HR Monitor correct on Wattbike, but incorrect on Zwift


I have just bought a new HR monitor to use on my Wattbike and Zwift. Tonight I have used it for the first time. My problem is the HR reading on the Wattbike is correct, while the HR when paired with Zwift fluctuates and is around 30 BPM lower than expected.

The HR monitor is a Polar T31 coded and I pair from the Wattbike via bluetooth on a MacBook Pro.

Many thanks for your help.


How are you connecting the HRM to Zwift? If you are trying to connect it from your Wattbike to Zwift I think that is what is causing the issue. You should connect it directly to Zwift or use the Zwift Mobile Link to bridge the connection.

Hi Paul, thanks for your advice. I connected the HR monitor to the Wattbike firstly and then selected the HR monitor in Zwift when logging in. I’ve had a thought and possibly the HR monitor can’t send readings to two devices at once (e.g. Wattbike and Zwift).


If it is using Bluetooth for both connects it will not work, but if you use Bluetooth and ANT+ or ANT+ for both it should work depending on the distance to the computer and the Wattbike.

Hi Paul, I’ve just tried the HR monitor with my laptop without the Wattbike on and it isn’t recognised. I’m not near the Wattbike at the moment so possibly I would need an ANT+ dongle to make it connect correctly? All very confusing. Thanks for your help, Matt


Bluetooth can only connect to one device at a time so if you are connecting the HRM to only your Mac using Bluethooth it should work. You can also using the Zwift Mobile Link to bridge the Bluethooth signal to your Mac as long as your phone and Mac are on the same network.

This is why I have a duel band Wahoo HRM.

Hi Paul, I don’t know if the Polar T31 Coded is bluetooth compatible (can’t find out anywhere on the web). It does connect fine with my Wattbike though. I wonder as my Wattbike is over 1m away from the MacBook if the signal is interupted. However, I don’t think this is the case as the power and cadence come through fine. 

I’ve tried bridging via the mobile app and the HR monitor doesn’t pick up.

Ideally I’d like the HR monitor to connect to the Wattbike and then the Wattbike broadcast power, cadence and HR via bluetooth to the MacBook.

Hi Paul,

I think I’ve found out my answer at the top of page 4 on this link

I think I need a ANT+ dongle to connect HR from the Polar T31.


An ANT+ dongle is the way to go and they are cheap. 

I also looked up your HRM and it does not seem to broadcast in either Bluetooth or ANT+ so your only hope is that the Wattbike can do the bridging.

If it does not I would suggest getting a Wahoo Tickr HRM since it broadcast in both Bluetooth and Ant+.

Thanks for your help Paul.

I also found out on the questions section of the Evans website someone asked if the Polar T31 connects via ANT+ dongle for Zwift and the answer is yes. I’ll buy a ANT+ dongle online now. Many thanks again. Matt

Hi Paul,

ANT+ dongle arrived today and the Polar T31 Coded still doesn’t link up. Maybe it isn’t ANT+ compatible…

Matt: an old quote but seems to still apply to your Polar T31 Coded heart rate monitor:

“While I believe that Polar devices are currently lagging behind the competition – I’ve always agreed that their HR straps themselves are superior.  Unfortunately, the straps themselves aren’t natively compatible with Garmin.  Garmin uses ANT+, and Polar uses their own protocol (depending on coded or non-coded).”

Thanks Steve. I think I’ve come to the conclusion a new ANT+ HR monitor will work with both Zwift and Wattbike at the same time. Otherwise its stick with my existing Polar bluetooth smart HR monitor for Zwift only or Polar T31 Coded for Wattbike only (I don’t fancy wearing two HR monitors at the same time!).