Results 1 to 4 of 4

Thread: PM questions

  1. #1
    RoadBikeReview Member
    Reputation:
    Join Date
    Jun 2005
    Posts
    551

    PM questions

    I've had a Stages PM since July, and I'm slowly learning how to use it to train.

    I want to point out that the first one I got had an error in the software. The temp curve was set to 11 (cue the Spinal Tap Jokes) instead of -.02, so it was reading way too high on warmer days.

    Yesterday, I was out for a ride, and it seemed like I was getting high readings. A soft pedal might make it jump to 250w. I have my Garmin 500 set to display 3sec average, and N.P., so I imagine that I could have been just looking at the jump from when I start pedaling after a coast.

    To try to check everything out, I set up the bike on the rollers, and it seemed like it was reading consistently, and the 3sec average was about what I normally see.

    Here's the other strange thing though. When I pedal at 90 RPM, and I have the bike geared so that I'm traveling at 20mph on the rollers, I get a reading of around 135w. Then if I upshift, so I'm riding at around 22mph, the power output is around 150w. That would make sense on a flat road, but my perceived effort on the rollers is about the same. Essentially, it "feels" like I'm not working any harder, but the PM is reading 15w higher.

    Could it be that I am working slightly harder, and 15w just isn't enough to feel the difference? Or is it that the Garmin calculates power using both torque and speed? Or is it that something else is wrong?

  2. #2
    RoadBikeReview Member
    Reputation:
    Join Date
    Jun 2008
    Posts
    7,331
    Try setting you PM at 30 second average and make sure your lap average is also showing. It is my experience that even 10sec average is a bit too twitchy on both the G3 powertap and the Stages.
    Quote Originally Posted by TiCoyote View Post
    I've had a Stages PM since July, and I'm slowly learning how to use it to train.

    I want to point out that the first one I got had an error in the software. The temp curve was set to 11 (cue the Spinal Tap Jokes) instead of -.02, so it was reading way too high on warmer days.

    Yesterday, I was out for a ride, and it seemed like I was getting high readings. A soft pedal might make it jump to 250w. I have my Garmin 500 set to display 3sec average, and N.P., so I imagine that I could have been just looking at the jump from when I start pedaling after a coast.

    To try to check everything out, I set up the bike on the rollers, and it seemed like it was reading consistently, and the 3sec average was about what I normally see.

    Here's the other strange thing though. When I pedal at 90 RPM, and I have the bike geared so that I'm traveling at 20mph on the rollers, I get a reading of around 135w. Then if I upshift, so I'm riding at around 22mph, the power output is around 150w. That would make sense on a flat road, but my perceived effort on the rollers is about the same. Essentially, it "feels" like I'm not working any harder, but the PM is reading 15w higher.

    Could it be that I am working slightly harder, and 15w just isn't enough to feel the difference? Or is it that the Garmin calculates power using both torque and speed? Or is it that something else is wrong?

  3. #3
    RoadBikeReview Member
    Reputation:
    Join Date
    Aug 2010
    Posts
    2,542
    How big are the rollers? If you have the really large ones, i.e. 4.5in, the resistance is very little and doesn't grow quadratically like it does on the road. I had 4.5in rollers and I could spin them out in my 50x11 @ 100RPM (speeds of 40+mph) while I was in my tempo zone.

    I would recommend keeping the reading to 3s. I use that to try to keep my watts constant as possible. On my 'interval' Garmin screen I show both 3s and 10s.
    Stop caring about other people's FTP and ride your damn bike.

  4. #4
    RoadBikeReview Member
    Reputation:
    Join Date
    Nov 2014
    Posts
    1,712
    A 15w difference when you're going easy wouldn't be that readily perceptible. 15w when you're going flat out can be pretty big!

    So it's all a bit relative.

    I wouldn't worry too much about going from 135 to 150, though.

    And yes to 3s avg. 10s is a bit too high if you're riding around with terrain variations and with 30s you might as well not even worry about it for shorter work.

Similar Threads

  1. fit questions.
    By mrfizzed in forum General Cycling Discussion
    Replies: 2
    Last Post: 05-22-2012, 09:00 AM
  2. I have questions.
    By 10ae1203 in forum The Lounge
    Replies: 28
    Last Post: 05-05-2012, 04:21 AM
  3. More bar-end questions
    By rodar y rodar in forum Commuting, Touring and Ride Reports
    Replies: 3
    Last Post: 09-15-2008, 09:27 PM
  4. Hey MB1, a few questions
    By bigrider in forum General Cycling Discussion
    Replies: 8
    Last Post: 08-01-2004, 04:46 PM
  5. a couple of questions questions...
    By Kaboom in forum General Cycling Discussion
    Replies: 2
    Last Post: 05-09-2004, 11:11 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •