The SRAM S975 Quarq crankset is a crank-based power meter and is an ideal training and racing aid. It’s easily transferable from your training to your racing bike, which means you can measure power with one device in any situation.
The Quarq system consists of a series of strain gauges placed on the crank spider and a magnet attached to the chainstay. This enables torque and angular velocity measurement, which can be converted into power.
The data is sent wirelessly via Ant+ to a head unit capable of picking up a signal, such as a Garmin. Quarq doesn’t make its own head units, so these have to be bought separately.
We tested the SRAM Quarq crankset with a Garmin 705 and, for comparison (on the same bike), a Powertap SL+ with Joule 2.0. First time out we noticed a 10W drift between the two meters over the course of the ride – they read the same at the start but were 10W apart by the end.
By the second ride this had stabilised and we saw a consistent 5-8W difference between the two. This is to be expected as the Quarq measures power at the crank whereas the Powertap measures at the hub and will be lower because of drivetrain losses.
In sprints, we noticed that 1sec peak power was actually 10-40W lower on the Quarq compared with the Powertap. This also skewed 10sec power downwards on the Quarq compared with the Powertap. The two devices sample power at different rates though, which could explain these short-term differences.
The SRAM S975 Quarq Crankset is available in four different crank lengths, from 170-177.5mm; 53/39 chainrings are standard, although there is a compact version available that’s compatible with SRAM’s GXP bottom bracket as well as BB30, BB86 and BB90, but doesn’t come with BB cups.
Priced at £1749.99, it’s more expensive than a Powertap but cheaper than an SRM.
This article was originally published in Cycling Plus magazine.
Source: BikeRadar.com Road Bikes & Gear