Quarq calibration problem!!??

Brad Marcus

I have a Quarq Riken that a purchased about 4-5 months ago. I've used it primarily on my trainer over the Winter and this past weekend I took my bike and trainer to my weekend house. I set things up early Sunday morning outside on my deck and did a standard calibration from the Quarq to my garmin. I got a reading of -43. Normal calibration readings for me in my basement have almost always been in the range of -2 to +2 (pretty tight range). I didn't think much of this and honestly don't know what the number itself means. But when I started riding I noticed right away that my effort vs watts shown on my garmin seemed much lower (easier) than normal. My heart rate confirmed this. Also my trainer (which has a power meter built in) confirmed. The two are never equal but I generally know about how much difference there is between the two (about 10 watts). I did a 3 hour workout and tried to re-calibrate a few times by pedaling backwards but problem did not change. I got home yesterday and set things up for a ride this morning and calibration again showed around -43!. This time I began the ride and after about 10-15 minutes, I could tell that something changed and effort went back to "normal". I didn't try to calibrate again since I was just happy to get the workout done. Maybe I'll try later to see if the readings are different.

Anyway - has something similar happened to anyone before? Was it caused by elevation difference (about 1000 ft between 2 locations) or something that happened while bike was on back of my car? I don't know but would hate for this to happen while traveling to a race and not riding to my proper potential by getting bad data....

Apologies for the LONG question but any advice is appreciated.

jsumara

Brad, I have a Quarq Riken too that I've had since last November and it has been very solid. The only time I've seen anything flaky was when the battery needed replacing. And that was obvious.

When I ride (trainer or outside) I use both my Garmin 910 and Garmin 510 and found that they track very close - as you might expect. 

We know that Power = Torque x RPM. So power is a calculated value and not measured directly.

The PM uses strain gauges to determine torque and the frequency from the strain gauges and in a no-load situation (zero torque) is what we calibrate.

I set (establish) the no-load frequency at the beginning of every ride – "calibrate" – and this produces a number which is the “zero offset”. All winter mine has been right at 200 (+/- 5) but this week I changed to a Q-ring on my chain-drive and the cal number changed to 88. 

We need to calibrate the strain gauges every time we ride (and should do so during rides as well) because they are sensitive enough to be affected by changes in ambient temperature, chainring bolt de-torquing, etc..

If the battery is OK then the odds are that things have changed on your bike and the zero offset is now -43

morpheus

Brad, mine had a problem. I couldn't ever put a finger on it, but, I knew it was off. It became very unpredictable. Sometimes, I would have a hard time lasting 6' into an interval and then have to abort to what I felt was z2 spinning. Would chalk it up to fatigue/overtraining. Then, not long after, I may go outside and RIP a long session with a 30% bump in Pnorm. With so many variables involved, I had a hard time believing it but the thought that things were just starting to fire in my legs kept me believing it. So, I'd go back in the basement a few days later and try some more intervals. Would fail on, say, 2 x 12's, then would drop down to a high cadence z3 interval and all of a sudden the watts would spin up and hold at about 20% higher than my FTP. I would actually continue that interval for the 20' and give myself a new FTP! Then, later, I'd try to workout with the new numbers and wouldn't even come close. Andddd, the whole process would repeat itself over a couple of months.

zero offsets were drifting. no idea why. I tightened the chainring bolts to specs and that was about all I could do. Did some kinda flip the battery backwards to reboot thing that they advised, but that didn't help either.

keep in mind that this was an older Cinco model. Finally, I sent it in to Quarq and they just replaced it with a Riken. Haven't had any probs with this one except that I'm not riding at 4w/kg anymore But, at least, I am now working in the proper zones.

Brad Marcus

@Jim- ok, assuming zero offset is now -43...I checked it again this evening and got the same reading. But this doesn't explain why the feel I was getting while riding at certain power levels (z1 through z4) seemed easier than they should've. I'd like to chalk it up to improved FTP, but I'm pretty in tune with where my fitness is. As I mentioned, the issue seemed to correct itself on today's ride.

@chris - sounds similar to what I experienced, but this was a one time issue. Maybe actually moving my bike around so much had an effect on the strain gauges.

Maybe I will call Quarq and run it past them...as I said, I'd hate for this to happen while traveling to a race and be off on my power numbers. Thanks for the input guys! I'll let you know if I find out a cause for this.