Cycling Wattage Table

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Postby veganjosh » Wed Nov 12, 2008 4:37 pm

[quote="fredrikw"]Just out of curiosity for all of you number posting people: how and how often do you calibrate your power meters? I guess there's no such thing as a stable measuring technique that doesn't need recalibration after some time. Did your power meter come calibrated?


The SRM needs two types of calibration: setting the zero offset and setting the slope. The slope comes calibrated and supposedly doesn't need to be redone for some time. Since the batteries in the crank need to be replaced every 1-2 years, I figure I'll have them recalibrate at the factory when I get my batteries replaced. The zero offset, on the other hand, changes regularly, and I re-zero every ride, sometimes even multiple times in a ride.
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Postby fredrikw » Wed Nov 12, 2008 4:57 pm

Ok, I guess the zero offset takes care of the reliability (the same power means the same readings every the time) and the slope is the validity (the readings are the actual real value). It would be interesting to know how much they differ in average after 1-2 years of use when they're being recalibrated.

My trainer does power measurements, but I have no idea about how well it measures the actual power, what I do know/assume is that the reliability is quite correct since I calibrate is against some software program each time I use it...
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Postby ultra_whippet » Wed Nov 12, 2008 6:45 pm

Don't think I can recalibrate my ergometer, but when you buy it you get a printout of the calibration data for that actual unit, so you can see exactly what the margin of error is.
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Postby Mr. Cleetus » Wed Nov 12, 2008 8:14 pm

I know with the PT that the only way to recalibrate it is to send it back to the factory. It can get a bit out of whack tho and you can reset that quite easily everytime you ride if you wish (ie, "zero the torque"). you can generally tell when that is necessary cuz the watts will be way off (but not always).

The calibration can be funny on them tho as I am learning. It is pretty clear now that my new one is reading 5 to 10 watts lower than my old one. nothing I can do about it w/o sending it to the states.
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Postby JohnBarleycorn » Wed Nov 12, 2008 11:46 pm

My road powertap is maybe 5-10 watts harder than my trainer powertap. But as long as I zero the torque before each ride, each system is consistent with itself. Thats the important thing !
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Postby fredrikw » Thu Nov 13, 2008 8:22 am

[quote="JohnBarleycorn"]My road powertap is maybe 5-10 watts harder than my trainer powertap. But as long as I zero the torque before each ride, each system is consistent with itself. Thats the important thing !

yeah, unless we're starting to make a table comparing with eachother ;)

but yeah, it really doesn't matter too much, the main point with a table like this is rather to get encouragement to improve, and in doing so the consistency, or reliability as I called it, is the most important feature.
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Postby Dave Noisy » Mon Nov 17, 2008 12:08 am

In theory they should all be accurate within' the percentiles listed (i think PT is ~1.5%, SRM 2%?).

Age shouldn't matter.. With the PT, you can do a weighted test (ie, hang 10lbs off the crank arm) to see if it's out of whack..

But yeah, we typically recalibrate every ride or two. I'll also occasionally check after getting a PB to see if my meter is off..

PS: Table's been updated:

http://spreadsheets.google.com/ccc?key= ... eg99loC-Kg
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Postby Dave Noisy » Wed Dec 10, 2008 5:34 am

A surprising update for me this weekend, in our group ride sprint, i somehow managed to up my 1min PB from 518w to 530w...!

Surprising since i've really not been training a whole lot...

And i won the sprint by about a bike length, it was a *big* group too, with many of our regular heavy hitters. Felt good. =)
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Postby JohnBarleycorn » Wed Dec 10, 2008 7:10 pm

Animal ! :lol:
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And probably the former fastest British Vegan 10, 25 and 50 mile TT rider. Probably.
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Postby helmut » Thu Dec 11, 2008 12:11 am

:lol:

no... machine!!!!
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Postby JohnBarleycorn » Thu Dec 11, 2008 12:27 am

You are catching me up.......track boy ! :lol:
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And probably the former fastest British Vegan 10, 25 and 50 mile TT rider. Probably.
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Postby Dave Noisy » Tue Dec 16, 2008 7:24 pm

[quote="JohnBarleycorn"]You are catching me up.......track boy ! :lol:

haha - i better!

I aim to focus more on sprinting again for 2009, in the context of points races and Madisons...so will have to get that 1mins figure up a bit more. ;)
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Postby JohnBarleycorn » Tue Dec 16, 2008 8:45 pm

I'll never be a sprinter !

But if I don't loose some weight this winter, people will start to mistake me for one ! :lol:
I eat to nourish my compassion, not my greed

I'm the man they couldn't kill ! I cannot be destroyed with conventional weapons !

And probably the former fastest British Vegan 10, 25 and 50 mile TT rider. Probably.
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Postby Dave Noisy » Thu Dec 18, 2008 8:01 pm

Yes, that's always a concern. ;)
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Postby JohnBarleycorn » Fri Dec 19, 2008 12:33 am

I'm not fat !

I'm a sprinter !

Do you think thats what Chris Hoy says ? :lol:
I eat to nourish my compassion, not my greed

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