zPower and speed on the high side

Hi Guys

I’m new to zwift and indoor trainers, I just bought a basic indoor trainer (Minoura B60) and I already have my wahoo speed, cadence and heart-rate monitors.

I just installed zwift and did a 20km cycle to get the feel of it, I connected my sensors and set the resistance of my trainer to L which is what zwift told me to do.

At the end of my ride I looked at my stats on strava and they are saying I averaged 39.7 kph and my average power was 260W.

A normal outdoor 20KM cycle on the flat for me I would average about 27kph and 155W. I don’t have a power meter, this is what strava is calculating (I know none of it will be hugely accurate but my outdoor sessions are pretty consistent).

I know I won’t get the full zwift experience unless I have a smart trainer (may happen down the line). How do I get the most accurate readings from zwift with my current setup, is it just a case of upping the resistance to get the numbers more inline with strava’s outdoor sessions?

Cheers for taking the time to read this and look forward to getting some tips on how I can get the best out of zwift with my current setup.

Hi Phil, welcome to the forums.

With wheel on classic trainers like you have it is very important to make sure the tire pressure is correct and that you are tightening the trainer against the wheel to the proper tension. Also, it is recommended to use a trainer tire to prevent slippage and not damage your outdoor tire. If Zwift says you have to put this at a certain level on the magnetic resistance remote, then you should always leave it set at that recommendation. Zwift uses a power curve to estimate your watts based on the trainer you have, so changing the resistance level will alter the power curve, but Zwift won’t know that so your watts will be even more inaccurate.

zPower is pretty inaccurate, so comparing to what Strava might estimate is not going to help. Also, when on Zwift you aren’t stopping or coasting, etc. Make sure your weight and height are correct as well, as this also effects your speed in Zwift.


Hi Mike, thanks for your quick reply and welcome!

Maybe I didn’t have the wheel tension correct, I just checked the instructions again next time I will tighten it up to see if that helps, my weight and height are both correct.

I will look at getting a training tyre although I’m running tyres that are towards the end of their lifetime (I have new ones ready to go on). As for tyre pressure, I normally run them between 100-110 PSI, do I need to adjust this to use on my trainer?


Use the recommended pressure that is stamped on the side wall of the tire, usually between 100 -120 psi for road tires.

You also should be using a trainer tire.


Hi Phil and welcome to Zwift! It’s very addictive!

I started on Zwift in Feb / March with a Minoura B60 and had a lot of fun with it. I didn’t really have a reference point for checking the estimated power output, but on the “L” setting ride averages were around 220 watts. I’m 60 and just getting back to cycling after a 5-year break so suspected something was wrong. Did lots of tinkering with tire pressures and tension, but nothing changed much.

Anyway, I recently updated to a Wahoo Kickr Core (with its fairly accurate power meter) and ride averages have dropped to a more realistic 150-160 watts. So, it looks like my average output was being overestimated by around 40%. And there I was thinking my decrepit old legs still had it. Even got a KoM one day (apologies to whoever really took it).

I have noticed that while the B60 overestimated significantly at lower power outputs I never got it over 420 watts. I think this is a limit applied by the Zwift power curves which would probably be fair on the L setting. On the Kickr I managed to hit 600 watts on the first attempt, even if only for about half a second!

For me, the Minoura B60 was a lot of fun to ride, but there is no way that the “L” setting gives a real approximation of power output. The “M” setting would probably be closer, but Zwift will still limit the top end to around 420 W.

Enjoy it for what it is, but probably not good to enter races. I will overestimate your power at normal speeds, and you will never beat anyone in a sprint.

The other side effect is that I rode Alpe de Zwift without too much problem on the B60. On the Wahoo I’m gonna need a bigger cassette!

Hope you’re still enjoying Zwift.

Cheers Peter