Massive difference in effort per watts between climbing and flat

The only differences I can see are cadence and trainer non-linearity. If you maintain a different cadence in erg mode than when climbing in sim mode, you are exercising different types of endurance: for example, if you ride 300W at 95rpm in erg mode but climb at 300W and 60rpm, the former will be easier on muscular endurance but harder on your aerobic system, and vice-versa.

Trainer linearity is the ability of the trainer to actually measure the same power at the same output but at different spindle/roller speeds. Some trainers will indicate 300W at 60 rpm on your easiest gear standing up (low spindle/roller speed) and at 95 rpm on a long gear (high spindle/roller speed), but the actual power will be different.

First thing I’d do is to see what gear+cadence you are “comfortable” with in sim mode going up, and then try in erg mode at that same gear+cadence. This eliminates both issues above.

I have the same issue - on the flats I can hold 270 watts at around 170 bpm but going up hill on Zwift I can barely hold 200 watts at the same hr no matter what cadence I am producing. It is really frustrating surely the watts and HR should have some correlation.

On the road I find it much easier to hold higher watts going uphill as other people have mentioned above. But in Zwift I find it impossible- I am heavy rider at around 85kgs and use a kicker snap. The power metre on bike also tells a very different story - it shows the watts being very similar going up or on the flat.

Why not pair your powermeter to zwift, if you already have one on the bike?

I’ve just found that the Snap is really aggravating when it comes to resistance. I don’t know what’s accurate and what’s not. Erg mode is basically useless to me because resistance will get so high it’s like doing lunges with 50 lb weights. I’ve recalibrated the Snap a dozen times now and it feels way different each time. Incredibly aggravating from a training standpoint, where I want to at least feel like my progress is consistent and linear. Actually quit Zwift for a competitor as a result.

I have tried that also Ben.

So, if you pair your powermeter with zwift, your Watts in zwift will always be accurate (as accurate as the powermeter)

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This is interesting. I have a Kickr Snap too. Flats are fine, going up hill my power drops off even though I am putting in much more effort. Going downhill and it feels easy yet I can pump out a lot more Power (well Zwift shows lots more power but is is easy for me). I thought Zwift must be adding the ‘energy’ gain you get from going down hill or subtracting off my power going up hill but apparently the power Zwift shows is your actual power. I get killed every time there is an uphill slope. The other odd thing that made me think Zwift was subtracting power when I go uphill is when I warm down on a slight slope, eg 2% uphill tonight after Yorkshire I am outputting power to my trainer but Zwift shows no power, 0 Watts. It’s like it has ignored the 20 or 30 warm down Watts I am putting out - hence I come to a dead stop. OK I understand that the 30 Watts I feel I am putting out may not be enough to get me up that slope, but why does Zwift show 0 Watts, 0 speed yes but power is power. Could it be the Kickr Snap, seems to be a common theme.

That is not normal.
Have you done a firmware update on you kickr snap?
Did you do a spin-down calibration before every ride?

As Ben said, make sure that you do a calibration using the Wahoo app.

Also, has this ever worked correctly or always been like this? Just wondering if it is paired correctly as a power source or just as a dumb trainer.


@Nick_Williams what device do you use for Zwift, Apple TV?

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Hi All,
Thanks for the replies. I must say I generally don’t calibrate the Kickr Snap every time I ride as it’s 10 minutes faffing plus the iPhone Wahoo Fitness app gets confused and often can’t see the speed on my Kickr. At that point I generally have to add it back in again, that is delete it and add it back.
Also I am slack and only turn the Knob 1 3/4 turns. I always felt 2 turns was just too tight, at my power level it was never going to slip.
Also I hate pumping up the tyre so I only do this every week or two.
Last calibrate I did was via the Zwift app and it gives you no feedback on ramps time, temp etc. Firmware was up to date.
Anyway I reasoned the power would just be a few Watts to high or low, no issue as I don’t race these days.
This is all by way of excuses, hopefully this helps someone else…
So, I pumped the trye up hard to the recommended 100psi or so.
I turned the knob a full two turns.
I found my trusty old Galaxy S4 had the Wahoo Utility App on it. I did a few Spindowns while I was warming up. I was getting times of just over 15 seconds for the Spindowns, so I tightened the Knob a bit more, like a few degrees until down to 15 seconds.
After 10 minutes I did 2 more Spindowns and ended up with 14.9 seconds, 19.3 Deg C and 0.703 braking factor (yes Android app has braking factor). After my 30 minute ride I did another spindown, 15.3 secs, 28.2 DegC and 0.703 braking again (that seems a little odd to me, all my braking factors were bang on identical). There doesn’t appear to be an advanced Spindown anymore, unless it is hidden in yet another Wahoo app.
The result of all of this anyway was a completely changed ride experience, I have more power than before on the flat and it doesn’t all vanish when I go uphill, more effort uphill now results in more power. I have however lost some power going downhill, but that always seemed wrong. Also I think the Kickr Snap flywheel feels a lot cooler at the end of a ride (another indication it was robbing power).
So yes, being spot on with the Spindown, Knob tightness, 10 mins warmup, tyre pressure will do the trick. As long as the knob is put back to the same position for the next ride or two the calibration seems fine. I think it would spoil it if I did another spindown at present, unless via Android app. I have no confidence in the Zwift Spindown because it doesn’t show me the numbers.
Sorry for the long story but hopefully this will save someone else from grief or give them what they need to figure out what is going on.
The Spindown it seems is needed to determine much power the Kickr reports on the flat and equally importantly to adjust the resistance downhill and uphill.
If you have 10 minutes to faff before a ride you can get it spot on. If you are slack like me find something that doesn’t need this (wheel off). Anyway its spot on now.
Thanks for reading this!
PS - running on Apple TV 4k. Very good mostly, although tonight it wouldn’t pick up the Kickr Snap or Wahoo Tickr. Had to turn off everything, a restart of the ATV didn’t fix it.

I did another pump the tyres up, warm up for 10 minutes, correct tightness and spindown time last night, The uphill effort per Watt output seemed a little harder and the downhill a little easier again. I noticed the braking factor is still bang on 0.703. This doesn’t seem right unless the Spindown on the Wahoo Andoid app only shows it but doesn’t adjust it. I suspect this is the case. I finally found a link to the Advanced Spindown, so I may try this.

Tonight I did the all the standard check tyre pressure, warm up 10 minutes etc and a couple of standard Spindowns to get my time around 15 secs etc.
Then I went through the procedure to do the Advanced Factory Spindown. After I had completed this, which is essentially another 3 minutes warm up and two Spindowns I went back into the Android Wahoo app and did a standard Spindown. Results were 15.7 secs, 20.7 DegC and 1.055 Braking Factor (previously 0.703).
Back out on Zwift tonight I did Richmond UCI. The ride difference was day and night. I have suddenly gained about 0.3W/kg, I’m still solid D grade but tonight riding in Z2 Hr instead of being in the bottom 5% (sprints, Kom, course) I was in the last 20%.
Hit a hill now and more effort = more power, previously hitting a hill more effort was less power.
I always assumed it was me at fault, but no the Kickr Snap was way out of Cal. I had suspected something since I had a go on a Spin bike which showed power and I could make heaps more than on the Kickr, but I just assumed it was the Spin bike that was wrong. Another benefit is the flywheel on the Snap is way cooler at the end of a ride - maybe this was a clue I missed as it had been burning my power way too aggressively for the last year.
Wahoo how could you hide the advanced Spindown from me for so long?