Went from dumb trainer to smart. Why does it feel harder?

So I trained the past 8 years or so on a KK road machine. My sweat ate through 2 of them and they replaced it through warranty and after this third one went I decided I should just buy a new trainer rather then continuing to milk KK for new ones for the $225 I spent almost a decade ago.

I have the typical TT style rider, strong at holding higher wattages for a long time. Never had problems holding 8, 10, 15, 20 min efforts very steady on the KK with a Quarq (like easy to stay within a 3-5 watt range) so I figured erg mode or any of the other modes would feel normal. Well now upgrading to a Wahoo Core I find that the interval efforts feel harder to hold. I am not using the Kickr powermeter, I am using my Quarq.

Any reason why I am finding the intervals harder then I normally did on the KK? I do have it on a riser which I thought I read thats level without one, so is it giving me that going up hill feel? Is this something I’ll just adjust to? Just a little tired towards the end of the year? Any other ideas?

Thanks everyone!

Erg mode makes you hold the watts which is why it feels harder. Also depends on your cadence.

1 Like

Along with what @ericallenboyd said there’s also the flywheel inertia or flywheel speed to take into consideration. A dumb trainer usually requires you to be in a fairly high gear to hit the correct wattage while with a smart trainer you can be in whatever gear you want. If you go off what Trainer Road recommends and use the small chainring and use a gear in the middle of the cassette you’re not spinning the flywheel very fast. This sort of simulates a steep climb on a road bike or riding a cyclocross bike in grass because both of these require a lot of power at a relatively low speed. It’s something you’ll get used to. I had the same problem when switching to KICKR Core last month.

Also there’s been some discussions of this on the podcast if you want some other opinions. They usually refer to it as flywheel inertia.


Right I get that, but at the same time I usually hold within about 3 watts before when doing intervals on the dumb trainer, so I was thrown off by this.

I have the same issue…switched from a KK road machine I’d had for close to ten years, got a Kickr Snap and everything feels harder, especially recovery intervals. My natural cadence is 85-87, it seems if you get below 90 ERG just tries to murder you. In a long steady state interval I start out above 90 rpm, but once I drop down below 90 it just gets increasingly harder to the point where I am dragged down into the 70’s. I’m half tempted to go back to the KK. I’ve been using the Snap in standard mode lately and I really prefer the feeling of the KK with its fluid resistance comapred to the magnetic feel of the Kickr.

1 Like

Felt the same when I got my kickr snap almost 2 years ago. Eventually got used to it.

I’m sure there is a period of adaptation with these things but I’ve just gone back the other way from a TACX Flow Smart to a Cycleops Jet Fluid (dumb) trainer.

The Tacx (admittedly a very entry level smart trainer) always seemed a bit too in control and really annoyed the hell out of me, wattage readings were also not always comparable to my power meter. But essentially it just seemed to be stopping me pedal as smooth as I’d normally do and I believe this used to fatigue my legs. On the dumb trainer the road feel is so much better, ok I’ve lost the smart features but as I don’t want to use anything but Trainer Road I don’t think you need them.

I am in the same boat here as well. For the past three years I have used a “dumb” trainer with virtual power on TrainerRoad. For this upcoming season I upgraded to a “smart” trainer (Wahoo Kickr Snap) due to a few reasons it was best for me and my training. I did the FTP Ramp Test on TrainerRoad and had a marginal decrease in FTP in comparison to the virtual power (even after only be off 2 months) I hear that Virtual Power overestimates it and although I questioned it I figured I will retest it again in 6 weeks and see what happens. My biggest question/issue is that at 175 W (~85% of my FTP) I am only going 15.5 mph. Can this be correct? I was doing 3 x 20 mins and it is the hardest I have ever worked yet only going 15.5 mph just seems very low? I have it on the small chain ring in the front and roughly middle on the back.


Well I’d imagine that going 175 watts in the middle of the small ring would equate to that speed. Think of it like climbing up a hill. I had something similar doing like 95% of threshold in the small ring, 5th gear and “speed” was being shown around 15-16 mph.

Thanks for the reply. That is what I thought since I am in the small chain ring and not the big one. I am in the small chain ring because I have heard from TR and Wahoo that it puts less stress on your chain and it is quieter (which the girlfriend enjoys). So should I really be worried about going that slow (mph) and be more worried about how many watts I am putting out? Just seeing an avg mph of 15.5 after being on the trainer for 1:30:00 is a bit concerning.

1 Like

No reason to ever worry about mph on the trainer. Who cares about that. Watts are watts while riding inside. Now I kinda figured last night that the small ring felt a bit harder then big ring because of the flywheel spinning slower. But I couldn’t care less about what overall mph it shows my trainer ride.


Remember the indisputable fact…your mph is zero on a trainer. Any number you get is made up.


Perfect that is exactly what I needed to hear. I am training for Worlds in April and was quite worried I was going to get blown out of the water if I was covering 15 miles in one hr! Happy training!

1 Like

I had the same experience…going from virtual power to the Snap…I lost about 40 watts in my FTP. I’m thinking that virtual power needs to be looked at again and maybe the algorithm tweaked a little…I always hear “a watt is a watt” …well I guess that isnt true if you used virtual power. I always read article that certain trainers or power meters are accurate to 2 or 3%…my question is 2 or 3% of what? Is there a standard that they are measured to?

Personally I use my Quarq all the time that way I don’t have to worry about power differences.


First time i’ve heard this, is this important / do you have a reference? On my KK it takes a long time to settle when changing power, i’m guessing this is less of a problem when the flywheel is spinning slower ??

The core issue is related to this:

The rule of thumb is to try to match the flywheel inertia to the majority of your events.

  • Flat and Fast Road Riding = Use Higher Bearing and Faster Flywheel Inertia

  • Hilly and Off-Road = Use Lower Gearing and Slower Flywheel Inertia

Additionally, resistance changes generally happen faster with a Slower Flywheel, because it has less inertia for the resistance unit to overcome and make adjustments.


I keep hearing that, but not so sure…

On my Kickr I run big chainring and middle of cassette, yesterday I was jumping from 96 to 204 watts in 2-3 seconds. Do you want it faster than 2 seconds? That seems really fast to me, and better than hitting an instantaneous “wall” of watts. There were six 15-minute intervals in Wright Peak -2 yesterday, and by the last two I was getting tired and those took 5-6 seconds but that was my body and not the trainer.

FWIW my Kickr is configured to measure power using Stages PM instead of the Kickr optical sensor (its Wahoo’s version of TR “power match”)

I’m reluctant to try small chainring again because big chainring feels more natural given my usual flat and fast rides. And going from 2-3 seconds down to 0-1 seconds isn’t worth it (assuming small ring drops resistance change down that low).

It probably varies from trainer to trainer. I know my PowerBeam Pro had issues keeping up with the 15-30 changes in shorter intervals in the big ring.

My Kickr and Hammer are better, but probably more because they have a much stronger resistance unit. The Hammer is more sluggish compared to the Kickr when in the big ring. That 20 lbs flywheel really likes to hold inertia.

My quads were a little cooked tonight and I definitely didn’t see 2-3 second ramps during the 5x10 sweet spot intervals of Antelope +2. At least for me, I seem to have quicker ramps when fresh. Weird.

1 Like