Garmin Vector Usage

[Enda Marron]

Thanks for all the replies
I used the pedals in anger on Friday. I decided to carry out an FTP test on myself; I used the protocol as advised in Hunter Allen & Andrew Coggan's EXCELLENT book Training and Racing with a Power Meter. This is a structured warm-up followed by a max 5 minute piece and then the crucial 20 minute maximum steady piece and a wind-down.
I had the Garmin Edge 500 reading the data from the Vectors and my old Cat-Eye computer set on speed and cadence for everything.
The upshot was that the Vectors/Edge did not drop out (go to "0:00W") BUT they did fluctuate throughout the session (320 -280W). Meanwhile I and the Cat-Eye held a steady speed and cadence throughout the session.
At this point I have two questions:
1. Are such fluctuations normal (even when speed and cadence are steady) ....or is it the dished/uneven cranks .... or is it me?
2. Any thoughts on how to solve the problem [new cranks? smoothing existing cranks?]

[SLCBrandon]

Are you asking if displayed wattages would vary like that in this kind of test? The answer is yes, on any power meter/head unit combo.

You can change the "smoothing" (sampling shown on the screen. i.e. 1/3/5 secs typically.....although your head unit will still record all data for later download) displayed so the fluctuations are less pronounced. Still, you will get minor fluctuations like you stated based on terrain or even on a trainer, because, well, you aren't a robot.

[ironman1]

Has anyone tried the vectors with THM clavicula's. If I remember correctly the cranks can't be more than 15mm thick to work.

Does anyone know the thickness of the clavicula's or if they work ?

[sebo2000]

Thanks for all the replies
I used the pedals in anger on Friday. I decided to carry out an FTP test on myself; I used the protocol as advised in Hunter Allen & Andrew Coggan's EXCELLENT book Training and Racing with a Power Meter. This is a structured warm-up followed by a max 5 minute piece and then the crucial 20 minute maximum steady piece and a wind-down.
I had the Garmin Edge 500 reading the data from the Vectors and my old Cat-Eye computer set on speed and cadence for everything.
The upshot was that the Vectors/Edge did not drop out (go to "0:00W") BUT they did fluctuate throughout the session (320 -280W). Meanwhile I and the Cat-Eye held a steady speed and cadence throughout the session.
At this point I have two questions:
1. Are such fluctuations normal (even when speed and cadence are steady) ....or is it the dished/uneven cranks .... or is it me?
2. Any thoughts on how to solve the problem [new cranks? smoothing existing cranks?]

I'm sure it is You, why? becasue I have the same. Try testing at half of your FTP and you will see you will be able to keep power within 10W, but it takes time before you learn such a steady pedaling.
Post link to garmin connenct from that ride.

[djconnel]

I think I made a mistake in not installing those washers:





It's remarkably consistent in its wrongness, though. L-R balance is probably fairly good. I see this every single ride I check: right-leg dominant at lower power, 50-50 at higher power. Note the power axis is approximately 84% actual:

[ergott]

I hear there is a version of the pedals that will be designed for thicker crank arms. Should be out soon enough.

[djconnel]

I think I solved my problem. I went into Vector Updater and it said my cranks were 144.5 mm, rather than 170 mm. I have no idea how that happened.... That's 85% the correct crank length.

Curiously, after I added a spacer and did a ride I got 91% ratio Vector:Powertap. So divide that by 85% and I get 1.07, which would be 7% power lost to drivetrain. That seems like a lot, but certainly it's in ball-park. I'll do another ride with the revised crank length.

[Causidicus]

.

[djconnel]

This is after adding a spacer but before fixing the crank length:



The power ratio increased from 0.84 to 0.91. After adjusting for this, the curves are impressively similar. Note you'd expect the ratio to drop slightly at higher power, since drivetrains are fractionally more efficient at higher power (there's fixed losses from pulleys spinning, etc). Here's the LR-balance, which is remarkably reproducible:



I tried a ride after fixing the crank length but I had a problem with my Edge 800 and didn't get a record of the Vector power.

[djconnel]

Problem solved! I found the "crank length" line under the bike properties. In my Edge 500 this was set to "auto", which makes sense, but under the Edge 800 it was set to 144.5 mm, which seems (ahem) not the most common crank length around. I don't know how that happened.

Anyway, I set it to 170 mm so should be seeing great agreement next ride with the two meters.