Wattage not accurate with 29'er mountainbike

I am trying to get my mountqinbike going on zwift, but I seem to be having an issue with inaccurate wattage. I have a 29’er on my Saris Fluid 2 trainer and I am using the saris speed sensor. I set my tire size to 700x32cc but can’t seem to get my wattage accurate. Any help?

Hi @Ferdinand_de_Villier

What do you use to compare power?

Did you pair as a speed sensor with the correct trainer?

Hi Gerrie.

It doesn’t matter how hard I peddle, my watts stay under 65. Which does not make any sense. Using my road bike previously with my speed sensor it was very accurate. And Yes I did pair it correctly with the correct trainer.

My guess is that the gearing on the MTB is the limiting factor.

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wattage not going to be “accurate” without some kind of power meter anyway :3

doubt it’s gearing, 65w is literally nothing, no reason you can’t hit 1000w in hardest gear on a MTB :3

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I found that speed sensors can be very inaccurate on a mountain bike because of the increased clearance between the wheel and frame.
The hub mounted ones probably work better.
Accuracy is always questionable with all speed sensors.