Different bikes, different PM's, same Smart Turbo

power-meter
trainer
bike

#1

I’m pretty sure this is a topic that has been done to death but without going through each and every post, I’m confused as to a decent answer…

I have a number of different bikes, each with a different power meter. They all link up to Powermatch ok (now that I’ve sorted a few things) however, I also have a frame set that I want to set up as a permanent turbo bike. This bike doesn’t have a Powermeter so I’ll have to use the Smart Turbo (Elite Direto) to control the power.

My question essentially is this…how do I set/calculate the manual offset between the Direto and my PM (the one I use for testing)? My PM offset is generally around 885 and the Direto is around 2860


#2

Those offsets are relevant to the particular meter only, and can not be used to adjust a different meter.

IF you want to know the difference between the Direto and any (all?) of your other power meters, you will need to do a workout on the trainer with a power meter, record the data on 2 devices, and compare with something like the DCR analyzer tool. That will show you the relative difference of the meter and trainer at different points of the power curve.

But even when you know that, there is no way to adjust that on the trainer or in the TR app. You just have to know the difference relative between them. Ultimately, you are best to perform a FTP/Ramp test on the trainer and use that direct value for your training.

Then you need to know the difference from that to the PM’s so you can consider how different (or similar) they are to the trainer, so you can set your training appropriately for outside rides and races.

There is no “easy” button here.


#3

I think I understand what you’re saying…I thought there was a function where you could set your own offset to match your individual PM…my mistake :slightly_smiling_face:

So, in a nutshell, it’s easier to do a ramp test (my normal testing protocol) using my Direto as the power source and then just train indoors to that? As long as I use that for all indoor sessions, my zones should correlate to all of my other power meters as I’ve tested with them too (assuming all efforts etc are equal)…if that makes sense.


#4
  • You are half right. There is a “manual” option to offset (as opposed to the “automatic” mode) with PowerMatch, between the power meter and the trainer… but it is only possible when you have both… a power meter and trainer paired, at the same time. It is not meant as a “correction” tool to change the trainer values when the power meter is absent.
  • Yup. Use the same “yardstick” to set zones and train, and you are all set.
  • Kinda. Again there is likely a difference in what each meter and trainer says at a “real power” value. They are likely all off by some amount, and not necessarily even in the same direction.

  • That’s why testing with a meter and the trainer together can help you see how and where they read different.

  • Ex: If PM says 100w, and trainer says 200w, you know that there is a 100w delta between them.

  • That needs to be known so you don’t try to train (inside with the trainer) or race (outside with the power meter) at the same “power” between devices. If you do, one will feel too easy or the other too hard.

  • The above example is an exaggeration, but common difference like those can lead to Sweet Spot becoming Threshold work, or VO2 Max being Threshold, and the like.

  • It all gets more complicated once you introduce 2 or more power measuring devices. :stuck_out_tongue:


#5

Another thing to note, is that the offset between powermeters may not always be a constant number.


#6

I’m in a very similar situation to you. Four bikes, four different PM’s and a Direto trainer. I’ve also very occasionally used another that’s currently on my wife’s bike.

This is what I’ve ended up doing. Most PM’s (some more than others) have a element of temperature drift especially noticeable indoors as temperatures can change significantly during a ride. It’s therefore sometimes not as simple as saying there’s X amount of difference between the Direto and the PM as it can change over time if you don’t recalibrate during a ride. The Direto with the way it measures power isn’t susceptible to heat changes so at least will be give stable power readings.

FWIW with the units I’ve got my PT hub seems the most stable with regards to temperature fluctuation, the P2M Type S suffers the most and is significantly worse than a P2M classic despite the fact it’s supposed to have inbuilt temperature compensation built in which the classic hasn’t.

The Direto will almost certainly be the best option to use indoors so I just use that and ‘get to know’ the PM on my race bike as the race season comes around.

I’ve driven myself mad measuring different the relative differences between a good number of PM’s over the years. Make you realise that chasing an FTP number (or any other metric) to anything other than a range rather than a single figure is daft :exploding_head: