Tire size change


So, I’m using a cycleops mag trainer. I just went from 700x25 to 700x28 size tires. My trainers meter now reads about 40 watts lower than my power meter on my pedals. It’s back breaking. Is there a setting in Zwift to adjust this, will it make a difference, or should I just use the meters on my bike.

It used to be the opposite, about 20 watts lower on my bikes meter than my trainer. I used to have a meter that read about the same as my smart trainers.

Anyway, any thoughts?

If you have power pedals why are you using your mag trainer estimated power? Your pedals are much more accurate and what you should be using.

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I warrantied them, and the 2nd pair read different results. They seem to be more accurate now though.