Getting off pavement brings freedom not found in traditional road riding. It also brings more rolling resistance; pedaling becomes heavier as soon as you roll off the asphalt and onto the dirt, robbing you of either energy or speed.
You have some options to minimize this energy cost. Adjusting tire pressure is the zero-cost method and can make a large difference in the power required to maintain a given speed. Changing to a different tire width can also reduce rolling resistance, as can switching to a different brand and model of tire that has a more supple tire casing, a more flexible puncture protection layer, and/or a tread compound with lower hysteresis (the lag in rebound following impact).
To find the fastest tire models, widths, and pressures for gravel riding, we sent 24 tires to Wheel Energy Oy, in Nastola, Finland. Wheel Energy is the world’s leading independent lab for measuring the rolling resistance of bicycle tires.
You can read about how we tested tires, along with an explainer on what makes a tire roll fast.
The results below rank the tires from fastest to slowest, when tested with a suspended 40kg load at 35kph on a rim with a 23mm internal width from 1.5 bar (22psi) to 6 bar (87psi).
Below the chart is an analysis of various tire-construction factors, including the carcass, the tread compound, the protection layers, the tread design, and air pressure.
Wheel Energy rolling resistance test results
|29 psi||36 psi||43 psi||51 psi|
|2 bar||2.5 bar||3 bar||3.5 bar|
|Fastest to slowest||mm||grams||watts||watts||watts||watts|
|1||Challenge Strada Bianca Pro TLR 36||36||387||28.4||24.7||22.3||17.7|
|2||Specialized Pathfinder Pro TLR 38||38||492||32.0||28.3||23.2||18.9|
|3||Challenge Strada Bianca Pro 36 — Latex Tube||36||371||31.0||28.8||25.1||20.4|
|4||Challenge Gravel Grinder Pro TLR 36||36||415||36.8||32.5||24.8||21.8|
|5||Schwalbe G-One R Evo Super Race TLE 40||40||500||31.0||28.2||25.8||21.8|
|6||Panaracer Gravel King SS 38 TLC||38||419||32.4||31.2||29.7||26.4|
|7||Specialized Tracer Pro TLR 42||42||556||30.3||28.1||26.8||25.3|
|8||Schwalbe G-One Speed Evo Super Round TLE 38||38||483||38.0||33.1||28.9||23.6|
|9||Specialized Pathfinder Pro TLR 42||42||553||34.7||31.0||28.7||24.5|
|10||WTB Byway TCS 34||34||373||43.0||38.6||35.1||27.5|
|11||Specialized Tracer Pro TLR 38||38||461||33.7||29.4||27.6||26.3|
|12||Challenge Strada Bianca Pro TL 40 – Tubular||40||499||42.8||38.6||35.9||33.9|
|13||Panaracer Gravel King SS 43 TLC||43||483||34.7||32.7||30.6||26.8|
|14||Vittoria Terreno Dry TLR 38 2.0 Graphene||38||456||43.5||38.8||36.5||33.3|
|15||Challenge Strada Bianca Pro Team Ed. — Tubular||40||546||36.8||32.5||28.5||26.1|
|16||Panaracer Gravel King SK 43 TLC||43||487||33.8||31.8||27.7||26.1|
|17||Panaracer Gravel King SK 38 TLC||38||420||35.2||33.3||31.8||27.5|
|18||Challenge Strada Bianca Pro 36- Tubular||36||526||41.7||38.5||35.3||32.9|
|19||WTB Byway Light TCS 40||40||452||41.0||36.8||35.5||31.0|
|20||Challenge Gravel Grinder Pro — Latex Tube||36||422||38.5||34.6||32.3||30.7|
|21||WTB Riddler Light TCS 37||37||470||43.0||38.8||35.9||33.7|
|22||WTB Byway Light TCS 44||44||519||40.8||37.8||36.4||34.0|
|23||WTB Riddler Light TCS 45||45||522||41.8||39.2||36.8||33.5|
|24||Challenge Gravel Grinder Pro 36 — Tubular||36||543||42.9||39.0||36.2||34.7|
Note that the power required to maintain 35kph decreases as air pressure increases. But as with many things in cycling, it’s a balancing act, as higher pressures can compromise comfort and traction, as well as potentially your speed if you are riding on a rough surface.
Tire carcass: How vulcanization works
The fastest and third-fastest tires in the test are 36mm versions of the file-tread Challenge Strada Bianca Pro, with the tubeless TLR clincher version being faster than its non-tubeless clincher cousin. The fourth-place tire is also a tubeless Challenge Pro 36 model, namely the mixed-tread (file center tread with side knobs) Gravel Grinder Pro TLR.
The low power required to drive these three Challenge Pro tires appears to illustrate that a supple, drum-wound, super-high-thread-count (260 threads per inch, or tpi), non-vulcanized casing can make a tire roll fast. While the second-place Specialized Pathfinder Pro 38mm tire and the other non-Challenge tires in this test are fully vulcanized, the hand-glued tread strip is the only part of a Challenge Pro tire that is vulcanized.
Vulcanization is the heat process discovered in 1839 by Charles Goodyear that hardens rubber, making it elastic and durable. Commercial use of rubber would not be possible without it. In high-end, racing tubulars, only the tread is put into a mold and vulcanized, while all motor-vehicle tires and almost all bicycle tires are vulcanized in their entirety inside a mold.
Challenge Pro clinchers (including tubeless clinchers) are among only a handful of clinchers on the market that are built with the same method as racing tubulars. The casing on both tire types is wound on a drum, and the thickness of the threads determines how many of them fit in per inch; the threads in these 260tpi Challenge gravel casings are about as thick as a human hair.
There is one construction difference between the two types of tires. A racing tubular’s casing edges are lapped back on themselves, wrapped around a latex inner tube, and stitched together at a sewing machine. Conversely, a handmade clincher’s casing edges are instead lapped around foldable aramid beads for engaging clincher rims. The tire casings, whether tubular or clincher, are then mounted onto rims and inflated. A highly-skilled worker glues the vulcanized tread strip on by hand on both types of tires, carefully lining up the big rubber-band of a tread loop before letting it touch the tacky glue.
Leaving these spun casings in their raw state allows the super-thin casing threads to move independently and absorb bumps with less energy loss than if they had been impregnated with rubber and vulcanized. This construction method is the same as in the Specialized Turbo Cotton Hell of the North tire that was fastest in our Paris-Roubaix rolling-resistance test.
By contrast, the non-Challenge tires in this test are made like most tires: the flat, sticky, “green tire” loop (“green” indicating that the rubber compounds in it are uncooked and malleable), consisting of rubber-impregnated casing fabric lapped over tire beads with a sticky, formless tread strip stuck down onto it, is put into a mold. Hot steam injected through channels in the mold and into a bladder inside the green tire heats and expands it, imparting on it the mold’s overall shape, the tread pattern, and the embossed lettering of details like tire size and inflation pressure. The high temperature melts the layers together, and subsequent cooling stiffens the tire to hold its shape and make it tough and elastic.
Tread compound and puncture breakers
Creating a tread compound is a balancing act between grip and rolling resistance. Attaining more grip requires a softer tread to conform to and grip the ground. But softer rubber generally means higher hysteresis (which converts kinetic energy into heat) and higher rolling resistance.
Similarly, puncture breakers can be super flexible to roll fast at the expense of puncture protection.
It is an art and a science to come up with a tread compound that grips well and also has low hysteretic energy loss. Many fast-rolling bike tread compounds are developed by German engineers who cut their teeth at Continental Tire, whose automotive division responds to demands from car manufacturers for lower tire rolling resistance to meet Corporate Average Fuel Economy (CAFE) standards. Wolfgang Arenz is credited with coming up with Continental’s Black Chili compound, then Specialized’s Gripton compound and, most recently, Schwalbe’s Addix compound.
By mixing other materials into natural rubber, a tread-compound developer can affect that balance between hysteresis and grip. For instance, silica, when mixed in the proper concentration and at the proper time and temperature, can decrease rolling resistance while also increasing grip without sacrificing durability. Vittoria claims that graphene added to its compounds fills spaces between rubber molecules and improves grip, durability, and speed. A compound’s exact mixture and how to mix them are closely-held secret recipes, and the mixing machinery must be extremely high-tech and precise to yield repeatable results.
There can also be multiple compounds on a tire. The Dual DNA Compound in all WTB tires in this test consists of two rubber compounds. The center tread’s firmer rubber compound rolls faster and resists wear, while the softer, slower-rebounding rubber of the side knobs improves control and grip.
|Tire Model, Fastest to Slowest||Breaker||Compound||Casing||Tread|
|1||Challenge Strada Bianca Pro TLR 36||
|2||Specialized Pathfinder Pro TLR 38||BlackBelt||Gripton||Endurant||
|3||Challenge Strada Bianca Pro 36 with Latex Tube||
|4||Challenge Gravel Grinder Pro TLR 36||
|5||Schwalbe G-One R Evo Super Race TLE 40||V-Guard||Addix Race||Super Race||knobby|
|6||Panaracer Gravel King SS 38 TLC||Anti-Flat Nylon||ZSG-file center||AX-α||mixed|
|7||Specialized Tracer Pro TLR 42||n/a||Gripton||Endurant||knobby|
|7||Schwalbe G-One Speed Evo Super Round TLE 38||V-Guard||AddixSpeedGrip||Super Ground||low|
|9||Specialized Pathfinder Pro TLR 42||BlackBelt||Gripton||Endurant||
|10||WTB Byway TCS 34||SG2||Dual DNA||single-ply||
|11||Specialized Tracer Pro TLR 38||BlackBelt||Gripton||Endurant||knobby|
|12||Challenge Strada Bianca Pro Tubular TL 40||
|12||Panaracer Gravel King SS 43 TLC||Anti-Flat Nylon||ZSG-file center||AX-α||mixed|
|14||Vittoria Terreno Dry TLR 38 2.0 Graphene||1-layer||Graphene 2.0||Nylon||
fish scale center
|15||Challenge Strada Bianca Pro Tubular TL 40 Team Ed. S3||
|16||Panaracer Gravel King SK 43 TLC||Anti-Flat Nylon||ZSG-knobby center||AX-α||knobby|
|17||Panaracer Gravel King SK 38 TLC||Anti-Flat Nylon||ZSG-knobby center||AX-α||knobby|
|18||Challenge Strada Bianca Pro Tubular 36||
|19||WTB Byway Light TCS 40||SG2||Dual DNA||single-ply||
|20||Challenge Gravel Grinder Pro with Latex Tube 36||
|21||WTB Riddler Light TCS 37||SG2||Dual DNA||single-ply||knobby|
|22||WTB Byway Light TCS 44||SG2||Dual DNA||single-ply||
|23||WTB Riddler Light TCS 45||SG2||Dual DNA||single-ply||knobby|
|24||Challenge Gravel Grinder Pro Tubular 36||
A slick-center Gripton tread atop a BlackBelt puncture-protection strip (on a supple Endurant casing) can account for the Specialized Pathfinder Pro 2Bliss Ready 38’s second-place finish. The same can be said for the Addix Race and Addix Speedgrip tread and V-Guard breakers of the Schwalbe G-One R Evo Super Race TLE 40 and G-One Speed Evo Super Ground TLE 38. There is a similar story with the Zero Slip Grip tread, Anti-Flat nylon breaker (on an AX-α casing) of the Panaracer Gravel King SS 38 TLC.
The Schwalbes have 67tpi casings yet have a similar rolling resistance as tires with much higher thread counts (other than the 60tpi Tracer Pro 42, which does not have a puncture belt). This would seem to demonstrate lower hysteresis in their respective Addix Race and Addix Speedgrip compounds and translucent Souplesse construction, Super Race, and Super Ground casing designs.
We tested a few tires in multiple widths. The only time where bigger was faster than the narrower version was the Specialized 2Bliss Ready Tracer Pro — and that’s because the 38mm has a BlackBelt puncture-protection belt and the 42mm Tracer Pro does not. There is a rolling-resistance cost for puncture protection.
Tread smoothness and thickness are critical to rolling speed. The 36mm Challenge Gravel Grinder Pro TLR’s more aggressive tread requires 6 watts more per tire to go the same speed as the winning 36mm Challenge Strada Bianca Pro TLR, since they share the same tire carcass.
Of course, the file tread will be a liability when cornering on loose dirt, where side knobs or extra caution will help. On courses with few turns relative to the length of the straight stretches, file tread won’t be as much of a liability.
The Specialized Pathfinder Pro 38 also requires the rider to put out 6 watts less per tire to go 30kph as the Specialized Tracer Pro 38. Their puncture breakers and side knobs are alike, but the Pathfinder’s rolling resistance is reduced both by its slick center tread and 120tpi casing. The Tracer has small knobs down the center and a less-supple 60tpi.
The Vittoria Terreno Dry’s unique angled “fish scale” center tread is designed to let the roll fast while offering braking and cornering traction.
As we found in our test of rolling resistance of tires raced by pros in Paris-Roubaix, tubular tires sucked up more power than clinchers of identical construction. Despite sharing the same hand-glued file tread, 260tpi polyester-thread casing and two-layer Puncture Protection Strip (PPS2), the Challenge Strada Bianca Pro Tubular 36 pulled 27 watts versus the clincher versions in tubeless at 15.7 watts, and tubed at 20.4 watts. Similarly, the Challenge Gravel Grinder Pro Tubular 36 soaked up 32.2 watts, 10.6 and 3.6 watts more than the clincher versions in tubeless and tubed, respectively.
Tubeless construction, eliminating a separate inner tube that can move relative to the tire casing, sped up the tubulars as well. The tubeless Challenge Team Edition Strada Bianca Pro TL 40 S3 Tubular, while being slowed down by its larger size and sped up by its slick tread, took about a watt less to ride at 30kph than did the file-tread Strada Bianca Pro 36 Tubular.
Clinchers may roll faster than identically-constructed tubulars due to energy absorbed by the tubular’s cotton base tape and the adhesive bonding it to the rim. Tubulars in this test were attached to the rim with a 3M/Challenge co-developed tubular tape.
Gravel tubulars, of course, are quite rare, as tubeless tires dominate the market.
Tire pressure — More is faster… to a point
|29 psi||36 psi||43 psi||51 psi||58 psi||65 psi||72 psi||80 psi|
|2,0 bar||2,5 bar||3,0 bar||3,5 bar||4,0 bar||4,5 bar||5,0 bar||5,5 Bar|
|Fastest to slowest||watts||watts||watts||watts||watts||watts||watts||watts||watts|
|1||Challenge Strada Bianca Pro TLR 36||35.5||28.4||24.7||22.3||17.7||15.7||15.9|
|2||Specialized Pathfinder Pro TLR 38||36.5||32.0||28.3||23.2||18.9||20.2|
|3||Challenge Strada Bianca Pro 36 with Latex Tube||36.0||31.0||28.8||25.1||20.4||21.2|
|4||Challenge Gravel Grinder Pro TLR 36||41.4||36.8||32.5||24.8||21.8||21.6||22.5|
|5||Schwalbe G-One R Evo Super Race TLE 40||35.4||31.0||28.2||25.8||21.8||23.2|
|6||Panaracer Gravel King SS 38 TLC||36.1||32.4||31.2||29.7||26.4||22.9||24.1|
|7||Specialized Tracer Pro TLR 42||34.2||30.3||28.1||26.8||25.3||23.8||23.6||24.6|
|7||Schwalbe G-One Speed Evo Super Round TLE 38||44.1||38.0||33.1||28.9||23.6||24.7|
|9||Specialized Pathfinder Pro TLR 42||39.4||34.7||31.0||28.7||24.5||24.1||23.8||24.4|
|10||WTB Byway TCS 34||51.8||43.0||38.6||35.1||27.5||25.8||24.7||23.9||25.2|
Rolling resistance drops with each increase in tire pressure until the roughness of the road combined with the damping by the rider’s body will overcome efficiency gains from higher tire stiffness. This will cause the rolling resistance to shoot up. This transition point will vary based on the surface and your combined bike and body weight.
Beyond what the chart says, you can also likely feel the negative effect of putting too much air in your tires as you get rattled around on the gravel. Very few riders would select the highest pressure options shown above for rough courses, for instance.
In 2018 we did an outdoor roll-down test with gravel tire pressures at 15, 30, 50, and 70psi. Although the riders felt that their 70psi runs were the fastest, they were in fact slower than their runs at 30 and 50psi. For the two 150lb test riders, 30psi seemed to be the sweet spot.
All that to say, the absolute fastest tire pressures listed above are, by definition, for the surface tested in Wheel Energy’s lab at the 40kg load and 35kph wheel speed.
Takeaways — As always, it’s a balancing act
For gravel, tubeless tires are faster than tubed tires and tubulars of similar construction. Tread compound is important. Tires with the smoothest tread with sufficient traction for the course will be the fastest. Supple and delicate casings roll faster than thicker and tougher ones. Less puncture protection results in faster rolling speed. These last three items point to a tradeoff to make between reliability and speed. Super-fast tires are not fast when flat — or when you have skidded off the road due to lack of traction.
On this test, narrower tires rolled faster than similar tires in wider widths, and they would be lighter and accelerate faster as well. While the separate chunks of steel welded onto the surface of the test drum are rough and 30kph over it is fast, rougher surfaces demand bigger tires. There is also an energy-saving benefit to the rider to have more comfort and not be bounced around as much.
As for air pressure, testing by top teams with power meters on the roughest Paris-Roubaix sections found the fastest setup that also prevented rim damage and pinch flats was 0.5-1 bar lower than the pressure we found to roll fastest on this same lab test. This also applied to the winner, who won on the second-fastest tire in our test. The damping in Wheel Energy’s pull shock is probably less than the damping of the human body. It may make sense to use 0.5-1 bar (7-14 psi) lower pressure on rough dirt than this test predicts. On smoother dirt, using the same pressure for minimum rolling resistance in this test is likely the fastest.