Bicycle wheels comparison
Thanks to JP Ballard from Swiss Side for making this possible.
An oft repeated wisdom is that the most efficient bicycle upgrades are, in order, tyres, tubes and wheels. Here I attempt to quantify the benefit of a rather extreme upgrade of all three of them. Something done repeatedly in YouTube and peer-reviewed science. Why bother? Because in this mockery of science, we do the N=1 experiment focused on the one demographic I care about: mid-aged below-average enthusiast.
Hypothesis
The difference will be measurable, but below marketing/theoretical claims.
Why I think so: neither peer reviewed science nor industry research take into account how slow I am ;) Their model of a very slow rider is a speed-obsessed CEO of aerodynamics company, who calls 25 km/h the slowest and a 10% gradient insignificant. Both are a bit of an achievement for me. My best gains will be finally moving a spacer above the stem and I will get there one day. But free speed from throwing money at the problem is real too, so there will be some.
Why I might be wrong: high school math suggests that over a constant distance the cycling speeds nearly cancel themselves out, leaving the time difference between different setups constant. I.e. a fast rider will go from 22 to 20 minutes, I will go from 37 to 35 minutes.
What are the claims? Hard to say, I don’t have all the data and what it takes to work out the nonlinearities. Swiss Side calculates the gains at about 1 minute over a 40km ride and 2.5 minutes over a 90km ride. That’s compared to aluminum road wheels, so should be a conservative estimate for the comparison at hand. On top of that BRR measured the rolling resistance of my gravel tyres at 2*19.5W and the road wheels at 9.3W+9.1W, resulting in 20.6W difference. Which according to bike calculator should give about 7 minutes difference over a 40km ride and 15.5 minutes over a 90km ride. Primary school math tells me that’s about 2 minutes of total gains per 10km, ignoring the difference in inner tubes.
The system
Experiment: Swiss Side HADRON² Ultimate 500
These aerodynamic road wheels are ridden by the Decathlon team, which sits in the middle of the Tour-de-France ranking. The 500mm rim depth is widely recommended around the Internet. The wheel is built on the top of the line DT Swiss 180 hub. As recommended by Swiss Side, it’s equipped with 26mm Continental Aero 111 on the front and 28mm Continental GP 5000 on the rear and TPU tubes. Both wheels inflated to 6.5 bar before each ride.
This is JP’s personal prototype set, into which I imagine he put an astronomical number of kilometres. He was also kind enough to mount them on my bike himself.
Control: DT Swiss G 1800 Spline
This is the base model in DT Swiss gravel wheels lineup. An all-around reasonable choice for someone who wants to explore nearby forests. Equipped with Pirelli Cinturato Gravel H 40-622 tyres and whatever butyl tubes the shop had around. Both wheels inflated to 3.0 bar before each ride.
Bicycle: Arc8 Eero
After extensive research this is the best bike I have found for myself. It is pretty light and aerodynamic… For something with a very relaxed riding position. Equipped with a 1x2 GRX 820 its list weight is 8.4kg and comes with a massive 42:51 granny gear - something I’m very thankful for whenever the gradient exceeds 10%. Have I mentioned below average?
Rider: me
The weakest link. I could say I have decades of cycling experience. That would refer to commuting, visiting places or just goofing around a bit. But truth be told, I have only decided to treat it as a sport about a year ago. Some years ago I have been given an old school road bike and my spine was having none of it. Hence, it took me a couple months to bite the bullet and try a drop bar bike again (and a very relaxed gravel bike at that). Then I spent a large part of the winter sick. All in all, one can say that by the time I do this test, I have in total about half a year of cycling experience.
The protocol
Ride consistency
I’m not an ex-pro YouTuber who can stay in same position indefinitely. And I don’t have all day to do the rides back-to-back. But I do try to control as many variables as I can:
- Effort: I do not have a power meter and my heart rate monitor does not connect to my head unit. Hence, I ride to perceived exertion. I do short sprints out of saddle for short punchy climbs (think: overpass) or when safety calls for it (think: exiting a busy intersection). Otherwise I stay in seat and put in a solid effort (accepting some pain afterwards).
- Position: I cycle between tucked in on hoods and in drops as much as my spine will allow (again accepting some pain afterwards). But sometimes need to stretch a bit in hoods or tops.
- Route: I record the route on the first ride and use that for navigation in my Garmin. I then follow the same exact route, down to repeating the wrong turns where I got a little bit lost.
- Gear: I wear the same clothes and bring the same gear. Anything I don’t actually need goes to a jersey pocket.
- Behaviour: Nobody is paying me to risk my health, so I ride safely. I stop on red lights, when among pedestrians I slow down to a brisk walking pace.
- Rest: Two full days of rest before the flat ride, then one day of rest before the hilly ride.
- Nutrition: I start the day with a large carbs-heavy breakfast, then eat an extra apple before the ride.
- Fueling and hydration: Or lack thereof. I put a couple spoons of honey into a single 750ml bottle of water. Then throughout the ride get angry at all the fountains along the way being disabled due to a ground frost warning.
- Traffic: The flat ride goes through some relatively high traffic roads. Hence I do the experiment-control pairs of rides on the same day of the week, before noon but after the morning traffic subsides.
Measurement
I measure the time, speed and heart rate using a smartphone with a smartwatch. Analyse all this with Strava. Use a Garmin Edge as a backup.
As this time of the year I need to stop quite a bit, I use moving times (excluding faffing around time) whenever available.
60km flat
When you want a flat route in Switzerland, you go around a lake. So I went on a 60km counterclockwise ride, starting about the middle of the west coast and ending at Zürich Hauptbahnhof. Going around the lake is beneficial for comparisons too - smooths out somewhat the effect of wind.
Speaking of wind, it was generally the same direction for all the rides. But it was much stronger on the day of the control ride (with the gravel wheels and tyres on).
Observations after the ride
- The first surprise I haven’t seen anyone mention: a road tyre is less stable. Being narrower and without knobs around the contact patch, it doesn’t want to stay upright as much as a gravel tyre. Some people might like their bike dancing like that. I was a bit concerned about falling, given that…
- Deep rims are more sensitive to crosswinds. It’s an obvious difference and
frankly not hard to predict. Even the Swiss Side calculator
comes with a warning to not hurt yourself with too deep rims. In fact I was
surprised how easy it was to control that. At some point I surprised myself by
noticing I have only seen the left rim for a couple minutes, only then to
notice I’ve been countering a slight crosswind. On the other hand, it makes
passing cars way more impactful. You can tell the car’s aerodynamics just by
how much your bike moves to the sides.
- Note, however, that this sensitivity to crosswinds is somehting I noticed despite the windspeed being just a third of what it was on control ride. I wonder how bad a fair comparison would be.
- A 26mm tyre at 6.5 bar is more chatty than a 40mm one at 3 bar, news at 11. Again an obvious difference, but again I was surprised by how little effect it had in practice. I didn’t end with any more pain than usual. I didn’t feel like I’ll fly off the seat just because of some cable or a bit of cobbles. But it did make me appreciate how smooth Swiss tarmac is.
- Riding on these wheels feels faster. Whether it’s because of the chattiness and instability, placebo effect, or actually being better at translating effort into movement, it does feel like it.
- There was no noticeable difference in grip or stopping distance. But, this was dry tarmac at medium speeds.
Conclusion: road wheels are a tiny bit less comfortable, but still perfectly fine on smooth tarmac.
Results
Control - gravel wheels and tyres:
Experiment - road wheels and tyres:
Conclusion: This is nowhere near the 12 minute expected difference. Between Zürich’s traffic and weather differences, the signal to noise ratio calls for a repeat though.
Segments
As this ride ends in the city, where your speed is determined by the traffic, the door to door time is not entirely reliable. Hence the table below compares the best times on a bunch of distances and a couple longer segments.
| Segment | Gravel time | Road time | Gravel speed | Road speed |
|---|---|---|---|---|
| Best 10km | 22:09 | 20:38 | 27.1 km/h | 29.1 km/h |
| Best 20km | 47:31 | 44:10 | 25.3 km/h | 27.3 km/h |
| Best 30km | 1:15:21 | 1:08:57 | 23.9 km/h | 26.1 km/h |
| Best 40km | 1:42:35 | 1:32:59 | 23.4 km/h | 25.8 km/h |
| (Best 50km) | 2:10:42 | 2:04:36 | 23.0 km/h | 24.1 km/h |
| Horgen-Wädenswil | 18:31 | 15:45 | 24.2 km/h | 28.5 km/h |
| Wädenswil-Rapperswil | 36:01 | 31:08 | 20.8 km/h | 25.8 km/h |
| Rapperswil-Meilen | 37:28 | 37:20 | 25.5 km/h | 24.1 km/h |
| Meilen-Riesbach | 32:08 | 29:22 | 19.9 km/h | 22.5 km/h |
Wädenswil-Rapperswil was the segment seeing most of the headwind for both rides. I went 5km/h faster on aero wheels there, but it was also 10km/h less of a headwind.
Horgen-Wädenswil and Meilen-Riesbach were primarily crosswinds, here aero wheels fared better by respectively 4.3 and 2.6km/h. Judging by the heart rate plots, the former might be a larger difference because I had a bit of a slow start on the control ride.
Rapperswil-Meilen was the only segment where at some moments there could have been a bit of tailwind. It’s the only moment gravel wheels won, by 1.4 km/h.
Finally, comparing best stretches, road wheels consistently won by about 2 km/h. The 50km stretch touched a traffic jam around road construction, then the city.
Conclusion: at my speeds and on good roads, there’s about 2 km/h, or 8.5%, speed to be gained by upgrading the wheels.
Heart rate
On the control (gravel wheels) ride:
| Z1 | Endurance | < 112 | 10:17 | 6.7% |
| Z2 | Moderate | 112 - 148 | 1:03:58 | 41.8% |
| Z3 | Tempo | 148 - 166 | 1:15:53 | 49.6% |
| Z4 | Threshold | 166 - 184 | 2:46 | 1.8% |
On the experiment (road wheels) ride:
| Z1 | Endurance | < 112 | 17:21 | 11.6% |
| Z2 | Moderate | 112 - 148 | 51:01 | 34.2% |
| Z3 | Tempo | 148 - 166 | 1:17:05 | 51.7% |
| Z4 | Threshold | 166 - 184 | 3:42 | 2.5% |
Conclusion: apparently on the road wheels I spent more time both sprinting and slacking off. That’s likely due to the traffic in Zürich.
30km with 600m elevation gain
This is much closer to the stereotype of Switzerland. A category 2 climb lets us leave the urbanised valley behind and commute down a rural one.
Observations after the ride
- Crosswinds are even scarier on downhills. A sudden gust on this ride was my first close call for years. The data shows I ended up being slower on average on sharp descents, with my top speed for the day being about 5km/h lower.
- This settup climbs surprisingly well. Not sure why, it isn’t that much lighter and I’m sure aerodynamics doesn’t matter that much when I’m grinding the granny gear at 8km/h. But it felt much faster and less tiresome. The time Strava classified as threshold heart rate zone went down from 6:20 to just 18s and the number of breathers I needed went from two to zero.
- I also felt this in my commutes back home. I live on top of a hill and on both days the climb was surprisingly good. But I won’t do gravel on these things - wrists started hurting already on the smooth part, I bailed out before reaching a proper forest road.
Results
Control - gravel wheels and tyres:
Experiment - road wheels and tyres:
Conclusion: If this was a flat ride, the expected time difference would be 6 minutes. The measured difference is over twice that.
Segments
| Segment | Gravel time | Road time | Gravel speed | Road speed |
|---|---|---|---|---|
| Best 10km | 24:30 | 21:13 | 24.5 km/h | 28.3 km/h |
| Best 20km | 56:47 | 51:09 | 21.1 km/h | 23.5 km/h |
| Best 30km | 1:56:13 | 1:50:09 | 15.5 km/h | 16.3 km/h |
| ↑ Langnau am Albis - Albis Pass | 34:43 | 34:53 | 6.7 km/h | 6.1 km/h |
| ↑ Landikon - Uitikon | 13:11 | 12:03 | 12.1 km/h | 13.2 km/h |
| ↓ Albis Pass - Türlen | 2:42 | 2:53 | 39.4 km/h | 36.9 km/h |
| Türlen - Landikon | 30:21 | 28:44 | 22.1 km/h | 26.1 km/h |
| ↓ Uitikon - Albisrieden | 3:35 | 3:39 | 25.6 km/h | 22.5 km/h |
Garmin, with its more aggressive pause removal, recorded the first climb (which it classifies as Cat 2) as:
Control - gravel wheels and tyres:
Experiment - road wheels and tyres:
The second climb was way easier (Cat 4). Garmin’s numbers:
Control - gravel wheels and tyres:
Experiment - road wheels and tyres:
In any case, this shows that I was no slower when climbing on the aero wheels.
Now, the two sharp descents show that I was way more comfortable on the gravel set. Especially the first, sharper one, where I’ve been 2.5km/h avg and 5km/h max faster on them was a surprise. Also, I triple checked the numbers for the last segment. I don’t understand the math used by Strava, my calculator agrees that this difference in time does not correspond to this difference in speed. But I’m sticking with the software.
Finally, the long 1.3% descent in the middle was 4km/h faster on road wheels, both in average and max speed.
Conclusion: aero wheels come with slight wins on climbs, large wins on the long section in the middle and make me squeeze the brakes much more on descents.
Heart rate
On the control (gravel wheels) ride:
| Z1 | Endurance | < 112 | 16:37 | 14.0% |
| Z2 | Moderate | 112 - 148 | 38:46 | 32.7% |
| Z3 | Tempo | 148 - 166 | 56:46 | 47.9% |
| Z4 | Threshold | 166 - 184 | 6:20 | 5.3% |
On the experiment (road wheels) ride:
| Z1 | Endurance | < 112 | 12:58 | 12.3% |
| Z2 | Moderate | 112 - 148 | 42:25 | 40.2% |
| Z3 | Tempo | 148 - 166 | 49:51 | 47.2% |
| Z4 | Threshold | 166 - 184 | 18s | 0.3% |
Importantly my average heart rate on the long climb was solid 10bpm less. The difference was critical to the point of needing a breather at one point on the gravel set, but not on the road set.
Conclusion: the ride on the road wheels and tyres was tremendously easier.
Bonus
