Setting the correct tire size

I got bored of my numerous indoor training sessions (recovering from an accident) with just music to listen to, so when I found Zwift a whole world opened up, thanks!

As it states a simple speed sensor and ANT+ dongle is sufficient to ride. My problem is is that I have a spinningbike set up at home and since Swift assumes my wheelsize is 700C, which it isn’t cause I got a small flywheel, the speed is messed up big time (like 210%).  Somehow that also seems to mess up my cadence which I don’t understand.

Is there anyway to let me change the wheelsize (or any other setting to get the speed in order)?

Is it the magnet based?


Or garmins hub style.


If magnet based then you will need to borrow a garmin head unit or similar, to calibrate and flash the firmware in the unit.


What you should do is just this pack.

I got a GSC-10 installed on the spinningbike connecting to a Suunto Movestick. Your saying I can tweek the internal firmware of the sensor?

My regular bike is rigged with Polar sensors and headunit. Basicly I only got the GSC-10 to connect to Zwift :slight_smile:

Yeah.  just see if you can borrow a garmin

No luck so far. Haven’t been able to get my hands on a headunit.


Nobody knows of a simple software program I can run to get the correct settings going?

I got my hands on a head unit, calibrated, but it didn’t solve my issue. Seems like Zwift uses a default tire size which doesn’t come close to my trainingbike.

Free Trial is ending, so won’t really be an issue after that, I will be looking into different software until this gets fixed. 

+1 on this. Training on an old mountainbike (650B), quite disheartening