Trainer Difficulty Setting in Zwift?
 

Just started on Zwift and the Trainer Difficulty setting description is a bit hard to process.

It's set at 50%. I'll fool with it and see what the effect is for me, but how do other users set this control?

Zwift communicates with your Smart trainer to tell it how much resistance to apply. If Trainer Difficulty is set to 0%, then there's no change in resistance no matter what virtual gradient you're climbing. A 6% gradient will feel the same as 0%. You could climb Alpe du Zwift in the same gear you use on the flats.

If Trainer Difficulty is set to 100%, your Smart Trainer will apply resistance that will FEEL LIKE whatever the virtual gradient is, so a 6% gradient on Zwift will feel like a 6% gradient in real life. You'll have to shift to a smaller gear to be able to keep going, just like on the actual road.

If it's set to 50%, a 6% virtual gradient will feel just like 3%. You'll have to gear down, but not as much.

BUT your speed on the virtual road is ALWAYS a function of your power output, your weight, and the virtual gradient. No matter what the Trainer Difficulty setting, if you're putting out the same power, you'll climb at the same speed. If you tell Zwift you weigh 200 lbs, and the virtual bike you choose is about 18 lbs, and you put out a constant 200w, you'll climb a 6% gradient at about 6.5 mph, whether you set Trainer Difficulty at 0%, 50%, or 100%. It doesn't make you faster or slower.

On downhills, "100%" is actually reduced to 50%, so that a 6% downhill gradient feels like a 3% descent.

I set it at 100% for free riding, because I like mimicking the real world experience. I have to work hard at a climb, and then when I get to the top and start descending, I shift into higher gears, just like real life. This does make it harder to put out a constant level of power, though. I tend to put out a lot more power on climbs than on the flats, and when I'm descending it's difficult to put out even the power level I do on the flats - just like real life, I spin out. If you're racing, you might reduce trainer difficulty, so that you can put out more constant power. You might not climb as fast, but you can still put out power on the descent, which might make you faster going downhill than someone who's at 100% and spinning out.

Does that help?

Thanks for that genej. Especially the insight on how it feels/works for you. I will play with the setting.

Having knocked off some intervals in zwift this morning I am totally digging the experience.

I leave mine set at 100% as well.

"Trainer difficulty" is really poorly named for this setting. Adjusting it to 100% doesn't make climbs any more difficult, you just shift through more gears, which to me feels more realistic. I don't really understand why Zwift defaults this to 50% or why people prefer lower settings.

I also find flat road riding in Zwift to be really boring, so maybe that has something to do with it?

Also worth noting that some Zwift gradients exceed the limit of most trainers. Kickr Core maxes out at 15%, for instance. There are portions of the radio tower climb that are 16-17%. There's a section on Richmond that is over 20%. These will all feel like 15% on a Kickr Core, even at 100% trainer setting, but your avatar will ride slower based on the steeper grade.

I also read that if you're a heavier rider, the maximum gradient is even less. Apparently the calculation of maximum gradient is based on something like a 165lb rider, but if you 200 like me, it applies more resistance at the same gradient - because that's what gravity does - and so your 15% max might work out to more like 12%. I know that my Kickr Snap, which supposedly can mimic a 12% gradient, feels the same to me at anything over about 9% on 100% trainer difficulty.

This is true and the calculation also assumes a minimum cadence (not sure what value though). So if you are a big guy, riding at a very low cadence then your maximum realistic gradient could be considerably lower than quoted. It all boils down to how much resistance the trainer can put out at low cadence.

Zwift racers tend to prefer the lower settings so they can more easily bang out the Watts on descents and maintain a relatively high cadence on steep climbs. I always set mine to 100% and while I much prefer the more realistic gradient simulation, it does make it hard work racing against guys who are clearly set at 50% or less.

doesn't that imply that zwift should be setting the difficulty level during racing rather than the rider?

you only go as fast as your power output will drive a rider of your weight/height. So if a rider choses a setting where they don't have to shift as much, it really isn't a significant advantage. I leave the setting at 50% so I can pedal downhills, but not shifting would be a bonus.

It sort of does, but Zwift is focused on revenue, not fair racing. Having the "difficulty" setting allows users to effectively adjust their gear range to suit their climbing ability or if the bike they happen to have on their trainer has gearing too high for the terrain.

I'd say it's fair, because anyone can set their trainer difficulty wherever they find it works best for them.

I have a pint in me now so not thinking everything through...but a race is the Same distance for everyone, right? So if I race at 100 and another races at 0 how is that equal?

Because for riders that are the same weight, bicycle setup, and no drafting the amount of work (joules) needed to complete a course is the same for both and not dependent on the trainer difficultly or gearing.

It depends if you want the course to be realistic or not. Setting the trainer difficulty to what works "best" to win a race is not the same as the best setting (i.e. 100%) to provide a realistic road simulation.

I cripple myself in Zwift races by using the 100% setting, which means I can't put the power down on descents and I have to grind up the steeper climbs. It would be nice if all the other competitors were forced to observe the same basic laws of physics!

Yeah, that's definitely the beer talking nonsense! lol

Because you both still have to put out the same w/kg to go the same speed, no matter what the setting. It's not any easier for people running at 0% than it is for someone running 100%.

hmmm, when i am climbing i can put out a pretty high wattage (for me) and i am crawling up that hill. on a flat with less power i can go faster. if the descent is steep enough i can put out 0 and still go faster than the ascent.

is this still the effect of the pint i had last night. (it was a big pint...22 oz followed up with two 5 oz samplers).

You could set difficulty to zero, and you'd still be crawling up the hill. Probably slower! Take me, for example - I run 100% normally. When I'm free riding, I tend to do about 170-190w on the flats, but when I get to hills, I'll do 220-350, depending on how long the hill is. Then on the long descents it's more like 75-150w. Sometimes zero, yeah. If I were at 0%, I might put out a constant 190w. So, on a 6% gradient, the way I ride, at 250w, I'd be going about 8 mph up the hill. If I were at 0%, and just doing a constant 190w, I'd be going about 6.2 mph.

The Pace Partners provide an excellent example of this, at least as originally configured - running at a more-or-less constant 2.3-2.5 w/kg Coco Cadence is pretty easy to keep up with on the flats. Once you get to a hill, you naturally work harder, and you get ahead. Then on the descent you go softer, and if you're not careful she'll shoot past you.

BTW, I can't make out your avatar. Looks like a small English sports car?

Good eyes, '79 Triumph Spitfire.


https://cimg8.ibsrv.net/gimg/bikefor...2ad8e9a8cf.jpg

I have a special place in my heart for English sports cars. My first car was a 1966 MGB. A coworker just got a TR6 in that color. It's a bit...rougher than yours.

Trainer difficulty simply changes the magnitude of resistance Zwift sends the trainer. Resistance has bupkis to do with avatar speed in Zwift, they only care about power. Setting the trainer difficulty to 0 will essentially turn a smart trainer into a dumb trainer.

Your avatar speed in Zwift is proportional to your power output and the virtual road gradient, not the trainer difficulty setting - which only affects resistance. So with a lower setting, even though it feels like you are riding on an easier sliope because of the reduced resistance, your avatar still goes at the speed it would on the full gradient for whatever power you are producing.

As surak states above, difficulty at 0% is the same as riding in Zwift with a dumb trainer i.e. there is no gradient simulation, but your power still drives your avatar according to the virtual road gradient.