I bought some Garmin vector 2 pedals, single sided, from ebay. Liking everything to match I then bought the Garmin vector Shimano pedal adapter kit for my existing Shimano 6800 pedals, and its there that my troubles started. I think the pedals now under estimate power.
I have been through the installation method twice, I have used a torque wrenches for everything. With the wind today where I live, I would say I wouldn’t have had a lot left in the tank, same again for my ride two weeks ago.
I think my pedals are under reporting. My reference point for power is a Kurt Kinetic RR dumb trainer, but also, when I had the Garmin cleats on the numbers were higher and I feel would have been fairly accurate to my output and exertion.
I have vector 2 pedals but I have the standard pedal bodies.
With one power meter there’s no way to know how accurate the readings are. However, the same would be true for before you changed the pedal bodies.
Are the readings consistent with the new bodies? If so, even if they read lower, they should be fine for the purpose of training / pacing your efforts.
Could you change back to the garmin pedals?
You may be able to get some help from garmin but it might be a while before they’re contactable given their current problem.
Your only real reference for power is a virtual power reading from a dumb trainer. This has led you to believe the pedals are under reporting power.
Two things I think you should do…
First, read up on virtual power and what the estimates from a dumb trainer mean. Short version - they will be consistent with your setup but not comparable to any other power data. They are not a direct force power meter and should not be compared to any others.
Second, beg borrow or steal a second power meter from a friend and put that on your bike at the same time as the vectors to get a good comparison point with another power meter. This will likely give you the confidence you need.
Essentially - you are currently in a spot where your virtual power measurements from your dumb trainer have given you a perception of your power that isn’t matching your power meter readings. You have taken the easier to swallow option of presuming the lower number of the two measures is the inaccurate one, but it could just as easily be the opposite (the virtual power number has been high all along). Go out and compare to a second real power meter and you’ll have your answer. My guess is your Vectors are correct and you just have to swallow the bitter pill, my apologies in advance.
Not sure that’s strictly true - I think there is also a comparison with the same pedals but with the native Garmin body.
Personally I find my Vector 2 pedals report power lower than my kickr. This is consistent though to the point where I drop outdoor workouts by 5%. The bike with my Vector pedals won’t fit on my kickr so I can’t just use the pedals all the time and use powermatch.
I read up on swapping spindles to fit Shimano bodies but decided it wasn’t worth the risk of damaging a pedal. With Garmin unavailable for hep right now I think as long as they read power consistently you just need to accept you have a different ftp value when using them compared to your trainer as I have.
Without a comparison point there’s no way you can make an empirical comparison. It is just based on ‘feel’ which is something humans are consistently bad at assessing.
Look at the rides he linked, he’s setting multiple all time power PRs in all of them - both the ones that are allegedly reading too low and those reading ‘consistently’ with his virtual power from his dumb trainer. There’s not enough data to compare the before and after of the pedal swap - he needs a second comparison point
On a quick look I can’t really see much wrong. Only looked at the Strava files.
Even if you had an Elite, Wahoo or Taxc direct drive train it will be typically 10 - 20 watts @ around 250 watts, drive chain losses etc. Dumb trainer with slope, you can’t really compare as others have said.
Every crank power meter I’ve had over estimates compared with the trainer - Wahoo Kickr in my case, (also did have an Elite.) I say they are correct’ish at that point in the power chain in which they measure, Stages (left only), Vector 2S. Single side over read a bit for me as my left side is stronger and that is doubled with single sided meters.
Basically to cut to the point I don’t think it is under reading, those numbers look consistent with that pace on the terrain to me.
Yeah n=1 here but when I switched from virtual power on a wheel-on dumb trainer (KK Roadmachine) to Favero Assioma duos I saw an 8% reduction. After 6 months of training it was a bit of a bummer to slide it downward but it’s just a number after all.
FWIW I’ve gone from Stages, to Kicker, to Garmin Vector to Neo … and they weren’t even close to each other, I’ve come to the oppinion that most accurate power meter is the one you are currently riding, and trying to get them to line up is an exercise in futility
Agree with this. My Kickrs and Vector3 are usually pretty close, within 3-5% but it varies by day, temperature, and power output. Some days the Vectors are higher, others the Kickr is. Best to pick one (preferably a power meter you use outside too) and stick with it IME.
Virtual power is an estimate and shouldn’t be compared to a direct power meter or smart trainer measurement at all. It is essentially meaningless in the real world. It is OK as a basis for indoor training only. Assuming the Vectors are setup correctly, that’s your real number.
With my hardware the opposite is true. My kickr gives me higher power than my Garmin Vector 2 pedals. Both are consistent though so I’ve learnt to live with it.
Thanks for all the replies and suggestions. I agree, I do think that maybe the best course of action here is to see how I get on with a second Power Meter and probably my numbers have been clouded by the KK trainer. I’ll let you know how I get on!
Dan