It's a trade off between precision and cost.

The cheapest solutions aren't too expensive. If living with maybe 10% error after calibration, the Polar chain tension solution has a quite acceptable price.

The solutions with sensors in hub, pedal axis or cranks most definitely have a higher price. Not because they are rocket science but because of the few potential customers.


But then it's basically enough to use a GPS. No need to buy a bike computer that presents a wild guess.

People who do pay for a power meter aren't interested in potential energy. They are interested in amount of work the body does. Especially as balanced to the work their heart does. Matching output power to heart rate gives a very good indication of training level. Or which rpm (cadence) that the specific person have the highest efficiency - best power output in relation to pulse.


Which is a reason why it is sold to "hobbyists" because it is cool. But does not bring anything to the table for people trying to optimize their training.


Most definitely. But a race bike would get into lots of other issues quite quickly at too low tyre pressure. The surface area is minimal - less than the size of a thumb print for each tyre. Only a very high air pressure will manage to keep the tyre away from the rim if you hit a stone or hole in the asphalt. So while people on city bikes may run around with really low tyre pressure for comfort, no sane person steps on a race bike without tyres almost hard as stone.

There have also been quite a lot of improvements in the material and goves of the bike tyres to reduce the roll losses while still maintain the require friction when cornering on wet surfaces. By the way - bike tyres can get a quite "interesting" look after a couple of too hard turns in combination with a bit of sand. If they slip just a bit, they get a flat part on left or right side that will then grow larger and more market as each rotation produces extra wear where the tyre is a bit flat.

But the thing is that friction losses from tyres etc are most important at low speeds. The square factor from the wind drag will quickly make it the #1 factor. Next thing is that after the bike have been bought, it's only the riding style (where on the road, where behind another rider and how to sit) that the rider can change to affect the friction losses. So it isn't too important to try to measure the actuall loss between tyre/ground or in the hubs. It's enough that the manufacturers cares about those issues.