Okay so i am going to try and keep this clear and simple
I think we all agree that a powermeter is the best tool a triathlete and cyclist can buy
Currently as far as i know there are 6 powermeter options. I will try and give a quick run down on each
Each of them has their pro’s and cons and depending on what you want should help you make your decision on buying one
plus then everyone can say their opinion to help aswell.
First up is the Grandfarther of powermeters - SRM (strain gauges in the crank set)
The SRM power meter is the oldest and first commercially available power meter for mass market coming from Germany. The SRM measures power output with strain gauges in the crank set and has become the standard by which all power meters are measured. Depending on the level of purchase (Amateur, Pro and Lab) it tends to be one of the most reliable of the power meters. The SRM measures wattage in the spider of the crank. The downside to SRM is the cost. It is the most expensive of the power meters. Another downside is the battery inside the power meter itself must be replaced by the factory when it is dead, and this requires some downtime for the user while you mail it in and wait for it to be returned.
Next up is Powertap (strain gauges in rear wheel hub)
The PowerTap is a complete rear hub for the back wheel of a bicycle that houses a power meter. The hub contains a “torque tube” with strain gauges similar to those used by the SRM. These strain gauges measure the torsion inside the hub as it twists from the load that is applied to the pedals by the rider. The bicycle chain wraps around the cogs on the hub and, as it moves, causes small twists in the hub itself. This torque is measured and then converted into wattage at the PowerTap computer. The wattage that is measured in the PowerTap is the wattage that is actually getting to the road, as it has to “go through” the drivetrain from the crank. This causes the wattage to be about 5–10 watts lower than what would be measured by the SRM at the crank. A major disadvantage to the PowerTap is that you are stuck into the wheel that the hub is built to. If you want to use your super trick wheels for racing, you’ll need to get an additional hub for racing and then keep your standard wheel for training which increases cost significantly.
Next Up is the Ergomo - (measures the torsion, or twisting, of the bottom bracket spindle)
Ergomo, also made in Germany. The Ergomo measures power differently from the units reviewed above in that it measures the torsion, or twisting, of the bottom bracket spindle. Every time you pedal, there is a small amount of twisting that occurs on the spindle, similar to the twisting that might occur with a wet towel if you twisted it into a whip. The Ergomo contains an optical sensor that allows it to measure the distance the axle twists, and from this distance it calculates the torque and the corresponding watts that are being applied in order to make that caliber of a twist. A complete Ergomo consists of the Ergomo bottom bracket and crankset.
The downside of an Ergomo is the sensor measures power at the bottom bracket spindle, resulting in a measurement of the side that twists—the left side. The right side of the spindle is attached to the crankset so there is no real twist on the right side. The Ergomo can only measure the rider’s left leg power accurately. Ergomo takes the power output from that left leg and doubles it in order to get your wattage. This may seem to be a problem, but in reality it has not proven to be one for a majority of the users. Only cyclists with a big discrepancy in the strength of their legs would have inaccurate reading. Every rider has a small discrepancy in leg strength, but this discrepancy is usually less than 5 percent.
Number 4 on the list is Polar (tension in the chain)
The Polar power meter features a unique measuring system to measure power. The Polar systems measure chain tension via a chain stay mounted sensor that detects vibration in the chain; similar to how a guitar string “hums”, a chain vibrates faster as its tension increases. This translates into an amount of force, which is then multiplied by chain speed, as measured by a sensor mounted on the rear derailleur, to come up with power output: Power (in watts, or W) = chain tension (N) times chain velocity (in meters per second, or m/s). If installed correctly, the Polar can be an accurate beginner power meter.
Number 5 is the ibike
The iBike Pro power meter needs no special wheels, hubs or cranks making it easy to transfer to any bike. The lightest power meter weighing in at 62 grams. The iBike Pro power meter delivers precision and innovation at a fraction of the cost of the competition and is a great beginner power meter with a simple user friendly screen and easy to navigate programming. Not as robust as the competition.
And the newest to the market is Quarq (strain guages in from the crank spindle)
A new power meter, the Quarq CinQo, shows tremendous amount of promise in function, build quality, and simplicity. The Quarq powermeter system is comprised of two distinct products, the cinqo - which is the power measurement device and the Qranium - handlebar mounted computer. At this time only the CinQo has been produced and it integrates wirelessly with the Garmin 705 computer.
The Quarq was introduced at Interbike September 2007 and the first production models of the cinqo were shipped to customers in June of this year. CinQo is a crank based system that measures power output with strain gauges in the crank spyder. As I understand it, SRM’s patent expired this year and Quarq is using simliar technology with their system. While the CinQo is still in limited supply. The CinQo replaces the crank spyder and is currenly available for FSA team issue and SRAM S900 cranksets. Quarq is planning on introducing units compatible with more cranks in the near future.
So there are the 6 and by the way these words are taken from online sources and there are other reviews if looking for more info. This is just to help distinguish the difference to help you cut down the list. For me Powertap is not an option because of the number of wheels i have. The power and ibike are just to hard to set up and not reliable enough.
To me it comes down to SRM, Ergomo and Quarq.
SRM is proven to be the king but the king comes at a hefty price
Ergomo only tells you what the left leg is putting out and seems not to be as easy to set up as the SRM and Quarq
Quarq is well priced but hasn’t even been out for 14months yet as it came out near end of 2007.
To me buying a powermeter is a very important buy and should be bought with the knowledge of the product
I am looking for the same as everyone else
I powermeter that i can afford, like the design,is reliable, functional, is avaqilable, easy to use, easy to set and has a warrenty if any problems arise.
So which to go with… What do you think?