Why set Tire size on Kickr Core with Zwift one

General Discussion
1

Probably yet another noob question.

I’ve got my MTB connected with the Zwift cog on a Kickr Core smart trainer.

Why do I need to set the tire size as it’s a smart trainer without tires?

And if I do need to set it what should I choose? I normaly ride with 29” 2.25

2

Hi @Gijs_van_Erp

Are you talking about this screen in the Zwift app? If yes, you’re starting down the wrong path. This flow is for Zwifters using a wheel-on classic trainer.

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As you have a KICKR Core smart trainer, you should select the Power Source tile on the left.

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Then pair over Bluetooth in this order:

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  1. Power Source.
  2. Resistance (your controllable trainer signal will take ~10 seconds to appear. This lag is expected over Bluetooth).
  3. Cadence.
  4. Controls (e.g. Zwift Click / Zwift Ride / Zwift Play controllers or a combination of two of those)
  5. Heart Rate Monitor (if using).

Does that answer your question, or are you talking about something else where tire size is set?

3

Pretty sure this relates to the wheel size setting in the Wahoo app

4

Does wheel size setting matter in the Wahoo app? I think there’s other settings like for pedal-based powermeters where setting crankarm length definitely does matter.

5

I imagine it would be used to scale the resistance you feel on the trainer, so that the resistance feels the same as if you were riding that bike outside.

It would likely only matter if you were using the wahoo app to control the resistance, and only for the sim mode.

If the resistance is being controlled by zwift I doubt it would impact anything.