First ride with power meter. no power even if i am pedalling

I got a power2max. with rotor cranksets and shimano chainrings.

i went for a quick test ride and i notice that sometimes even if i am pedalling the power readings are 0w.
this seems to happen while going downhill is it because there isn’t enough torque? or there is something wrong?

is it because i am going slightly downhill? am i supposed to always get power when pedalling or if there is no resistance then there is no power?

should I have the installation of the power meter reviewed… maybe i did not do it correctly?

Did you set the zero offset?

Are you actually applying significant torque during those periods of zero power, i.e., are the pawls of your freehub engaged?

Only if the answer to both of the above questions is “yes” do you definitely have a problem.

Otherwise, it takes very, very little power just to rotate the crank (unless your bearings are shot), so not surprising that values of zero might be recorded.

what does it mean? the crankset is new (chainrings and rotor cranks

it was the first ever ride with it. I do not think i did a manual offset. according to power2max that would not be necessary.

I try next time…

Technically speaking, pedaling backwards would be cadence.

That said, I can’t imagine you backwards pedaled for that many minutes at 90RPM :slight_smile:

In short, yeah, something is definitely broke. Sure, there’s something smoothing in that graph, but nothing that’d disappear your power.

(Side note: When I saw the title, I thought - 'Huh, must be on a IQ2 PM."

i noticed it happens when going slightly downhill so basically spinning out.

i got the p2m based on yours and on gplama reviews.
does power get reported when spinning out, running out of gears?


It would be be reported, and even spinning out is going to be putting some power into it (usually about 30-50w in my experience).

I’d say if you’ve got more data that’s like this, then I’d circle back with Power2Max for a fix. The only other thing I could think would be if it’s got calibrated/offset with some big load on it, but then your other numbers would look a bit odd too.

Are you using a cadence dohickie too? Is that where the 90rpm came from?
Did you have any other devices- like your phone - connected to the PM are that time?

The pawls inside your freehub are what allows you to stop pedaling and your wheel still coasts. Without getting super into it, when you pedal forward they engage with ratchet teeth and allow you to push forward. But when you stop pedaling then disengage and skip past the ratchet teeth. That’s what the buzzing sound is when you coast.

So you can move the pedals forward but if you still hearing the buzzing sound then you aren’t “engaging you freehub” and would be putting near zero torque through the pedals.

Power = Torque X Cadence

So if you aren’t putting force through the pedals then your power will be zero even if the pedals are moving.

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the head unit a garmin 1030 plus running beta firmware has a garmin cadence sensor…but this was not present. it is installed in the old cranks not in the rotor cranks that were installed along power2max.
i am pretty sure that i was pedalling and saw 0w reported on the headunit. albeit it only seemed to happen when i was kinda spinning on on the small ring and downhill…
so the cadence here i am pretty sure it comes from the powermeter.
I did not have any phone with me. it was a short spin ride to see the numbers. i had it installed yesterday.

What is this installed in? What spacers are you using? If you take the chain off the ring and give the crank a hand spin, how freely does the crank spin (should be 1.5+ rotations or so)?
If youre feeling a bit of resistance in the pedals, but zero power is coming out, you might have the bottom bracket bound up. As a warm fuzzy, Id back the preload all the way off and give it another try.

This is a crank spider PM. So a bound up BB would still be registered as additional power by the PM.

Nope, the BB would provide the resistance and the spider wouldn’t register that drag. The P2M only measures whats between the spindle and the chain. The BB eats the power between the crank arm and spindle.

Pedals-> Cranksarm → spindle → spider → ring → chain → cassette → hub → rim/tire → Road.

Itd only be a bit of power. If he feels hes putting basic tension on the chain while going downhill, keeping the freehub engaged, he might be putting 5lb of tension on the pedal but 3lb of resistance is getting eaten by the BB bearings and the remaining power is too little to measure.

I’ve got this setup and it’s easy to overload the bearings because there are spacers, the high tq on the single bolt, and then the preload. Your needs may differ from the instructions based on chainline and the outer bearing seals you’re using. Rotors instructions also suck.

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Hmm yeah you might be right…

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to be honest i don’t know i gave it to a bike shop to install them
i have this bottom braket Bottom Brackets - TF38624 - TOKEN Cycling Products
on a 24mm rotor gravel axle with shimano 50/34 chainrings and rotor aldhu 170mm crankset
the bike is a 3t exploro pro grx 2x which came with grx cranks but i converted it to road.

what do you mean to bound up the bottom bracket?

When you install the crank, you set the ‘preload’ which puts the right amount of side-pressure on the two bearings in the bottom bracket to get the balls in the bearing rolling correctly. This also adjusts for the small differences in setups.
The adjuster is on the left side (opposite the rings) . if you over tighten it, the crank won’t spin freely. It wont spin super freely because of the water seals on the bearings, but it should spin 1+ rotation when set right. Take your chain off to the inside of the little ring and give the crank a good spin. If its overly tight, you’ll feel it.

You can see the preload here, on the crankarm on the far side, it has the tiny silver bolt on it. If the crank isn’t spinning freely, loosen the silver screw and backoff the preload all the way (you need spread the collar with a flat screw driver in the gap to spin). Repeat spin test. Retighten collar to just touching the BB seal - it should be applying a tiny amount of pressure- and retighten the silver screw. Retest.

(Not for this, but special note: The BB90 Token threaded Bottom bracket is an avoid item. They used TINY TINY bearings to make everything fit. I think other ones might be fine - I think Canyon uses them in fact, but the BB90 Trek one is an avoid)

this is my bottom bracket picture:

i believe this is pressfit.
do you suggest i change the bottom bracket by something better? what are best option? I hear people use ceramic bearings.

I am fit dissapointed i bought this pm almost 3 weeks ago and haven’t been able to start training.

That should be fine, dont mess with it. That is a threaded tube design that goes into a pressfit frame. The tube holds the bearings in alignment in cases where the frame is slightly off. The bottom bracket is really just two bearing in a bearing holder (the tube here) that you put into your bikes frame, which encompasses the frame-bottombracket interface. The Trek design is different because those tabs on the outside need to fit inside where it says ‘token’.
If you have the crank out, just give the bearing spin a feel with your finger pushing down a bit. It shouldn’t roll with much ‘texture’

To be clear (as this statement was a bit unclear to me)… when you say “small ring”… are you talking small CHAIN ring OR small cog?

The elevation profile circled above in your graph seems fairly shallow to my eyes (perhaps 10-15m over a minute or so??). If you are spinning out at that profile, that suggests to me you were in the small CHAIN ring? If you were, there likely was little to no torque at the PM to read… resulting in 0w at the head unit…

Talk to Power2max. They were very responsive when I had issues.

i meant small chainrings…
i stay on the cassette around the middle for better chainline.