why are power meters soooo expensive?

craigw99

the title really says it all - down to limited knowlege as far as i can tell are they not just a couple of strain gagues a battery and a wireless transmitter if so then why so much?

schweiz

Accuracy (which has a direct impact on allowable production tolerances of components) and amortisation of development costs.

Think how many people own a bike
Then think how many of those people own a 'good' bike
Then think how many of those people train rather than just ride
Then think how many of those people train with a power meter
Then think how many different products are on the market

The reality is that there's not that many people with power meters and of those that have one, there's a realistic choice of half a dozen products.

I'd hate to think how much Garmin have invested in the Vector pedal and it's still not on the market due to it not being able to produce reliable and consistant power figures!

cooldad

As someone who likes to ride bicycles in the dirt, who cares?

craigw99

thanks good answer - i see them getting hyped everywhere and im like they are how much :shock:

bennett_346

Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

MountainMonster

bennett_346 wrote:

Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

The numbers do have their use, you can measure performance if you are training hard and develop power baselines for different terrain.

That said, I don't think 95% of people have any use for one.

njee20

bennett_346 wrote:

Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

Do you mean that in reference to power generally, or an inaccurate power meter?

If the former then you don't really understand power do you? :?

Stages Cycling are doing a $600 power meter, from January, but only for sale in the US, pain, as I fancy changing my PowerTap.

bennett_346

njee20 wrote:

bennett_346 wrote:

Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

Do you mean that in reference to power generally, or an inaccurate power meter?

If the former then you don't really understand power do you? :?

Stages Cycling are doing a $600 power meter, from January, but only for sale in the US, pain, as I fancy changing my PowerTap.

I meant an innacurate power meter would be as useful as a chocolate teapot, hence they're all expensive.

But i also don't think many people need a power meter.

njee20

Aah, I see! No one needs one. They're a useful training aid.

ilovedirt

I don't know much about the workings of these power meters (didn't really know they existed), but as an electronic engineering student, we're constantly being told that being an engineer is all about compromise. Do you really NEED a really expensive circuit, or can you get away with a cheap one that does the job? I'm guessing if these are a fairly new technology, then they'll have some fairly complex digital circuitry inside them, which isn't cheap to begin with. The more accurate you want something to be, generally the more work goes into designing it, and the more components go into it, all of this incurs cost, particularly the man-hours. I haven't looked at anything any where near as complex as these things, but as with all new technologies, it'll start off expensive and then get cheaper as certain components get cheaper to produce and these things become easier to design.

Stu Coops

For your average rider/racer who wants training zones a HR monitor will do the job perfectly and at a fraction of the cost.

The Northern Monkey

i STILL have no idea what a power meter is.

bennett_346

http://en.wikipedia.org/wiki/Cycling_power_meter

Was that difficult?

The Northern Monkey

Yep... mainly because I don't really care.

bennett_346

Why complain then?

The Northern Monkey

I wasn't complaining.. just pointing out I didn't know what it was, since the last thread about this mystical training thing baffled me.

If you can justify the cost for something, you can't really need it that badly imo.

njee20

They're not new - Lemond played with one in the late 80s. They're getting more affordable as new ones come out, and they're making inroads into MTB, and BMX. But they're not new.

cooldad

The Northern Monkey wrote:

i STILL have no idea what a power meter is.

They're obviously for racing snakes not fat bastards.

The Northern Monkey

cooldad wrote:

The Northern Monkey wrote:

i STILL have no idea what a power meter is.

They're obviously for racing snakes not fat bastards.

This may be the reason, however I did think they were more of a lycra brigade thing.

njee20

They're an expensive training aid. If you're not fussed by training and quantifying your fitness levels they're totally useless. If you are interested in that,they're great. As overweight weekend warriors it's unlikely, ergo they'll offer you nothing, and you should spend the money on beer, bacon and the latest tyres which will revolutionise your riding.

The Northern Monkey

Can't you just quantify your fitness by comparing lap times around the same route...or by actually competing against others.

free v $600. hmm.

njee20

No, because changing bikes, weather, tyres, suspension set up etc all affect that. Other people isn't a constant metric, what if they're getting fitter, or less fit?

A watt is a watt. Whether on an MTB in the alps, a BMX on the track or at a road race. Higher power:weight = fitter.

Like I say, it's a training aid, if you don't train then it's of no interest.

cooldad

njee20 wrote:

They're an expensive training aid. If you're not fussed by training and quantifying your fitness levels they're totally useless. If you are interested in that,they're great. As overweight weekend warriors it's unlikely, ergo they'll offer you nothing, and you should spend the money on beer, bacon and the latest tyres which will revolutionise your riding.

You got me there.

The Northern Monkey

njee20 wrote:

No, because changing bikes, weather, tyres, suspension set up etc all affect that. Other people isn't a constant metric, what if they're getting fitter, or less fit?

Surely though, 'power output' is also affected by this?

(i'm not not trying to seem argumentative, genuine questions now lol).

ilovedirt

The Northern Monkey wrote:

njee20 wrote:

No, because changing bikes, weather, tyres, suspension set up etc all affect that. Other people isn't a constant metric, what if they're getting fitter, or less fit?

Surely though, 'power output' is also affected by this?

(i'm not not trying to seem argumentative, genuine questions now lol).

Nope. You're confusing power and work. Two totally different things.

cooldad

Those with power do the least work. Simple.

njee20

Surely though, 'power output' is also affected by this?

Nope, as above its absolute. If you do a ride and average 200 watts, then repeat it at 220 watts you've got fitter (or gained loads of weight), even if one ride was on a TT bike with a 50mph tail wind and the other was on a 16" kids bike! Hence why it's the gold standard for training. Even HR doesn't mean all that much, a decrease in HR could be increased fitness, overtraining or illness.

The Northern Monkey

ok.. so I assume that things like Strava use calculations such as Power = (weight x height risen)/time
Do the powermeters measure force and convert that to power (using velocity) or?

Gold standard stuff is for top level though, not really the average forum user... so I'm not surprised it costs a lot!

scarbs85

A watt is a measurement of energy and time (joule / second).

Consider yourself as an engine. The watts you can produce is how much power you can put through any given bike. If your putting that power through any given bike in any given conditions, the time, distance etc will be different, but the watts will always be the same.

Think fitting the same engine into a hummer and a mini cooper. The engine still produces the same power, but will drive one vehicle faster than the other.

Edit// don't know what calculation Strava would use, but it would have to involve velocity as a flat trail still requires power.

njee20

Yes Strava has a wild guess based on weight and speed, and it's just that!

Power metres measure torque either through the hub or the crank, or the deflection of the crank against a known value in the case of the new Stages power meter, that means it only measures on the left though, and doubles the result for a total power output, so doesn't really work if you have an imbalance in legs. But as NM says, gold standard = pricey. Love mine though, even though I don't really use it to its full potential any more.

schweiz

Strava use an algorithm that, amongst other things, takes into account rider weight, bike weight, height gain, distance, speed, an 'average' road surface coefficient of friction and an 'average' wind resistance. I have a power tap (i'm a roadie who has wandered onto the MTB forum) and the strava calculations are close for average speed (without actually checking, i'd say within 5-7 %). If it was particularly windy then it is way off. Strava can also give stupidly high max power values. Most power meters claim to be accurate to +/- 3%.

Also, in response to previous comments strain gauges are nothing new but they can be a PITA to get reliable, repeatable data from. I worked on an aircraft that had them installed in various positions to help calculate the fatigue life if the airframe. In the end the stress and reliability Engineers gave up trying to get any meaningful data out of some of the gauges.