Elite Direto (not Direto X) ERG & Big Ring Nearly Impossible

[CaptainThunderpants]

So this is aimed at mostly Elite Direto owners, but anybody can chime in. I’ve done some workouts recently using both the big ring (50t) and the little ring (34t), and noticed intervals in the big ring are terrible, oscillating wildly making it nearly impossible to complete near the prescribed power target. So much so that SS/Threshold intervals often go way over FTP. Here’s the workouts.

This is Carson +2 (5-7 min SS) in the small ring.

Same workout (Carson +2) in the big ring. You can see how many times it goes over FTP, making this SS workout into a supra-threshold workout.

Bluebell +1 (1min on/1 min off) in small ring.

Bluebell +1 in big ring, then small ring.

Antelope (10min SS) in small ring, then started the second interval in the big ring before having to downshift.

Same interval, zoomed in on big ring portion.

To be honest, I don’t really mind doing workouts in the small ring, and that’s what I’ve been doing. But just curious if this is a widespread problem of Diretos or just my unit.

[Turnier]

Mine does same.

[ValeCyclist]

Mmm, initially I’m thinking thise traces don’t seem tooooo bad, I have an Elite Zumo and the traces I see from that aren’t hugely different tbh. I see your cadence is pretty high so it rules out any chance of the trainer ‘hunting’ to stay on track.

Have you been doing spindown checks through the Elite app? I had mine new in November and have been doing them monthly. I sent the figures to Elite just to see what they made of them and they just commented that you don’t really need to keep doing the spindown and they only ask for the value during fault diagnosis. The number is in milliseconds by the way, I didn’t know this until they told me.

[bbarrera]

My own experience on a Kickr and training outside - use the big ring on trainer, work on your pedal stroke / pedal economy, and you’ll benefit out on the road.

Also, FWIW, do you want to train to be a robot? Cycling is a sport where power fluctuates. Your body doesn’t respect strict power zones. Embrace the power fluctuations on a trainer. Erg is a just a tool and it’s easy to get caught in the trap of thinking flat power lines lead to superior adaptations.

[Stringwise]

I do 100% of my training rides in TR in ERG mode on the Direto big ring only (other than ramp/FTP tests and Z racing). The only spikes like that I get are when I stand and drop the cadence, otherwise I can pretty much keep it pinned on the prescribed wattage.

[Stringwise]

@bbarrera

use the big ring on trainer, work on your pedal stroke / pedal economy

@bbarrera makes a good point. I went through my workouts and I knew I had one where I blew up and in the notes I wrote I was “pedaling squares” by the end of the the interval.

Pretty big difference between the beginning and end of this interval in terms of tracing. Maybe you can improve your stroke economy? I’m no expert but perhaps there is information there to think about.

[bbarrera]

@Stringwise

Maybe you can improve your stroke economy?

I did. You can either see it as a reason to use the small ring (easy way to get straight lines in power graph), or as an opportunity to work on your pedal stroke in the big ring.

[dcrainmaker]

This will happen on every trainer, to varying degrees. In short, the faster the speed, the more variability of the trainer’s ability to hold a set point/control. Reduce the speed, and the trainer has more control.

In fact, it’s why when you first pair a trainer, TrainerRoad shows this screen (note the last bullet point):

[loxx0050]

Direto user here and it’s the same for me on big vs small ring. Big ring is easier at first to maintain a higher power…until cadence/power delivery/focus starts to waver. Then the oscillating target power waves make it so much harder to finish an interval or make it so I have to take an extra break or reduce intensity. I noticed it’s easier to avoid this in the small ring so now I mostly do my sets in the middle 3 cogs of the cassette (with an 11s). One workout that was 3x20 threshold I gave up erg partway through the 2nd set and put it to resistance mode instead. Just couldn’t handle the power swings into the V02 max and above territory then down to tempo and back up again.

I also didn’t perform a spin down calibration for a couple of years because I use powermatch. The offset in reported power appeared to be close to 30w difference this year (Direto being higher) thank my crank based power meter. I decided last month to finally do a spin down and the values were right on target to when I first got it (but still a bit lower than the factory number written on the bottom sticker of the trainer).

Now it seems the power match doesn’t fluctuate as much during high SS/threshold/over-under sets as it used to when I start to get tired and can’t keep a steady pedaling effort. Or basically starting to pedal squares like another has mentioned. It will still fluctuate but while before I’d see +/- 20% swings over target power to more like +/- 10-15% or so. I haven’t tracked it exactly but it appears much less a amplitude.

[Brennus]

I have a Direto and don’t notice power swings that big. Also, haven’t ever done an erg workout 53-11…or 52-11 or 50-11. I usually pick a gear combination that gives me a good chainline.

TR’s recommendation would probably be to select your smallest chainring in the front & whatever gives you a good chainline in the back. From the data you’re presenting here seems like that might be your best bet, too.

[Power13]

When I had my Direto, I never had any issues like those noted…ran a 52xmiddle cog for my ERG workouts. Now, the Direto would let me go over the prescribed wattage if I wanted to, but I didn’t really have any huge power swings.

My replacement Direto X has been more consistent about keeping my power in check with the prescribed wattage. I can ride over the prescribed wattage on recovery intervals, but not so much on work intervals anymore.

[oldcrank]

My only smart trainer experience is with my Direto, bought in 2017. (Together with a 4iiii left only PM).

@loxx0050

oscillating target power waves make it so much harder

Yes, sometimes my experience as well with Power Match in Erg. Thanks for the description, because it clarifies that it’s not just the quick jaggies vibrating pretty evenly around an even center (flattened completely by Kickr’s default), nor the big spikes from shifting, standing, etc. It’s waves with a frequency of 10-30 seconds where the jaggy line consistently averages 10-30 watts above or below the target – even though cadence is “smooth”, at least within 1 or 2 rpms of the center for same period. And yes, it does interfere with the workout by increasing “cognitive load” (our new buzzword). My frontal lobe weighs the evidence and blames it on the interplay of gadgetry, as does TR support. My lizard brain if I’m tired says “Uh oh, REACT!” and I do, trying to fix it, which often compounds the problem.

Like you, I find spin down calibration of the Direto has always been consistently very close to the factory value, and enough of a PITA for various reasons that I do one only as a last resort – that has never shed any light.

And like you, I also find the left-crank PM 10-30 watts different from Direto, as repeatedly verified on @dcrainmaker 's comparison tool. However in my case the Direto reports consistently lower values than the 4iiii. Leg strength difference? Plausible, except that I know from stuff like lunges that my left leg is weaker, not stronger, which should make the 4iiii calculate lower not higher combined power.

Finally, like you, I find the more recent Power Match more usable than the old one (when I first got the Direto). That was bad enough that I just turned it off. These days the problem seems vexatiously intermittent – like the engine noise that wakes up the neighbors but disappears as soon as you get within a mile of the shop.

Another complication: I spend a lot more of my time below 200w than most people (and other Direto users) here – and remember reports saying the Direto got dicey at the low end. If so, maybe part of problem.

And two last ones: This is actually my second 4iiii left only. The first packed up after 2 1/2 good years, and Precision sent me another. It also reads about the same amount higher than the Direto! Since the 4iiii can be tweaked, a dilemma has been whether to turn it down to match the Direto, or let Power Match sort it out. Another question is whether the difference between the Direto and 4iiii is not constant, but changes at different powers – for instance, as I go from 120 watts to 220 watts. If it does, that would seem to put the whole feedback loop into some possibly weird gyrations. Is that where the “waves” come from? I don’t know. Obviously.

[Stringwise]

@dcrainmaker

In fact, it’s why when you first pair a trainer, TrainerRoad shows this screen (note the last bullet point):

That’s not the issue though is it? It isn’t an interval that requires responsive resistance changes like an O/U interval. For intervals that require the trainer to adjust power frequently, sure, what you say makes sense.

[OreoCookie]

@Stringwise
It actually is. At higher flywheel speeds (which comes with choosing a higher gear) making resistance changes is much more difficult as small changes in rotational speed with result in larger changes in the rotational energy. Power is energy divided by time, so if you ask the trainer to hold a certain power, this is more easily done accurately at lower flywheel speeds, which amounts to smaller gearing.

@oldcrank

If it does, that would seem to put the whole feedback loop into some possibly weird gyrations. Is that where the “waves” come from? I don’t know. Obviously.

The “waves” are caused by the electronics trying to adjust the power levels, periodically over- and undershooting. If you have a dumb trainer, you also likely see similar patterns when you work out. Most power meters usually report their readings only once a second, and most of the time you add 3- or 5-second smoothing on top of it. So if your power is too low, you have a tendency to overshoot to get the average where it needs to be, but that means your current power is already above the target. A few seconds later that is reflected by the average, you let off a little — but probably too much. And the downwards cycle starts. With practice you get a feel for what 300 W feels like and you will overshoot less.

Smart trainers do the same thing, but are evidently much better than humans. Still, the same principles apply.

[Stringwise]

@OreoCookie

It actually is. At higher flywheel speeds (which comes with choosing a higher gear) making resistance changes is much more difficult as small changes in rotational speed with result in larger changes in the rotational energy. Power is energy divided by time, so if you ask the trainer to hold a certain power, this is more easily done accurately at lower flywheel speeds, which amounts to smaller gearing.

All true and fair point. But if you could pedal at a steady 300 watts the trainer wouldn’t be doing much to adjust to your steady power. That is more the point I was making. Since some seem to have a more challenging time holding steady power than others there is a user component that obviously matters but everyone is quick to point to the trainer. So if you can hold power steady then big ring isn’t likely as much of an issue relative to someone that naturally delivers power with more spiky output.

[OreoCookie]

Here is the problems as best as I understand it: the difference is that it is more difficult to regulate power accurately when the flywheel spins more quickly. Let me assume that your trainer uses electromagnets to generate resistance, and this is done by moving magnets closer to or farther away from the flywheel. Braking force is usually applied in discrete (digital) steps, so you only have a limited amount of accuracy. What is regulated by stepper motors is the distance between the flywheel and external magnets.

At higher flywheel speeds you need smaller steps to achieve the same level of accuracy in the applied braking force to produce the same resistance. That is because the flywheel energy to leading order is quadratic in the flywheel speed. At lower flywheel speeds, you inherently have more accuracy. Think of it this way: at high flywheel speeds, the trainer has to pick between 290 W, 300 W and 310 W as discrete power levels, whereas at lower flywheel speeds, it can do 290 W, 292 W, 294 W, etc. This is a bit of an exaggeration, of course, but I think it accurately brings the point across.

The second difficulty is how often you measure power. On-bike power meters give you one measurement per second. Some power meters (e. g. by Rotor or SRM) have special modes that allow for more frequent power measurements. Rotor uses it to determine your pedaling smoothness and to recommend settings for its oval chain rings. I don’t know how often the built-in power meters of trainers measure power, though. But the lag is an inherent problem. Humans don’t apply power very evenly, so you need to smoothen the power data. This is why for most intents and purposes, having 1 measurement per second is sufficient. Smoothing introduces lag, which makes applying resistance difficult. This is an old engineering problem. If you just go by current data plus the trend (i. e. the slope/derivative), you can easily induce oscillations. So you need to average (integrate) and add some more smarts. This works way worse if you have less discrete levels of braking that you can apply. Roughly speaking, these are the two main issues as I understand it. (I’m a physicist, not an engineer, so if anyone more knowledgable can chime in, please do.)

That is why TrainerRoad recommends you use your small chain ring for Erg mode. However, there are cases when you may want to use the big chain ring nevertheless, and that has to do with trainer feel. A faster flywheel will feel more like riding fast on the road, a slower spinning flywheel will replicate the feeling of climbing. So with a slower flywheel, if you let off the power, the flywheel will spin down more quickly, which is similar to you slowing down very quickly when you stop pedaling on a climb. On the flats at high speed, you can coast for quite a bit longer without significantly slowing down.

PS Let me add that trainers should get better and should be able to handle you being in the big ring better. On the other hand, all technology comes with inherent limitations, and once you know them, it is usually smarter to work within them.

[bbarrera]

@OreoCookie

Here is the problems as best as I understand it: the difference is that it is more difficult to regulate power accurately when the flywheel spins more quickly.

Yes. Either accept and train to improve riding on the flats, or gear down to small ring and engage muscles earlier to better simulate climbing. High gear and raise front end? Maybe best of both worlds? IDK.

[ValeCyclist]

I do pretty much everything indoors on the big ring (54) and seem to have pretty smooth traces, mind you, since I bought the trainer I haven’t followed any training plan so haven’t done consistent hard workouts like over unders. Warm ups I tend to do on the 39 though.
Think I’ll do today’s session on little ring and see how it goes.

[CaptainThunderpants]

@bbarrera

Also, FWIW, do you want to train to be a robot? Cycling is a sport where power fluctuates. Your body doesn’t respect strict power zones. Embrace the power fluctuations on a trainer. Erg is a just a tool and it’s easy to get caught in the trap of thinking flat power lines lead to superior adaptations.

I get that, but that’s not really the root of the problem. It’s not that I want a flat tracing, it’s more that it’s changing the workout. I’ve done outside workouts on flat roads and get closer to power targets, maybe +/- 10-15W with occasional spikes of 30W. But on the trainer, I’l get spikes of 100-130W over the target, and I can definitely fell them. When the entire interval is either 40W under or 40W over the target, it’s not really a sweet spot workout anymore. So, in order of hitting power targets closest, it’s trainer in small ring, outside workouts, trainer in big ring.

@Brennus

TR’s recommendation would probably be to select your smallest chainring in the front & whatever gives you a good chainline in the back. From the data you’re presenting here seems like that might be your best bet, too.

Yea, I think I’m just going to stick with that to get the most productive workout.

@oldcrank

Yes, sometimes my experience as well with Power Match in Erg. Thanks for the description, because it clarifies that it’s not just the quick jaggies vibrating pretty evenly around an even center (flattened completely by Kickr’s default), nor the big spikes from shifting, standing, etc. It’s waves with a frequency of 10-30 seconds where the jaggy line consistently averages 10-30 watts above or below the target – even though cadence is “smooth”, at least within 1 or 2 rpms of the center for same period.

I am using power match with Assioma pedals. May be part of the issue. And this is exactly the issue for me. I can maintain a steady cadence and have gotten to the point where I can feel the power pretty well, and do outside workouts just fine. But it’s not even the same workout in the big ring, it’s just a constant oscillation above and below the target.

[OreoCookie]

@bbarrera

Cycling is a sport where power fluctuates.

Yes, but you benefit from becoming smoother. Especially if you are close — especially above — your FTP, those spikes will not just hurt, they may prevent you from finishing the intervals. I have a dumb trainer, so I’m responsible for all spikes. And I have learnt this the hard way. Especially once I am between FTP and VO2max, overshooting your port target by 10-15 W can significantly increase RPE and make it much, much more difficult to finish your workouts as prescribed.