Turbo confusion

itboffin · May 2019

I'm totally confused by my Tacx Vortex ERG mode when not using Zwift, Trainerroad or the likes i.e. just using it as a semi smart resistance trainer.

I've been using cadence, HR & power data with my gears, which means speed is artificially high not that that's important anyway, I'm thinking now should i use the app with ERG enabled and let the software dictate the session and if I go down that route is it true people use the 34T and middle of the cassette?

The few Tacx official workouts I've done always felt way too unrealistic, if the above is right then me attempting to ride Alpine virtual stages in the 50T (as you would on a manual trainer) makes a lot more sense.

:oops:

dhope · May 2019

itboffin wrote:

should i use the app with ERG enabled and let the software dictate the session and if I go down that route is it true people use the 34T and middle of the cassette?

Yeah. My Kickr sits in the small ring and middle of the cassette on ERG mode and I let the software sort out the resistance. Happily works anywhere from 100W to 1000W.
It's happier at 1000W than I am to be fair.

N0bodyOfTheGoat · May 2019

In my experience, yes. In ERG mode, each gear on the bike has a power range where the turbo can dictate the power, depending upon the cadence. For example, 34/18 on my Direto gives an ERG range of approx 84-484W, providing my cadence is somewhere in the 70-95rpm ballpark.

I did a Zwift ramp test a few months back where I somehow managed to keep pedalling, despite my cadence dropping to ~50rpm as I got near the 400W interval. ERG was only able to provide ~325W of resistance at this cadence.

itboffin · May 2019

Thanks for the clarification, I'm yet to find anything that clearly states gear setup when not using ride simulation software, i guess its time for some trial and error

chris_bass · May 2019

I think it varies trainer to trainer, so like you say probably a bit trial and error - i find that little ring is needed for low wattages (anything below 150 or so) but big rind works a bit better above that - i tend to put it in the little ring for warm ups then switch to the big ring and leave it there. Except for the neo, it can handle low wattages in any gearing

not used the same trainer as you have though so just play around with it.

itboffin · May 2019

Thing is if i use the 50T and the full cassette range i can get 80W to +600 for a few seconds due to me not the turbo, but thats in resistance setup.

Should i even bother with ERG sessions as I've built my own set of workouts from way back when i started on my mag trainer, bloody technology what next phones without cords ...

chris_bass · May 2019

I use erg mode and quite like it - it helps if you want to work on cadence or hold a particular watt or something.

I guess only you will know - it seems like you have it all set up to give it a go so maybe try it and see what you think.

try different gearing and see which works best.

itboffin · May 2019

Turns out by using the 34T and the middle-ish of the cassette while riding an ERG workout does work with the Tacx, if you dont mind pedalling about 100rpm, which i'm not a huge fan of but anyway, i'll persevere and try a few more sessions of differing power / cadence

itboffin · June 2019

Right then another Tacx specific weirdness, they have Zwift style virtual rides for instance Central Park, which i've ridden 4-5 times now but today I tried with the turbo setup in the 34T and as you might expect for that gearing I was spinning like a loon and doing 13-15 MPH with power well below 100W

So what setup do you need for Tacx virtual rides?

Naturally with the Garmin takeover Tacx support forum has vanished for the net.

itboffin · June 2019

before I box up my Tacx unit for a warranty return has anyone else had a similar issue, if I drop my cadence the power drops as expected but then I can not resume as the brake resistant is too hard, i’ve double check the calibration every time I use the unit.

Is this an issue with the brake or my selected fixed power (200W) workout, it almost seems like once started any significant change in cadence will cause the brake resistant to increase to meet the configured power but doesnt pick up the increased cadence and back off the brake accordingly, i managed to get cadence back to 85RPM but power stuck around 70W, all that happens is my tyre starts falling apart and a lovely burning rubber smell.

https://blog.tacx.com/tips-for-training-in-erg-mode/

jspash · June 2019

itboffin wrote:

before I box up my Tacx unit for a warranty return has anyone else had a similar issue, if I drop my cadence the power drops as expected but then I can not resume as the brake resistant is too hard, i’ve double check the calibration every time I use the unit.

Is this an issue with the brake or my selected fixed power (200W) workout, it almost seems like once started any significant change in cadence will cause the brake resistant to increase to meet the configured power but doesnt pick up the increased cadence and back off the brake accordingly, i managed to get cadence back to 85RPM but power stuck around 70W, all that happens is my tyre starts falling apart and a lovely burning rubber smell.

https://blog.tacx.com/tips-for-training-in-erg-mode/

I don't have a definitive answer for you but I have experienced the same and it just seems to sort itself out over time. My entirely non-scientific theory is that it needs to warm up a bit like an old car. My trainer is in the shed out back and paranoia prevents me from keeping it plugged in to the mains. So each workout begins with me plugging it in, struggling with the bluetooth connection for 10 minutes, calibrating, then finally riding. For the first 10 minutes or so I'll experience the "pedalling in quicksand" effect about 50% of the time. But... if I happen to leave the trainer plugged in overnight, the next time it works perfectly.

itboffin · June 2019

i think what is happening is by design but there's a flaw in the power application once cadence drops, I think what should happen is if cadence drops off suddenly due to a dropout or on purpose then the ERG should auto disable for a few seconds or at least significantly reduce enough that you can actually get back up to speed without chewing up an entire tyre in the process.

Just imagine the real world equiv. of stopping out on the road (in the wrong gear) you start back up and its very hard to get going, either you just press on or you drop a few gears and spin back up, that wouldnt be possible is say your power meter had control of the brakes and jammed them on whilst you attempt to get going again.

ERG needs to emulate this situation, otherwise what happens if you need to adjust your fan or music settings etc. the workout is effectively over.

N0bodyOfTheGoat · June 2019

If you're in ERG mode being expected to produce say 400 Watts and for whatever reason your cadence drops from say 90rpm to below 70rpm, you enter the what I think of as the "spiral of death." To try and get your cadence back up towards 90rpm will take a massive effort.

Every time I've done the Zwift ramp test since its release this year when I've tried to push myself to the limit, my cadence gets lower and lower. Only once did I finish all the intervals, but because my cadence had dropped to ~50rpm, ERG on my Direto was unable to give anything like 600W of resistance at that cadence. ERG only works within a certain power range in each gear within a certain cadence range, 34/18 is something like 84-484W on the Direto, providing you pedal at a cadence in the approx 70-95rpm ballpark.

itboffin · June 2019

Yeah i can get the CAD back to where it needs to be but the power and resistant stays put, my blue indoor tyres is now square and starting to split, I guess that's not helping.

Turbo confusion

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