I read that under the “device recommendations” after selecting the smart trainer from the “devices” menu. Here’s what they (Trainer Road) say about it under the “Gear Selection” section.
Using a lower gear in ERG mode tends to allow for more responsive resistance changes. We recommend putting your chain in the smaller front chainring (middle chainring if you have three), and shifting into the middle of your cassette. This will allow for a quieter experience with minimal stress on your chain.
Sounds like riding a single speed/fixie to me. 
Just way less fun.
My understanding (mainly from the podcast) is that consistency is the most important thing with training with Power, rather than accuracy. fwiw I also had a similar drop off going from Virtual Power to a power meter.
The testing I did had the virtual power consistent, but it’s accuracy (compared to a power meter) wasn’t the same at all watts. Higher up the power curve, it was less accurate, but seemed to be consistently less accurate.
I subsequently upgraded to a Hammer, and I found that accurate compared to my single sided 4iii crank power meter. I can’t say I’ve found workouts harder, but maybe that was going virtual power → power meter → erg mode.
One thing I was aware of was that I was generally overshooting power targest on a dumb trainer, which doesn’t happen with ERG mode, so again that maybe a factor in not really noticing it being harder.
I just switched from a KK Road machine to a Core too. There is a huge difference in inertia between the two and you also have a ton of “adjustability” in the inertia based on what gear you are in. My guess is that is what you are experiencing. You’ve moved from a device with a 6 lbs fly wheel to a 12 lbs fly wheel plus the Core lets you pedal at any cadence you want in any gear you want while holding the power the same meaning you can experience wildly different inertia at the same power out put. The Road Machine had a basically fixed ratio of power to fly wheel speed.
Play with your gear selection and you will be able to adjust the feel. For me, the Core feels much easier at the same power but I can make it harder at the same power if I shift. On my Road Machine, I often felt like i was pedaling through mud. The Core lets me spin and to me feels very roadlike.
On the riser - I thought I read you needed one so used one for the first week then measured the front and rear hub heights. Turns out a road bike does sit level without a riser.
You might want to check your power match settings. TR by default uses the power meter for power readings, then tries to match the KICKR power setting so your Quarq power and KICKR power match. I’ve found that using the KICKRs “Use ANT+ Power” setting gives me better results. I’ve had cases where my power meter (Assioma) is showing power 30W higher than what the KICKR SNAP was reporting. I imagine that would be less on a wheel-off trainer, but it could still be there. I still have power match going with ERG mode, but having them both seems to work even better. YMMV.
I’m sure there are a lot of technical, logical answers to this question – and many of them have been outlined in this thread. But to me it all boils down to one unassailable truth:
ERG mode is a pitiless bitch
Yeah, it penalizes you for drops in cadence that lead to the spiral of death. This issue is often misunderstood and the most common complaint that I see with people getting their first controlled trainer.
You HAVE to keep that cadence steady and preferably in a higher range, to keep from getting bogged down. Once people learn that fact and how they can actually control it, life is at least understood… even if it’s cruel in the unrelenting nature of the mode. It works perfectly as intended.
Exactly. ERG mode is like a Chicago winter…once you’ve adjusted to the cold and the snow and you think you’ve settled in a period of chilled misery. That’s when the wind starts to blow.
I routinely practice at cadences down to 55-65 range, seated and standing, all in ERG. It’s possible, but you REALLY have to stay alert and on top of the gearing. If you slip a bit, it will bite you hard.
I’ve noticed that it wants you to hold it right at a number. I see a normal range of like 91-96 when spinning my legs, trying to do that roadie thing more, and it still fluctuates. Biggest thing I’m starting to realize/get use to is that I won’t always be at the exact number I’m supposed to be at. On the road machine I could hold within 3 watts but on the smart trainer I’m seeing watts dip down upwards of 20 while it’s adjusting to an random slow down of my cadence.
That variability in ERG is the price we pay in order to have something you DON’T have to think about.
It’s possible to be more precise on a manual control with shifting and cadence control. BUT you have to pay attention in order to do that. Start daydreaming and you will commonly return to seeing your numbers are off. This is one way some people train, in order to make the time on the bike less boring, since they need to be in the moment more.
Both methods are great and can be used in various ways to best suit the needs of each rider.
I’m 5 yrs older and am now training with cadence 90-95. Outside rides I drop back to 85-90, except on climbs where it drops lower.
Sometimes on my Kickr its not a problem pushing at 85rpm. Other times, when legs are tired, it is definitely a problem. At least with sweet spot intervals its never felt like a death spiral, just feels like I’m pushing up a 2-3% grade with tired legs.
In my experience it isn’t that having a low cadence makes erg mode unsustainable or that having a high cadence makes erg mode easy - it is that decreases in your cadence hurt on erg mode.
That is to say - if you go from 85 cadence to 80 over the course of a few seconds or minutes - you’re down into the death spiral. If, however, you’re happily spinning at 85 and never changing it - erg mode will work fine for you.
The opposite is also true - going from 85 to 90 or 95 within a few seconds or minutes you get a little bit of a break (but then have to watch out for the pain of dropping back to 85).
I try to hold very consistent cadences with the one notable exception being in the 10 seconds prior to a sudden jump in power. This is almost second nature to me now - but last night I was going from 143 watts to 365 watts to do my threshold intervals and before every one I would spin up from 90-95 recovery cadence to 100-105 and then settle in at 95-98 for the duration of the interval. This feels like it makes the 220 watt jump a little smoother and more survivable for me
Thanks. That sounds like a great tip.
Oh, that reminds me…it’s Mary Austin this morning.
On my dumb trainer. 
Thread necromancy, check!
So i just tried non-erg mode for the first time ever and gosh it felt so easy. holding within 5-10 watts, im just not smooth yet.
And it was so hard to get in low enough gearing for the recovery sets.
But i’m doing this because i have a Gendarme coming up next week and the erg mode on my wheel-on trainer won’t cut it. I wonder if other than these short interval workouts, i should just stick to erg mode for now to get more effort in
Here it is Dec 2019 and like many have said on this thread and others, I’m also in the same boat of smart trainer adjustment. It may sink as I add my weight to it.
I’m on my first week using a smart trainer (Wahoo KickR) and yesterday – wow - it was harder. I did Reinstein and the “easier” parts of the Reinstein intervals were super hard. Harder than going above my FTP. So hard, as a mater of fact, that I could barely move the peddles. I thought something was wrong. It probably did not help that I stopped peddling and checked my settings . . . twice. So hard to resume. Its probably just what @trpnhntr said regarding the way ERG mode handles sudden decreases.
One more thing to note. My ramp test was a 264 after 5-weeks off. I thought it would be lower because last winter season, after using TR, it was 256. I did not expect that. Also due to the more accurate reading of the smart trainer?
PS: Anyone know what the “Wheelbase” should be set to? Obviously not zero as mine is. This should be the axle’s (I think) distance from the ground.
Wheel base is the length between your front and rear axles. Around 1000mm to 1100mm for road bikes.
It only matters if you are using a Wahoo Climb.
Embrace the new felt pain!!! My transition a couple of years ago was the same but would never go back now.
@mcneese.chad Got it, thanks. @ericallenboyd That is actually good to hear! Yesterday surprised and annoyed me. I’ll keep at it!