Understanding the Trainer Difficulty Slider

The Trainer Difficulty slider… The Voodoo setting…

Step 1.
FORGET GRADIENT.
For the purposes of this, completely ignore what Zwift officially say about this setting changing the gradient.

Step 2.
ITS ABOUT THE GEARING.
SLIDER @ 100% = YOUR ACTUAL GEARING

I will use my own setup as the example:
I am a TT’er and I use my TT bike on a Tacx Neo.
I race with 53/39 on the front and 11-23 on the rear.
I mirror this on the Tacx Neo with an 11-23 cassette.
(my FTP is 290, weight 87kg, w/kg 3.33)

As you can imagine for TT’ing, my setup works for me. However, when riding in Zwift, 39/23 is not the ideal gear ratio for the steeper gradients. Imagine using this gear outside for real on a really steep long climb…

This is where the Trainer Difficulty slider comes in.
100% on this slider for me would = my actual gears (53/39 11-23)
However, If I want to ride say the Epic KOM or Alp Du Zwift and I want to mimic a lower gearing setup of say 50/34 12-28 which would give me better climbing gearing and a better higher cadence during the climbs, then I would lower the difficulty slider to MIMIC SMALLER GEAR RATIOS

THIS is what the slider does, it allows you to alter your gearing to mimic smaller and smaller gear ratios.

I don’t know the ‘exact’ ratios it mimics as you adjust the slider downwards from 100% but this I would say, would be down to experimenting with finding a setting that gives you the cadence you require for the course you are riding.

SUMMARY
The Gradient is always the same (ignore zwift’s official wording if this helps), its your gearing that changes.

So, if your bike and trainer have the same cassette then 100% = your actual gears
Want to know what riding Alp du Zwift would be like on your real bike,with your actual gearing? use 100%
Have large gear ratios like my TT bike but want to do a hilly course with lots of climbing? - drop the slider down until you get a comfortable cadence on the steepest gradients in your lowest gear.

Works for me.

Your explanation is exactly how I have interpreted the Difficulty slider, but you have expressed it more clearly, thanks.

I have thought of this slider simply as: Anything under 100% it like having additional lower gears available than the actual gears on your bike; and at the same time, not having access to the highest gear or two on your bike.

Everyone will land on a setting they feel comfortable with. As you suggest, there is no single universal right setting for everyone. I have set it at about 75%. I rarely have used the lowest gear, but it is good to know it is there!

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Nice write-up @Guyver1.

This is a good explanation. The “trainer difficulty” slider should have been called something different.

but be ready for those that will say that it need to be on 100% to be real, altho they have compact gears ie 50/54 12-34 on their training bikes.

But… but… there’s a tiny morsel of truth in here. I have two bikes I routinely use on my trainer. One is my road bike w/ 11-25t cassette, the other is my ‘cx/gravel/go anywhere’ that has a 12-36t cassette.

The bikes have different geometry and very different intended uses, and I swap cassettes on the trainer to match what I use on each bike IRL instead of changing trainer ‘difficulty’. Why?

If I’m training for a long, hilly gravel event, I’m just as interested in getting a feel for my power output while climbing @ given cadence in the different gear combinations that I actually have at my disposal IRL.

So, sure, watts = watts and I could use my road bike w/ trainer difficulty < 100% to spin better up Alpe du Zwift (instead of mashing up at 60 rpm) - and still build fitness… but I lose a bit of valuable ‘brain training’ in doing so.

OTOH, if I want to do some faster-paced riding or racing on flat or gently rolling terrain, the road bike is the ticket - not because I can’t ‘go fast’ on the 12-36, but because the 11-25 has smaller gaps between gears. I can’t do anything with trainer difficulty settings to make my cx bike gearing ‘feel’ more like my road bike’s tighter cluster.

Maybe I’m crazy (or just being difficult :D)… but I don’t mind the few minutes it takes to swap cassettes on my trainer.

Very easy to understand explanation. Thank you! I wonder where most people keep the slider set.

You could start a poll.

I leave mine at 100%.

I am a totally new to Zwift, but my guess is that the slider on less than 100%
changes what the trainer sees, making the hill longer and less steep, such that at a constant power you will get to the top at the same time as on 100%.
The longer distance is then mapped (making it the ‘right’ shorter length) back to what it would be at ‘100%’; because that is what you see in the virtual world, distance and speed don’t change, but your gearing does.

I guess the way to test it would be to monitor your bike stats on a separate device, change the slider, and see what happens to the numbers on that. This should then tell you what the gearing ratio change is.

Hi, apologies for the very Johny come lately on this but a recent zwifter and just stumbled across this thread.

I’ve just ridden with a friend and we noticed he was barely pedalling (by comparison) and I was blowing out my backside to keep up. He’s 80kg and I’m 100kg so appreciated I’m going to require more effort than him but this was ridiculous.

However, we also discovered he was on 100% trainer difficulty and I was on 50% (default). He got away from me a couple of times but no matter how hard I i tried to catch up I just couldn’t. I appeared to be putting out more watts but my speed wasn’t really increasing. There also didn’t appear to be any draft for me to benefit from when riding behind him. Again I was just burning myself out trying to maintain his pace.

Do you think the difference in settings will make a difference? I’ve just changed my 100% trainer difficulty. I think I’ve also read somewhere this will make me quicker on the down hills as again he’s been flying past me and 20kgs lighter. Probably should say I have the tacx neo 2t so can benefit from the free wheel.

Apologies for the long post, hope I’ve explained the situation right.

What bikes in game were you riding? TT bike is heavy and isn’t able to draft others.

Higher hearing/trainer difficulty means you won’t spin out so much on the descents.

We are both on road bikes, though I think he has upgraded his frame and possibly wheels. I don’t think that would make that much difference though? I was using the Aero but stopped when I realised it didn’t allow power ups.

We’re riding again today both with our trainers on max difficulty so hoping that allows a more accurate reflection of the watts being put out.

His better road bike wouldn’t make anywhere near as much difference as the extra 20 kg you have. Just make sure you both calibrate your trainers after a 5/10 minute warm up.

Neo for you. What for him? Also flat or hilly course. 20Kg will make a big difference just like real life when riding outside.

As mentioned in the original post trainer difficulty to the max keeps you honest on the gears on your bike in a virtual world. To me a 7% grade on zwift feels pretty close to outside as I typically use the same gear in like situations outside.

Cheers Eric and Ben, sadly i’m all too aware the difference the 20kg makes (need to do some more fork put downs) but that’s also what’s confusing he’s even getting down the hills quicker than me which should be the only time the extra weight helps me (it does outdoors on descents, definitely a hinderance on the ascents).

He’s on a kickr snap and me on the neo. I have also had a few issues with intermittent problems with the neo. Been a couple of times where I’ve gone to start pedalling and there’s been no resistance and I’ve had to quit out of everything and start again which is frustrating when you’re doing an event.

Final point, any recommendations for a bike and wheels upgrade? I’m level 10 and have about 690k drops burning a hole in my pocket

I personally have never spent any drops as I worked my way towards the Tron bike and wear my Rapha CC kit. Here is a good guide though below n

Based on what you said might be a bad Neo day as no calibration required or your buddies snap is not calibrated (use advanced spindown).

Hi Andrew,

another problem you may have with keeping up with your friend whilst Zwifting, is that the Tacx Neo is generally seen as more accurate in its estimation of a Zwifters power, than the Kickr Snap.
The increased accuracy could also put you at a disadvantage.

Thanks guys appreciate the follow up and answers.

We did another ride yesterday and I put my trainer difficulty up to about 90%. Had to range through my gears a lot more but felt like when I put the pedal down it was replicated more on screen. Though the hills were much tougher so given my heavier status probably more of a true reflection. However, when we came out of the tube line in London 18/20% up the boards it was as if I’d hit a brick wall :frowning: and Box Hill was awful, but in a good way.

My co-rider also said it was much tougher to stay with me so hopefully we’re making it a bit more calibrated. He’s an eternal drafter, which $h1ts me!!!

I’m loving the idea that my trainer is more accurate and he’s getting an easier ride on the snap. I’ll be sure to quote that any time he beats me.

I opted for the Ridley Noah fast and Enve wheels. Halfway through California and will then switch it over to the ridiculous Everest challenge.

Thanks again for the replies, much appreciated.

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Yeah…that’s the “Escalator”. I learned (the hard way) to begin ramping it up and/or using a power up just about where that left turn is before it. If you ramp it up ahead of time, you can get up that thing much faster/easier.

At the bottom of Fox Hill you go back out the way you came in, which means powering up the 15% escalator," warns Marius. “Treat it like a sprint–try not to lose momentum.”