Your speed in Zwift is determined by three things:
- Watts: the more power you’re putting into the pedals, the faster you will go.
- Weight: lighter riders will go faster on flats and climbs than heavier riders if both are putting out the same wattage. Heavier riders will descend faster.
- World (game physics): inclines, draft effects, road surfaces and which bike/wheels you’re using all affect your speed.
So Zwift mirrors the real world, mostly. The most obvious detail missing in the speed equation is the lack of wind. But that’s kind of nice, isn’t it?
So How Do I Get Faster?
You don’t have much control over the game physics, although you can upgrade your wheels and swap out bike frames for small gains.
Experienced cyclists can’t easily lose significant body weight (although new cyclists certainly can: I dropped 25lbs in 3 months when I returned to cycling). “Weight doping”–people entering lower weights so they can go faster–happens in Zwift of course. But that just skews effort data and makes the race experience less enjoyable for everyone else–so let’s stay away from that.
This leaves us with watts: if you want to go faster, you’ve got to power up. There are a variety of training strategies and workouts for doing so, including Zwift’s library of flexible training plans. Digging into these plans and methods is beyond the scope of this post, but you should check them out if you’re looking to add structure and maximize results.
Speaking of watts, here’s a fun little video featuring a guy with big legs, lots of watts, and… toast:
Keep riding… keep pushing!
Thanks alot Eric. Really useful stuff. But you are making a strategic mistake. You live in California with your beatiful wife, right? Other than that everything else is perfect:))
Ah, good point. Updated! š
The Zwift group rides and races only use watts/kg to put riders into categories or for group rides to specify the range for that ride. That might be fine for those with a lot of climbing but for flat rides your real world speed is more a function of total watts than watts/kg. Being a light weight guy I am going to average a much higher watts/kg on the flats than a big guy. Do you know if Zwift is using real world physics on getting the speed?
Hi Eric, love your notes man, thank you!
Any possibility of Zwift entering calculations for Aero drag from the rider? I’ve seen the aero value given to the different bike frames and wheels but I am referring to the aero drag from the rider itself (which in real life is a key aspect of speed). Based on height/weight (which we are entering), and even leaving wind as a “constant”, you could assign aero drag values due to the rider size that would make the game more realistic (and fair to smaller riders….one of the disadvantages I hear female Zwifters complaining about). A 1.60m rider not only sees smaller aero drag than a 2m tall rider, but should also be on a smaller bike frame… so less drag from both bike and rider.
Height IS taken into the CdA calcs. Bike frame size is not, as far as I know. I don’t see how Zwift could ever let us enter our own CdA numbers, but I know they’ve done a lot of work to try to make CdA fairly accurate based on rider size.
Yes. Zwift uses real world physics. Light riders are in fact at serious disadvantage with current category system.
Hello all, when ive investigated this before, I’ve read various posts from this site that suggests heavier riders will be faster on the flats than lighter riders and the reverse when going up the hills… This post contradicts the previous which can be misleading… Just my 10p and happy to be told otherwise… I’ll try to find the link and update the comments.
How does this post contradict other posts, Ian?
Zwift physics basically boil down to this: the rider with more watts will be faster on the flat, while the rider with a higher w/kg will be faster on the climbs. I think all my posts are pretty consistent when it comes to this.
hi Eric, it was from a post that had this “Because of this, when we take drafting out of the equation on a flat course a heavier rider will always be faster than a light rider when both are doing the same w/kgābecause the heavier rider is putting out more watts. This is true outdoors as well”, this. makes perfect sense against point 2 from this post, I. e. if both are outputting the same watts then slim Jim will cream plump Ian all day long. my bad āŗļø all good on planet Eric now? š
All good!
Someone tried to tell me once that rider height mattered in terms of draft effect. Other than that conversation (in the Zwift Riders Facebook group, which is always a little suspect), I’ve never heard this suggested. I’m a tall rider at 6′ 5″. I think Zwift over emphasizes the weight penalty for climbs. I’m heavy, at 245lbs. I find that I climb faster in the real world than I do in Zwift, even though my descending and flat rides are much faster in Zwift overall than in the real world.
Yes, height matters on Zwift. From https://zwiftinsider.com/tests/
“The taller you are, the slower youāll go. The test laps weāve done show that it works out to ~30 seconds longer on a full Richmond lap for each 15cm (approximately 6ā³) of height added. Or to put it another way: a 5ā² rider will be ~1 minute faster than a 6ā² rider (all other things being equal).”
I am sorry, I don’t get what means
> Weight doping just skews effort data
Effort data is estimated in percentage of FTP, isn’t it?
Effort data comes in all shapes and sizes, Aleksei. Certainly some effort data wouldn’t be affected by weight doping (your watts, for instance). But I was thinking of speed and elevation numbers, as well as VAM. Those would all be messed up if you weight doped.
I asked a Zwift engineer at an event about height and yes there’s a greater drag for being taller. And you’re right on the weight penalty on climbs not matching real life. In Zwift you can be dropped on 45 sec 6% climbs in a race that in real life would never happen. Though heavier riders probably benefit disproportionately from the half draft on flats.
Several simple reasons I can think of – The high speed descents help my Zwift average. In real life I never hit 50-55 mph going downhill. The fear of crashing and the ability to brake lowers that number. Also, IRL I end up having to make starts and stops at intersections that really mess with the average. I never have to slow down on Zwift, not at intersections, and not for other cyclists either, as I vaporize right through them. IRL, I have to start at 0. On Zwift, if an event, I can start on a trainer already at speed and I finish at speed going through a banner.
Just wondering I’m 84Kg’s. Does weighing more make you decend quicker?
Yes it does, just like outdoors.
In the calculation of zwift speed, zwift uses the riders weight, height, wattage, and some aero details like draft and wheels etc.
But what about the weight of the bike ?
Is there a fix number added to the equation ? 8kg’s for example.
Or is the weight of the bike not added to equation, hence the speed is not that ‘true” ?
Just wondering ?
Yes, bike weight is included in the speed calculation. That’s why I mention above in the list of factors determining speed “World (game physics): inclines, draft effects, road surfaces and which bike/wheels youāre using all affect your speed.”
For more on that, see https://zwiftinsider.com/tests/
What wheel size do the calculate use, if I calculate my rpm, wheel size and the gear, I get another speed that I get in Zwift. Who is to blame for this, Zwift or Elite ?
How do you calculate downhill speed, Iām a 115 kg guy and normally I goes faster that many peoples with a -5%, in Zwift I get passed almost every time and last night I tested downhill and it stopped the avatar going downhill when I didn’t pedal, that’s is not a normal behavior.