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

Poll

Comfort While Cycling
How much does comfort while cycling influence your overall race performance?
View Results


Home > Forum > Triathlon Forum > P2M vs Stages - big differences?

Triathlon Forum

Back To ForumPrint Thread

Login required to started new threads

Login required to post replies

Tri
Classifieds
Lavender
Jobs
Notices
P2M vs Stages - big differences?
Quote | Reply
SBRcanuck
Oct 5, 18 6:30
Post #1 of 13 (1502 views)
Does it make sense that for whatever reason, my newer stages single side PM (latest version) reads a lot lower than my previous P2M crankset??

For comparison:
2015 Tremblant 70.3 - 180w avg (p2m), 2:39, 88.7km.

2016 Tremblant 70.3 - 186w avg (p2m), 2:39, 88.5km

2018 Tremblant 70.3 - 160 avg (stages), 2:35, 87.7km


The 1km difference in 2018 could account for ~ 2 minutes difference I guess. But then I still went 2 minutes faster while pushing 20 watts less (and I was in fact trying to push less, pedestrian, in order to run without cramps for once on this course...). I also had a disc wheel in '15 and '16, and a 90mm rear in '18, so that should have cost me more time...

I -think- my position is a little better this year and was able to hold aero better/longer. But I still didn't expect that time in '18 while pushing so little watts...

I have noticed similar in a couple sprint races, where my P2M had me at an avg around 275, and stages has me around 240....
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
gmh39
Oct 5, 18 6:50
Post #2 of 13 (1477 views)
Have you done a weight test where you hang a weight on the end of the crank and compare the measured power to the theoretical power? (or something along those lines)
Strava
Quote Reply
Re: P2M vs Stages - big differences? [gmh39] [ In reply to ]
Quote | Reply
SBRcanuck
Oct 5, 18 6:51
Post #3 of 13 (1473 views)
nope!
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
FatandSlow
Oct 5, 18 6:53
Post #4 of 13 (1470 views)
It makes sense. A single-sided Stages will always give you double your left leg's power. It may or may not be your actual power output.
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
Benv
Oct 5, 18 6:54
Post #5 of 13 (1465 views)
Comparing rides from different years to each other makes no sense. Too many variables that can impact your speed and power. That said, they should be very close. My P2M, Stages and Powertap are all really close to each other (within a few watts at the most).
Quote Reply
Re: P2M vs Stages - big differences? [FatandSlow] [ In reply to ]
Quote | Reply
SBRcanuck
Oct 5, 18 6:54
Post #6 of 13 (1465 views)
Odd thing is that my left leg is stronger.....lol.
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
SBRinSD
Oct 5, 18 6:58
Post #7 of 13 (1453 views)
I am every so slightly right leg dominant. Like 49/51 at most power ranges. Therefore my P2M reads higher because the power output is higher.

I cannot understand why my P1’s read 3 - 5 watts lower than the P2M as I believe most reports are that the P1’s over report on power.

Really, it doesn’t matter much as long as you race off a number derived from training on the same PM. You can over cook yourself if the PM you race off under reports and you are trying to hit a bigger number.
Quote Reply
Re: P2M vs Stages - big differences? [SBRinSD] [ In reply to ]
Quote | Reply
SBRcanuck
Oct 5, 18 7:01
Post #8 of 13 (1449 views)
Thx, yeah, I do most my training on a kickr, which of course reads different as well, but I know if I want the stages to be useful for pacing, I need to take the time to do a proper ftp test with the stages controlling the kickr...
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
sciguy
Oct 5, 18 7:03
Post #9 of 13 (1441 views)
SBRcanuck wrote:
Does it make sense that for whatever reason, my newer stages single side PM (latest version) reads a lot lower than my previous P2M crankset??

Perhaps there's a bit of asymmetry between your two legs. The Power2max measures your combined right plus left power output while the Stages measures twice your left side power. If your left is a bit less powerful than the right you'll see a very understated output.

YMMV,

Hugh
Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
AlexS
Oct 5, 18 14:19
Post #10 of 13 (1337 views)
SBRcanuck wrote:
Does it make sense that for whatever reason, my newer stages single side PM (latest version) reads a lot lower than my previous P2M crankset??
It would be more surprising if they read the same.

For a start your Stages is not measuring the same thing as your old P2M was.

Then of course comparing power and speed from different rides without considering differences in resistance forces (especially the multitude of factors influencing air resistance if it's the same course) is somewhat problematic.
http://www.cyclecoach.com
http://www.aerocoach.com.au
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
Khilgendorf
Oct 5, 18 14:43
Post #11 of 13 (1310 views)
SBRcanuck wrote:
Thx, yeah, I do most my training on a kickr, which of course reads different as well, but I know if I want the stages to be useful for pacing, I need to take the time to do a proper ftp test with the stages controlling the kickr...

Do you have any rides where you compared the P2M to your kicker? Then compare the stages to the kicker to get an idea of how far apart the P2M and stages are.
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
marcag
Oct 5, 18 15:03
Post #12 of 13 (1290 views)
Do you calibrate regularly ?
I have a Stages on my Quarq crank. If I forget to calibrate, the numbers diverge considerably.
Quote Reply
Re: P2M vs Stages - big differences? [SBRcanuck] [ In reply to ]
Quote | Reply
Jason N
Oct 5, 18 16:40
Post #13 of 13 (1241 views)
Were all the other variables constant each year? Bike, wheels, position, helmet, tires/tubes, weight, road conditions, wind, ability to legally draft, etc. You can also see some pretty significant gains simply if the race changes how traffic runs alongside the bike portion of the course. If you're riding along at 20 mph and there are cars constantly passing you at 30-35 mph, it makes a huge difference in breaking up the wind for you as compared to if that road was shut down to vehicle traffic.

It would be pretty easy to do a similar time on 20 less watts simply by improving your race suit and going from "okay" tires and butyl tubes to a well fit sleeved tri suit with fast tires/latex.
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.