Knowing the difference between SIM mode and ERG mode makes Zwifting more fun and efficient. Learn all about both as well as when to use them.
- Smart trainers have multiple modes. They affect how resistance is applied when you ride. The most
common modes are ERG and SIM.
- ERG is great for workouts because it applies specific resistance. Whether you’re going uphill,
downhill, or rolling hills, the resistance is consistent. That’s why it’s is the default for workouts and
Let’s say your Zwift workout includes a 10-minute interval at 250 watts. You’ll want to be in ERG
Start at your desired cadence because the smart trainer will adjust your resistance based on your
cadence. No matter how fast those pedals are going, ERG holds you at the target wattage.
Resistance changes based on your relation to the desired wattage: if you’re going above your
desired wattage, resistance will decrease. Not hitting your desired wattage? Resistance will
For example, if you start at 90 rpm and drop to 60 rpm, the trainer will increase resistance due to
your slowed pedal stroke. If you start at 80 rpm and increase to 100 rpm, the resistance will
decrease due to your higher cadence.
The takeaway? When you’re in ERG mode, your only job is to manage cadence. You don’t even have
to shift if you don’t want to. Some folks in ERG mode even use cogs they don’t often use to squeak
a few more miles out of their cassette.
- SIM, or simulation, is phenomenal for free rides—rides where you’re just cruising around—because
the resistance mimics the road you’re on. Going up means more resistance. Going down means
less. And flats translate to consistent resistance.
- Want to switch between the two modes? Zwift does it automatically. Sign up for a workout and
ERG is the default.
- Now you’re ready to ride and play with SIM and ERG modes. Have fun!