Rolling Resistance Changes in Zwift: Comparing Old and New Roads

Zwift’s last major update included this note:

Various wheels and tires now have different rolling resistance based on the surface they are rolling on. IE, a mountain bike or gravel tire may be the best on the Jungle circuit, while a road/TT bike is fastest on the tarmac. More to come here in a future update.

This weekend’s update to version 1.041097 seems to have rolling resistance working the way Zwift intends, so we’ve started running tests to see how different wheels perform on the course with updated rolling resistance values.

First: About Crr

The change in Zwift’s latest update means the game is now setting a value for the Coefficient of Rolling Resistance (Crr) based on the wheels you are using in game and the type of surface you are currently riding.

Crr is simply a number which quantifies how much friction your tires are creating against the road surface. A fast-rolling tire has a lower Crr, while a slower tire has a higher Crr.

Our educated guess is that, before this update, Crr was a constant on Zwift, not changing based on road surface or wheel type. But now, every time the road surface changes, Zwift checks the Crr for your particular wheel for that particular surface, and uses that value to help determine your in-game speed. Zwift also sends that value to your smart trainer, where it affects the resistance you are feeling in standard Sim mode.

Here’s a snippet from the ANT+ spec showing how rolling resistance is calculated, then used to determine the resistance your smart trainer gives you:

(section 8.10.2)… the standard calculation for rolling resistance.
Rolling Resistance [N] = (Bicycle Mass + Cyclist Mass) x Coefficient of Rolling Resistance x 9.8

Calculating Total Resistance (Simulation) The total resistance applied by the fitness equipment is a sum of the wind resistance, rolling resistance and the gravitational resistance as shown in Equation 8-15:
Total resistance [N] = Gravitational Resistance + Rolling Resistance + Wind Resistance

Speed Comparison: Road Bike

We used Strava’s Effort Comparison tool to compare the speeds of an identical bike setup before and after Zwift’s Crr updates.

The frame used is the Specialized S-Works Venge, with Zipp 858/Super 9 Wheelset. One of the fastest setups in-game. Click here to access the Strava Effort Comparison, or simply watch the quick video below:

As you can see, our test bike definitely slows down in the dirt sections compared to past performances.

Speed Comparison: Road Bike vs Mountain Bike

Here’s a comparison of the same road bike above and Zwift’s new mountain bike, which is supposed to perform better than the road bikes on dirt.

While the mountain bike steadily loses ground to the road bike on most of the course, it keeps up with the road bike (and even gains a little time) on the dirt sections. (More on MTB performance in dirt coming soon!)

What Does It All Mean?

There are a few key takeaways here:

  • All dirt sections are slower with road tires, not just the Jungle Circuit (where it’s most noticeable because it’s a long stretch of dirt). The lava dirt around the volcano appears to roll at the same speed as before.
  • Soon, dirt performance will be a factor in wheel choice. Currently, all road tires perform the same in dirt, and only the mountain bike (with its MTB tires) performs differently. This will change when Zwift begins releasing more wheelsets, and they may even change the Crr values of some existing wheelsets.
  • Expect more dirt attacks. Racers already like to attack in the dirt, where dust clouds mean poor visibility. But the increased resistance on road tires in the dirt means power numbers will bump up even more in these sections.

Your Thoughts

What do you think of Zwift’s Crr changes? Chime in below!

Eric Schlange
Eric Schlange
Eric runs Zwift Insider in his spare time when he isn't on the bike or managing various business interests. He lives in Northern California with his beautiful wife, two kids and dog. Follow on Strava


Notify of

Newest Most Voted
Inline Feedbacks
View all comments
scott Brown
scott Brown
3 years ago

I cant get rid of the mountain bike any guidance ? deleted the app turned computer off I don’t know if I’m stupid or what?

Greg O
Greg O
3 years ago

Make it clearer in game which routes have dirt and/or what percentage is dirt now that the rolling resistance is different depending on bike/tires. I bet most Zwift subscribers had/have no idea this has changed and they’re getting unknowingly screwed in events.

2 years ago

Hi Eric,

What about cobbles? Would a Tron bike be superior on a given patch of rough cobbles than say an Aeroad with DT Swiss? I don’t know how Zwift handles that.

2 years ago
Reply to  Eric Schlange

i rode the jungle today for tour de zwift stage 7 – did most of the 3 laps on road bike and only switched to MTB for the last half a lap. The difference was huge. In particular it was noticeable that the power data was higher on the MTB than the road bike for the same cadence and HR data, or at least i am pretty sureit was. Does that make sense? ie in strava, having ridden most of it on road bike, my HR data and power data are otu of sync, riding HR at threshold and power… Read more »

Dan H
Dan H
2 years ago

Thanks, I was beginning to thinks I was experiencing a major breakdown in performance. My time on the jungle circuit while riding the Zwift Tour was significantly off by past times. Your explanation makes it clear what has happened.

Get Started on Zwift

Newest Featured Posts

Support This Site

Write a post, shop through us, donate or advertise. Learn more


Zwift tips and news every 2 weeks! Click to subscribe.

Would love your thoughts, please comment.x