Power meters · Public discussion

Torque Issues with PT SL

Started by Pureshot78 · · Last activity · 12 posts · 1,209 views

← Back to Power meters

This thread is locked and is currently read-only.

Thread navigation

Jump through the discussion

Go to the original post, the replies on this page, or the latest preserved contribution.

01 / Original postTorque Issues with PT SLPureshot78 · 29 Jan 2007 02 / This pagePosts 1–12Page 1 of 1 · chronological order 03 / Latest replyPost #12Alex Simmons · 1 Feb 2007

Thread details

What we know about this thread

Original section
Power meters
Published
29 January 2007
Last activity
1 February 2007
Original author
Pureshot78
Posts
12
Discussion status
Public discussion
Total views
1,209
Views / 30 days
0
Topics
Power metersSingle-speed and fixed-gear

The navigation and discussion metadata provide context. Posts remain in their original chronological order.

Showing posts 1–12 of 12
Posts remain in their original chronological order.

Text size
  1. Original post
    Pureshot78
    Archived post
    #1

    Last week I got a set of Zipps (rear laced with an SL) to go along with my Mavic Open Pro. Saturday I rode the Zipps and got rained on pretty good, PT data went out the last half of the ride, so i took out the free hub and put the wheel next to a fan to dry it out. Come this morning watts were being displayed so i thought i was good to go.

    Had a crit today and when i looked at my power numbers they were pretty rediculous, 600 watts when by RPE i was pretty sure it was more like 280-300.

    After I got home, I tried zero'ing the torque, but then nothing but 0 would display in the watts display when i spun the crank by hand.

    Took the computer to test mode, option 6 (torque information). Manual says 512 is the baseline value. 582 was displayed both in the lower and middle display for a variance of 0.

    Threw on the other computer that I have and spun the back wheel. watts in the 110 - 150 were displayed. Took that computer to test mode, option 6 and 582ish displayed, 512 baseline for variance of 70.

    Has anyone else encountered something like this?
    If you have two PT wheels, do you use two computers? or does do you zero the torque after swapping out?

    Thanks!

    Report
  2. Uhl
    Archived post
    #2

    You should zero the torque after swapping PowerTap wheels or changing the batteries.

    To be safe, I just zero the torque before every ride. It only takes a few seconds. All it took was one ride where my wife swapped PowerTap wheels on me and I had a similar situation. I though I was riding like Superman...until I realized I needed to zero. Bummer, I thought I was in for some personal bests that day!

    BTW, just because it reads "0" in torque mode, doesn't mean it is zero. On my older yellow CPU it doesn't show negative torque; so I still zero it by holding down the Select button, even when "0" is displayed.

    Report
  3. Alex Simmons
    Archived post
    #3
    Uhl said:

    You should zero the torque after swapping PowerTap wheels or changing the batteries.

    To be safe, I just zero the torque before every ride. It only takes a few seconds. All it took was one ride where my wife swapped PowerTap wheels on me and I had a similar situation. I though I was riding like Superman...until I realized I needed to zero. Bummer, I thought I was in for some personal bests that day!

    BTW, just because it reads "0" in torque mode, doesn't mean it is zero. On my older yellow CPU it doesn't show negative torque; so I still zero it by holding down the Select button, even when "0" is displayed.

    Ditto
    (that's twice today)

    Report
  4. Pureshot78
    Archived post
    #4
    Uhl said:

    BTW, just because it reads "0" in torque mode, doesn't mean it is zero. On my older yellow CPU it doesn't show negative torque; so I still zero it by holding down the Select button, even when "0" is displayed.


    Thanks for the response.. I followed the directions from the manual to zero the torque. Hold select to enter torque mode, hold select until 0 shows, tap Select to return to normal mode.

    Can anyone chime in with the torque number that your PT gives in test mode?
    I'm still confused about the difference between the two hubs. Zipp = 582 Mavic = 512

    Report
  5. Uhl
    Archived post
    #5
    Pureshot78 said:

    Can anyone chime in with the torque number that your PT gives in test mode? I'm still confused about the difference between the two hubs. Zipp = 582 Mavic = 512

    Each hub has it's own "set point". My wife's is in the 400's and mine is 583 (eerily similar to yours :eek: ). But when you zero the torque, you're essentially telling the CPU what each hub's set point is. Once you zero you should be fine.

    You can also do a calibration/stomp test to validate.

    http://midweekclub.ca/powerFAQ.htm#Q23

    Report
  6. Uhl
    Archived post
    #6

    Another situation to zero: Swapping CPU's! Just wanted to clarify since it's not obvious that it's the same thing as swapping wheels...at least to the CPU!

    Also, there's a torque auto-zero setting (in Setup 3) that will zero if a negative torque is measured. This typically only needs to be turned off if you have a track hub. But if you swap CPU's for testing purposes...it can also screw you up. Even if you test Bike #1's CPU on Bike #2 for a few seconds, it may auto-zero. Then when you put it back on Bike #1, it may not reset (depending which hub has the greater offset).

    Hope this isn't confusing you, but again, just zero the torque after doing any swapping (batteries, wheel, cpu...spouse? 😉 )

    Report
  7. Pureshot78
    Archived post
    #7
    Uhl said:

    Each hub has it's own "set point".

    Thanks, I think this clears it up for me. 🙂

    Now to be really annoying.. can anyone help me "clean up" the data i gathered today? I've attached the file here.. if I assume that the value sent at 0 by the hub was 582 but the computer thought the 0 value should have been 512, is there a way to recalculate the torque and / or watts??

    Report
  8. jbvcoaching
    Archived post
    #8
    Pureshot78 said:

    Thanks, I think this clears it up for me. 🙂

    Now to be really annoying.. can anyone help me "clean up" the data i gathered today? I've attached the file here.. if I assume that the value sent at 0 by the hub was 582 but the computer thought the 0 value should have been 512, is there a way to recalculate the torque and / or watts??


    midweekclub.capowerFAQ.htm

    Report
  9. Pureshot78
    Archived post
    #9
    Pureshot78 said:

    Thanks, I think this clears it up for me. 🙂

    Now to be really annoying.. can anyone help me "clean up" the data i gathered today? I've attached the file here.. if I assume that the value sent at 0 by the hub was 582 but the computer thought the 0 value should have been 512, is there a way to recalculate the torque and / or watts??


    Looks like I attached the .WKO file the first time.
    Here is the .CSV file.

    Report
  10. Uhl
    Archived post
    #10
    Pureshot78 said:

    Looks like I attached the .WKO file the first time.
    Here is the .CSV file.

    Yeah, the file is screwed up! :eek:

    The torque values for periods of coasting keep changing throughout the file. I still tried to manually adjust it for the different ranges and used the formula to re-do the Watts column, but it didn't help much.

    Oh well...I gave it a shot.

    Report
  11. Pureshot78
    Archived post
    #11
    Uhl said:

    Yeah, the file is screwed up! :eek:

    The torque values for periods of coasting keep changing throughout the file. I still tried to manually adjust it for the different ranges and used the formula to re-do the Watts column, but it didn't help much.

    Oh well...I gave it a shot.


    no worries! 😄

    I appreciate the effort..

    Report
  12. Alex Simmons
    Archived post
    #12
    Pureshot78 said:

    no worries! 😄

    I appreciate the effort..

    At least with freewheel data you have a chance of repairing. On a fixie there's no hope😉

    I've only had to repair one file, while there was a little drift in the torque zero point, it wasn't that large - sounds like your file was pretty cactus but I didn't look. Uhl would know!

    Report

Keep exploring

Browse the sectionPower meters Return to CyclingForumsStart at the home page Search discussionsFind another thread

Active in the last 60 minutes

Active in this thread

0 users · 0 guests ·0 bots ·0 total

No signed-in users are active right now.

No known search crawlers active right now.