TRAINER DIFFICULTY - naming change

AFDG

Ambiguous Forum Debate Generator.

3 Likes

Maybe it’s an idea to start a poll first with a few options and then see wat the best description will be.

1 Like

In order for people to vote for the best name or description for the slider is, they have to first understand what it does. The evidence is that most people don’t, so they’re in no position to determine the best description.

2 Likes

Don’t call it anything…just use this:

2 Likes

We need this sorted for MTB 1x bikes on the trainer - I’m struggling to figure out how to get proper intervals with the lower gearing and suspect the slider coupled with a change to the models would make it work –

Just call it % of gravity and be done with it.

Another problem here is zwift also sends notes to the trainer that are already halved (if I remember Lama’s video correctly) while you descend. So if you’re descending 10%, on a 50% adjuster your trainer only simulates 2.5%. For 100% you get a 5% descent.

Yes, that.s part of the Indoor-thingy.

Imagine, 100% TD would get you full 10% decline on descents…
Your highest gear would not be big enough, you’d spin out, and while on the outside you can stop pedaling and cruise down, you’d look very silly just sitting on your bike indoors, doing nothting except staring at the screen :rofl:

2 Likes

IRL your theory is exactly correct. You and your bike are physically connected to the road. IRL you crest a hill and shift up, you can pick up speed as you actually produce lower power. On Zwift the w/kg moves the avatar, so when w/kg falls, avatar slows down. I had this debate with Zwift back in the beginning. So I shift up a cog or two and my avatar slows down, even though cadence is approximately the same and IRL I gain speed. That is when the w/kg method was explained.
I know a lot of riders that have compact cranks, say 50/34 and a 11-30 cassette. 100% is like real world. They have the gearing to handle hills, climbs, etc on Zwift. Then you have riders like me that have 53/39 and 12-23 cassettes. IRL with that combo, the Alpe or whatever would not be doable by this ‘Average Joe’; maybe a pro can do it. The TD setting allows me to lower to around 40% and it is exactly like having a compact set up. How do I know this? I have a second bike that has compact cranks and big cassette. I only used it a few times on Zwift for fitting purposes and testing out everything. With this I have to move TD back to 100%. TD being lower does not mean anyone is getting an easier ride, or cheating. It is simply allowing a rider to pedal 250 watts (example watts) up the Alpe at 80-85 rpm versus blowing out the legs at 250 watts and 50 rpm (big difference in how the muscles fatigue). This could all be solved if every single rider with non- compact set ups went out and bought a 34 tooth cassette, TD back to 100%. But, it did not make them any faster. They still can only produce 250 watts (as my example), they did not suddenly gain the ability to put out 300 watts.
Maybe Zwift could make the slider on one end read 11/34 cassette working across maybe 5 choices and ending at 12/23.
Everyone misunderstands the gist of the ‘slope’ and thinks people are cheating with a lower grade climb. Since the days of CompuTrainer the input to cause the trainer to raise or lower resistance was based on a grade percentage fed to the resistance unit. So if we have a 10% grade IRL and two riders have the above mentioned gearing set ups, the compact rider will go up it with ‘normalcy’. The non-compact rider will be doing leg presses up the climb. So they go over to a 5% grade. Both riders are able to get over it with ‘normalcy’. They go back to the 10% grade. The non-compact rider changes his cassette to a 34 tooth (like sliding TD to 40%). Now he can climb the 10% grade at a normal cadence like the compact rider. Did he cheat? Nope. He ‘changed’ his cassette.

2 Likes

Lots of good points @Paul_at_PCG

I dont agree with the w/kg statement, watts drive your avatar not w/kg. The formula for calculating speed is a lot more involved than w/kg.

see this information of one way to calculate speed from power. Bicycle Speed (Velocity) And Power Calculator

Incorrect, assuming we are still discussing TD and climbing - w/kg move avatar. That is why a dozen riders can ride up a climb at 3.5 w/kg and all stay together. The dozen riders will have a wild variance between the watts due to everyone weighing different. So if your theory was correct, the guy that weighs 250 lbs putting out 400 watts would drop the rider that weighs 150 lbs putting out 300 watts. Not gonna happen :wink: I have played around with that website before. So I just did a 5% grade, everything else unchanged except rider weight and power.
250 lb rider at 400 watts - 11.8 mph
150 lb rider at 300 watts - 13.0 mph
I agree if it is flat terrain, the heavier rider can really crush others with more watts << Same in real life. I have been shocked on real rides by some really hefty riders that had the watts on flat to gently rolling terrain - us lightweight guys literally struggling to hold their wheel - lol.

Your example was actually cresting a hill, so - the end of a climb, the beginning of a flat section, where in the model (and in real life) power-over-weight stops dominating the motion equations, and power-over-aero start to dominate. With an emphasis on “dominate”, since the motion equations are always the same, but some terms become more important depending on conditions.

This is an interesting example. The simplest theory is climbing VAM is proportional to W/kg. So I can extract an exponent from the following. Grade is the same so speed is proportional to VAM.

speed proportional to power / mass^n (for some n, presumably 1 if W/kg is what matters).

mass^n proportional to power / speed

So if I have two riders, one with speed, mass, and power S₁, M₁, and P₁, and the other with S₂, M₂, and P₂, I can divide one equation by the other:

(M₁/M₂)^n = (S₂/S₁) (P₁/P₂)

n ln (M₁/M₂) = ln(S₂/S₁) + ln (P₁/P₂)
n = [ ln(S₂/S₁) + ln (P₁/P₂) ] / ln (M₁/M₂)

n = 0.75

So based only on these two points I’d estimate that speed on the 5% gradient isn’t proportional to power / mass, but instead power / mass^0.75, which implies that heavier riders have an advantage.

Using this formula, to match the same speed, the 250 lb rider would need to produce 440 W, which is 1.76 W/lb, less than the 2.00 W/lb of the lighter rider.

The actual equation is more complicated (although I don’t know what equation Zwift uses, specifically: it may simplify for computation speed).

2 Likes

P.S. The main issue I have with the trainer setting isn’t the name, but that when I change to 100%, my GF also has hers change to 100%, and she gets mad at me. It should be allowed to differ between users.

What sort of setup are you using? Settings should definitely be user-specific.

shared iPad, shared KICKR, different user accounts, latest Zwift version. Most settings are user-specific, but trainer difficulty clearly appears to be tied to the trainer, not the user.

I don’t think it was always this way.

Disagree. If you are riding a 6% gradient you are still riding a 6% gradient not a 3% gradient no matter what setting. You just effectively have a different set of gears to tackle it with.

1 Like

“Gradient feel” makes the most sense to me. It is hard to misunderstand.

1 Like

I would go for something simple like Slope Realism with the slider from 0 meaning slopes are represented as flat and 100% meaning slopes are realistic (as in real life).

2 Likes

maybe “cassette choice”

It’s not really that, because on level ground on a smooth road “trainer difficulty” doesn’t matter at all (I believe), while cassette choice would matter IRL.

Consider a dumb trainer. Power is proportional to some function of how fast I can make the cassette turn. That’s basically 0% difficulty. And different cassettes will allow for different cadence ranges.