Too much power uphill, too little downhill - unable to pack ride

Hi all.  Im riding a Tacx Vortex Smart and love the experience on Zwift with it.  However Im having trouble during group rides and races - my power is great uphill when the resistance kicks in, and too low on downhills and the pack gets away from me.  This results in a bad yoyo effect where I catch everyone uphill, and lose them all downhill.  Any suggestions to get the power output more stable so I can stay with the pack and not have to hammer it uphill every time to catch up?

Im sure this is answered somewhere, but I searched and couldnt find it, so posting.


You  could try to set the “realism slider” (in the settings page) more to the left.

This makes your speed drop on the upslope, instead of making the going harder. As consequence you have to change gear and cadance less.

agree with the above, i use a smart trainer (cycleops) and have the setting about 40% of the max and find this gives a good balance between uphill, downhill and flat. Just to be clear, this does not make it any easier it just adjusts the impact on the trainer of gradient but your speed in Zwift is still driven by your watts and the actual gradient.

G  - This is a characteristic of smart trainers.

As you would expect uphill demands more effort if you do not want to slow down too much and it is easy to do this in Zwift as it sends the signal to your trainer to make the effort harder.

Likewise on the downhill Zwift sends a signal to make the effort easier as a consequence the smart trainer reduces it’s resistance. This is what makes it hard to get good power on the downhills just like in real life. Unfortunately this does reduce speed unlike in real life where you can coast.

Non smart trainer riders have a distinct advantage on the downhills as their resistance isn’t controlled by Zwift and they can keep riding at the same intensity which keeps their speed up.

This is what bugs me in many group rides, as on the uphill you’ll have people often telling you not to surpass the 3w/kg mark. However, on the downhill segment often they can’t be bothered with waiting for people to regroup.

It’ll be nice to just be able to create group rides on the fly, and have a mandatory smart trainer toggle to just eliminate this problem without dropping the realism.

Till then, I’d just say to completely ignore any 3w/kg uphill shoutouts and simply do your thing, head downhill at your own pace and wait up for people on the bottom of the hill. Generally speaking you won’t be the only smart trainer user doing that.

May be helpful:

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Very helpful Eric - thanks.  Will drop the setting and try it out.  Thanks to all for your input.  Rideon!

If i want to do a group ride when i am on my smart trainer, i have a kickr so its easy i open the wahoo fitness app.

Set the resistantace to erg mode, and i adjust wattage to maintain with the pack.  Basically it overrides the ant+ signal being sent by ZWIFT.

I have a KickR and run the resistance at 100%. This setting is the most realistic to road riding in my opinion. There is a slight spike in watts when you suddenly hit a steep section that you would not get in the real world but overall, the simulating of road riding is my priority.

Talking of the real world. I weigh 58 kilos and I can climb well. On the decents I struggle to keep up with heavier riders who have gravity on their side. Getting aero and sitting on the wheel of bigger riders is the only way I can keep on on the decents and flats in races. 

I would be interested to know if the OP is a light rider and if Zwift takes into account rider weight for decents and accents.

It makes sense that it does.


David T

David–Zwift absolutely takes rider weight (and height) into its equations. See speed tests here:

Not super light - 72kgs, 5’10".  Downhill it should be easy in real life to stay on the wheel of a rider - the power output isnt so important as gravity is doing most of the work.  Its almost as if zwift is too sensitive to power output downhill?

The other posts have me toning down the realism to 25-40% or so which works - I work hard uphill but stay in sync with riders and downhill I can stay with the pack.  But its not as realistic as Im in 5th gear up a 8% grade which Id be in the granny gear in real life.  If I arc it up to 100% I totally lose touch on a downhill of any length.  Its not a huge deal, but does affect the realism of zwift when racing in large groups I find.  I dont want to drop it to 25% as then I dont even feel the hills and question why I bothered buying a smart trainer!

Eric’s article sums it up well.

Thank you Eric fro the information. Very interesting. 

G Running the resistance at 100% is just like riding on the road. I have used a Powertap on the road for the last 5 years so plenty of data. If I look at a similar climb in training peaks to compare it to a climb on Zwift, power and speed are very similar. Yes I get dropped on the descents in Zwift but in real life I just have to tuck in behind the bigger rider and work harder. I would rather go for realism though. After all, we are using Zwift to maximise our training for when we are out on the road or in a race.


Perhaps the solutions will be to combine a smart trainer + speed sensor at rear wheel.   

Setting the simulator at maximum difficulty will acurate power sensibilty, combined with a simultaneus exact reading of speed, will correct simulation speed problems of users with smart trainers during downhill.

My question is:  Is possible to combine smart trainer with a speed sensor on rear wheel?

As I think, this will be achieve maximun realism to the simulation.


I have noticed an improvement descending with a group. As long as I’m right behind the rider then I don’t have to work as hard. I still have my power to weigh ratio advantage though which is good.! The Trek Emonda with 202 wheels helps. 


David T

I felt this sensation as well, yesterday when I was doing the McCarthy workout and had the last intervall starting in the last downhill part of Watopia (before finish line). The downhill gradient made it impossible to pedal as the resistance boosted up hard.

I was using ERG-mode on the workout and I do feel I get a higher watt output at a easier resistance when going uphill.

Now I don’t blame the resistance for failing the last interval, it was tough. But when I couldn’t pedal at all, it kind of drained the energy of me.

Oh, and I’m using a tacx Neo, direct drive and I also get the same issue with downhills when riding with groups…

The latest Wahoo Kickr firmware update is supposed to have fixed this “loss of power on descents” problem.  I haven’t had the opportunity to do a group ride since the update, so I can’t confirm.