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Trainer Road vs Power meter

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  • January 23, 2015 at 11:36 pm #23087
    ianrobo

    Finally got my power meter set up and did a session tonight on the trainer. Usual set up and trainer road showed watts on average 50 above what the Vector was showing.

    Is this something others have found as Trainer Road claims to be more accurate than that. For example for the session Vector was 174W and Trainer Road 231W.

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Viewing 14 replies - 1 through 14 (of 14 total)
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  • January 27, 2015 at 4:38 am #828445
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    giobox

    fenix wrote:Check out DC

    fenix wrote:
    Check out DC Rainmaker and his reviews of powermeters. He’s ridden with 4 or 5 on the bike and the read outs were very consistent – even Stages.

    Thats a very superficial reading of DC Rainmakers ludicrously detailed reviews. Sure the averages over a ride usually are in the same ball park, but there can be significant variations for a given data point, especially with the single sided models like the Stages or Vector S. (By data point I mean a single fixed point in time, comparing numbers from all meters).

    Does this matter? Nope. But the idea that any of these are ‘accurate’ tools allowing accurate comparisons between them is wrong. Doesn’t mean you can’t train on them though, or that the FTP numbers you get off them won’t be consistent too.

    January 26, 2015 at 11:23 pm #828443
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    fenix

    Check out DC Rainmaker and
    Check out DC Rainmaker and his reviews of powermeters. He’s ridden with 4 or 5 on the bike and the read outs were very consistent – even Stages.

    January 26, 2015 at 10:29 pm #828441
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    mtbtomo

    You’d expect different brands
    You’d expect different brands of power meter to be within 5 or 10% of each other surely?

    Trainerroad virtual power is consistent enough to be a useful training tool for mere mortals. Ditto any type of power meter. Keep tyre pressures the same, just as you would out on the road. There are so many other variables and life choices to make before worrying that your power meter might not be accurate or that there’s a small percentage variability in virtual power over an hour’s session.

    I won’t care what power I’m putting out when it comes to that first race of the year. I’ll care that I can keep with the bunch, not get dropped or some other target that I can experience – not just a number.

    If you don’t race, why not just trounce your riding pals on the sprint for the town border sign rather than worrying that your max power is 50Watts down on your mates 😉

    January 26, 2015 at 6:07 pm #828439
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    700c

    Power meters are still pretty
    Power meters are still pretty expensive – it’s pretty poor if there’s no consistency.

    If I regularly measured my power I’d want it to be consistent across devices, not only for referring back to an FTP as a baseline figure, but also in calculating power to weight ratio etc. If there’s no consistency then there’s no ability to compare stats with peers…

    So when they say ‘Bradley Wiggins puts out 400W over a 1hr TT’ or whatever – is that just meaningless because it’s inaccurate? can that really be the case?

    Surely car manufacturers have a consistent way to measure power, to enable consumer choice – so why can’t the makers of expensive bike gear?

    January 26, 2015 at 3:26 pm #828437
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    ianrobo

    yes you can and tested it at
    yes you can and tested it at the weekend. The only problem is of course taking the pedal on and off all the time as I swap with training/road bike.

    Will sort it out and use the vectors all the time on TR.

    January 26, 2015 at 3:26 pm #828435
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    ianrobo

    yes you can and tested it at
    yes you can and tested it at the weekend. The only problem is of course taking the pedal on and off all the time as I swap with training/road bike.

    Will sort it out and use the vectors all the time on TR.

    January 26, 2015 at 3:16 pm #828433
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    Scrufftie

    Trainer road estimates the
    Trainer road estimates the power from the typical resistance profile of the turbo trainer you use. It’s better than nothing but I can’t see it being as accurate or consistent as a ‘proper’ power meter. My, quite good, turbo varies in resistance over time and tyre pressure can make a big difference. My turbo has it’s own power reading but it’s very dependent on tyre pressure and I rely on my Vectors instead.

    AS long as they’re installed properly, I’d trust the Vectors. You can use them with trainer road, I believe.

    January 25, 2015 at 10:30 pm #828431
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    kentos1978

    I recently got a stages and
    I recently got a stages and trainer road was about 70w too low for me. As others have said it doesn’t really matter, although I found short efforts above ftp really difficult before. Obviously pm responds much more quickly than the lag in winding the speed up.

    January 25, 2015 at 3:43 pm #828429
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    ianrobo

    first full ride today for the
    first full ride today for the vector outside, worked perfectly giving me an average of 157W through the ride but obviously as discussed no comparisons yet to other rides.

    January 24, 2015 at 5:50 pm #828427
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    ianrobo

    OK thanks guys, my training
    OK thanks guys, my training will switch over to the vector once I am used to them, will be giving it a whirl out on the road tomorrow

    January 24, 2015 at 4:27 pm #828425
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    JimboBaggins

    To the original poster – if
    To the original poster – if you’ve got a Vector power meter, why would you need TrainerRoad’s virtual power figure? The Vectors *ought* to be “right”. But as @giobox says, accuracy doesn’t really exist in power meters for normal folk like us. I have Vectors and a Kickr trainer – which has a power meter – and they seem to randomly move around between rides. For ages the Kickr was higher by 10-15W than the Vectors, then some rides they are effectively identical, then sometimes more recently the Vectors are higher. I think it’s to do with temperature, and/or how well I install them after swapping between bikes (always using a torque wrench to get to 34Nm though…). I always calibrate both (although haven’t been bothered to do the real hardcore calibration, hanging weights off etc).

    You basically just go until it hurts so much you don’t want to go on anyway, so it’s all good…!!

    January 24, 2015 at 3:24 pm #828423
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    mtbtomo

    I find that trainerroad gives
    I find that trainerroad gives me about 50 watts less than my Stages power meter.

    As per previous post, doesn’t matter if its accurate, just that it’s repeatable for each system. Yes you will need to have different zones for different systems. Shouldn’t need another ramp test, just compare the readings for both systems on the same work out and adjust accordingly.

    January 24, 2015 at 12:22 am #828421
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    ianrobo

    OK I understand that, so I
    OK I understand that, so I will need to change my power zones to fit in with the lower figures for the vector to have the same consisentcy on the road as on the trainer.

    A call to my coach and another ramp test beckons 🙂

    January 24, 2015 at 12:10 am #828419
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    giobox

    If you’re asking is it
    If you’re asking is it accurate you’re asking the wrong question. There is no way to know if any power meter is ‘accurate’ (at least for normal people…), no matter how fancy it is. The important thing for any power meter is are its numbers consistent? If its consistent you can train on it.

    In this regard TrainerRoad is as pretty much as accurate as any other power meter, so long as you keep tire pressure and wheel pressure against the flywheel the same.

    It doesn’t even matter if it says you output 100 Bananas, so long as the effort needed to generate 100 Bananas is always the same.

    There’s a good explanation here.

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