Tacx Flow ERG Mode - Sufferfest issue or Tacx?

supermurph09

Hi

A few years ago a friend told me he never calibrated his Tacx Flow Smart, I found this odd because if I didn't calibrate mine the feel of it was horrible, it wasn't smooth like when it was calibrated.

Recently I have started with Sufferfest again, the first few videos I did the ERG mode was fine, not perfect but in general it was pretty smooth. The last few videos I have done the motion on the trainer is really "lumpy", like if it wasn't calibrated (it is) as if it cant quite decide the resistance needed, so it kind of grabs and jumps. It's not horrendous, but it's not right. I need to check 100% that there is nothing external causing slippage, but I always use the same tyre pressure, its calibrated in the middle of tight and loose.

Do people think this could be Sufferfest related or more likely an ERG mode issue? It's making the session briefs not quite accurate as I'm sometimes having to use a much higher cadence or putting out more power (reading my powermeter) to what is being reflected onscreen.

thoughts welcomed.

Dave_P1

It sounds more trainer related to me.

supermurph09

Dave_P1 wrote:

It sounds more trainer related to me.

After last nights session I am inclined to agree. Basically when in ERG mode the trainer is not smooth, it makes pedaling even lower powers harder than they should be.

Half way through a sufferfest session I switched the ERG off and put it on level 3 and this made things much better. It was far smoother and my power delivery was matched to the effort but not having ERG mode hampers things somewhat.

One things I do notice as well is when I first start my session, on screen the cadence required is 90 and 146W, if I spin up to 90 I am actually doing over 200W when looking at my Garmin, things settle down and get closer but to start with it is way off.

Comparing power outputs, my Garmin showed an average 298W for 20 minutes, the Sufferfest session with the power coming from my Tacx was 304W. Not a huge difference there but the shorter efforts including sprints are way out, 5s power particularly, Tacx showing around 490W, Garmin 650W, the latter being correct.

Not really sure what to do as it will be out of warranty period.

stevie63

I imagine the problem is that you are operating in a gear that is out of the trainers optimum range. Shane Miller has posted a few videos on this type of issue on Youtube. Basically at a given roller speed the trainer can only operate within a range of powers. So for example at 20 mph it could be for example 200 to 450 watts. Then if your power needs to be below 200 then it can't lower the resistance enough for you to hit the required power and if it needs to be over 450 then it can't increase it enough (these are just hypothetical numbers but it should give you an idea).

The solution for this issue is quite simple though, just change gear-down for lower numbers and up for higher ones. This issue is less of a problem for more expensive trainers as they can increase the resistance over a bigger range.

supermurph09

stevie63 wrote:

I imagine the problem is that you are operating in a gear that is out of the trainers optimum range. Shane Miller has posted a few videos on this type of issue on Youtube. Basically at a given roller speed the trainer can only operate within a range of powers. So for example at 20 mph it could be for example 200 to 450 watts. Then if your power needs to be below 200 then it can't lower the resistance enough for you to hit the required power and if it needs to be over 450 then it can't increase it enough (these are just hypothetical numbers but it should give you an idea).

The solution for this issue is quite simple though, just change gear-down for lower numbers and up for higher ones. This issue is less of a problem for more expensive trainers as they can increase the resistance over a bigger range.

Thanks for this, does changing gear mean that you may as well just turn the ERG mode off though and opt for a level number instead? I was under the impression that constantly changing gear in ERG mode would confuse the trainer.

I think some experimentation might be needed.

stevie63

Supermurph09 wrote:

stevie63 wrote:

I imagine the problem is that you are operating in a gear that is out of the trainers optimum range. Shane Miller has posted a few videos on this type of issue on Youtube. Basically at a given roller speed the trainer can only operate within a range of powers. So for example at 20 mph it could be for example 200 to 450 watts. Then if your power needs to be below 200 then it can't lower the resistance enough for you to hit the required power and if it needs to be over 450 then it can't increase it enough (these are just hypothetical numbers but it should give you an idea).

The solution for this issue is quite simple though, just change gear-down for lower numbers and up for higher ones. This issue is less of a problem for more expensive trainers as they can increase the resistance over a bigger range.

Thanks for this, does changing gear mean that you may as well just turn the ERG mode off though and opt for a level number instead? I was under the impression that constantly changing gear in ERG mode would confuse the trainer.

I think some experimentation might be needed.

TBH I think you only really need to change down to a lower gear when doing the recovery portions of the workout, for all the stuff around threshold, VO2 and AC you should be able to keep it in the same gear. It is definitely worth trying a particular set wattage out in different gears to see which is most efficient. BTW how are you finding The Sufferfest stuff compared to training you have done in the past?

wongataa

Supermurph09 wrote:

Thanks for this, does changing gear mean that you may as well just turn the ERG mode off though and opt for a level number instead? I was under the impression that constantly changing gear in ERG mode would confuse the trainer.

I think some experimentation might be needed.

If you need to change gear to be in a wattage window the trainer can do then you will need to. If these needs to be done you are unlikely to be continuously changing gear. If you change gear in erg mode the trainer will be a little confused at first but it will sort itself out after a few seconds as it realises the power it is recording doesn't match its target and it will adjust.

Dave_P1

There's no need to change gear in ERG mode

supermurph09

Some conflicting opinions, I guess this is good and bad. As I say I will have to try and experiment, my feeling is that my trainer is not quite working correctly.

How am I finding the Sufferfest from what I have done before? Pretty good, I've done a lot of structured stuff before but I find that a mix of Sufferfest and club rides is a good balance for me. I really like the new videos and app, I'm confident that my performance will be grow over winter.

stevie63

Dave_P1 wrote:

There's no need to change gear in ERG mode

In an ideal world that would be true, but all smart trainers have a range that they can operate when the roller is spinning at a particular speed. For example on the following review of the Vortex smart(similar to OP trainer) it said the following:

"You can look at the image above and we have power graphed against wheel speed. You will not be able to go down below your (red line) baseline mag resistance. Resistance can be added above your baseline resistance through the use of the electromagnets, but we cannot go below. The only way to reduce resistance is to lower wheel speed. This means the TACX Vortex Smart may require some shifting to stay on target. I used the warmup video “Ignitor” from the Sufferfest Training Centre to test this theory out. As you can see from the power profile below, at a 28 mph wheel speed I was above my target power. This was in ERG mode. I needed to shift up a few gears so I could stay on my ERG target."

Link to review page:
http://athletictechreview.com/2016/12/05/tacx-vortex-smart-review-part-2-spin-down/

You'll see in the chart of the page that at 30 km/h that the roller can operate within a 190 to 410 watt range. So if you suddenly needed to recover at 90 rpm when in a gear that had you doing 350 watts at 90 rpm the resistance couldn't drop low enough for this so you would have to change gear. This issue doesn't effect trainers like the Neo and Kickr so if you have one of them then great stick in a gear and ride (though a recent video on youtube showed that the flywheel speed does effect the way you pedal-slower flywheel speed means you need to more power at the top of the stroke.)

supermurph09

stevie63 wrote:

Dave_P1 wrote:

There's no need to change gear in ERG mode

In an ideal world that would be true, but all smart trainers have a range that they can operate when the roller is spinning at a particular speed. For example on the following review of the Vortex smart(similar to OP trainer) it said the following:

"You can look at the image above and we have power graphed against wheel speed. You will not be able to go down below your (red line) baseline mag resistance. Resistance can be added above your baseline resistance through the use of the electromagnets, but we cannot go below. The only way to reduce resistance is to lower wheel speed. This means the TACX Vortex Smart may require some shifting to stay on target. I used the warmup video “Ignitor” from the Sufferfest Training Centre to test this theory out. As you can see from the power profile below, at a 28 mph wheel speed I was above my target power. This was in ERG mode. I needed to shift up a few gears so I could stay on my ERG target."

Link to review page:
http://athletictechreview.com/2016/12/05/tacx-vortex-smart-review-part-2-spin-down/

You'll see in the chart of the page that at 30 km/h that the roller can operate within a 190 to 410 watt range. So if you suddenly needed to recover at 90 rpm when in a gear that had you doing 350 watts at 90 rpm the resistance couldn't drop low enough for this so you would have to change gear. This issue doesn't effect trainers like the Neo and Kickr so if you have one of them then great stick in a gear and ride (though a recent video on youtube showed that the flywheel speed does effect the way you pedal-slower flywheel speed means you need to more power at the top of the stroke.)

Thanks for this, I was actually using Ignitor (and Stages PM) too so makes the link even more apt.

Having read through it, I'll start by warming up for 5 minutes first and ensure that each time the pressure is the same and the calibration line is in the same place.

EBEB

I have a Tacx Bushido with a ‘virtual flywheel’; does the flow also have one? The Bushido has no wire and is meant to be a bit more portable so maybe it is an odd one.

The thing that hasn’t been mentioned (& may not be relevant if there is no virtual flywheel) is that the machine can make a mistake in simulating a flywheel and it can feel jerky when it happens. I find it only happens about once an hour (&then I’m isolation), but when I used to cycle with a low cadence between intervals it was more common.

Personally for Sufferfest I don’t bother with erg mode. With no power match I found having two FTPs annoying even though they were only 12W apart.