Speed Tests: Supertuck (Solo + 2 Riders, Race vs Free-RIde)

Zwift’s supertuck is a fun feature, a sort of Easter egg which can be combined with strong course knowledge to give the legs a bit of respite during a race. The concept is simple enough: if the road is steep enough, and you’re going fast enough, stop pedaling and your avatar will get into the aero supertuck position. This will allow you to coast at zero watts while keeping pace with riders who are holding some significant power on the descent.

For details of how the supertuck works, read “All About the Supertuck on Zwift“

But did you know the supertuck actually behaves differently in races than it does when free-riding? This is because of an update released in May 2019 which changed two key race physics, but only in race events:

1. The slight braking force when descending is entirely removed. So you will descend faster in a race event than you would in a group ride or free ride, assuming all other variables are equal.
2. Zwift made the supertuck more aero. Zwift didn’t share the exact numbers, but they’ve said the supertuck’s aero advantage is similar to the aero powerup (which reduces your CdA by 25%).

This means our experience supertucking in group ride events and free rides might vary significantly when compared to races. What does that difference look and feel like? I decided to run some experiments… for science!

Test Goals

This test set out to answer three questions:

1. How much faster is the supertuck in race vs non-race mode?
2. Is it faster to supertuck with additional riders vs solo supertucking? If it is faster, how much faster is it?
3. If I’m supertucking, how hard do riders around me need to pedal in order to drop me from the group? Does this change in race vs non-race mode?

Test Parameters and Methodology

All of the test riders were set to 183cm height, 75kg weight, and rode Zwift Aero bikes with 32mm Zwift wheels.

Tests were done on the Fox Hill descent in London. (I prefer the steady, steep, long descent of the Alpe du Zwift, but no race events ever descend the Alpe, so it wouldn’t work for these tests.) We would hold 300 watts steady once the descent began, then cut power to 0 as soon as the riders hit 60 kph.

Two-rider tests were done either in “Meetup-Only View” or on deserted courses, to eliminate the possibility of speed-influencing interference from other riders.

Test Results

Conclusions

There are several conclusions to draw from the results of our tests:

1. The supertuck is much faster in race mode: our solo supertuck tests showed a difference of over 8kph between race-mode and non-race mode. And while this difference is magnified somewhat because the non-race supertuckers actually came out of the supertuck on slower portions of the descent, clearly race mode supertucking is significantly faster.
2. Supertucking works well in pack and solo race situations: it allows you to rest while staying in a pack of riders who are putting out significant wattage (see “Supertucking In a Mixed Group” below). In fact, if the race is strung out and riders are solo, our numbers show that supertucking will let you keep pace with a rider holding 300W. That’s huge!
3. Supertucking with others is faster than solo: by now smart Zwifters know this – that the “churn” of riders swapping places at the front makes a group go faster than a solo rider could in the same conditions. Here’s a quick video showing the supertuck churn in one of our tests.
4. Solo supertucking isn’t a fast strategy outside of races: in our test, a solo supertucking rider is 9 seconds slower than a rider holding just 150W (2 w/kg). This tells us that if you supertuck in a free ride or group ride, you’ll probably be slower than if you simply pedaled at a recovery pace. And you certainly won’t keep up with others who are putting out higher wattage – unless you’re sitting in their draft.

Although I didn’t test it here, it’s also worth noting that the steeper the road gets, the smarter it is to supertuck. We know from our w/kg tests that as a decline gets steeper, putting out higher wattage makes less and less of a speed difference. So the steeper the road gets, the more others would have to hammer to keep up with your supertuck.

Supertucking In a Mixed Group

The tests above give us some solid numbers to work from, but they don’t answer our final question: “If I’m supertucking, how hard do riders around me need to pedal in order to drop me from the group? Does this change in race vs non-race mode?”

Based on the race numbers above, we can see that a solo supertucking rider travels at the same speed as a solo rider holding 300W. And two supertucking riders will actually travel significantly faster than two riders holding 300W! So clearly, a supertucking rider can sit in with other riders who are putting out 300W (4 w/kg) on a descent like Fox Hill.

It is possible to supertuck behind one or more “powered” riders in a group ride or free ride situation as well, but the supertuck doesn’t offer as much of an advantage in this situation, due to Zwift’s modified physics for races. Still, we ran a simple test with two riders – on supertucking, and the other holding the highest power we could hold without dropping the supertucker. The results are far from perfect, but our “powered” rider was able to hold 275W with the supertucker still holding on all the way down Fox Hill.

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