Wahoo Speed/Cadence all the sudden sporadic

All was GREAT until today…Cadence is not reporting RPM correctly. I was pedaling really hard and could barely get over 110. I know the rate at which I was pushing I am usually over 200…and I can barely hold 110. A friend of mine had a similar experience this afternoon with spikes in power.

Bluetooth and Windows connection. Again. No issues at all until today.

Batteries are brand new. Wi-Fi connection is great. Not sure what’s happening.

You’ll need to give more info about your hardware setup, especially which exact trainer you’re using, is cadence integrated etc

I am using a spin bike and Wahoo sensors. Connected via Bluetooth to my desktop PC.

Let me know what other information you need.

Which spin bike?

What wheel size are you using on the Zwift Pairing Screen.

Sunny Health. The wheel is 18.5" so I am using 20". But like i said, up until today…everything worked just great. Today…it all connected…and the cadence sensor was off.

Sounds like communication from sensor to the app is screwy, so it could be an issue with the Zwift app or the sensor.

App - you might want to check what version of the app you’re running, and try to figure out if that has been updated since your previous ride. The last PC update was Dec 28.

Sensor - one idea is to remove the battery from the sensor, wait a minute and replace it. Another is to connect via Ant+ (this sensor is dual band I think) instead of Bluetooth if you have an Ant+ dongle.

Are you saying your friend is using the identical setup somewhere else, or the exact same machine?

I am not sure the app version. I do know that I have zwifted a few times since Dec 28th without issue.

I removed the battery on the sensor for a few min, then replaced it all together. I do not have an Ant+, just a regular bluetooth connection. I Will need to buy an Ant+ dongle.

My friend is using a similar setup, but with a road bike on a trainer (non-smart) and has a different Speed/Cadence sensor. His issue was that his speed was spiking really badly.

Mine wasn’t spiking, just reporting lower than what I feel it should have been.

Only other suggestion would be to contact Wahoo for advice. Still not clear to me whether it’s the app or the sensor where the problem lies, so if its actually a defective sensor then the Ant+ dongle might not fix the problem (unless its a specific issue with its ability to broadcast via Bluetooth alone). However, the fact that we’re not seeing the forum being over-run by others saying their Wahoo cadence sensor no longer works properly tends to point towards a specific defect with your sensor.

Hi Matt @roastincoffee ,
All had been well with my cadence until a ride on Jan 6th when it all went crazy. Pedaling like crazy to get where I needed to be and every few seconds a reading of 64 rpm or lower. I powered everything down after the ride and changed the battery for the next ride. I’ve now had three good rides. Have you tried again since your initial problem? I have a Wahoo Kickr Snap, Bontrager Duo Trap cadence, and AppleTV. I was amazed that the previous battery had gone bad so quickly, as it seemed like I had just replaced it. I guess it would be smart to start keeping track of that. Hope you get your problem solved! Ride On!

@Justin_Thackeray I am working with Wahoo. They are putting me thru the normal “its not our fault” paces…will report back.

Last night however, I attempted to do an SST Short and the RPM would run up to like 130ish…then drop down to 60ish…than back up again. I really had to pedal hard (way harder than I would have to) to get even close to the 185w the SST asked me to do. My Cadence was well over 100. Like 112 ish and couldnt get to 120w.

@Beth_Klawun I am going to buy fresh CR2032’s today. I tried last night. Exact same issue you were having it sounds like.

This cannot be a sensor issue. I have tried the sensors in the Wahoo app and it records Cadence and Speed (MPH) just fine.

I noticed…In Zwift…my power output varies as i choose a wheel size (for speed sensor). With 20" I can hit a Cadence of 115-120 and I am only seeing 160w. That cannot be right. I am pedaling so hard!

I tried setting it to 700x20c and I was at 350w. In order to get down to the 185w in SST Short I had to slow down to like 70 cadence.

My Spin bike has an 18" diameter front wheel. What should I pick for that? Also, I only have the option of choosing a trainer or rollers so I end up just picking an unlisted trainer.

Another question…where should the sensors be? I have one on my pedal crank arm up by the crank (opposite where the arm connects to the pedal) and the speed sensor I have placed against the spin wheel (flat against it top facing out) as close to the hub as I can. Do either placements matter?

I have never had an issue with the Cadence. Just the speed sensor (which I assume is what calculates the power in rides like SST or FTP).

@Justin_Thackeray thoughts?

Really frustrated with this. I cannot figure out what is causing the problem. The sensors appear fine, reporting fine in other apps. Maybe I just need to nail down settings in Zwift. I don’t know.

Can someone also please suggest a good ANT+ Dongle I can pick up? I assume the ANT+ dongle works the same as a bluetooth dongle? Just allows for dual band?

Bluetooth problems seem to crop up frequently with Zwift, so I’m not surprised if your issue is there. There’s a good zwiftinsider article you should probably check out:

Zwiftinsider Ant+ dongles for Zwift

As far as the trainer and wheel size question, maybe someone else can advise.

@Justin_Thackeray I really appreciate you and the community riding with me thru this thing. I went ahead and ordered an ANT+ Dongle. We will see how it goes.

Hopefully someone else can chime in on the wheel size issue. I may start another thread for that though.

Good luck, I wish I could say I’m confident this will fix it, but with Zwift things that should just work often don’t, or work for a while and then seem to get broken again by a later patch…

Hi @roastincoffee

With a spin bike Zwift does not know the power curve of the bike therefore it will be imposable to calculate power from a speed sensor.

I have used other sensors and have found they are not vary accurate if placed flat they are made to be around the hub.


@Gerrie_Delport_ODZ Impossible or not accurately? Zwift in fact calculates something, but without the curve its an incomplete calculation.

I managed three good rides before this issue. Each time I was able to keep pace with the SST Short target power (180 and 165).

I would say Impossible because Zwift no power curve. Even if you select a power curve changing the resistance knob will effect the results.

This is how a power curve look like. This show two different trainers. You can see a big difference between the two, so which one do you pick?

To add more variability is the spin bike can change the curve by turning resistance knob.


@Gerrie_Delport_ODZ Sorry, I guess I am just getting technical with you. “Impossible” would be, if you don’t have a supported trainer with a useable power curve, the game wouldn’t even let you connect because you are missing an important part of the calculation. Therefore, its “impossible” to use anything other than what supports a power curve.

“Not accurate” is, you are not providing a power curve that Zwift can use in its calculation, but the game gives you its best calculation anyway. Which is why, even with my spin bike, I get a power output value on screen with just an RPM and Cadence sensor.

I see your point though.