Zwift’s physics model includes varied rolling resistance of virtual wheels across different surfaces. Smart racers think strategically when choosing frames and wheels for unpaved or mixed-surface routes like Road to Ruins and Two Village Loop.
Here’s a complete rundown of all the rolling resistance numbers and resulting wattage effects for Zwift wheelsets.
(Note: we update this page as new wheelsets are released–see the changelog at the bottom for a list of changes.)
Zwift’s Road Surfaces
Zwift worlds use several different road surfaces. Here’s the complete list from fastest to slowest:
- Pavement
- Sand (introduced in the Urukazi expansion of Makuri Islands)
- Brick (example: part of downtown Innsbruck just before the Leg Snapper)
- Cobbles (example: Italian Villas)
- Wood (examples: Watopia fishing village piers and bridges)
- Ice/Snow (found only on the Radio Tower climb, as far as we know)
- Gravel (found only on the Sgurr climb in Scotland)
- Dirt (examples: Mayan Jungle, Yumezi’s Temple KOM)
- Grass (found only on Repack Ridge, as far as we know)
Zwift has built the game so each wheelset can have its own Crr (rolling resistance) value for each road surface type. So a set of TT disc wheels may roll super fast on pavement, but terribly on dirt. Just like you’d expect outside.
When the Crr increases, two things happen in game: your speed drops, and resistance increases on your smart trainer.
Zwift Wheel Categories
Right now, there are three categories of wheelsets in Zwift:
- Gravel: includes the “Zwift Gravel” wheelset plus some name-brand wheels which (oddly) perform better on dirt than the Zwift Gravel wheels
- Mountain: includes only the “Zwift Mountain” wheelset
- Road: includes all other wheelsets (40 at the time of this posting)
See the full list of Zwift wheelsets >
Generally speaking, each of the three wheel categories above has its own Crr values for each surface in Zwift. This makes each type of wheel perform differently across different surfaces.
Example: on pavement, Road wheels have a Crr of .004 while Gravel wheels have a Crr of .008 and Mountain wheels have a Crr of .01. This means Mountain wheels will roll slower than Gravel wheels which roll slower than Road wheels.
The only exception is gravel wheels. Here, Zwift chose to do something different and make all the newer name-brand wheelsets roll faster on dirt than the Zwift Gravel wheelset, giving them a dirt Crr of .016 while the Zwift Gravel wheels have a dirt Crr of .018.
Wheelset Crr Values
We’ve done some testing to determine the Crr of all the wheelsets on each of Zwift’s surface types. Here are the current numbers:
| Surface | Road Crr | MTB Crr | Gravel Crr (Namebrand) | Zwift Gravel Crr |
|---|---|---|---|---|
| Pavement | .004 | .01 | .008 | .008 |
| Sand | .004 | .01 | .008 | .008 |
| Brick | .0055 | .01 | .008 | .008 |
| Wood | .0065 | .01 | .008 | .008 |
| Cobbles | .0065 | .01 | .008 | .008 |
| Ice/Snow | .0075 | .014 | .018 | .018 |
| Gravel | .02 | .015 | .012 | .012 |
| Dirt | .025 | .014 | .016 | .018 |
| Grass | .042 |
You can see why the jungle dirt feels much tougher on a road bike than a mountain bike. Because it is! The rolling resistance is nearly double!
It’s also worth noting that the Crr value for road tires on pavement (.004) is quite low. We’re virtually rolling quality tires on fresh tarmac. Living the dream!
Wheelset Wattage
If you know the Crr value of a particular tire/wheel, you can extrapolate the wattage required to overcome the rolling resistance at a particular speed. This is commonly done outdoors, and in our tests, it seems to work with Zwift’s physics as well (nice work, Zwift programmers).
Doing this tells us how much of our power is going toward overcoming rolling resistance. In turn, this tells us how many watts we can save just by moving to a wheelset with lower rolling resistance.
Here are those values, assuming a 75kg rider on a 7kg bike traveling at 40kmh (24.9mph).
| Surface | Road | MTB | Gravel (Namebrand) | Zwift Gravel |
|---|---|---|---|---|
| Pavement | 36 | 89 | 72 | 72 |
| Sand | 36 | 89 | 72 | 72 |
| Brick | 49 | 89 | 72 | 72 |
| Wood | 58 | 89 | 72 | 72 |
| Cobbles | 58 | 89 | 72 | 72 |
| Ice/Snow | 67 | 125 | 161 | 161 |
| Gravel | 164 | 123 | 98 | 98 |
| Dirt | 223 | 125 | 143 | 161 |
| Grass | 375 |
Now things are getting interesting. So if you’re in a race on Watopia tarmac traveling at 40kmh, and you’re on a road bike while the guy next to you is on the Gravel bike using the Zwift Gravel wheels, he has to put out 72-36=36 watts more than you just to overcome rolling resistance.
But if we move to the Jungle Circuit, suddenly that Gravel rider has the advantage, able to keep up with you while doing 223-161=62 fewer watts! (Of course, in the jungle nowadays we don’t usually go as fast as 40kmh, so this difference would decrease a bit.)
The numbers will get wild once we have more wheelsets with different Crr’s available. Pull out your calculators, kids!
Note: the wattage numbers in these examples don’t take into account additional differences that could occur based on varying rider weights, heights, drafting status, bike frame used, etc.
Fighting Resistance
Of course, rolling resistance isn’t the only thing you’re feeling on your smart trainer. In fact, it’s typically the least of the three factors which determine overall trainer resistance. Just like outdoors, we know that wind resistance and/or gravitational force are usually the biggest things slowing our avatars down on Zwift.
Changelog
- Jan 31, 2023: added data for Scotland’s new gravel surface
- Nov 10, 2022: added sand surface data, and explained how newer namebrand gravel wheels have a different Crr than Zwift’s original gravel wheels
- Dec 8, 2019: added gravel wheelset numbers to the tables
The changelog.. 2019? 😉
More important, if I understand this correctly Sand is just a visual effect then, with same figures as pavement?
.. .And then I read the article specific to the new expansion which clearly stated this.. 🤦♂️😅
Oops. Fixed that year!
“When the Crr increases, two things happen in game: your speed drops, and resistance increases on your smart trainer.”
Are you sure about that? It always seemed to me, that the surface in Zwift only affects your speed, but not the resistance. That’s why it feels a bit “off” to ride the gravel in Zwift, you just get slowed down, but feel no difference…
In contrast to pavement, I have the feeling of increased resistance/effort on different surfaces. I use a Tacx Neo; besides the “road feel” on cobbles and brick, it is harder to pedal on surfaces other than pavement.
I’m just glad I didn’t endo on the big rocks in Urkazi. 😅
A road bike tyre is better on sand and ice than either a gravel or MTB tyre? This makes absolutely zero sense.
we need FAT BIKES for the sand and future snow expansions
Presumably your position (left-to-right) on a surface doesn’t impact the Crr?
For example, on the Temple KOM on Makuri Islands, in some races in a pack you can get pushed to the side where you appear to be riding on the grass rather than the main dirt path?
Is the Crr different out there on the grass to the main path?
I’ve often wondered this as well. Then I get dropped by the pack and am back into the center of the dirt and forget about it until the next race.
Why doesn’t Zwift adjust trainer resistance when you’re sitting in the draft? Surely that would be similar to how they adjust for different terrain?
Does the Tron bike perform better on dirt than normal road bikes??
Nope.
Crr scales like slope, so a Crr of .01 is like riding on a 1% slope, a Crr of .004 is like riding on a 0.4% slope, and a Crr of .018 is like riding on a 1.8% slope.
Ice-snow remains very strange, where both road and mountain bike are better than gravel. Does that make any sense?
Ok – I see a CRCA Jersey!!! What is that? 😲
Sand rolling resistance needs to favor gravel and mountain bikes, currently having the same rolling resistance as tarmac is wrong.
I found this out the hard way in a Country to Coastal race. I picked a gravel bike in the belief sand would favour the gravel bike. It was a nightmare to hold the wheels! I should have read this article first. But come on Zwift, have some common sense…I’ve never seen Van Aert on a road bike in a sand cyclo-cross race!
Do you have a list of routes with a recommendation of wheelsets to use on them somewhere? Is there enough dirt in the jungle routes to just use a MTB wheelset or would they slow you down on the pavement sections that it isn’t worth it or a gravel wheelset would be better?
Geeky question: Based on your data, the relationship between Crr and Watt is linear. Watt = 8930 * Crr. I reckon that this is a general formula, but the constant will depend on eg. speed and weight? Would it be much work to give us some observations with different speeds (eg. 20, 25, 30, 35 mph, Crr= 0,01 , weight = 75) and different weights (eg. 70, 80, 85, 90 kg , Crr = 0,01 , speed=40)? Based on that it might be possible the make the general formula and get some more information regarding cycle choice dependent on route… Read more »
How are we supposed to tell the difference in game between sand and dirt? They look identical. But a massive rolling resistance change biased off equipment. This is such a ball drop for Zwift! Why even make sand? Is a paved road along the beach that bad?
Hi Eric, do you know if road, gravel and MTB bikes have the same CdA in Zwift?
If for example the CdA is 0,32 for MTB, 0,28 for Gravel and 0,24 for road bikes it can change a lot time spend on different surfaces, not only taking into account Crr.
Thank you!
Every frame on Zwift has its own CdA and weight setting.
That said, some frames share the same CdA and weight (you can see that when the flat and climb times match between two frames.)
What affect or difference is there in watts for lighter or heavier riders then what you compared above? It would be nice to see the what a 65 and 85 kg rider looks like.
I’ve often wondered about this. I’ve sort of assumed that what determines acceleration is not W/(kg of rider) as is displayed on the game, but W/(kg of rider + bike), which, as a heavier rider, would mean that I pay less of a relative penalty for riding a heavier but more aero bike. On the other hand, as a taller and wider rider, I probably receive less of a benefit from that aero bike (because the bike’s contribution to my total CdA is smaller than it is for a shorter, skinnier person), so it probably balances out at some point.
hey @eric!
Can you please add some Fotos of the Surface-Types (Sand, Gravel & Dirt) and some example Destinations to each? Because I don’t see much visual difference to it. That’s why I don’t know on which Surface I am at that time 🙈. Would be good to know on Routes where swapping Bikes makes sense to better your overall lap time.
Or make another Article about that.
thanks in advance!