Wondering anyone is using add-on cadence and speed sensors with their Powertap. I’m using a Garmin 910XT as the head unit. It seems to me that the cadence is not consistent. Would Garmin’s new Speed sensor work when strapped to the hub?
When I had a Powertap I didn’t use one as it seemed to be reasonably accurate. My wife has a Powertap now but for her she gets inconsistent cadence numbers. When she is riding at a lower power (less than 120w or so) during warmup or a recovery, the cadence numbers jump all over the place. Once she crosses a certain power threshold things suddenly lock on and give steady numbers. Putting a speed/cadence sensor clears it up.
I’m using a GSC-10 with my PowerTap. My PT’s cadence reading seems to be ±5, that’s too variable for me.
Wondering anyone is using add-on cadence and speed sensors with their Powertap. I’m using a Garmin 910XT as the head unit. It seems to me that the cadence is not consistent. Would Garmin’s new Speed sensor work when strapped to the hub?
I used to use the Garmin GSC whatever with my powertap, and it was so close to what the powertap actually reported without it, I stopped using it. True, it is more on-the-second than the Powertap which seems to lag just a bit, but nothing that has ever influenced my training or racing.
I’ve had my Powertap for a few weeks and I noticed right away that cadence was off. When riding at lower watts the pt will be telling me my cadence is as low as 40-50 rpm but in reality I’ll be riding around 80-90 rpm.
The powertap cadence reading is a bit of a guess, so if you have important uses for accurate cadence data, you should get a dedicated cadence sensor.
the speed data should be spot on though, assuming you enter accurate tire circumference, no need for a different sensor.
Wondering anyone is using add-on cadence and speed sensors with their Powertap. I’m using a Garmin 910XT as the head unit. It seems to me that the cadence is not consistent. Would Garmin’s new Speed sensor work when strapped to the hub?
You mean, will the speed sensor produce reliable cadence when it’s strapped to the hub? Um, no. If you want more reliable cadence you should attach it so it reads the crank.
The PT estimates cadence by looking at the difference between high torque and low torque at the hub. If you’re soft-pedaling at low power that difference can be hard to spot because it’s not very big. Once you get up to reasonable levels of power that difference is quite a bit easier to spot, so the cadence becomes more reliable. That said, 1) if you’re really, really, interested in cadence from a PT, there are ways to clean it up post hoc; and 2) unless you’re riding a single-speed you don’t usually have to be really, really interested in cadence.
Speed from a PT seems to be pretty accurate up to around 90 km/h. I’ve never checked the speed above that.
- unless you’re riding a single-speed you don’t really have to be really, really interested in cadence.
wut about force/velocity analysis?
I’ve not used that to great effect personally but I figure one could, or could at least try.
- unless you’re riding a single-speed you don’t really have to be really, really interested in cadence.
wut about force/velocity analysis?
I’ve not used that to great effect personally but I figure one could, or could at least try.
Once you get up to the power levels where you’re typically interested in it, the cadence becomes more reliable. Besides, if you’re really interested in it, you can clean up the cadence post hoc before looking at PF/PV.
I described this clean up process a long time ago. Basically, you know speed = cadence * gear ratio * wheel circumference * some number. You have your speed, you have your wheel circumference, you know what your chain rings and cassettes are and, importantly, you know 1) that you can’t get a gear ratio other than the permissible ones from your rings and cogs, and 2) you know that you don’t typically shift over and between gears every second. So you can calculate the “virtual gear ratio” from your data based on speed plus those other things, then “bin” the virtual gears to the nearest actual gear (I use an odd span median smoother first). Then with the accurately measured speed you can back-calculate the cadence, and from there you can get PF and PV. Works pretty well. Just a couple of lines of R code.
Wondering anyone is using add-on cadence and speed sensors with their Powertap. I’m using a Garmin 910XT as the head unit. It seems to me that the cadence is not consistent. Would Garmin’s new Speed sensor work when strapped to the hub?
The new hub-strap sensor is speed only. No cadence. Garmin also has a new cadence-only sensor that straps to the crank arm. You could try that.
And DCRainmaker encountered troubles when strapping the new speed sensor to a powertap hub. Too much ANT+ too close together.
That’s what I use (the Garmin cadence only sensor on my crank arm), with mine and it works like a charm.
Thanks for the input everyone. I’ll be adding the new Garmin Cadence Sensor to my Christmas wish list.