its placement and the locking mechanism, which is very positive.

TroubleShooting
The powertap system is Ant+ so the headunit is paired with the hub. If the two aren’t talking it is normally a battery issue. Replacing the battery in the LYC is very straight forward with the cover easy to access. However on the MTB powertap you have to remove the disc rotor to be able to replace the hub battery and this is a 15 minute job, which luckily you should only have to do every 6 months or so.
The other issue with the powertap wheels their bearings. Basically, they are sh!t. I had to replace mine after only 3 months of getting a fresh rear wheel earlier this year. While getting the bearings is easy it’s about ¾ process to disassemble the hub punch the bearings out, press the new ones in and reassemble. The new bearings I got down the road are miles better than the originals and still going strong 6 months later.

Calibration
I wrote a piece a couple of months back about how to check the slope for a powertap. This is all that can be done by the user. If there are any issues the hub has to be sent back to Saris for repair.
Setting the 0 offset in the headunit is done so that every time a user coasts the offset is re-set. This is a good function and means that you don’t have to manually perform this as with a SRM.

Quarq
The new arrow in my quiver and so far so good.

Installation
So it’s and integrated crank and the installation is the same for any such similar crank set. I had to remove my existing BB and put in the SRAM specific GPX model that came with the crank set. Here I hit my first snag, the BB tool I had did not fit the non-drive side cup...seems that the axle hole on this cup is smaller than the drive side. So I tightened up by hand and continued with installing the cranks.
With wireless cranks (both SRM & Cinqo) you need to place a magnet close to the spider to activate the electronics when you begin pedalling. To start with I just used insulation tape to fix the magnet as I wasn’t sure whether the position I had chosen was going to activate the cranks.
Next I pushed/tapped the cranks through the BB using a rubber mallet as the machining tolerances are very tight. The fixing for the SRAM S950 is a single 8mm allen bolt on the non-drive crank arm. Basically tighten this up and that’s it. There is no ability to adjust play in the bearings and it relies upon the machining tolerances to ensure no side to side movement.
Next I mounted up the Garmin 705 on my stem and set about pairing the two up. The Garmin fixing is fairly weak. So far I have lost my GPS through user error with the bracket no engaging correctly and in a crash at Wagga earlier in the year. I don’t see the system being a problem on the roadie but time will tell.
Pairing the Garmin 705 & cranks was very easy it took less than 20 seconds...it seemed I had placed the magnet in the correct location.

Trouble Shooting
I got my first taste of this on my second ride! Was riding home from work and the cranks wouldn’t work. The night before I had rolled back the firmware as the latest stuff from Garmin is buggy with speed drop outs so it was back to version 2.90. So to start with I tried re-pairing the devices and that didn’t work. So I rode home with no power. Next I thought the magnet had moved so I spent ½ hour playing with that...still no joy. Then I went back to the settings in the Garmin and had another play with that...no luck. Finally I started going through the on-line trouble shooting guide till I got to the battery. I thought what are the chances? So I popped the battery on the cranks... and low and behold the Garmin flashed up a “low battery warning on power meter message”.
Back up stairs and scratching through the spares in the bottom draw and do you think I had the right one...nope. So I dashed off to the mall on the off chance that Coles/ Woolies/ K-Mart might have the right on in stock. But no dice.
Next day it was a trip to Dick Smith at lunch time and $13 later I had 3 new batteries and it was all good again.
So from this I learned that the system is more complicated than my previous SRM with potential sources of problems from both the head unit and the cranks themselves.

Calibration
The Cinqo transmits the 0 offset to the head unit so this viewable by the user. There are two method of re-setting this. Either by manually doing it using the options on the Garmin or alternatively backpedalling 4 times. The Cinqo is setup to detect this movement and resets the offset.
The slope is basically non-changeable....but I did read it is possible using Linux, a Garmin ANT+ USB stick and some programming knowledge. This is way beyond anything an average user/ me perform themselves.

So this concludes the second part of the series. I’ll post the next in a couple of days.