Fliiiight's maximum 7% gradient is lower than some trainers. Why? What does this actually mean for my training? – 4iiii Innovations

Summary
Understanding Fliiiight's Power Curve
Does the maximum gradient affect ERG mode?
How does this affect my training experience in SIM mode?
Why do some popular apps set hill strength to 50% by default?
Will 4iiii increase the maximum gradient in future updates?

Summary

In Sim mode, Fliiiight isn't able to represent hill grades greater than 7% using realistic gearing. To simulate the experience of climbing a steeper hill, you will need to use a higher gear than you would outdoors.

This limitation has less significance for your training experience than many people assume:

It does not effect your maximum power in ERG mode (TrainerRoad, Sufferfest).
In Zwift, Fliiiight will perform equivalently to a trainer with a higher maximum gradient unless you've increased the default 50% hill strength in the trainer difficulty settings.
You can still experience resistance equivalent to a steeper hill climb by staying in a higher gear.
Lower hill strength doesn't allow you to cheat competitors. How fast you go Zwift and other simulations is determined by your power.

Understanding Fliiiight's power curve

Fliiiight's signature zero-noise, zero-contact resistance is created when the aluminum in your wheel rim passes through a magnetic field, generating eddy currents that resist the wheel's motion. Doubling your wheel speed doubles the eddy currents, which doubles maximum resistance.

Speed x Resistance = Power

Therefore, doubling your wheel speed quadruples Fliiiight's maximum power.

This gives Fliiiight a power curve with low maximum watts at the slowest wheel speeds, but high maximum watts at relatively high wheel speeds. Your bike's gears let you take advantage of this, by allowing you to spin your wheel faster (increasing Fliiiight's maximum resistance and power) while maintaining a reasonable cadence.

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What is maximum gradient?

Outdoors, you'll climb steep hill gradients using your bike's low hill-climbing gears. You might also slow your cadence. To realistically represent a very steep slope then, the trainer needs to provide high resistance, while your wheel travels at slow speeds.

Maximum hill gradient therefore is defined by the resistance the trainer can provide at very slow wheel speeds.

For Fliiiight the maximum amount of resistance per unit of wheel speed is limited by the amount of aluminum in a typical bike wheel.

Does the maximum gradient affect ERG mode (TrainerRoad, Sufferfest)?

No. In ERG mode, you should stay in one gear. In your higher gears, Fliiiight's maximum power is comparable with trainers in higher price brackets.

How does this affect my training experience in SIM mode?

In Zwift, unless you've changed the trainer difficulty setting, it won't have any effect. The default setting is 50% hill strength, and the hill grades almost never exceed 14%.

With a hill strength at 100%, if you compared 2 trainers, one with max 7% grade one with max 14%, you'd travel through the simulation at the same speed on both trainers. You'd require the same total effort to finish the course. But on the trainer with the higher grade you'd use your gears more. You can still experience what feels like a steep climb resistance-wise on the trainer with the lower grade by not gearing down as much.

Neither the 50% hill strength setting, nor the 7% grade limitation has an effect on how fast you'll go in the game. Your speed in Zwift and other simulation games depends on your power, and you'll need the same total power output to get up that big hill or to finish your course either way. It does affect how much you'll have to use your gears.

Why do some popular apps set hill strength to 50% by default?

That's up to the app developers, but likely because many riders don't enjoy realistic representations of very steep grades in indoor riding- on the climbs or the descents.

The more you turn up the hill realism, the more you will need to gear down for a big climb, and the more you will need to gear up and increase your cadence in order to produce any power on the descents.

Tip: If you want to stop "spinning out" on the downhills, you'll want decrease, not increase hill strength.

Remember, the relationship between your power and your speed on the simulated course is the same whether the hill strength is 25% or 50% or 100%.

Can you increase Fliiiight's maximum gradient?

Yes and no. The absolute limiting factor for Fliiiight's design is the amount of aluminum in a bike wheel.

Depending on your wheel and set-up, you may be able to decrease the default minimum distance between the wheel and magnets in the 4iiii app, effectively increasing resistance.

Open the Chrome troubleshooting app and set the motion limit in a couple steps at a time. Note that while adjusting this setting can increase Fliiiight's maximum resistance, power, and slope, and increase the strength of virtual inertia, it will also increase the likelihood of wheel-magnet contact. How far you are able to customize this setting depends on your individual wheel and set-up.