Virtual Power vs Power Meter FTP

power-meter

#1

Hello Folks, Hopefully this sparks some healthy & fun discussion:

The painful reality: My power meter FTP ramp test results are Significantly Lower than my my virtual power. I did a ramp test this week with 2 computers running TR, 1 using my new Vectors & the other using good ol’ Virtual Power. The Power meter FTP was 190 & the Virtual Power was 265.

The back story: I just bought my first power meter (Garmin vector 3) after using Trainer Road’s virtual power for roughly 1 year. FWIW, I’m on a cyclops super magneto pro & I was using Garmin speed & cadence sensors. Now I had read that one should expect a drop in power when switching to an actual power meter… But i was a little disheartened to see that my virtual power “big gains” from 190-265 over the past year were probably not all that real.

Now I’ve kind of accepted that I’m a significantly worse cyclist than I thought. Just curious what others experience with the difference between virtual power & power meter results.


#2

I wouldn’t worry about it. You are what you are and you’re trying to improve.

Now you have the same power indoors and out you’ve got the best setup.


#3

Does it really make a difference? I trained for a couple of years with virtual power and had a ridiculous figure for my FTP. Retested when I got a power meter and the result was much different. The important thing is that the figure is consistent and you’re training at the right intensity. Be that 400W or 200W. And that change does not make you a significantly worse cyclist, nor negate any gains you’d made while training with vitual power.


#4

I think you are thinking about this incorrectly. Those gains were absolutely real! You are just using a different, more accurate method to assess power now. So you got a ton stronger over the past year - you built your FTP up to 190 on an accurate power meter - this just means you started lower than that a year ago


#5

Yup. Gains are gains.

Look at the same “ruler” and measure the delta on that one only. To that end, look at the percentages between your start and end point. That delta is a REAL way to measure the gains.

Having a more accurate (true to life number) is nice, but not necessarily any better. One of the only advantages of real power vs virtual power is the ability to compare to other riders with similarly accurate equipment.

Having said that, DON’T do it :stuck_out_tongue:
Focus on your own training, and gains relative your own starting point. Try to resist the temptation to measure yourself against others. It really doesn’t help much and can lead to poor choices in some cases.


#6

Wow- Thanks all for the therapy session! Hopefully this is helpful for others when they drop $$ on a power meter & have buyers remorse for similar reasons lol.

But in all seriousness, thanks for the encouragement!


#7

No need for remorse. The common mistake is to take virtual power for more than it is. Sadly, since we still call them watts, people often consider them the same as a PM wattage. Sometimes they are, but often they are not.

So, ignore the past values as they are irrelevant in an absolute sense, but the percentage gains are still what matter.

Take your new power meter, run a Ramp Test (or your other FTP test preference), and use that value as your new baseline. Use that new FTP and measure against it in the future to see your continued progress.

The simple idea is that you just swapped measuring sticks. It might as well be like thinking you switched out an old Imperial tool with a new style Metric tool. They both measured stuff, but with different values.


#8

The other benefit of real power is in having faster response to output, virtual power is dreadful for short power work.


#9

I am in a similar situation with only using virtual power currently. I am considering investing in a “real” power meter for when I go outdoors this coming spring.
Could an update to Trainer Road better “adjust” the conversion of virtual power to a real power number so we don’t see as large of a change when we transition to a to real power meter?


#10

Not really. You have look at and understand what drives VP.

The base is a particular trainer from a particular manufacturer. TrainerRoad takes one unit, and uses it, along with a power meter (often several) and records the measured power at a full spectrum of speeds. They correlate the power and speed to generate the Virtual Power curve.

This is done with a particular bike, wheel tire, tire pressure and roller pressure. Each one of those details has an influence on the overall results.

The reason that matters is that of you change even one of those variables, you will get different speed to power results.

So, if you have a tire with different rolling resistance, different tire pressure, different roller pressure than what TR used, you will likely get different values.

They follow standard trainer protocol for setup, but the tire alone can have a massive impact on the results. Unless they publish that info, and you use the same one, you can’t know if you have the same setup.

Virtual Power is great since you can use it for excellent training, if you maintain a consistent setup. But there is no real way to know if it is “accurate” to real power unless you check with a real power meter. Just too many ways it can be shifted from the curve TR created.


#11

Sorry to drag up an old topic but out of interest, I’m in the same position currently using virtual power and considering a power meter purchase soon.
Is it possible to share the setup protocol, tyre details and pressure etc? I’m on a Cyclops magneto…
In keeping with the spirit of the topic i know it doesn’t make any real difference and what i get with the power meter i get but I’m curious and would be nice to manage my expectations if i can try and match the protocol as close as possible prior to purchase :slight_smile:


#12

Hi Sammy,
Just get the power meter. I did a while back and wouldn’t hesitate to replace it if needed.
Even if you had the info you’re asking for it wouldn’t give you a good indication of what to expect.
My experience is with a Qubo Power Fluid and going from virtual power to running a Stages PM on my mtb.
The power changes by up to 20watts depending on my weight distribution at a given cadence/speed. Then there’s the tiny tyre pressure changes and fact that the oil/fluid changes resistance a heap based on temperature.
I’m pretty sure each unit would be out by several magnitudes on the cheaper units as well. Don’t quote me on it, but it’s what I’d expect on mass produced units that don’t have to be accurate.

Anyway, the best thing about using a power meter is the ability to assess your performance outdoors, as well as on the trainer. They’re great for adding accurate TSS figures for those outdoor rides as well.

HTH.
Ross.


#13

I was in exactly the same place as the OP three years ago. My VP had me pegged at solid 4.5w KG. I eventually took the plunge and got a Stages Power meter. Re-tested with the Stages and low and behold I wasn’t the amateur power god that I thought I was. Initially I was in total denial… so much so I contacted Stages to see if I’d got a bum product hahaha. I finally accepted where I was and knuckled down and set myself a goal of getting to my VP power with “REAL” power - fast forward a couple of years and I’m as good as there :grinning:
I’ll echo what others have said and as long as the data is consistent you’re golden :wink: