Garmin Vector S reading lower than Kickr Core

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wilwil
Posts: 693
Joined: Thu Sep 23, 2010 5:47 pm

by wilwil

My Garmin Vector S reads 20 watts lower than my new Kickr Core. Which one is accurate? I expect a slight discrepancy but not 20 Watts.

TobinHatesYou
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by TobinHatesYou

Impossible to tell with just two references. It’s common for KICKR CORE units to read high, but a Vector “S” is only single-sided. My old Vector 2 units also eventually started to read low after a few years.

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toride
Posts: 153
Joined: Fri Sep 02, 2011 6:19 pm
Location: Lincolnshire

by toride

Wilwil, I’m also experiencing this but I’m using the(well used) vector duel sided version and I’m on a new ThinkRider trainer and my early indications are even more than the 20 watts you mention.
Have you had any light shed on the issue?

Butcher
Shop Owner
Posts: 1917
Joined: Sun Jan 03, 2010 4:58 am

by Butcher

I would suspect the power reading to be higher at the pedal than the cassette/hub. I know that my Hammer reads lower than my Vector while on Zwift. Simple to fix, I now have Zwift looking for my Vector power vs the Hammer.

toride
Posts: 153
Joined: Fri Sep 02, 2011 6:19 pm
Location: Lincolnshire

by toride

Butcher, where is the hammer getting its data from, Is it not the Vectors ? Also do you find the reading of watts from the Vectors very jumpy? Or do I need to replace my batteries

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skidrrr
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Location: Moldova

by skidrrr

Some of that issue could be caused by your R/L balance.
I get 54/46 ratio quite often
Image

Butcher
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by Butcher

Like most trainers, the Hammer is measured internally.

I'm no engineer but I can understand there are loses from where the power starts and where it ends. Since I can measure the pedal force [Vectors] and I can see what the hub sees [The hub is the trainer, you know, take off rear wheel, install trainer, ride], there is always a bit less. Before I switch Zwift to look for the Vectors, I could see a good 10w and sometimes more on a steady flat section of Zwift.

I was able to go a bit faster just by having Zwift look for the Vectors. One of the quickest ways to raise my FTP :D

toride
Posts: 153
Joined: Fri Sep 02, 2011 6:19 pm
Location: Lincolnshire

by toride

Sorry Butcher I had the Hammer confused with it as a head unit.. and wasn’t aware of the smart trainer. Therefore I can see what your saying
I’m still wondering though ? Does your readout from the Vectors jump up and down considerably even when you try to be as smooth as possible?

warthog101
Posts: 846
Joined: Wed Sep 25, 2013 10:05 am

by warthog101

My kicker core reads about 15-20% higher than my L side 4iiii.
The 4iiii I suspect is a bit low from comparing my power to others on the road who are a similar weight I ride with.
I have had several people tell me the kickr core is well known for measuring high.

Butcher
Shop Owner
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Joined: Sun Jan 03, 2010 4:58 am

by Butcher

I have my settings at 3sec so there is no jumping. I also have dual pedals.

maxim809
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by maxim809

I have an assortment of PM's (L-Stages, Favero, Garmin Vector's) and a Kickr Core gen3.

My Kickr reads 12% HIGH for any interval from 1 min to infinity. For sub-15 second sprints the Kickr will read 100~200W lower than outdoor.

All spin-down calibrated, etc etc blah blah blah.

I recorded both Vector PM vs Kickr power on the same indoor ride and fed both .fit file recordings in ZwiftPower's power data analysis software to arrive at that 12% difference.

My Stages/Favero/Garmins all read similar to each other. I have high confidence that these PMs are reading correctly, because I've done hundreds of 20~60min TT hill climbs on my local roads under all sorts of conditions including ideal non-windy days... and plugging my numbers into www.bikecalculator.com or https://www.gribble.org/cycling/power_v_speed.html my expected finish times / average speeds match perfectly with my power to weight. And I know my Crr and I measure Rho some days, so there's even that level of noise being mitigated fwiw....

Because we don't have a ground truth reference point, you could follow similar steps to validate your pedal PMs if you had a longish climb handy nearby. The approach is to build confidence in your theory thru a large enough number of runs (in that, are the pedals truly reading accurate, or actually reading too low?)

FYI I've observed that 75% of my friend who haves Kickrs have stated they read higher than expected, but one guy's actually reads lower. Lotta other things can be going on here, but that's a whole separate topic.

TobinHatesYou
Posts: 12444
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

A good number of KICKR Cores report high. A good number of KICKR18 and KICKRv5 report low. This is based on browsing dual-analysis at major pro-am Zwift races and my own experience with a KICKRv5.

OnTheRivet
Posts: 728
Joined: Sat Jul 24, 2010 9:41 pm

by OnTheRivet

maxim809 wrote:
Sun Feb 20, 2022 2:15 am
I have an assortment of PM's (L-Stages, Favero, Garmin Vector's) and a Kickr Core gen3.

My Kickr reads 12% HIGH for any interval from 1 min to infinity. For sub-15 second sprints the Kickr will read 100~200W lower than outdoor.

All spin-down calibrated, etc etc blah blah blah.

I recorded both Vector PM vs Kickr power on the same indoor ride and fed both .fit file recordings in ZwiftPower's power data analysis software to arrive at that 12% difference.

My Stages/Favero/Garmins all read similar to each other. I have high confidence that these PMs are reading correctly, because I've done hundreds of 20~60min TT hill climbs on my local roads under all sorts of conditions including ideal non-windy days... and plugging my numbers into www.bikecalculator.com or https://www.gribble.org/cycling/power_v_speed.html my expected finish times / average speeds match perfectly with my power to weight. And I know my Crr and I measure Rho some days, so there's even that level of noise being mitigated fwiw....

Because we don't have a ground truth reference point, you could follow similar steps to validate your pedal PMs if you had a longish climb handy nearby. The approach is to build confidence in your theory thru a large enough number of runs (in that, are the pedals truly reading accurate, or actually reading too low?)

FYI I've observed that 75% of my friend who haves Kickrs have stated they read higher than expected, but one guy's actually reads lower. Lotta other things can be going on here, but that's a whole separate topic.
Just switched out my Hammer for a Kicker V5 and my first set of Vo2 max intervals was brutal. Not sure how it reads compared to my Quarq Dzero's on my bikes (I'll have to check) but it definitley reads lower than my Hammer.

by Weenie


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