miyata man

I would define flaky as inconsistent or greatly wavering in performance over a significant amount of time and rides. It behooves the manufacturers to forward an easily accessible "zeroing" measurement that only represents a potential sign of declining reliability. Without putting a means for diagnosis into the hands of consumers or competitors. I'm not interested in the complex equations unique to each firmware/device at this juncture.

A fair number of you have had long term exposure to multiple iterations and makes of PM's. Are they getting more consistent, more accurate, more durable? Do you believe the numbers reported in your head unit are unaltered or significantly defect free?

revchuck 

Power meters on bikes (as opposed to those on trainers) have generally been consistent over time. The two oldest players in this market, SRM and Powertap, have excellent reputations for reliability of operation and data. Some of the newer ones such as Power2Max and Pioneer seem to be solid as well, as do the recent Powertap additions of chainrings and pedals. Stages had some teething pains but seem to be much better now. Quarq has a bad rep on this forum in terms of reliability, but that's a relatively small sample.

Can you find individual examples of well-regarded PMs that are flaky? Sure, but they're exceptions.

TMonk

The Ptap G3 is great. I've had 0 problems with mine for 4 years now. I have once sent it in for routine service (bearing replacement) and didn't experience any issues.

Doge

I'm not so into them, but have 8 or so years of Power Tap - which I find reliable and I guess is accurate, hard to tell. That is what I bought. I will get the DA crank one when it is out as I see Dura-Ace as a high value brand and have a history with it.
Before that I used the Polar hall efect chain device which of course I didn't trust but nobody had anything to compare to. On trainers the old Cateye Cyclesimulator was used from about 1993 to 2015. I trusted that.

Posting power more often than not leads to arguments.

rubiksoval

Based on my non-scientifically conducted observations:

I had a powertap in 2005. The numbers I got from that (based on records of about 30 mmps and workouts) and the numbers I got from a PT G3 in 2014 were close enough that nothing popped out as being extraordinary. Major differences between the two were that I had to send my original powertap back two times over the course of a year because the bearings kept going out. I also bought an SRM PCV in 2013 and the numbers from that were within a few watts of the G3 I got the next year.

I later bought another G3 and then a p2max and finally settled on a PT C1 for my daily powermeter. All so close as to not noticing any difference between switching (even now, still have the SRM, and one G3). I'm not running multiple computers and powermeters all at the same time to truly distinguish the minutiae, but after a good number of years or so, I think I have a decent enough feel for efforts in relation to numbers and with strava and wko4 any big changes would show up pretty quickly.

miyata man

Thanks to everyone who replied. Accuracy, consistency, and stability. I expected a little more fluctuation of those oft stated basis of evaluation in your responses. This gives me more confidence the measuring device itself is less rarely the issue interfering with training.

I understood that and just asked for clarification the latter part held true over time and numerous owners. My intent wasn't to derail the other part of the conversation so fully establishing that. It would appear what the offset scale references in a technical sense is more a mystery than that it roughly actuates a zeroing function.

TheKillerPenguin

fwiw, both my g3 powertaps seem to be just fine, and they're both about 2.5-3yrs old. They make reliable gear.

globecanvas

To sum up: powermeters generally work.

JuiceWillis

Has anyone done an ftp test on a track bike/fixed gear? Today I crushed my old FTP (341w) and got 377w. Test was done with a 48x14 ratio on the same course I do all my testing...maybe it was because I had no option to coast?

TheKillerPenguin

Your speed noticeably quicker, power meter calibrated properly, etc?

JuiceWillis

Speed about 1mph faster, meter properly calibrated pre ride, and then again after warmup before test

johnybutts

Just cleaned all the salt out of my bottom bracket. Crank is spinning much smoother. Hoping for some free watts.

TheKillerPenguin

huh. Nayyyce

beeef

I've been using a power meter for about 6 months and have a hill climb coming up on Saturday. This will be my first race with a power meter. I've done some 2x20 workouts on flat roads in the past few weeks, with a 5 minute rest between the intervals, averaging 315W during the intervals. The intervals were difficult but I didn't feel completely destroyed afterwards. The hill climb is 5.5 miles, should take somewhere between 22-26 minutes for me.

I'm planning to pace myself using the power meter, at least for the first half of the hill climb. What would be a reasonable wattage target to shoot for? I feel like it's easier to hit higher power numbers while climbing, but I haven't done a climb this long recently.

globecanvas

If I were you, I'd try to hold 320 ish watts for the first half of the climb, then aim for 330ish on the second half. If you feel like there's even more in the tank for the final 5-10 minutes, go harder.

Assuming this is High Point, if you're not familiar with the climb, it would be well worth your while to pre-ride it. There are several flat to slightly downhill portions, especially after you enter the park, and the last quarter mile or so is very steep. Targeting 5-10% higher power for the steep parts and 5-10% lower for the flat parts will improve your time.

topflightpro

Which PM are you using? And how do you like it for track work?

beeef

Thanks! That helps. The grade fluctuates a ton so I'll try to adjust my power accordingly during the race.

JuiceWillis

I have the power pod meter on my track bike. I have tested it with my stages on my road bike and the readings are within 3-5 watts of each other. I was skeptical about the power pod at first but it's been great. Easy to set up and it's USB rechargeable

Hermes

I assume that Power Pod is the newer version of IBike. Here is DC Rainmaker's review. https://www.dcrainmaker.com/2016/03/...th-review.html

I use the Garmin Vector 2 at the track and it is okay but not great and not acceptable for fast transients such as standing starts and fast changes in cadence. Plus Garmin only samples every second such that max torque in a standing start is at zero speed. I assume PowerPod somehow captures that via an accelerometer.

Also, at 250 meter tracks on pulls 2Gs in the turns at 35 mph for constant speed but with a transient increase in power as frictional forces increase. It is not clear that PowerPod can capture that but maybe there is a way.

Not an SRM salesman per se or proponent but only SRM has a track power meter version with a head unit that captures power variations at 1/8 second intervals

Is capturing power for fast changes required? Not really assuming one has another person on the track with a stop watch. For standing starts, it is easy to capture times at various portions of the track. It ones 50 meter start time improves, one can assume the power is increasing. And of course, there are always other variables such as wind, tires and surface but tracks many times are pretty constant. The indoor track at Carson is very constant other than changes in Rho.

However, I like the FTP test fixed gear. I will give that a booyah. I would really be impressed with an FTP test on the indoor track at Carson riding the turns.

JuiceWillis

I did it on a short 1.2mi lap circuit, not being able to coast through the turns probably had something to do with it as well as having to really mash down on the pedals through the headwind

globecanvas

You buried the lede pretty deep here! The old FTP was measured with a direct force power meter and the new FTP was measured with an indirect power estimating device. So you really can't even compare them meaningfully IMO.

JuiceWillis

The last 2 FTP tests were both done using the power pod power meter.

mattm

Thinking of switching from hub-based power to crank-based.

Tricky part is I'm using Campy, and don't plan on switching. For me that seems to eliminate SRM (based on price), but leaves a few options:

- power2max
- stages

Thoughts on either? (not campy-specific thoughts, just general usage thoughts)

rubiksoval

I wouldn't waste your time with anything that only measures one leg.

I had a p2max. The pm part was great, but I got the FSA one BB386 one. I hate everything FSA. Couldn't put it in or take it out without a sledgehammer. Utterly insane. Knocked my bearings out every time. Bothered me so much I sold it a few months later for like a $400 loss.

mattm

That's a good point..