Stages PM - anyone had issues with indoor use?

Sammyw23

Twice now I have had issues on the turbo and it seems to be when indoors and not specifically turbo use. Readings are consistently 50-75w too low and last night it even cut out altogether and said zero despite saying connected.

Can't find anything posted elsewhere other than the renowned battery issues.

meanredspider

I've used it quite a few times on my Tacx VR turbo (with pretty aligned results) and had no issues. Any sources of electromagnetic noise anywhere close by? Have you tried BT with a phone or ANT+ ?

Sammyw23

Yeah had my iphone running in sync and it was down on numbers too so its definitely the unit and not the output sent as a result. I can only think its the temp adjustment but I did recalibrate (many times!) so would expect it to sort itself out.

I've used outside on the turbo without any issues and have had no problems at all in races. Annoying though as obv one of the key uses is to train at the required power!

Will have to try it again

meanredspider

The Stages doesn't need calibrating for temp (it does it automatically - one of its strong points). I can only think that there was some interference. Do you have the latest (not very recent) firmware installed? Easy to check via the app.

frisbee

DC Rainmaker did tests on a turbotrainer that measures power and the stages tied up pretty close to his trainer.

If it dropped out completely it sounds like interference. All sorts of things operate in the 2.4GHz band that Bluetooth devices use, cordless phones, wifi, car alarm sensors, microwaves.

wavefront

I'd go with interference, especially indoors where there are lots of signals bouncing around.

I run a P2Max meter and had problems recently with it dropping to 0, or reading very oddly. For me this happened outdoors, but I narrowed it down to it happening on some club rides where it seems someone elses sensors interferes. After a few days it bounces back to normal.

P2M suggested a Garmin reset and repair - maybe check no bluetooth / wireless signals are nearby, and try repairing? Do you run Trainer Road and ANT + ? Does the signal drop on that aswell as your garmin (assuming you're using a garmin?)

RChung

Sammyw23 wrote:

Readings are consistently 50-75w too low

Then no problem. Everyone says that accuracy is unimportant. They say that consistency is the only thing that matters.

Sammyw23

Just thought - I am using bluetooth Headphones to avoid cables to the laptop.....possible culprit? Can't think what else as there are no other devices in the kitchen nearby. Will test this again next time it happens!

frisbee

Sammyw23 wrote:

Just thought - I am using bluetooth Headphones to avoid cables to the laptop.....possible culprit? Can't think what else as there are no other devices in the kitchen nearby. Will test this again next time it happens!

In theory Bluetooth devices shouldn't interfere with other Bluetooth devices but they are a likely possibility.

By boiler caused my airplay speakers to drop out when I had them on the countertop near it. Fridge or combi boiler coming on?

Stalin

RChung wrote:

Sammyw23 wrote:

Readings are consistently 50-75w too low

Then no problem. Everyone says that accuracy is unimportant. They say that consistency is the only thing that matters.

Sorry but who is everyone?

The whole point of a power meter is that you know power, be it on the road, on the turbo, on a different turbo, on the same turbo with a different back wheel or different pressure in the tyre, up hill, on the flat, with the wind behind you, against the wind, trying really hard with the left leg or right leg, with a rear disc, or a 32 spoke Open Pro, wearing an aero helmet up your arse, or whatever.

You can set up a turbo to be consistent. If all you want is consistency you don't need a power meter.

A power meter is supposed to measure power in watts. If it does not do it to the claimed accuracy it isn't fit for purpose, even if Sky use it.

RChung

[quote="Stalin"
Sorry but who is everyone?[/quote]
Everyone who has purchased the Stages, of course.

Stalin

RChung wrote:

[quote="Stalin"
Sorry but who is everyone?

Everyone who has purchased the Stages, of course.[/quote]

The sad thing is a lot of people have purchased them that don't know that.

charlie_potatoes

Stalin wrote:

RChung wrote:

[quote="Stalin"
Sorry but who is everyone?

Everyone who has purchased the Stages, of course.

The sad thing is a lot of people have purchased them that don't know that.[/quote]

Try and make sense please Stalin. FFS.

RChung wrote:

Then no problem. Everyone says that accuracy is unimportant. They say that consistency is the only thing that matters.

meanredspider

RChung wrote:

Everyone who has purchased the Stages, of course.

Are you trolling again? We get that you don't like the Stages PM - move on.

There's accuracy (+/- a few percent) related to L/R balance (and still nobody has explained what exactly you're meant to do with that information - maybe RChung you could be the first?) and then there's a problem (losing 50-75W).

There's clearly a problem in this instance. Given that it's indoors, it's almost certainly some type of interference.

Stalin

meanredspider wrote:

RChung wrote:

Everyone who has purchased the Stages, of course.

Are you trolling again? We get that you don't like the Stages PM - move on.

There's accuracy (+/- a few percent) related to L/R balance (and still nobody has explained what exactly you're meant to do with that information - maybe RChung you could be the first?) and then there's a problem (losing 50-75W).

There's clearly a problem in this instance. Given that it's indoors, it's almost certainly some type of interference.

Why is it that people can't cope with people disagreeing with them without making trolling accusations.



Why should RChung move on? His opinion is valid. It is your problem you can't cope with it.

Stages will always be inaccurate by a percentage that is twice the difference in left right balance.

meanredspider

Stalin wrote:

meanredspider wrote:

RChung wrote:

Everyone who has purchased the Stages, of course.

Are you trolling again? We get that you don't like the Stages PM - move on.

There's accuracy (+/- a few percent) related to L/R balance (and still nobody has explained what exactly you're meant to do with that information - maybe RChung you could be the first?) and then there's a problem (losing 50-75W).

There's clearly a problem in this instance. Given that it's indoors, it's almost certainly some type of interference.

Why is it that people can't cope with people disagreeing with them without making trolling accusations.



Why should RChung move on? His opinion is valid. It is your problem you can't cope with it.

It's not trolling if it's making a valid point but his/her comment was just a snipe at Stages users. It adds no value and is trolling. I'm more than happy to have people disagree with me - I learn stuff and I don't mind a good argument. But comments that basically say "Stages users don't care about 50-75W going missing" are just meant to be provocative. Has it helped the OP? No. Has it introduced a valid argument? No. In fact, the issue for the OP is that the number ISN'T consistent. If people don't like the Stages PM, start up a thread about why Stages is crap. And explain why It gets tedious to have every thread have someone chime in about L:R balance. Soon it'll be the new "Leg Strength" topic.

Stalin wrote:

Stages will always be inaccurate by a percentage that is twice the difference in left right balance.

Why twice the difference? (See - I'm happy to take a valid discussion) 45:55 L:R gives a difference of 10. At 100W true power, Stages would read 90W (2x left leg) (10/100)x100=10% error

I'm still waiting to hear how that helps me though - all I get is tumbleweed. Let's change the units to Horsepower - I get a completely different number but the number itself doesn't matter to most of us. I want to know what's happening to the number and how it relates to me.

Stalin

meanredspider wrote:

Stalin wrote:

meanredspider wrote:

RChung wrote:

Everyone who has purchased the Stages, of course.

Are you trolling again? We get that you don't like the Stages PM - move on.

There's accuracy (+/- a few percent) related to L/R balance (and still nobody has explained what exactly you're meant to do with that information - maybe RChung you could be the first?) and then there's a problem (losing 50-75W).

There's clearly a problem in this instance. Given that it's indoors, it's almost certainly some type of interference.

Why is it that people can't cope with people disagreeing with them without making trolling accusations.



Why should RChung move on? His opinion is valid. It is your problem you can't cope with it.

It's not trolling if it's making a valid point but his/her comment was just a snipe at Stages users. It adds no value and is trolling. I'm more than happy to have people disagree with me - I learn stuff and I don't mind a good argument. But comments that basically say "Stages users don't care about 50-75W going missing" are just meant to be provocative. Has it helped the OP? No. Has it introduced a valid argument? No. In fact, the issue for the OP is that the number ISN'T consistent. If people don't like the Stages PM, start up a thread about why Stages is crap. And explain why It gets tedious to have every thread have someone chime in about L:R balance. Soon it'll be the new "Leg Strength" topic.

Stalin wrote:

Stages will always be inaccurate by a percentage that is twice the difference in left right balance.

Why twice the difference? (See - I'm happy to take a valid discussion) 45:55 L:R gives a difference of 10. At 100W true power, Stages would read 90W (2x left leg) (10/100)x100=10% error

I'm still waiting to hear how that helps me though - all I get is tumbleweed. Let's change the units to Horsepower - I get a completely different number but the number itself doesn't matter to most of us. I want to know what's happening to the number and how it relates to me.

The point you miss is imbalance is not static. It changes. So at one time your Stages will be over reporting power and others under reporting. You might think you have seen an improvement in total power when all that has happened is in that particular session your imbalance has shifted. You can never be sure the numbers you see are correct because all you ever see is double the left leg power. I'm not arguing you need to know about any imbalance, or that you can do anything with that data, but I am arguing you need to know total power.

slowbike

Stalin wrote:

The point you miss is imbalance is not static. It changes. So at one time your Stages will be over reporting power and others under reporting. You might think you have seen an improvement in total power when all that has happened is in that particular session your imbalance has shifted. You can never be sure the numbers you see are correct because all you ever see is double the left leg power. I'm not arguing you need to know about any imbalance, or that you can do anything with that data, but I am arguing you need to know total power.

Unless you have a significant problem with balance then no. The differences are small enough that makes no difference.
If you mean that the balance changes throughout a ride then whilst that may be slightly more pronounced I would suggest that anyone using a powermeter would be aware of the change in dynamic. Also, with a more significant reduction in power in one leg over than the other it would still show as an overall decline in overall power which could still be analysed.

Eitherwhichway, none of this has anything to do with the OP's issue of a powermeter display being wrong whilst used indoors.

Stalin

Slowbike wrote:

Stalin wrote:

The point you miss is imbalance is not static. It changes. So at one time your Stages will be over reporting power and others under reporting. You might think you have seen an improvement in total power when all that has happened is in that particular session your imbalance has shifted. You can never be sure the numbers you see are correct because all you ever see is double the left leg power. I'm not arguing you need to know about any imbalance, or that you can do anything with that data, but I am arguing you need to know total power.

Unless you have a significant problem with balance then no. The differences are small enough that makes no difference.
If you mean that the balance changes throughout a ride then whilst that may be slightly more pronounced I would suggest that anyone using a powermeter would be aware of the change in dynamic. Also, with a more significant reduction in power in one leg over than the other it would still show as an overall decline in overall power which could still be analysed.

Eitherwhichway, none of this has anything to do with the OP's issue of a powermeter display being wrong whilst used indoors.

How can you possibly be happy with data which is the power from only the left leg doubled? Someone may be left leg dominant at low powers but right leg dominant at higher powers. At lower powers the Stages would over measure power but at higher powers underestimate power. The big joke is that with Stages you don't know what your power is. Anyone happy with this daft state of affairs is just playing with a new toy.

I found the fridge interfered with power readings. Power consistently went down when I opened the fridge door to get another beer.

meanredspider

Stalin wrote:

The point you miss is imbalance is not static. It changes. So at one time your Stages will be over reporting power and others under reporting. You might think you have seen an improvement in total power when all that has happened is in that particular session your imbalance has shifted. You can never be sure the numbers you see are correct because all you ever see is double the left leg power. I'm not arguing you need to know about any imbalance, or that you can do anything with that data, but I am arguing you need to know total power.

I'm not missing that point. Nor would I take a single data point as a trend. I'd look for improvement over time as a trend and I think that the variability you correctly talk of will be evened out. I suspect how well I slept the night before or how many miles I've already done in the preceding days will affect the results hence it would be dangerous to take a single data point or two as proof of anything. In an ideal world, of course it would be Nice to have a total power number AND all the convenience (and price) of the Stages system. I weighed up the pros and cons (taking all these arguments into account) and figured that, for me and my circumstances, Stages won out. I had considered (I think I even ordered then cancelled) the Garmin Vector system for instance. But it wouldn't have fitted my FSA cranks, I'd have needed a torque wrench everywhere and I'd have needed to either swap cleats or pedals as my other bikes were all fitted with SPD-SL. I don't need a pin-point accurate power figure that much. It's the 80:20 rule.

meanredspider

Stalin wrote:

Someone may be left leg dominant at low powers but right leg dominant at higher powers. At lower powers the Stages would over measure power but at higher powers underestimate power.

And I ask again - so what? You're looking at your power zones and they're slightly skewed. What will you DO differently? The important thing is to see how they change with your training. Again, I go back to the point (like a broken record) that it's the aerobic system that drives power. Power is the output of that system (the black box, if you like) that we're trying to improve. We do training and we assess whether it's working or not - is that output going up or down as a trend.

slowbike

Stalin wrote:

Slowbike wrote:

Stalin wrote:

The point you miss is imbalance is not static. It changes. So at one time your Stages will be over reporting power and others under reporting. You might think you have seen an improvement in total power when all that has happened is in that particular session your imbalance has shifted. You can never be sure the numbers you see are correct because all you ever see is double the left leg power. I'm not arguing you need to know about any imbalance, or that you can do anything with that data, but I am arguing you need to know total power.

Unless you have a significant problem with balance then no. The differences are small enough that makes no difference.
If you mean that the balance changes throughout a ride then whilst that may be slightly more pronounced I would suggest that anyone using a powermeter would be aware of the change in dynamic. Also, with a more significant reduction in power in one leg over than the other it would still show as an overall decline in overall power which could still be analysed.

Eitherwhichway, none of this has anything to do with the OP's issue of a powermeter display being wrong whilst used indoors.

How can you possibly happy with data which is the power from only the left leg doubled? Someone may be left leg dominant at low powers but right leg dominant at higher powers. At lower powers the Stages would over measure power but at higher powers underestimate power. The big joke is that with Stages you don't know what your power is. Anyone happy with this daft state of affairs is just playing with a new toy.

TBH, who cares what absolute power numbers you're chucking out at lower power or higher power - it's the consistency of those figures that matters - something that Stages can provide without constantly having to recalibrate.
If an individual is really serious about power meter training then they should spend time looking at how their body performs - left/right balance included - not something you can do with many powermeters. They (or more likely their coach) can bear this in mind when reviewing power data.

As an amateur, L/R balance will have no real bearing on me, nor does absolute power numbers - sure I could wander down to the club saying how I produced X00w for X minutes - but what does that mean? Absolutely nothing. However, if after say 6 months of training I could go down to the club and say I've improved my X minute power by 20% then that has more meaning.

In the end, it's just another statistic to be played with. All statistics need understanding of their origin and limitations before you can meaningfully interpret them.
For many, Stages provide a reasonable level of statistical data for them to use. For many others it doesn't. I don't believe for one minute that all Team Sky use are Stages PMs - they have the history in SRM and I'm certain they'll use other methods to monitor their athletes, but they seem to be happy that Stages provides them all the information they need during the race - time will tell.

Stalin

meanredspider wrote:

Stalin wrote:

The point you miss is imbalance is not static. It changes. So at one time your Stages will be over reporting power and others under reporting. You might think you have seen an improvement in total power when all that has happened is in that particular session your imbalance has shifted. You can never be sure the numbers you see are correct because all you ever see is double the left leg power. I'm not arguing you need to know about any imbalance, or that you can do anything with that data, but I am arguing you need to know total power.

I'm not missing that point. Nor would I take a single data point as a trend. I'd look for improvement over time as a trend and I think that the variability you correctly talk of will be evened out. I suspect how well I slept the night before or how many miles I've already done in the preceding days will affect the results hence it would be dangerous to take a single data point or two as proof of anything. In an ideal world, of course it would be Nice to have a total power number AND all the convenience (and price) of the Stages system. I weighed up the pros and cons (taking all these arguments into account) and figured that, for me and my circumstances, Stages won out. I had considered (I think I even ordered then cancelled) the Garmin Vector system for instance. But it wouldn't have fitted my FSA cranks, I'd have needed a torque wrench everywhere and I'd have needed to either swap cleats or pedals as my other bikes were all fitted with SPD-SL. I don't need a pin-point accurate power figure that much. It's the 80:20 rule.

How do you know that any trend you are seeing is a total power trend and not just a trend in the power output of the left leg alone, or that there is a trend towards the left leg increasing its share of power output.

meanredspider

Stalin wrote:

How do you know that any trend you are seeing is a total power trend and not just a trend in the power output of the left leg alone, or that there is a trend towards the left leg increasing its share of power output.

Because we've had enough leg strength threads to suggest that my left leg isn't going to improve power on its own.

RChung

Stalin wrote:

Anyone happy with this daft state of affairs is just playing with a new toy.

Well, nothing wrong with playing with a new toy.

Here's a plot of some data collected by a guy with a Stages and a Computrainer over the course of three training sessions where he had done intervals at different power levels. The x-axis shows the average of the reported averages from the CT and the Stages, the y-axis shows the difference between the CT and the Stages as a percentage of the average. Each interval is labeled by the session.



What this plot shows is that for session #1, the Stages read very slightly above the CT, with the exception of one point where the rider took a call on his cell phone, sat up, and soft-pedaled. During that period, the CT showed that he was soft-pedaling but the Stages thought he was still putting out reasonably high power; evidently, when he sat up to take his call his L/R balance changed quite a bit. More troubling is that in sessions 2 and 3, the Stages was reading lower than the CT (except for one interval). What this shows is that from session to session the Stages and CT were not consistent with one another. Session 3 was a low-power session to see whether his "soft-pedaling bias" was consistent. From this particular comparison, it didn't seem to be; that is, even his inconsistencies are inconsistent.

All that said, this rider seems to like his Stages because it gives him a chance to bring power measurement outdoors, and he'll just have to remember not to soft-pedal on outdoor rides. Maybe for other riders, they'd have to remember something different. I think as long as he understands the limitations of his power meter and he's happy with its idiosyncrasies there's no problem. People who believe that there is no difference, or that there are differences but those differences are unimportant? That could be a problem, depending on what they expect to be able to do with the data.

meanredspider

So - to be clear - "mean power" is what in this instance? The average of the mean power for the 5 minute interval for both systems - your chart isn't clear. And how do you know you're measuring the same 5 minutes? For the major "outlier" it would be useful to see the run-chart of the power data for both systems. Presented as it is doesn't really help us understand.

And what assumptions are you making about the Computrainer? I know from my Tacx, for instance, that I need to calibrate after a period not least of all because the tyre has warmed up (as well as the room). The load over time going through the tyre (let's call that "power") will affect the power measurement. How is that taken into account in this test?

My point is this: you have two systems that have very different transfer functions (one measuring direct left leg load (strain on the crank arm) and angular velocity and another measuring generated electrical power (presumably) through a trainer tyre to metal drum interface). Noise factor analysis would tell you that the sources of noise for these two systems is very different. I have no doubt, for instance, that transmission losses through a mechanical transmission vary with power. Equally, tyre hysteresis under differing loads will vary. I don't know how Computrainer calibrates but clearly that varies over load conditions. Am I surprised there are differences? Not a bit. In fact Run 1 looks spookily close - probably more luck than anything.

But, at least with the Stages (or any PM that's part of the bike) you can take it (by definition) with the bike. What you're seeing indoors should be the same as you're seeing outdoors. Which is why the OP is confused...

frisbee

The Stages measures power before the drive train and the tyre/roller interface, there is likely to be constant component to the losses, this will show up more when soft pedalling.

To be fair they are generally within a couple of % of each other, which is bloody good when you compare it to other far more expensive power measurement, for example car dynos.

RChung

frisbee wrote:

To be fair they are generally within a couple of % of each other, which is bloody good when you compare it to other far more expensive power measurement, for example car dynos.

Yes, but I generally try not to pay too much attention to expense when I do these analyses. That is, I know how much I'm willing to pay but I try not to presume that everyone is like me. So I generally just try to identify the strengths and weaknesses regardless of cost and let others figure out by themselves whether they find those differences worth it.

But since you bring cost-effectiveness up, training is one of the least demanding things you can do with a power meter. People have been able to train effectively without power meters for a long time, using nothing more than a wristwatch. That's because the power equation is so well understood that if you have a good wristwatch and a reasonably quiet road the correlation between power and either speed or time is extremely high. I just looked at the last 10 times I climbed a little nearby hill. Here is a plot of speed vs. power:



As you can see, the relationship is *very* consistent: there's only one odd point, and that's the "very windy day." If you exclude that point, the linear correlation between speed and power is .98 (and a linear fit isn't even the best thing to do because of the nonlinearity of the power-speed relationship).

So, if you're only interested in training, and you're not interested in accuracy but only in consistency, a wristwatch "is bloody good when you compare it to other far more expensive power measurement".

meanredspider

That kinda shows the nonsense of statistics without understanding of the underlying data. Power is proportional to the square of speed (the well understood relationship) but your chart would suggest that speed is directly proportional to power. One of the real insights that the Stages has given me is the effect of windspeed. On the flat exposed areas of North Holland I can be putting out 300W in one direction and doing only 12mph and only 200W in the other direction and doing 25mph. A stopwatch is pretty useless in those circumstances. Even air temperature makes a noticeable difference to power requirements even in completely still air.

mamba80

i think RC is saying you don't "need" a PM of any type, your example could easily be shown with a HR.

Plenty of riders get v fit and strong without one, as you said earlier, its the trend you should be looking at, not one session
btw I had a PM and it drove me crazy, I hated it, turned every ride (and post ride) into a physics session, BUT my turbo, a Vortex is great, just gives me targets to aim at.

To the OP interference is almost certainly your issue, if it is perfectly ok away from your headphones etc.

meanredspider

mamba80 wrote:

i think RC is saying you don't "need" a PM of any type, your example could easily be shown with a HR.

Well, not really. Whilst the trend in my power has been going up, the trend in my HR has been going down.