Power meters: Everything you need to know>>>
SRM – The original and still the best?
SRM cranks were used by Greg LeMond back in the late 80s and were quickly in high demand by pro teams and national squads as coaches saw the huge potential for measuring a rider’s power output reliably and accurately on the bike.
Today, the crank based SRM power meter is still considered by most as the gold standard. SRM still enjoys a huge market share among the pro ranks, although price reductions have made it more affordable to a wider market.
SRM now makes its power meter for all the major crank and groupset manufacturers, which has further increased its appeal. Current models transmit data on Ant+ and are therefore compatible with Garmin and other cycling computers, besides its own sophisticated PC-7 head unit.
Measurement: 8 strain gauges in the R/H crank spider
Claimed accuracy: +/- 1.5% – 2.5% (crank dependent)
Data transmitted by: Ant+
Pricing: from £1,549 (power meter and cadence sensor); from £2,099 for complete systems.
The main contender?
Initially developed by the Tune Corporation at the end of the Nineties, what we now know as Powertap was a product bought by Graber (now Saris) before it really made a stir commercially by becoming the first genuine contender to the SRM throne in the early 2000s.
As it collects data from the rear hub a major part of its commercial success is its ability to be built into a multitude of rear wheel types (even disc wheels) and swapped to other bikes with relative ease. More so since wireless versions became the norm.
Several top-end wheel manufacturers offer Powertap versions in their range, eg Mavic, FFWD.
Measurement: 8 strain gauges located on the rear hub axle
Claimed Accuracy: +/- 1.5%
Data transmitted by: Ant+
Pricing: from £675 hub only; rear wheel from £750; wheelsets from £865
Tried and never caught on…
Polar (with s710 and CS600)
Polar (with s710 and CS600) Polar is a brand already synonymous with training, dominating heart-rate monitoring, but its first stab at a power meter was, quite frankly, a big disappointment.
Choosing to ignore the more obvious route of integrated strain gauges to measure torque, the Polar system used a convoluted calculation based on chain tension, and chain speed.
The result was something far less accurate than was acceptable for the majority, especially as it was further adversely affected by road conditions and weather.
Using strain gauges to measure the torque directly on the bottom bracket axle, the Ergomo design showed great promise initially but the timing was off.
Unfortunately for Ergomo the industry rapidly embraced newer BB standards and its old-school square-tapered axle design very quickly became obsolete and a non-starter up against the likes of HollowTech, BB30 and so on.
A novel idea, but in a scientific field novelty only gets you
Granted, the iBike concept gets top marks for simplicity, light weight and ease of getting started, requiring just the fitting of the head unit to your handlebars, but its calculation of power was derived from an equation using wind speed measured through a port at the front.
Its limitations were obvious, and the data too prone to external influences, and inconsistencies to be taken seriously at a coaching and training level.
New Kids on the Block
Quarq, as one of the more recent to join the market, had the benefit of hindsight, market trends and perceptions to aid it. Similar to SRM, the Quarq system, first developed in 2006, uses integrated strain gauges within the crank spider.
Big money investment from SRAM, which bought Quarq in 2011 has helped the brand push the concept on to newer heights, with more features, more models (SRAM, Rotor, FSA, Specialized, Cannondale) and the latest versions are incredibly light.
Measurement: 10 strain gauges located in the R/H crank spider
Claimed accuracy: +/- 1.5% (new SRAM RED); 2% otherwise
Data transmitted by: Ant+
Pricing: from £1,799; (from £1,899 for new SRAM RED available June)
Look Keo Power
Look and Polar partnered to be the first to market a power meter built within the pedal spindles.
The main idea behind the much anticipated concept was a more user-friendly fitment and greater portability, interchangeability between bikes.
It was a significant leap forward towards getting more of the mass market on board.
The system adds very little weight and also has the capacity to measure left and right balance. Unlike other power meters the data is transmitted on a frequency unique to Polar systems to keep it all ‘in-house’.
Measurement: 8 strain gauges located in each pedal axle (16 total)
Claimed Accuracy: +/- 2%
Data transmitted by: Polar WIND (2.4 GHz)
Pricing: £1,499 without CS600x head unit; £1,699 complete
Still to come…
The Garmin Vector pedal has become a long-awaited product. It may have missed the boat in terms of being the first pedal-based system, but it is now in the luxurious position of having seen the reactions to the Look Keo Power and has an opportunity to try and go one better. We had some initial experience on prototypes, which on paper at least (as there is currently no finished product) suggests Garmin has achieved exactly that.
In a recent statement though Garmin announced: “After testing our latest advanced prototypes of the Vector system, we are still not satisfied with the results. As you can imagine, Vector is a complex, precision measurement instrument and as of yet, we are unable to ensure that this device will meet the expectations of the cycling community.
“Presently, we cannot estimate a delivery date but we do not expect the product to be ready in the summer of 2012, as previously targeted. We understand that this is a highly anticipated product within the cycling community, but Garmin’s commitment to quality necessitates this additional delay.”
They say the best things come to those who wait, so we wait with bated breath.
Projected price £1,150 (pedals only)
Brim Brothers is a little known Irish company with a very clever design up its sleeve.
Like Garmin, its only at the ‘working prototype’ stage right now but what stands the Brim Brothers system apart from the competition is that the power meter is housed on your shoe – not the bike – eliminating the ‘which bike?’ quandary.
The technical workings are encased in a small, neat little pod (weighing just 18g) that clips to your instep, on the shoe strap, with the power measurement taken from strain gauges under the ball of the foot at the cleat interface.
It’s currently based on the Speedplay cleat, and is likely to use ANT+ data transmission, but we see no reason why the concept cannot eventually be applied to other pedal brands. Up against such big corporations Brim Brothers may need some investment to make this product stick, but its potential is enormous.
meters: Everything you need to know>>>
This article was first published in the April 26 issue of Cycling Weekly. You can also read our magazines on Zinio and download from the Apple store.