Advice: Ergomo vs SRM

Discussion in 'Power Training' started by Bob Dopolina, Aug 1, 2007.

  1. peterpen

    peterpen New Member

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    You forgot about chasing and facing the BB - many people who do their own work don't own the necessary tools.

    And the "calibration" process you refer to just means that the unit is performing correctly in reference to itself, unlike PT's and SRM's whose ultimate accuracy can be verified with weights.
     


  2. Bob Dopolina

    Bob Dopolina New Member

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    To eliminate the idiot quotient: I have, and continue to, work in the bike industry since the mid 80's ( yes the 19 eighties). I have an extensive technical background as well as being a certified coach (CAA). I have raced on 3 continents. (successfully is another issue:D) and continue to race in Asia.

    As my riding career winds down, I am looking to choke another few years out of my tired, old engine and, in the process, learn enough about power training to make a transition into coaching full time.

    What I want is a system that will allow me to do that but one that won't force me to bust into my kid's college fund. My hope was that Ergomo users could convince me that this product was a worthy investment and that SRM was a luxury.

    It is becoming increasingly aparent that SRM is the best bang for the buck and that I may have to sell a kidney to get one.

    Last chance for all you Ergomo users to convince me otherwise before I book the surgery and bury this thread!
     
  3. rr9876

    rr9876 New Member

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    Is there any particular reason that you are not considering a Powertap?
     
  4. beerco

    beerco New Member

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    While the SRM is a fine PM, it is certainly not the best bang for the buck. That honor would go to used power taps.

    I've managed to pick up a training wheel, deep section race wheel, 3 harnesses, a standard head and a pro head for less than $1200 over the years.

    The PT also holds the "I can trust the accuracy right out of the box" award which apparently, the SRM can't quite claim (although I've never owned an SRM so this is really hearsay from me).
     
  5. Bob Dopolina

    Bob Dopolina New Member

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    We have a wheel sponsor and I do a lot of testing for them which involves changing wheels quite often. Lacing a hub into one of their wheels becomes problematic. I would likely be building a fresh wheel every 6-8 weeks.
     
  6. LarsEjaas

    LarsEjaas New Member

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    You REALLY should buy a used DA SRM crank - I think they are ok to buy used (and NO - I do not have a set for sale myself :D )
     
  7. pistole

    pistole New Member

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    - I had a look and that unit is close to USD$4,000 , new.

    - ouch.

    .

    - the PowerTap units seem alot more affordable , any views about their reliability ?

    cheers.
    .
     
  8. LarsEjaas

    LarsEjaas New Member

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    I just saw a used DA SRM for sale on Slowtwitch. I think it was around USD$2000 - sounds like a great deal.

    Sincerely Lars
     
  9. Rocket^

    Rocket^ New Member

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    I've been an Ergomo user for a little over a year now. I don't think any of the other PM's even come close to the amount of, or versatility of the data that can be displayed on the computer. While riding I can view NP/TSS/IF/Altitude. With the newest update I can configure the top two screens to display just about any combination of data I desire. The altitude function is also very helpful in the downloaded data.


    Installation: Peoplecan claim whatever they like, but the bottom line is installation is a PITA. I had my frame faced and chased and installed the BB with the specified Torque specs. The wires exited the bb at the nine o'clock position. With the offset complete and checked for the 0-5/15 watts the ergomo was reading approximately 10% higher at the 200-230 watt range. (checked against a PT). With the spacer combinations I basically had three options, wires exiting at the nine, eleven, or seven o'clock positions. After trying all three it turns out the seven o'clock position gave the closest reading to the PT. With the seven o'clock position the Ergomo was giving wattages that averaged 7% lower than the PT during a 20 min interval at 200-230 watts.

    I could have used either position (nine or seven) and basically made the same K factor adjustment. I chose the seven o'clock position because I just didn't want to take everything back off and re-install. I lost track of the number of times I had done this during this process. I increased the K factor to the point where the Ergomo would read approx 1 to 2 watts below the PT during a 20min interval @ 230 watts. As I understand it, the Ergomo should be reading 2-3% higher than the PT due to drivetrain loss. If I understand correctly, adjusting the K factor to something other than the factory recommended for your unit will result in a linear deviation (+ or - )depending on either increasing or decreasing the K factor. I decided to match the two at the 230 watt range. While I didn't write down specific numbers, the Ergomo started to read higher than the PT as the wattage increased. I didn't see more than a 2.5% difference up to the highest wattage I could produce.

    If I had to make the purchase all over again, I would still go with the Ergomo. In the last year of training it has remained consistent. Perhaps it is off by x % at the higher wattages but does that really matter? I am able to take the data it provides and see what I need to do to improve and that is why I purchased it.

    Ergomo offers the best display options of any PM on the market today. Contrary to some opinions, I believe they have very good customer support. Look at how many updates they have provided. Just recently they released an update that let's the user configure the top two screens to include up to eight items of data. All of the updates have come without charge. Sounds like pretty good customer support to me.

    As I said, it is a PITA when it comes to install. If absolute accuracy is important than another PM will be required during this process. As a customer this is something that certaintly doesn't make me happy. With that said, given the positives and negatives of all the PM's currently available, I am satisfied with the Ergomo. YMMV
     
  10. Bob Dopolina

    Bob Dopolina New Member

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    Lars, thanks for your input but (for reasons I won't go into) I am a Campagnolo guy and can't hang a DA crank on my bike. If I went with an SRM it would have to be their Campagnolo compatible version.

    Rocket, excellent input. A clear perspective on insatallation, and set-up woes and the fact that it remained consistant after the initial calibration. This answers a few of my initial questions. Interesesting that that didn't put you off the Ergomo and that you are still happy with it a year on.

    Are there any issues with the bearings? Are they replaceable? I live in a tropical climate so I get rained on a lot.
     
  11. Rocket^

    Rocket^ New Member

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    The bearings can be replaced, but it has to be done by Ergomo. I'm sure an individual could do the replacement themselves if they didn't mind voiding the warranty. With that said, mine has been used in the rain multiple times without any issues.
     
  12. dkrenik

    dkrenik Member

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    You'll find a wealth of information re: PM comparison here:
    http://mywebpage.netscape.com/rechung/wattage/
    http://www.freewebs.com/trainwithpower/index.htm
    and the FAQ talks about how each PM records the data (which explains a lot of the differences):
    http://midweekclub.ca/powerFAQ.htm

    Dave
     
  13. Bob Dopolina

    Bob Dopolina New Member

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    Dave,

    Excellent links. A gold mine of information that will take me some time to wade through!

    I am reading a lot about zero-watt readings. It seems that the sample rate (1 sec vs 5 sec) is the main factor here. Is this a correct assumption?

    As an example, I was given a computer (not a cheap one) that has a power function. Due to the fact that I quickly realized that the power function was near to useless, I didn't use it. Out of curiousity, yesterday, I used it to record my sprint intervals. I believe the sample rate is around 20sec for this computer. At the end of my workout, I glanced down at max power and it read 630w!

    Okay, I'm a little older but sprinting in the 55-58km/hr range should produce a MUCH higher reading than this, non?

    No need to comment on this. Just passing it on as an example to illustrate my question about sample rate.

    An additional question. Does anyone alter the sample rate (thereby recording time) based on the kind of training they are doing? 1sec samples for sprints or races and say 5sec samples for longer climbs or rolling rides focused on endurance?
     
  14. dkrenik

    dkrenik Member

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    Yep - or could be... Remember the obvious: coasting & soft pedaling. There's been a whole discussion on the http://groups.google.com/group/wattage?msg=subscribe ]wattage forum[/URL] as well about this lately too.
    There's a lot of "it depends" here: gradient, atmospheric conditions, your mass, etc. And yes, sample rate. 5sec power is significantly different than 20 sec power.
    Oui
    Of course. I would think that most "trackies" use 0.5 - 0.05 sample rate for sprints. Other folks might use longer recording intervals to suit longer, steady state training.

    I use 1 sec sample rates for everything. I don't run out of memory and I get all the detail I need from my SRM.

    Dave
     
  15. Speedskater

    Speedskater New Member

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  16. RChung

    RChung New Member

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    Correct. However, I think the BBs (and thus, the power sensors) are the same. The Ergomo Pro uses a newer head unit and, I'm told, an updated cadence algorithm that no longer oversmooths.

    I suspect that comparison was part of the stimulus for changing the cadence algorithm.
     
  17. acoggan

    acoggan Member

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    Sounds like a HAC4, which doesn't actually measure power.

    I do with our SRMs: 0.1 s for force-velocity testing, 0.1-0.5 s recording for track training and races (to get better resolution or split times), 1 s recording for everything else.
     
  18. Bob Dopolina

    Bob Dopolina New Member

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    Hac5. Good Guess. I understand it calculates/extrapulates power with the help of chicken bones and phases of the moon.

    Your sample rate makes sense. Thanks
     
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