Strava Est. Power vs Real Power Part 2. MTB

Just got a Stages Power Meter for the MTB. You all know what that is so I’ll save the explanation, but thought you might be interested in a comparison of the Strava Est Pwr on typical MTB XCO style courses.



Actually, one thing you might be interested in is compatibility. I did a lot of reading pertaining to Q Factor compatibility between different Shimano cranks. I was replacing a SLX M670/675 left hand crank arm with a Stages XT M780/785 Stages. The answer is yes it is the same Q factor and works fine. Obviously make sure you get the right length, but you already knew that.


The last time I did this was when I got a PowerTap for the road bike. In the end, the Strava Est. Power was hopeless. It was usually 20-30% out and hopeless as any kind of training tool. Well, I just thought I’d experiment and try the same thing with MTB. Here’s the course. It’s the course I co-designed for the 2015 NZ MTB Cup here in Tropical Wellington.

Screen Shot 2014-12-26 at 7.52.19 am


Here’s the data for the ride collected via Garmin/ Stages (top) and iPhone with set power (bottom)

Screen Shot 2014-12-26 at 7.55.56 am

Screen Shot 2014-12-26 at 7.57.00 am

You can see that the lines for power are, well, not even close…If we focus a bit on the 2 main climbs it becomes a bit clearer:

Climb 1:  Velodrome to Peak     1.3km     110m     8%     5:43 

Stages: Max 600, Avg 374: Strava Est. Max 1273, Avg 282

Climb 2: Selection     0.3 km     56 m     17.5%     2:31

Stages: Max 657, Avg: 398: Strava Est. Max 1229; Avg 194

So, the average power estimates are under by 33% and 105% respectively. So, yeah, I think that answers the question. You are way better off relying on heart rate if you want to estimate your power.

Merry Xmas y’all!! steve



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