BCTTT Forum

Hmmm... All this talk of power meters is ringing a bell....

All makes me quite pleased not to be running Vectors!


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CCS wrote:All makes me quite pleased not to be running Vectors!


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Cough. But isn't stages even worse?

Jack Hughes wrote:

CCS wrote:All makes me quite pleased not to be running Vectors!


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Cough. But isn't stages even worse?

Actually, after a few initial issues, I have been pretty happy with it - readings seem consistent, and dead easy to move between bikes (which from reading all this, Vectors don't seem to be). Not sure how the readings compare to other power meters - but that doesn't really matter, does it!
In fact, the only problem I have had recently proved to be user error, when some idiot might have put a new battery in the wrong way up, and wondered why she was getting no readings...

Not sure how the readings compare to other power meters - but that doesn't really matter, does it!

Perhaps, perhaps not. Certainly consistency is infinitely more important than comparing numbers between people, but the question is whether a single leg power meter can even be consistent within a single rider. My vector data shows that my L/R balance varies depending on what type of riding I'm doing: Normally TT efforts are very close to 50/50 (hence the red flag with my previous ride), recovery rides tend towards a left leg bias and short power climbs tend towards a right leg bias. If I had a single leg power meter my power would be over/underestimated even within a single ride. If you are always perfectly balanced (or you have a consistent bias) then it doesn't matter so much.

Finally got around to doing a static torque test on my Vectors. 4 of them, in fact. Concerningly, on the first attempt, one pedal was a whacking 10% out! It aligned much closer with the other pedal after doing a recalibration and testing again (which does match with sometimes getting iffy balance / data during warm up and before the 2nd calibration at 15-20 minutes in). The remaining 2 tests were very close to the 2nd test. It looks like the left pedal is 2-3% over reading, and the right pedal is around 4% over-reading. That assumes my local post office (digital) scales are properly calibrated... I'll probably take the weight to another post office soon to check it.

It's frustrating that I've not done this before as, at this time, I've got nothing to compare against. If for example the pedals were within 1% accuracy in October when I last properly tested (myself, not the pedals), then the drift would account for the bulk of supposed FTP improvement I've seen based on recent tests and races. I guess more races will show how any improvement in better times/relative positions, but a portion of that could/would come from changed position, skin suit, etc.

Training with power: bloody frustrating at times! I think the take home here is to test (and track results of) your PM regularly if you are concerned with accuracy & consistency.

Interesting... something to add to the to do list. How much of a faff is the test?

Ewan wrote:Interesting... something to add to the to do list. How much of a faff is the test?

The test itself is pretty simple - http://support.garmin.com/support/searc ... 0000000%7D. The problems are a) finding a weight that you can use that's big enough, b) precisely weighing said weight, and c) getting your bike off the ground. I solved a) by buying a 4kg kettlebell to zip tie to an existing pair of 4kg kettlebells and adding an S hook. b) I solved by weighing it at the village post office. c) was a wooden storage box for the rear wheel & turbo, and a cardboard box and Wii balance board (to get it roughly level) for the front. Once those are solved, it should be easy enough to repeat the test, so I plan to do it once a month or so.

IanM wrote: If for example the pedals were within 1% accuracy in October when I last properly tested (myself, not the pedals)

Conversely, they might have been 6% and 8% over then.

No point in getting too upset about it. Best thing to do is go and ride a local 10 which you have done before. And hopefully some "peers" turn up to compare against.

Logically, your training load has increased, you've been doing the right sort of training, so you should be producing more power. I'm still voting for "up". But the jury is out on what sort of "up" up is.

See the drift in a months time etc. etc.

(now, if you still had the power tap, you could have measured against that again).

A very cursory google doesn't turn up anything for "garmin vector measurement drift". Which possi bly points to them not drifting... (or nobody can be bothered to test).