Kickr Bike Reading Much Lower Wattage vs. Snap

Just purchased the Kickr Bike. Only a few rides in, but reading significantly lower wattage (like roughly 50w) vs. the same perceived effort and HR on my previous Snap and outdoor activities. I was very diligent in spinning down my Snap, so don’t feel that is an issue. Any other Kickr bike users experienced the same thing? I’ve got the bike set up as a 1 x 12. Thanks!

Hi @Tom_Welge5317 welcome to Zwift forums.
Wheel-on trainers generally have a larger margin of error for power meter accuracy compared to direct drive trainers.

Per Wahoo’s specs, the Kickr Snap has ±3% power accuracy, and their Kickr Bike is +/- 1%. There will be some inherent discrepancies between the two power sources. Don’t let this drive you too crazy - expect that the Kickr bike is going set a more accurate baseline than your previous trainer setup.

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I feel like the kickr bike is also reporting lower power. I’ve been having trouble keeping up with rides that I used to alway sit at the front of.

However, after 5 rides my kickr broke, so I can’t say conclusively if this is a problem or if I just need to get used to the slightly different riding position.

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Have you figured anything out here? I am starting to feel like this is a problem too. I got my replacement bike, and it feels like it’s showing lower power than my wheels-on trainer. Obviously, it may be the old trainer. I intend to do some testing soon to see if I can figure anything out.

Well, not really. I did some back to back tests of Snap vs. Bike. Bike read about 10% lower. I also borrowed some Garmin pedals and read those at same time as riding the Bike. Bike read about 5-7% lower than pedals. No other response from Wahoo. Not sure
which is “right” but mainly bummed there is so much variance out there. Let me know what you find out.

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I’m trying to motivate myself to do the side-by-side like you did. It’s pretty much a bummer to fall off the back of rides where I always used to be in the fence…

Interested to see what you find out. I know what you mean about the “new reality”. Last night sucked wind big time on a race that I used to finish in top 1/4 in my category!

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only real way to know is to test with some pedals or other power meter you know to be accurate.

how do you know if the new trainer is reading low or the old one was reading high otherwise?

I have a Wahoo smart trainer and have been having similar issues, especially when doing a training ride. For example, I will do 1:30 train ride and for the first 30 minutes it’s 80 W. No matter how much I push, it stays under 82 W. The ride continues to build on W, but it’s stuck at 80-82. I have tried system updates, re-connecting, etc. Nothing works.

Hello @Marisol_Levin, welcome to the forums!

Which one do you have and did you update the firmware using the Wahoo utility app?

Is this a workout in Zwift? It sounds like you are in ERG mode where the trainer will hold the target watts no matter your cadence, the resistance will stay the same.Check your settings for ERG mode and it should be off unless you are doing a workout.

Hi Mike,

I think the first part of this statement is correct but the last part about resistance maybe wrong because the whilst the watts will remain constant due to ERG, if cadence changes the resistance must change to keep the watts the same.

ie if the cadence increases the load will reduce to enable the watts to remain constant.

Yup, you are correct. The resistance changes so that the watts remain constant based on your cadence. Thank you for clarifying that!

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I have the Wahoo Kickr Smart Trainer, but I think your comment on ERG mode makes sense. I don’t feel resistance and the wattage stays the same. I will check in on this. Thank you.

I used these pedals and Zwift power https://cycling.favero.com/assioma to compare, and found the pedals were slightly LOWER than the bike. The next step is to try with the trainer.

You can zoom in and see the power is very similar, but slightly lower… https://zwiftpower.com/analysis.php?set_id=14624#

Wow, that is interesting.

Want to see what your trainer comes up with.

5% lower is a bit more than slightly IMO. Interesting analysis. I assume Wahoo will get the accuracy figured out in a firmware update soon enough.

Do we assume the pedals are correct? The bike and pedals both claim 1% accuracy

OK, here is the comparison of the pedals and the Magnus. Before I calibrated the trainer, it was wildly high - like 50% higher than the pedals. Afterwards, it’s a small amount higher than the pedals.

https://www.zwiftpower.com/analysis.php?set_id=15111#

My takeaway from this is that I may not have been calibrating my trainer often enough and it may have drifted higher. It’s impossible to know since the trainer was moved a few times since I got the bike and discovered it felt different.

I was pretty diligent with my spin downs, so that’s why I was so surprised.

Thanks for sharing what you did.

Guess we all just move on from this point. Ride On!