You already know your weight setting in Zwift affects your speed–especially up hills!
And you probably also know that the bike frame and wheels you select will affect your speed.
But did you know your height setting also affects your speed? Zwift uses your height in its equations to calculate CdA, which is a measurement of how much resistance your body gives to the air as you ride. Just like outdoors where aero is everything, Zwift calculates taller riders as offering more wind resistance.
We’ve done a lot of automated test laps with various height/weight/equipment setups, and confirmed this: all other things being equal, the taller you are the slower you’ll go.
The test laps we’ve done in the 225-watt power range work out to ~30 seconds longer on a full Richmond lap for each 15cm (approximately 6″) of height added. Or to put it another way: a 5′ tall rider will be ~2 minutes faster than a 6′ tall rider for every hour of riding on a fairly flat course.
Another way to look at this is every 15cm removed from a rider’s height is like adding 5-10 watts of power in terms of speed increase. We can figure this out by looking at average Strava speeds at different heights, and plugging those numbers into BikeCalculator.com to look at power differences.
These numbers fluctuate depending on the wattage range you’re looking at, and what type of route we are riding–long, slow climbs won’t be as affected by height as much as a flats or downhill.
But it is worth noting that Zwift, in attempting to emulate real-world physics, does take your height into account (even if your avatar doesn’t get any shorter or taller).