powertap pro hub

mjlough

Just bought a powertap pro hub and had it built up into a nice wheel by Paul Hewitt.

However, the data from the hub is poor. At present it is on my turbo trainer paired to a Garmin 500. But when I train, the data readout for power fluctuates wildly. For example, doing 3 min intervals at a steady 95rpm, speed 26.5mph, I was getting power readings of between 290 and 340 watts, the data almost seemed random, e.g. 330, 290,340,305.290,320,315,295,335,305 etc etc and I had no real idea of what power I was riding at. Seeing as I bought the hub to train at a specific output this is very dissapointing.

Other PT users - what is your data like when using these hubs - doesit vary wildly like this is or do you get a fairly steady consistent reading? Anybody who has had this problem, did you solve it and if so ,how??

Look forward to the replies

Mick L

amaferanga

That's the reality of training with power and in particular with hub-based power meters. Displaying 30s power average on your Edge will help. Trying to stick religiously to a number is not really the best way to do it - have your target for the interval and try to stay in the correct zone (say +/-10% of target) most of the time.

mentalalex

have it set to show avg of 3's is what i would do! try that and see how you get on.

i have a power tap as well! your not just going to sit at 300 watts it will fluctuate

mjlough

mentalalex wrote:

have it set to show avg of 3's is what i would do! try that and see how you get on.

i have a power tap as well! your not just going to sit at 300 watts it will fluctuate

I didnt expect it to be absolutely stable but didnt expect so much variation. What do you mean 'set to show avg of 3's'?

maryka

In your Garmin 500's settings under "Data fields" you can choose from a number of different ones for power -- avg. power, lap power, 1 sec power, 30 sec power, etc. 3 sec power is often most useful for on-the-fly power (I use lap avg as well for TTs) because it's not quite so variable as 1 sec power on the display.

Yes it fluctuates a bit, takes some getting used to but as long as you keep the values in the zone you want it's fine. Don't go chasing a specific exact number as it will just work against you -- e.g., if you see 290 and then pedal harder to get it to 300 it will then jump to 320, then you ease off to get it to 300 again, it falls below 300 and repeat endlessly. Rather, try to pedal smoothly in those intervals, keep your legs turning over nicely rather than on/off to try and get some specific watts number. If you use lap average you'll be able to keep an eye on the interval average as well as the "instant" (3 sec average) and that will help push you if you start to drop.

mjlough

maryka wrote:

In your Garmin 500's settings under "Data fields" you can choose from a number of different ones for power -- avg. power, lap power, 1 sec power, 30 sec power, etc. 3 sec power is often most useful for on-the-fly power (I use lap avg as well for TTs) because it's not quite so variable as 1 sec power on the display.

Yes it fluctuates a bit, takes some getting used to but as long as you keep the values in the zone you want it's fine. Don't go chasing a specific exact number as it will just work against you -- e.g., if you see 290 and then pedal harder to get it to 300 it will then jump to 320, then you ease off to get it to 300 again, it falls below 300 and repeat endlessly. Rather, try to pedal smoothly in those intervals, keep your legs turning over nicely rather than on/off to try and get some specific watts number. If you use lap average you'll be able to keep an eye on the interval average as well as the "instant" (3 sec average) and that will help push you if you start to drop.

thanks - very useful info maryka

bigpikle

as Maryka has said I find setting the Garmin to show 3 sec power and the Lap Av Power are the best ways of watching the numbers when indoors. There is a 10 sec option as well which I know many like to use. Just press the lap button at the start and end of every interval and you can then capture all the useful info you need when you review the data later.

I'd also suggest you buy and read (over and over...) the Training & Racing With a Power Meter by Coggan & Allen as this is the bible of power meter training and covers all this stuff and loads more incredibly useful points. Then get Golden Cheetah for your analysis.

napoleond

Mate, this is a cycling forum, I've fixed your post for you with added BR factortm.

mjlough wrote:

Just bought a powertap pro hub and had it built up into a nice wheel by Paul Hewitt.

However, the data from the hub is poor. At present it is on my turbo trainer paired to a Garmin 500. But when I train, the data readout for power fluctuates wildly. For example, doing 30 min intervals at a steady 125rpm, speed 32.5mph, I was getting power readings of between 390 and 440 watts, the data almost seemed random, e.g. 430, 390,440,405.390,420,415,395,435,405 etc etc and I had no real idea of what power I was riding at. Seeing as I bought the hub to train at a specific output this is very dissapointing.

Other PT users - what is your data like when using these hubs - doesit vary wildly like this is or do you get a fairly steady consistent reading? Anybody who has had this problem, did you solve it and if so ,how??

Look forward to the replies

Mick L

djhermer

NapoleonD wrote:

Mate, this is a cycling forum, I've fixed your post for you with added BR factortm.

mjlough wrote:

Just bought a powertap pro hub and had it built up into a nice wheel by Paul Hewitt.

However, the data from the hub is poor. At present it is on my turbo trainer paired to a Garmin 500. But when I train, the data readout for power fluctuates wildly. For example, doing 30 min intervals at a steady 125rpm, speed 32.5mph, I was getting power readings of between 390 and 440 watts, the data almost seemed random, e.g. 430, 390,440,405.390,420,415,395,435,405 etc etc and I had no real idea of what power I was riding at. Seeing as I bought the hub to train at a specific output this is very dissapointing.

Other PT users - what is your data like when using these hubs - doesit vary wildly like this is or do you get a fairly steady consistent reading? Anybody who has had this problem, did you solve it and if so ,how??

Look forward to the replies

Mick L

Brilliant! OP - I was similarly perturbed several months ago when I started training with a hub based power device. As others have said, I took fix my readout to give a 3s average. It still jumps a bit - but nowhere near as much as a realtime or 1s readout. That's not realistic given the equipment and the real fluctuations in output between strokes - admittedly this is more apparent on the road than the turbo.

ric/rstsport

Set the display to whatever time frame you want (i think i used to have mine set to a 3 sec average), but you should have your computer *record* the data at 1sec interval. Worse case scenario set it to 2 secs. If you set it to longer than 2sec recording it messes up the normalized power algorithm (or the equivalent in GC).

Lastly, don't chase numbers.

ric/rstsport

The display on the PT is 'jumpy' because of the way it calculates power over a fixed time resolution, rather than with say an SRM where it's calculated over each pedal revolution. This has a *slight* effect on differences in power output and their readings, which means that you shouldn't bother looking at data that is less than 5-secs long on a power tap (e.g., don't look at your 1-sec max power - it'll be wrong).

Once you move to a longer time frame (> a couple of seconds) the PT is fine . (i ride with both an SRM and PT on my bike and they're within a couple of watts of each other).