Swim Bike Run
Slowtwitch.com
  • Login >
Slowtwitch.com
Search menu
Hot Forum Topics

Poll

Best Recent Tech for Tri
What is the most beneficial recent bike tech used in tri bikes
View Results


Home > Forum > Triathlon Forum > Ways to alter a zero tare on a meter? for non-controversial reasons

Triathlon Forum

Back To ForumPrint Thread

Login required to started new threads

Login required to post replies

Tri
Classifieds
Lavender
Jobs
Notices
Ways to alter a zero tare on a meter? for non-controversial reasons
Quote | Reply
burnthesheep
May 18, 20 7:20
Post #1 of 11 (1141 views)
Just play along. I use my Kickr indoors, not my crank based meter. I usually don't even have a meter on whatever bike is setup for indoor Kickr duty. For outdoors until I can buy a replacement, I need something I can do to try to get it a bit closer to reality. Most riding right now is outdoors.


I'm sick of having my crank meter read wildly different from my Kickr. By the indication of my on-road meter, I'd have a world class wind tunnel tested super crazy CdA and CRR. I know the reality. It takes me a good bit more watts than indicated to do what I do.

I've tested it against other meter (longer arm gravel bike meter) and my Kickr, and it is woefully different.

I've always just said "I know that it reads xx watts different, so calibrate your mind". Now, it's getting annoying because I realized since I do mostly outdoor riding now.........it's messing up my training metrics a good bit. Especially on threshold workouts where you're at 30w or more less and your TSS winds up being a lot less tossing your metrics.

I will just bite it and buy another or different meter, but in the current time for budget reasons I need some way I can trick the zero tare to be closer.

I'm thinking a known mass of some amount hanging on the pedal or something. I know it looks for a downward position to tare, so that's out.

If I could get it down to "hang x small mass" each time, I'd be OK with that for a couple months to get the money to buy another.

Thoughts on what to do? Not interested in a bunch of hater-ade being poured out here. Just want to get by using what I've got for a bit longer.
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [burnthesheep] [ In reply to ]
Quote | Reply
jaretj
May 18, 20 7:38
Post #2 of 11 (1128 views)
Not that I've ever done anything like this to get a torque cell to pass a TS16949 or TS17025 audit but...

If you have a crank based power meter you can normally get a few inlb out of the backlash of the torque cell, meaning if you unclip from the PM and then push gently on the crank and let go, you will bias the strain gage signal high, then zero and leave the span the same (which you have to do on many crank PMs). This will artificially zero the PM high and may get you a few watts. If you stop pedaling during a ride and the PM re-zeros itself, that bias is gone.

If you want to create more bias you can pin the rear wheel and place a small weight on a pedal and zero the PM. Again if you stop pedaling during a ride the PM will re-zero itself.

I don't use my PT any more so I don't remember if that works for them too.
I don't know how to do it with Garmin Pedals, mine are relatively new to me.
Last edited by: jaretj: May 18, 20 7:38
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [jaretj] [ In reply to ]
Quote | Reply
burnthesheep
May 18, 20 7:46
Post #3 of 11 (1111 views)
jaretj wrote:
. Again if you stop pedaling during a ride the PM will re-zero itself.

Wait, so what's the initial zero tare for if it redoes it during a ride with no pedaling? I think I don't quite understand.

I'll maybe try what you suggest and do a test to see what happens when I stop and restart.
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [burnthesheep] [ In reply to ]
Quote | Reply
gregtay
May 18, 20 8:01
Post #4 of 11 (1085 views)
burnthesheep wrote:
Just play along. I use my Kickr indoors, not my crank based meter. I usually don't even have a meter on whatever bike is setup for indoor Kickr duty. For outdoors until I can buy a replacement, I need something I can do to try to get it a bit closer to reality. Most riding right now is outdoors.


I'm sick of having my crank meter read wildly different from my Kickr. By the indication of my on-road meter, I'd have a world class wind tunnel tested super crazy CdA and CRR. I know the reality. It takes me a good bit more watts than indicated to do what I do.

I've tested it against other meter (longer arm gravel bike meter) and my Kickr, and it is woefully different.

I've always just said "I know that it reads xx watts different, so calibrate your mind". Now, it's getting annoying because I realized since I do mostly outdoor riding now.........it's messing up my training metrics a good bit. Especially on threshold workouts where you're at 30w or more less and your TSS winds up being a lot less tossing your metrics.

I will just bite it and buy another or different meter, but in the current time for budget reasons I need some way I can trick the zero tare to be closer.

I'm thinking a known mass of some amount hanging on the pedal or something. I know it looks for a downward position to tare, so that's out.

If I could get it down to "hang x small mass" each time, I'd be OK with that for a couple months to get the money to buy another.

Thoughts on what to do? Not interested in a bunch of hater-ade being poured out here. Just want to get by using what I've got for a bit longer.

Which crank based meter are you using? ie: in the case of Quark you can send it to the factory and they can run a full calibration on it plus test it in their temp chamber. I'd start with trying to get your meter tested and calibrated if it is reading significantly low (which you seem to indicate by saying "It takes me a good bit more watts than indicated to do what I do." What is the delta? 30 watts? 50 watts?
______________________________________________
Team Zoot
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [gregtay] [ In reply to ]
Quote | Reply
burnthesheep
May 18, 20 8:21
Post #5 of 11 (1061 views)
gregtay wrote:
What is the delta? 30 watts? 50 watts?

30w not accounting for drivetrain loss that should be seen on the Kickr but not seen on the crank meter.

It's a Gen2 Stages. I may try a firmware update also. I heard there was a power in the transmitter update that for some weird reason helped with some issues. Not sure I've updated it in a while.
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [burnthesheep] [ In reply to ]
Quote | Reply
jaretj
May 18, 20 8:25
Post #6 of 11 (1052 views)
If it's 30 watts off then there's something wrong with the PM or the Kickr or both
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [burnthesheep] [ In reply to ]
Quote | Reply
jaretj
May 18, 20 8:29
Post #7 of 11 (1044 views)
burnthesheep wrote:
jaretj wrote:
. Again if you stop pedaling during a ride the PM will re-zero itself.

Wait, so what's the initial zero tare for if it redoes it during a ride with no pedaling? I think I don't quite understand.

I'll maybe try what you suggest and do a test to see what happens when I stop and restart.

Initial zero, because some people are really anal about their measurement in the first minute of their ride.

I didn't know you were on a stages. I have zero experience with that hardware.
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [jaretj] [ In reply to ]
Quote | Reply
burnthesheep
May 18, 20 8:38
Post #8 of 11 (1030 views)
jaretj wrote:
If it's 30 watts off then there's something wrong with the PM or the Kickr or both

The Kickr and my other cyclocross bike's crank meter are much closer (within the window of drivetrain loss).

This meter is the problem for sure. Might be something wrong with it. The delta is constant though.

It is a weird length though. It is a 167.5. It shows the correct length in the Stages zero app thing when it sees it. But have always wondered if perhaps it's not using the right length somehow.
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [burnthesheep] [ In reply to ]
Quote | Reply
Signal8
May 18, 20 9:26
Post #9 of 11 (986 views)
I have no experience with Stages, so I don't know if they allow you to set the crank length in your head unit. If you CAN set the crank arm length, you could set that value way longer than the actual 167.5 mm length. That should artificially inflate your power numbers captured on the head unit. You might have to play around with different artificial lengths until the power numbers displayed are where you want them to be. Maybe I have all of this backwards and you'd have to set the length shorter to get the desired effect. Again, I have no idea if a Stages meter even allows the length to be adjusted, and I personally wouldn't trust the results...but it may work well enough for your purposes.
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [burnthesheep] [ In reply to ]
Quote | Reply
beston
May 18, 20 11:23
Post #10 of 11 (926 views)
Single or dual sided Stages?
Quote Reply
Re: Ways to alter a zero tare on a meter? for non-controversial reasons [beston] [ In reply to ]
Quote | Reply
burnthesheep
May 18, 20 12:48
Post #11 of 11 (889 views)
beston wrote:
Single or dual sided Stages?

Single.

Worth mentioning, I also did a test of this single side Stages against my single side Stages that's on my cross bike. I used a fluid trainer at a steady speed. This issue also showed up there. This problem child device was also 20 to 30w lower than that single sided Stages meter.

So, I'm batting 2 for 2 on verifying it against other equipment. And batting 3:3 if I plug data from this meter into my Chung excel aero spreadsheet and it tries to tell me my CdA comes out to 0.200 or some bullshit with a road helmet and kit.

I did get it used, so who knows. I'm not mad at Stages, just trying to get by. They've got good deals going right now, but if this is the kind of performance I can expect.........not a good enough deal!

How are the Pioneers? Lol.

I need to try a firmware update, seriously though. There's something floating around in DC Rainmaker land talking about a transmisison power parameter that cured things like this for some Stages meters. Maybe this one could do it.

I found that just after posting this, so will try that and report back.
Quote Reply
Back To ForumPrint Thread

Our Partners

transition-DOT-area-AT-slowtwitch-DOT-com

Advertise with us

©1999-2024 Slowtwitch, Inc., and Slowtwitch.com
Reproduction of material from any Slowtwitch.com page
without written permission is strictly prohibited.