Power changes during climb

[RussPitcher]

I've recently got a set of Vector 3 pedals for my road bike so I put them on my MTB so I can get the PowerPod dialed in as accurately as possible. After going for a ride and analyzing the DFPM data with the PowerPod data I tweaked the Crr and CdA figures post-ride to get the best fit. I'm aware that my settings for the MTB were originally reading far too high but as I just wanted ride-to-ride comparisons that wasn't an issue for me until I got the Vectors. I've done the best I can and it seems to be about right, for this ride at least, apart from one issue. When climbing the PowerPod seems to read a lot higher than the DFPM. It seems to settle down eventually once the elevation comes down but it's consistently reading high after even modest climbs. It seems to me that the dynamic tilt calibration is not coping well with changes in grade.

I also find that the PP consistent reads high during the first 8 mins of a ride. I know that this is not unexpected if the tilt calibration is out due to poor mounting but this happens on every ride and I rarely take the PP off its mount as I am able to charge it in place. The PP is always rotated forward hard up against the stop and I haven't seen any signs of the PP moving and I generally tighten the bolt so much that I fear for the threads.

I'm just looking for a high-level view of power that will keep my stats from MTB rides roughly in line with those from my road bike and, given that I'm riding a full suspension MTB on varied ground and unlocked suspension, I'm happy that the power will only be right when averaged. However, I would like to sort out the constant 8-min errors at the start of the ride and, in particular, the climb power discrepancies. Can you give me any clues as to how I can improve matters?

Thanks a lot!

[Velocomp]

There are two things going on:

1) Your PP is recalibrating itself at the beginning of the ride. This takes 8 minutes. New FW 640 speeds this up to 90 seconds.

2) For mountain bikes, you should lock-out the front suspension on climbs. If you do this then PP should provide accurate power on climbs. If suspension is not locked out then you may get slope errors on hills.

[RussPitcher]

Thanks, I'll try to remember to lock it out on my next trial to see how it copes. The new firmware sounds good

Just one question - Why does it need to recalibrate on every ride? I thought that should only happen if the tilt is wrong? When I leave the house at the start of a ride I always have a short section of gentle up- or down-slope - 300 metres or so. Would this cause the tilt sensor to think it needs recalibration?

Either way, I'm still very happy with the PowerPod, it's a great tool and your service has been really good. Thanks!

[Velocomp]

If you're not using a lock out, PP is continuously seeing changes in slope; this is OK, but the slope number it remembers is "left over" from the end of your previous ride. So, if your bike is at a different angle at the start of your next ride, PP will take 8 minutes to figure that out. NOTE: the new FW will take only 90 seconds