Rolling resistance/aero/weight net gain

[Singular]

Width in a quality tire gives very, very little real-world difference in rolling resistance per se. What it can offer you is a greater level of grip and/or comfort for a given rolling resistance, which is not be negated (on decent road surfaces)

Aero difference is a bit trickier, but IIRC Hambini has shown this rather clearly in his big wheel test (as the difference between 23mm and 25mm).

[emotive]

What I wonder about re aero penalty:

Let's say a 2.2 tires (Continental Speed King) according to bicyclerollingresistance has 16 Watt rolling resistance. A gravel tire with a 42mm width has 22 Watt rolling resistance and is stiffer too (meaning harsher ride equals slower).

Would it better to go with 2.2 tire in 650b or the 42mm in 700c? In other words: is the rolling resistance advantage cancelled out by the aero penalty?

Most of the fast racers at the Unbound (Dirty Kanza) 206 mile gravel race last week were on 40-42mm tyres. These guys race on 650B for other races, where the conditions are rougher and more suspension is needed, so the fact they chose to use 700x40 tells me that at THEIR average speeds of 20mph, the aero penalty outweighs the rolling resistance gains

And accordingly one would wonder about the sweet spot between rolling resistance and aero penalty. Quite interesting that no one ever published wind tunnel testing about the difference between 50mm and 35mm and 25mm tires. However, I would bet that 25mm still is the gold standard because otherwise the roadie pros would use wider tires

DT Swiss did an Aero vs RR comparison between 25mm and 28mm GP4000 on their ERC1100 wheels. The sweet spot was 35kmh. Above that average speed, aero is more important, and 25mm was faster. Below that average speed, RR was more important, and 28mm was faster.  https://www.roadrevolution18.dtswiss.com/endurance/

Between a 700x42 and a 650b x 2.2 I would guess the aero becomes more significant at if your average is above 15mph/24kmh.

Gravel racing by pro level riders is relatively new. Hunt and DT swiss have done some wind tunnel testing
https://www.huntbikewheels.cc/blogs/new ... ero-matter
https://www.dtswiss.com/en/gravel

Gravel racing is now the biggest bike race segment in the US, so there are sales to be made, and more testing will come.

[coconutbuddha]

Between a 700x42 and a 650b x 2.2 I would guess the aero becomes more significant at if your average is above 15mph/24kmh.

https://www.dtswiss.com/en/gravel

The DT Swiss test is awesome. Thanks for sharing. According to the test (at 45 km/h):

- a 42mm knobby tire is approx. 15 Watt slower than a 35mm semi-slick tire.

- a 35mm semi-slick tires is between approx. 2-5 watts slower than a 30mm slick tire depending on the yaw angle.

Knowing that the Continental Speed Kind 2.2 are only 4-5 Watts per tire faster than a gravel tire in 42mm but are 25% wider it stands to reason that the aero penalty should outweigh any rolling resistance gain at 45 km/h.

I wonder what the difference would be at more normal speeds like 28-35 km/h

[Hexsense]

Then Speed King 2.2 rear wheel, and 35mm semi-slick up front for aero?

[TobinHatesYou]

For Huffmaster, I ran 35mm Terra Speeds. It was 50/50 loose gravel/find dirt and paved roads. I averaged >19mph for 90mi/4500ft elevation. Aero certainly matters.

[choochoo46]

Check out this AeroCoach test showing the contribution of rolling resistance vs. drag at 45kph (28mph). At that speed the drag contributes about 93% of the power required and rolling resistance about 7%. So a narrower 23mm tire could be beneficially vs 25mm (in the front wheel at least). As Hambini has mentioned pay attention to rim width vs rim depth for best attachment.

https://www.aero-coach.co.uk/aerodynami ... cing-tyres