Help with riding outside and new power meter user

tcattri

So, prior to the OS, I had not really been riding my road bike for a few years. I have been using the trainer and TR almost exclusively since starting with EN in Sep 2013. I have had my PT for 2 weeks and have been doing my intervals on the trainer and then the 85% work outside. Here are my questions:

1. My PT on the trainer is reading ~40 w lower than trainer road but seems to be accurate on the road. I calibrate before I start each time. I have also done the stomp test, which came out with a result of 6% accuracy. I assume I just ignore the TR and PT discrepancy - I will probably need to do an outdoor FTP test to get my real outdoor FTP (I will do that in week 14 of the short course plan in a couple of weeks). I was hoping to do it on the trainer but does not appear to be accurate. Any thoughts?

2. My outdoor rides are very hilly in my area. I know I am mashing gears a bit trying to maintain level watts. I am so out of practice and looking for guidance. On the trainer, I have been riding on the small chain in 4th gear, Normally on a flat ride, I ride on the small chain ring in 4th gear most of the time or I do the big chain in 1st gear. I seem to be all over the place on these hilly courses. Any suggestions? I have read and listened to the Power Training and Racing podcasts but need more specific guidance. Help?!

jaleslie

1. My PT on the trainer is reading ~40 w lower than trainer road but seems to be accurate on the road. I calibrate before I start each time. I have also done the stomp test, which came out with a result of 6% accuracy. I assume I just ignore the TR and PT discrepancy - I will probably need to do an outdoor FTP test to get my real outdoor FTP (I will do that in week 14 of the short course plan in a couple of weeks). I was hoping to do it on the trainer but does not appear to be accurate. Any thoughts?

It is not uncommon for TR and "true power" measured by a PM (crank, PT, pedal) to be off by 10-50 watts (I switched from TR to PT and "lost" about 20 watts (not really a loss....just had to check my ego and reset all my zones!)).  TR (if you don't have a PM) is giving you an estimate of your power, "virtual power".  I'm a little puzzled by your question though.  I understand that TR is giving you a number that is 40W higher than what your head unit is telling you (which is from the PT), right?  What then, do you mean by "seems to be accurate on the road"?  Are you saying that your perceived exertion matches what you are seeing on the head unit outside, but not inside?  

One thing to make sure, is that you have changed the settings in TR to tell it to listen to your PT and not to try to "calculate" your power from the speed sensor on your wheel and the template power profile for your particular trainer.  IOW, if you don't tell TR to listen to your PT, then you will see a different number on your head unit from what you see on TR.  If this is what you are describing is happening, then you need to change your settings in TR.  You don't want to use "virtual power" if you're riding with your PT on the trainer.  All TR is going to do for you now is give you a visual representation (graph) of what watts you are producing and goals for what you supposed to be doing (keep the yellow line on top of the bar graph!).  

Maybe I don't understand your question..?  or....maybe that helps?

As far as your second question, if you're riding a hilly course and trying to "flatten" it (maintaining steady wattage up and down hills) then you will be using all your gears and changing all the time.  That's completely normal and exactly what you WANT to do.  I don't really care how many times I shift gears and just do whatever I need to do (big chainring, small chainring, all the cogs in back) to keep power steady and cadence in my comfortable range.  I am pretty picky about cadence, so I probably shift more than others who are comfortable anywhere from 80-100, for example.  I like 94...and so if I'm going to be in a gear for more than 10-15 secs, and I don't like the cadence required to keep my watts on target, then I will shift.  Over and over and over and.....

 

 

 

 

 

 

tcattri

Posted By <span class='af-profile-name'>Jeff Leslie</span> on 29 Mar 2014 09:49 PM

<p>1. My PT on the trainer is reading ~40 w lower than trainer road but seems to be accurate on the road. I calibrate before I start each time. I have also done the stomp test, which came out with a result of 6% accuracy. I assume I just ignore the TR and PT discrepancy - I will probably need to do an outdoor FTP test to get my real outdoor FTP (I will do that in week 14 of the short course plan in a couple of weeks). I was hoping to do it on the trainer but does not appear to be accurate. Any thoughts? </p>
<p><span style="font-style: normal;">It is not uncommon for TR and "true power" measured by a PM (crank, PT, pedal) to be off by 10-50 watts (I switched from TR to PT and "lost" about 20 watts (not really a loss....just had to check my ego and reset all my zones!)).  TR (if you don't have a PM) is giving you an estimate of your power, "virtual power".  I'm a little puzzled by your question though.  I understand that TR is giving you a number that is 40W higher than what your head unit is telling you (which is from the PT), right?  What then, do you mean by "seems to be accurate on the road"?  Are you saying that your perceived exertion matches what you are seeing on the head unit outside, but not inside?  </span></p>
<p><span style="font-style: normal;">One thing to make sure, is that you have changed the settings in TR to tell it to listen to your PT and not to try to "calculate" your power from the speed sensor on your wheel and the template power profile for your particular trainer.  IOW, if you don't tell TR to listen to your PT, then you will see a different number on your head unit from what you see on TR.  If this is what you are describing is happening, then you need to change your settings in TR.  You don't want to use "virtual power" if you're riding with your PT on the trainer.  All TR is going to do for you now is give you a visual representation (graph) of what watts you are producing and goals for what you supposed to be doing (keep the yellow line on top of the bar graph!).  </span></p>
<p><span style="font-style: normal;">Maybe I don't understand your question..?  or....maybe that helps?<img alt="" src="http://members.endurancenation.ushttp://members.endurancenation.us/DesktopModules/ActiveForums/themes/_default/emoticons/ermm.gif" /></span></p>
<p><span style="font-style: normal;">As far as your second question, if you're riding a hilly course and trying to "flatten" it (maintaining steady wattage up and down hills) then you will be using all your gears and changing all the time.  That's completely normal and exactly what you WANT to do.  I don't really care how many times I shift gears and just do whatever I need to do (big chainring, small chainring, all the cogs in back) to keep power steady and cadence in my comfortable range.  I am pretty picky about cadence, so I probably shift more than others who are comfortable anywhere from 80-100, for example.  I like 94...and so if I'm going to be in a gear for more than 10-15 secs, and I don't like the cadence required to keep my watts on target, then I will shift.  Over and over and over and.....</span></p>
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Thanks for the feedback. Yes, I am keeping track of the virtual power just for the next 2 weeks - until I do my end of OS FTP test. Once I complete that, i will update tTR to read directly from the PT. I was just wondering if the 40 wattt difference between TR virtual power and PT piwer is normal. Thanks.

jaleslie

Thomas...good!  We're on the same page.  Yes, 40W is not surprising for the difference between PM power and TR virtual power.  Unfortunately, TR always seems to be higher.  Nothing but an ego check needed though (at least that's what I told myself!). I was so disappointed that I googled how to manually calibrate a PT and did a rather complicated test, only to find that is was ~1.5% off . Once you've tested again with PT, then you shouldn't need to use virtual power anymore.  

BTW, if you haven't ridden outside with power much, you may find this thread helpful:

http://members.endurancenation.us/Forums/tabid/57/aft/14974/Default.aspx

 

Al Truscott

Two thoughts …(1)  I've been using TR with a Powertap for three seasons now, and I have never once looked at Virtual Power on TR. I don;t even know how to set it up. Why are you paying any attention to the VP if you already have the *real* power data available?

(2) When riding outdoors, I let the terrain dictate what I'm doing. E.g, going uphill, short ones I do as VO2 effort, longer ones, I do as FTP effort. On the flats, I do either SS (80-85%) or more FTP work if I need it. And downhills I mainly use for recovery if they are steepish; if gentler, I try to focus on SS effort. 

tcattri

@Jeff - thanls for the feedback and the thread - i will use that guidance the next time I'm outside
@Al - i am only using virtual power through my end of OS test since I just got the power meter - will update the settings to real power the following week

Thanks guys!

Coach Rich

What Al said. Since you have a PT, TR is now simply a training venue. You should tracking and thinking in PT watts, as this is what you'll use outside and for racing.

Please read this wiki article on riding steady in training vs racing.