I’ve been cheating....my smart trainer

Mar 7, 18 22:59

Post #1 of 26 (6777 views)

The hardware:
Tacx Vortex SMART, data read on TrainerRoad.
PowerTap SL+, data read on Garmin 935.
I did the last FTP test a few months back and have been working through the TrainerRoad Half Ironman Base program. It’s 216, and about time to retest.
Today, I got my PowerTap back (the shop finally built it into a FLO90 I got for Christmas). I had seen differences between the PT and the Tacx in the past. So I racked the bike with the new wheel. I calibrated the PT (520 offset) and ran the Tacx utility to verify the tension was dead in the middle of the calibration at 100 psi.
I did TrainerRoad Denali +1, which has 4 x 6:00 at 110-112% FTP. I had to be in a really low gear for the 86W recoveries, but used the 53/16 for the 238-242W main intervals. I was in Erg mode the entire time. I was watching the garmin that was giving me lap power, and it was more like 190W, while the Tacx was reporting 240W. On the last interval, I dropped to the 39/19 gear, and while the Tacx still reported on target, my PowerTap was now reading 220W on the Garmin.
Most important, my HR on the last interval was a full 10 beats higher than the previous 3, so clearly I was doing more work on the last one, even though TrainerRoad and the Tacx reported the same Watts. My cadence was 93 on all 4 intervals. Very stable.
My question is whether you can “cheat” the watts on a Smart trainer by using a really tall gear and spinning the hell out of it? I had been using the Tacx, thinking that all Watts were created equal. But clearly, in tonight’s workout, I now think I might not have been truly working as hard as I thought.
When I retest my FTP, a few questions. Should I do the 20 min effort in aero position? Should I use both power sources?
Last question. I tried to do a workout last week in Resistance mode, and spun out the trainer just over 200W, yet when I put it back into Erg mode I easily hit the 350W targets. Is my Tacx just screwed up even though I’ve calibrated it? I was doing 100 rpms in my 53/12, and TrainerRoad was just showing 210W.
I know I’m all over the place on this, but I’m confused.

Michael

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 0:50

Post #2 of 26 (6712 views)

The vortex is known to overstate the power numbers compared to a power meter but as long as you keep the tyre resistance and tyre pressures the same you should see repeatble numbers every ride. Did you calibrate the Vortex after you have warmed up the trainer for 10 minutes or so? I always see a lower wattage after running the spindown in Trainerroad after a bit of a warmup.

Also, when you are in resistance mode it sounds as if you did not adjust the manual resistance level within the trainerroad app. Are you using IOS or the desktop version?

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 0:53

Post #3 of 26 (6710 views)

My experience? Tacx Vortex = random number generator. I used one for nearly 18 months, and now have a pile of useless data in WKO4. So many variables, so much inconsistency: warm up time, ambient air temp, tire pressure, 'turn screw' pressure, cadence, rocking-sprint motion... Toward the end of a hard 1:00:00 workout, the Vortex report power 40-50 watts too high, based on my checking against a Quarq, P1 dual-sided pedals, and 4iii single leg arm. In all cases, the Vortex started with low reporting then was 'ok' for about 10-15 minutes, then became an ego-meter (pun intended!) during the bulk of a workout.

I have since switched to an Elite Drivo, using PowerMatch against my Quarq for TrainerRoad.

I didn't bother to sell the Tacx, give it away, or even keep it as a backup. My Vortex was literally thrown into the trash.

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 6:55

Post #4 of 26 (6432 views)

I have a tacx vortex smart as well. It doesn't read high for me compared to the computrainer that I was using at a cycling studio. But my bike's stages power meter was slightly lower than both. I just don't try to mix and compare them. Last year I was mostly doing computrainer sessions and had ftp for that and for outdoor workouts my ftp was difference since stages gave lower readings. Last year I wasn't really using the tacx vortex smart much as my power meter and when I used it, I just followed what stages told me. The numbers were at least consistence. If I was really concerned I would upgrade to a kickr and a quarq or something.

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 7:12

Post #5 of 26 (6383 views)

I have Tacx Vortex smart and Powertap GS hub.

The Tacx Vortex consistently reads 11% more power over the hub. You would think this is a huge problem, but it really is not. The Vortex is super consistent with itself. Its not like one ride it is 11% higher and the next it is only 5%.

Power is a very personal number. Just make sure you are comparing your own numbers to yourself and using the same setup every time.

With very limited testing I found the 11% discrepancy. They very easiest way to test this was to have Zwift record the Tacx power and have my 920xt record the Powertap GS hub power during the same ride. I did this on a few rides... some long, some short, some super high power output, some easy spinning. The 11% was always the same when I compared to the rides on Garmin Connect or Strava.

Now I know to adjust my numbers on my personal training log to adjust for this dependency.

"If it costs you 30 minutes at Maryland so what" -dwreal

Re: I’ve been cheating....my smart trainer [bluestacks867] [ In reply to ]

Mar 8, 18 7:43

Post #6 of 26 (6305 views)

That was not my experience with the Vortex, particularly at higher intensities. I found (compared to my powertap g3) that the offset increased over the course of a high intensity interval and then decreased during a low intensity recovery interval. Basically I just totally ignored the data from the Vortex and used powermatch in Trainerroad linked to the powertap.

Re: I’ve been cheating....my smart trainer [cobra_kai] [ In reply to ]

Mar 8, 18 8:49

Post #7 of 26 (6150 views)

Big difference between "accuracy" and "precision", right? I feel the numbers have been consistent (Precise), but high (not accurate). Thankfully I wasn't actually doing any races in Zwift, but my over-statement of power production was still lower than most riders there.
If I set my FTP using it, and and 216 is actually higher than reality, then I simply need to have an outdoor test with the PowerTap, but the % effort stays the same? However, if I had used the PowerTap to get the 216, and have been using my Tacx for training, then I'm just not actually in the same zone I thought I was in. Do I have that right?
Last time I did an outside FTP test was in 213 (I'm just getting back to training) and my FTP was 223. I'd be fairly bummed to see it be <190!!!
Since the purpose of my power meter is to monitor effort in aero during a race, should I do my FTP test in aero?

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 9:29

Post #8 of 26 (6052 views)

Interesting...just bought this trainer. I followed all the steps, update software, use the Tacx tire at 110psi, calibrate after 10 min warm up. Seems my numbers are low if anything. My trainer bike doesnt have a power meter, outdoor bike has a stages, for comparison, 2 recent rides.

Outdoor with Stages (left only)
229W, 1 Hr 44 min ride, HR avg 150

Indoor with Tacx Vortex
218w, 1 hour ride, HR avg 154

I had it calibrated just right of the center line. Have only used Zwift, would Trainer road read different?

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 9:31

Post #9 of 26 (6047 views)

For purposes of Zwift I wish I never got a powertap hub because my FTP was consistently ~50W higher from my calibrated Tacx Vortex smart. I think I did the 2 hour pretzel loop at 340 "Watts" on the tacx while my real powertap FTP is ~300W. Additionally, tacx power changed as a function of wheel speed (decreased with increasing speed).

Summary: Tacx power is worthless unless you want to crush zwift races.

Re: I’ve been cheating....my smart trainer [ntc] [ In reply to ]

Mar 8, 18 9:40

Post #10 of 26 (6030 views)

I did my first real ride on this yesterday, after a software update, not sure if that helps.

If its an issue you could just increase your weight on your profile till it matches your power meter? After reading this I'm adding 5 pounds to my rider profile.

Last edited by: CP78: Mar 8, 18 9:43

Re: I’ve been cheating....my smart trainer [CP78] [ In reply to ]

Mar 8, 18 9:50

Post #11 of 26 (6009 views)

FTP test outside in aero?, but also test with the Tacx and use THAT number with TrainerRoad?

Re: I’ve been cheating....my smart trainer [CP78] [ In reply to ]

Mar 8, 18 11:48

Post #12 of 26 (5873 views)

Now that I have a real PM I ride in zwift using that value because it is the more accurate and matches my outdoor rides. Interesting your PM reads higher. Why not ride using the power from your Stages?

Re: I’ve been cheating....my smart trainer [CP78] [ In reply to ]

Mar 8, 18 12:06

Post #13 of 26 (5840 views)

I don't 'think' that adding weight to the rider will change the calculation of watts. (I could be mistaken)

The vortex just estimates watts based on wheel speed and trainer resistance. The key here is the word 'estimate' as the vortex isn't actually measuring watts. An easy way to demonstrate this is to start sprinting, and you'll see that power increases with speed, not by force applied to the pedals. Conversly, start coasting at you will continue to display watts so long as your wheel is spinning.

The calibration tool is of limited utility. It gets you in the ballpark, but not really good for establishing accuracy (aside from the fact that this trainer is not intended to be very accurate). However, I was able to better match the power from my Pioneer PM to my trainer by making slight adjustments to the roller contact pressure (to the tire). - if your vortex is reading lower than PM, lower the contact pressure. - if your vortex is reading too high, increase contact pressure.

In my case, I had to reduce contact pressure way down to match my Pioneer PM to the point that the tacx calibration tool read 'too loose'. I didn't have any issues with slippage, so I just left it there.

Re: I’ve been cheating....my smart trainer [cobra_kai] [ In reply to ]

Mar 8, 18 12:18

Post #14 of 26 (5814 views)

cobra_kai wrote:

That was not my experience with the Vortex, particularly at higher intensities. I found (compared to my powertap g3) that the offset increased over the course of a high intensity interval and then decreased during a low intensity recovery interval. Basically I just totally ignored the data from the Vortex and used powermatch in Trainerroad linked to the powertap.

Yes, the offset increases at higher intensities and decreases at lower intensities for me. But always 11%.

11% from 250 watts is 27.5 watts
11% from 160 watts is 17.5 watts

"If it costs you 30 minutes at Maryland so what" -dwreal

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 8, 18 12:31

Post #15 of 26 (5784 views)

HR is a rubbish metric. I can bump mine 20bpm with a pint of Ben&Jerry's the day before.

Re: I’ve been cheating....my smart trainer [ntc] [ In reply to ]

Mar 8, 18 12:34

Post #16 of 26 (5779 views)

Stages is attached to my outdoor bike, I like having this other bike, wich has no pm, just for the trainer. I can live with the numbers being off as long as its ballpark. If I do an ftp test Ill attach my bike with stages.

Do you all use the Tacx trainer tire (blue), thats what I use, supposed to help.

Last edited by: CP78: Mar 8, 18 13:00

Re: I’ve been cheating....my smart trainer [bluestacks867] [ In reply to ]

Mar 8, 18 13:07

Post #17 of 26 (5715 views)

Let me clarify: the offset was variable with interval time at a constant commanded wattage. So the percentage would grow at higher intensities as it heated up and shrink at low intensity as it cooled. So it was neither accurate nor precise.

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 15, 18 10:40

Post #18 of 26 (5295 views)

Have you compared wattage on hill climbs? On real rides I'm regularly at 300-400 watts on a 7% climb, however with the vortex smart on Zwift (at full difficulty) I am only getting up to 250 watts at my hardest. So in real life stages power meter, and on trainer different bike and vortex smart power. The vortex smart is in line with the mid range of my riding on flats, around 220-250 w, but on hills grossly underestimates my power.

Re: I’ve been cheating....my smart trainer [JRT_Racing] [ In reply to ]

Mar 15, 18 11:41

Post #19 of 26 (5205 views)

Other variables - ambient temperature, tire wear (especially if it is not a trainer specific tire), pump gauge accuracy, etc.

On tire based power meters=garbage.

Next races on the schedule: none at the moment

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 15, 18 16:28

Post #20 of 26 (5037 views)

Tacx Vortex is a piece of shit. I used one for a while and it added +50 watts compared to the powertap. Then it bricked on me. Turned into a $500 door stop.

---------------------------------------------
Of course it hurts. The trick is not minding it hurts.

Re: I’ve been cheating....my smart trainer [mpderksen] [ In reply to ]

Mar 15, 18 17:36

Post #21 of 26 (4991 views)

I have never been able to use my Vortex's power. always significantly lower than my P1 pedals.

My gripe now is it isn't working in erg mode and keeps dropping from Bluetooth to try to update or fix it. This happened about a month ago, but randomly fixed itself. Acting up again. Will show up on my phone and by the time I get to the utility app, it's gone. have to unplug and try again. Support was less than helpful last time and it randomly fixed itself. Hoping for the same, but the emailing back and forth gets me nowhere ....at least not quickly

Re: I’ve been cheating....my smart trainer [maukiwauw] [ In reply to ]

Mar 20, 18 10:03

Post #22 of 26 (4604 views)

I find it hard to believe the few users on here complaining have more experience than DC rainmaker, hes recommended this the last 3 years. I have this trainer, and bought directly as a result of his review. Its worked great now that I have the calibration right, my uphills short on watts but can live with that. I think you have not calibrated it right. I also use the trainer tire.

Annual Winter 2017-2018 Bike Trainer Recommendations
OCTOBER 11, 2017 by DC RAINMAKER|TRAINERS|COMMENTS (321)

MID-RANGE TRAINERS ($500-$600):

While this is a thin price bracket, it mostly captures the entire mid-range market. And to be perfectly clear: They’re all about the same. There are minor nuances between these trainers, for which you’ll want to look at closely depending on your needs. Specifically, look carefully at these four areas:

A) Maximum incline
B) Maximum wattage
C) Which protocols/standards/types they transmit on (i.e., power, but not cadence, etc…)
D) Flywheel weight

That’s about the only real tangible differences between them. They all have about the same road feel (and each company will tell you their road feel is better). They all have ANT+ FE-C, and they all work with Zwift and TrainerRoad. Seriously, it’s mostly a wash.
With that in mind, here are your five basic options:
Wahoo KICKR SNAP – $599
CycleOps Magnus – $599
Elite Rampa – $549
Tacx Vortex Smart – $529

https://www.dcrainmaker.com/...recommendations.html

maukiwauw wrote:

Tacx Vortex is a piece of shit. I used one for a while and it added +50 watts compared to the powertap. Then it bricked on me. Turned into a $500 door stop.

Re: I’ve been cheating....my smart trainer [CP78] [ In reply to ]

Mar 20, 18 10:10

Post #23 of 26 (4586 views)

I've never cared if mine was calibrated since I use the power from my P1 pedals. But the connectivity issues I've had twice are really starting to annoy me. Does anyone have a Tacx number for customer service. All I can find is email addresses, and it's a pain going back and forth.

Re: I’ve been cheating....my smart trainer [CP78] [ In reply to ]

Mar 20, 18 12:02

Post #24 of 26 (4509 views)

CP78 wrote:

I find it hard to believe the few users on here complaining have more experience than DC rainmaker, hes recommended this the last 3 years. I have this trainer, and bought directly as a result of his review. Its worked great now that I have the calibration right, my uphills short on watts but can live with that. I think you have not calibrated it right. I also use the trainer tire.

maukiwauw wrote:

Tacx Vortex is a piece of shit. I used one for a while and it added +50 watts compared to the powertap. Then it bricked on me. Turned into a $500 door stop.

I don't disagree with others who haven't had the same problem and come to a different conclusion. My statement is a fact from my n=1 and I would never recommend the product. If Tacx has variability in their product output that varies wildly (as evidenced by my trainer) then it's not worth buying IMO and people should know this is a possibility.

I have race results on zwiftpower showing 5+w/kg before I figured out the Tacx was grossly overestimating (turns out I'm not the next Froome...). Also agreed calibration is important but I assure you that was evaluated. Also Tacx's customer service is non existant- either for the overestimate of power or for the unit bricking out.

---------------------------------------------
Of course it hurts. The trick is not minding it hurts.

Re: I’ve been cheating....my smart trainer [maukiwauw] [ In reply to ]

Mar 20, 18 12:19

Post #25 of 26 (4486 views)

Interesting, did you use Tacx blue tire? All my problems were fixed with that, I dont see anyone who complained saying they used that.

Or maybe DC rainmaker and I just got the better model.

Edit: Mines also only 3 weeks old so still possible it will brick. Yours under warranty and no response?

Last edited by: CP78: Mar 20, 18 12:24

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