Vector Accuracy

purchased new Vector 3 pedals on Friday from my LBS. I installed them on my trainer bike in order check accuracy. I was surprised to find that they grossly over reported my power for 10 minutes by the order of about 25 watts @ 180 watts. It was measured against a properly calibrated and warmed up Computrainer. Also, the crank arm lengths and zero offset were entered for the Vectors. Last, I know there are drive train losses, but not 25 watts +/- @ 180ish. 4-5 watts maybe, but not 25.

Next step is to compare again with new batteries and adding in a PowerTap rear hub. Three power sources will tell me who is odd man out. Im afraid it will be the Vectors since it felt like 180, not 205.

I will contact Garmin if it is the culprit, but does anyone have other ideas? I can't do a static torque test as I just not set up for that (and new pedals should not require that).

I'm not upset since quality control will never be perfect.

0 bloom34 over 7 years ago

Been hashed out here.

https://forums.garmin.com/forum/into-sports/cycling/vector-3/1280489-vector-3-accuracy-thread

0 t_smit over 7 years ago

Can you post the .fit file recorded from that session?

0 kowi over 7 years ago

I did a quick 'n' dirty check against my power2max typeS indoors. V3 & p2m are pretty close and regarding drivetrain losses in the right order.
https://analyze.dcrainmaker.com/#/public/b3abe69c-37f8-42ca-5f13-6ede8466b582

Another indoor ride & a 3hrs outdoor ride is also logged, but not yet uploaded.
ciq.forums.garmin.com/.../1312087.png

0 mspeas over 7 years ago

Yesterdays Fit if it uploaded correctly.

0 t_smit over 7 years ago

There is nothing exceptional in that data set. I would suggest to make sure you do another static zero offset calibration at the start of your next ride and see how that compares against your computrainer. Depending on how flat your crank faces are and how tightly you installed them, it may take a couple of hard efforts to 'set' the pedals.

0 Former Member over 6 years ago

Hi there,

I purchased Garmin Vector 3 pedal set 2 months ago. Did some test rides, results seemed to be comparable with the previous Powertap G3 power meter (just reviewed average power / average HR), nothing suspicious.
After some time I started noticing the power readings from my Vector 3 seem to be a little understated. I moved my pedals to my MTB bike (the one with Powertap onboard, the same crank length 175 mm) and did the test ride.
Result: average power reported by Garmin pedals lower over 10% (205W on Vector vs 231W with PowerTap).
Moreover - the difference seems to be maintained with static value around 20W across the whole workout, not the constant percentage difference!

Here are recordings from both devices on the same ride (please do not be confused by one day shift for Vector ride - I had to change the date manually as Strava prevents uploading two overlapping rides.
Powertap + Garmin Edge 1000: https://www.strava.com/activities/2189607575
Garmin Vector 3 + Strava mobile app: https://www.strava.com/activities/2189608412

After that I performed static torque test as described here: https://support.garmin.com/faqSearch...vi3oBYZUUZdPV6. I just used different known load - 4.5 kg instead of ~11 kg (but does it really matter?).
Result: for both pedals the inaccuracy is below 1%

Any clue what might be wrong? Appreciate any suggestions, hints.
Going to perform some more detailed tests next week anyway.

BR,
Slawek

0 aweatherall over 6 years ago

Using the same weight you can also test the PowerTap hub.

See https://www.cyclingpowerlab.com/Powe...libration.aspx

0 Former Member over 6 years ago

Thx Alan,

Done, tested Power Tap. Result: measured torque is ~95% of the expected (calculated) value based on the same known weight. Meaning: there is some inaccuracy with PT as well (maybe partially related with drivetrain loses).
But now it's a little bit more confusing as on PT unit the measured torque is even lower than expected which may suggest my PT tends rather to understating the power readings.

S.