Quarq CinQo Saturn SRAM S975 Crankset
With the Quarq CinQo Saturn SRAM S975 crankset, we could only see upside. Our current crank is an SRM mated to a traditional square-taper bottom bracket. The Quarq crankset is lighter, doesn't need wires, and should be stiffer. It's like upgrading your frame to a lighter, stiffer model and de-cluttering your bike at the same time and giving yourself an equally-accurate, if Quarq's claims are to be believed, powermeter. And since the Quarq uses the ANT+ Sport transmitter, any ANT+ enabled head unit that can read power signals will work with it. Currently, that list includes CycleOps Joule 2.0 and 3.0, Garmin's Edge 705, 500, and 310XT, as well as units from Specialized and Bontrager. We're mating the Quarq to a CycleOps Joule 2.0, and that, too, appears on first blush to be only upside. The Joule will be reviewed separately in the near future.
Many questions have come up about the Quarq. One thing we want to point out is that the Quarq has been "around" since it debuted at InterBike in September 2007. Being an early adopter is fine, but something as complicated as a powermeter takes a long time to get right. SRM started in 1986, and we first noticed it when Greg LeMond was racing with one in 1994. PowerTap started in the mid 1990's, but the design was plagued with problems and it took several years and a change of ownership before the unit was reliable. That Quarq could dial in their product to the point it is reliable within four years is actually pretty impressive. Another misconception some people have is that the meter itself can be taken on and off the cranks. It can't. This misconception started with their earliest iterations, before the "Saturn" ring was added, because it looked as if the unit could just be clipped and unclipped to either a FSA or Truvativ spider.
Before getting to the power functions of the crank, let's discuss the mechanical functions. The cranks and bottom bracket we pulled weighed in at 151g for the bottom bracket (Phil Wood with steel spindle) and 809g for the rest. A total of 960g. The Quarq SRAM combo weighs 120g for the standard SRAM GXP bottom bracket, another 5g for the Q-ring, and 775g for the cranks, rings, and spindle. 900g. A 60g savings; a bit more if we weigh in the wires. Interestingly the S970-armed version of the Quarq CinQo is reported to be 60g heavier than the S975. It's rotating weight, but not moving around in big circles, and the potential added stiffness and larger-diameter bearings could make the Quarq more efficient even if the two cranks weighed exactly the same.
Assembly is easy. Probably the hardest thing is getting the Q-ring, a shim with a magnet on it that goes between the drive side bottom bracket cup and the frame, into the right place, and all that takes is a little attention.SRAM puts torque numbers on both the bottom bracket cups and the left crankarm, but considering the numbers posted; it's hard to over-tighten. The cranks tighten with 48-54Nm, which is hard to overdo with spindly cyclist arms.
We expected the thru-axle crank to be stiffer than our narrow-diameter crank, but in an effort to try to separate the chain ring stiffness from the crank/bb stiffness, we took off the included SRAM Red 53/39 rings and put on our standard FSA Pro Road 52/38 rings.
Weight-wise, there is a four-gram difference between the Red and FSA outer rings, 114g to 110g, and the inner rings both weighing at 31g. Regardless of the design, the differences are tiny.
Switching rings, however, brings up a compatibility issue. Quarqs are calibrated at the factory to the rings being sold with the cranks. This means the meter's accuracy is greatest when the rings match up exactly with what comes on the crank. In switching to the FSA rings, we might be experiencing, according to the people at Quarq, a 1% difference in power readings, still falling inside the +/- 2% that Quarq claims. However, thick time trial rings might see a 5-6% percent difference. If you want to run TT rings and want your cranks to measure power accurately, send the cranks back to Quarq and they'll recalibrate them for you.
Looking to the future, we asked Quarq about going compact, as it's easy to find 110mm bcd rings in 52, and we'd like the option to play with our rings to get a 52/36 Dolomiti Compact or 50/36, or 50/34 in addition to our preferred 52/38. At this point, Quarq doesn't recommend the 52/36 combo on their 110bcd cranks as the difference in power numbers between the big and small rings is at 4%, which isn't acceptable for accuracy.
A second note about accuracy. Quarq recommends torquing chain ring bolts to 10Nm. If you don't have a torque wrench, this is a very good excuse to get one. The bolts need to be at that value so the flexing that could occur from having them too loose or varied values from being uneven doesn't happen. Because of the high number, steel bolts come with the rings and steel is the recommended bolt material as there are few aluminum bolts that can withstand this force without cracking or stripping. You'll want to check it before your first ride, periodically, and whenever you're putting on rings.
Quarqs can't be calibrated at home, but they must have the offset zeroed to be accurate. They recommend doing it "manually" at home before each ride and automatically on the road during each ride. Manually means using your head unit to check the static calibration and then zero it out from there. This can be performed with a Garmin head, but not currently with a Joule. There should be a Joule solution in the near future. Automatically means backpedaling at least four revolutions. The Quarq firmware will take the signal over the last four backward revolutions, average the reading for those four, and use that as the new zero offset.
Sampling rate, how often a power number is sent out from the crank to the head unit, btw, is dependent on cadence. 60rpm once a second, 90 once every 2/3 of a second, 120rpm, twice a second. As measuring at even higher rates is possible with the current hardware, they report they're working on higher sampling rates not dependent on rpm for the future. We're used to one-second sampling rates with both the PowerTap and SRM, so more seems potentially better for even more precise measurement of effort. It will take up more memory in the head unit, but that shouldn't be a problem with most new ANT+ computers.
With the crank installed to the proper torque settings, it was time to ride. And ride. And ride. We've done over 2,000 miles on the cranks. The biggest thing to report is that there's very little to report. The cranks are stiff, a little stiffer than the SRM predecessors. The Red big ring isn't noticeably stiffer than the FSA. We've ridden the cranks in all manner of climatic conditions: hot days, cold days, downpours. No problems anywhere.
The carbon-fiber crankarms appear to be as durable as aluminum arms. One of our concerns when we installed the cranks was all the bashing we accidentally put the cranks through, like hitting them on steps and throwing wheels and stuff on top ofthem in a car and such. Too often we hear carbon-fiber component designers discuss how their parts are designed to withstand the rigors of the activity—like how a bike can be stiff yet can snap in half in a crash. Cranks we don't want to see fail, ever. In our time on the cranks, we've scratched off some of the clear-coat and a thick bootie has scuffed some of the finish, but the more we learn about SRAM arms, the more we're pretty convinced that our worries about catastrophic failure are misplaced.
We wanted to check to the calibration of the Joule the same way we check the SRM calibration, by hanging a weight off a crankarm while the bike is in a stand. Unfortunately, the current Joule firmware doesn't allow for this. We asked some of our friends with Quarqs mated to Garmin 500s. They've checked calibration and found it accurate and stable over time—and a spin around the Wattage Group seems to indicate that others have had few problems. From other reports, the Quarq does seem to be both accurate and consistent.
The people at Quarq work pretty hard. They seem to have excellent customer service and they seem to be feverishly working on improving their product. We expect the firmware will get better over time (upgrades currently need to be performed by Quarq) and things like switching rings will be less of an issue. It wouldn't be a surprise if a later firmware version could make it possible to calibrate the unit in the field, though we don't see how we'd be able to correct for ring imbalances like they've found with the Dolomiti Compact option.
They also seem to really stand behind their product. Water damage from riding in deluges to stream crossings to blasting with a high-pressure hose is covered in their two-year warranty. They believe the spider crash-worthy, but acknowledge that a pretty solid shot directly to the transmitter box could break it. They can even swap out SRAM crankarms for different sizes; they discourage people from doing this at home.
With the exception of the chain ring limitations, we see little to complain about and a lot to love about the Quarq CinQo SRAM S975 crankset. Another serious competitor has joined the power meter field, the first one in years that can challenge PowerTap and SRM for a piece of the power meter market.