Video summary

What’s fastest on gravel: 45mm, 55mm or MTB?

Main summary

Key takeaways

Product Review

Product reviewed (context)

The video is a gravel tire speed comparison focused on Schwalbe tires across different widths (45mm vs 55mm) and tread/compound types (slick vs knobby / MTB-style). It answers:

  • What’s fastest on gravel—narrower vs wider, slick vs knobby—and under which real-world conditions?

Testing approach / methodology (key info)

  • Real-world field testing over 2 days on two surfaces:

    1. Hard pack: magnesium chloride–treated surface (very firm/embedded rocks; “cat one-ish gravel”)
    2. Rough gravel: looser, deep sandy/rough “washboard”-type surface (“cat three-ish gravel”)

  • Chung method testing (ride-based physics calculation rather than only GPS time):

    • “Half-pipe” protocol: ride down, ride up, return to form a bowl-shaped loop
    • Repeat 3 times per tire condition
    • Four tires tested on two tracks

  • Variables measured/controlled beyond width and pressure:

    • Tire rollout under load
    • Air density
    • Wind speed/direction
    • Sealant amount
    • Wheel standardization using loaned matching Hunt/Magic sets with Schwalbe 40mm Limitless Gravel Air wheels
    • Rider aerodynamics measured with Ingmar Jungnickel’s Aero app (“CDA” for rider position)
    • Power meter used for accurate speed/power inputs (Favero Assioma pedals mentioned)

Main findings (speed results)

1) Hard-packed / firm magnesium-chloride surface

Comparison: Schwalbe RS Pro 45mm vs RS Pro 55mm

  • 55mm shows a small rolling benefit
  • 45mm shows a small aero benefit
  • Net result: at ~35 kph, both tires require ~the same power
    • ~206 W for each

Practical implications:

  • On fast, well-packed gravel, you may not need a bigger tire.
  • If you ride around ~35 kph or faster, width differences are small.
  • At slower speeds, the rolling advantage of wider tires becomes more relevant (aero matters less relatively).

2) Rougher gravel (looser, more demanding)

Comparison includes:

  • Schwalbe Racing Ralph (described as “Racing Ralph”) in two compound/speed variants:
    • Speed / fast compound (tan sidewall; faster/harder compound)
    • SpeedGrip (black sidewall; softer compound, “control,” especially wet)
  • Plus: 55mm vs 45mm RS Pro, and an MTB-style Racing Ralph/Speed option

Top-line speed ranking on rough gravel:

  • Fastest: 55mm RS Prime / RS Pro (the 55mm slick-style option in the test)
  • 45mm RS Pro: slower than the 55mm
  • MTB-style tire (Racing Ralph, fast compound): fast, but not the top winner in straight-line rolling speed

Notable numeric results (rough gravel at ~35 kph / ~21 mph):

  • Holding ~35 kph:
    • 45mm RS Pro: ~294 W
    • 55mm: saves ~23 W vs the 45mm (includes aero)
    • Racing Ralph (fast compound MTB tire): saves ~16 W vs the 45mm, but not as fast as the 55mm option

Pros (supported by the testing)

  • 55mm can be meaningfully faster on rougher gravel (notably ~23 W advantage vs 45mm in this test scenario).
  • On firm hardpack, the speed difference between 45mm and 55mm can be minimal (effectively equal at ~35 kph / ~206 W both).
  • A “one-tire” strategy may work well:
    • the video’s all-around preference trends toward 55mm for Colorado / mixed gravel variety.
  • Rolling resistance is hard to measure outside; the measured physics approach is more informative than casual tests or Strava comparisons.

Cons / limitations / caveats mentioned

  • “Slick-looking” doesn’t mean identical performance. Same casing / tread appearance can still differ due to rubber compound durometer.

    • The SpeedGrip version produced bad/unsatisfactory tests, so results weren’t published.

  • Straight-line speed ≠ real riding priorities.

    • More knobs may not win measured rolling-speed, but they can provide grip/handling on twisty or loose sections.
    • Analogy: the “fastest drum tire” may still be poor for flats risk or real cornering.

  • Reliability depends on rider repeatability. On extremely rough terrain, small changes in rider position can reduce confidence or affect outcomes.

  • External factors can disrupt a planned test site. Road construction/spraying magnesium chloride disrupted one intended rough-surface location, forcing a pivot.

  • Results depend on measured conditions (surface type, air density, wind, pressure/temperature). A tire that wins on one gravel type may not win on all.

Slick vs knobby / MTB tire discussion (qualitative)

  • On rough gravel, you might expect knobbier tires to be better due to traction/bite.
  • However, in the straight-line measured rolling-speed comparison, the 55mm slick-style gravel tire won.
  • For courses with climbing/descending and twisty sections, the MTB tire (knobs) may be preferred in practice since it can do more than just roll fast in a line.

User experience / practical guidance given

  • If you ride very hard-packed and fast, consider going a bit smaller (example guidance: ~40mm slick-type tires).
  • If you ride mixed-to-rougher gravel, don’t be afraid of extra width (often 5mm+, commonly 55mm), because it can:
    • improve speed
    • make the bike easier to pedal (less “punishing”)
  • Rider anecdote:
    • On rougher terrain, the wider tire allowed them to stay in a more favorable gear range.
    • They reported being able to use two more gears on 55s because it was faster.

Recommendation / verdict (overall)

  • Mainly firm / hard-packed: 45mm vs 55mm may be close at higher speeds—choose based on comfort/control and local preference.
  • Rougher / looser gravel or mixed surfaces: the video’s data strongly favors 55mm, which was faster by a meaningful margin (~23 W at ~35 kph) in rough straight-line rolling tests.
  • Overall: for most mixed gravel riding, the video leans toward 55mm as the safer “fast everywhere” pick, especially where surfaces aren’t uniformly smooth.

Unique points mentioned about the product (consolidated)

  1. Speed depends more on surface firmness/looseness than on width alone (“it depends”).
  2. On hard-pack, 45mm and 55mm are effectively equal at ~35 kph (~206 W each).
  3. On rough gravel, 55mm is clearly faster than 45mm (~23 W advantage at ~35 kph; includes aero).
  4. MTB-style Racing Ralph (fast compound) saves ~16 W vs 45mm on rough gravel but isn’t the fastest overall in that test.
  5. Slick vs knobby: knobs may win on grip/handling, but not necessarily on straight-line rolling speed.
  6. Compound matters (Speed vs SpeedGrip; same model/tread look doesn’t guarantee same performance).
  7. Some results (SpeedGrip) were not shown due to bad testing.
  8. Width guidance:
    • ~40mm for very hard-packed fast gravel
    • +5mm (commonly 55mm) for rougher gravel
  9. Bigger tires can make riding easier / pedaling smoother on rough terrain.
  10. Testing caveats: rider positioning repeatability and route/construction changes affect conditions.

Speaker-specific contributions

  • Ben Delaney (host/organizer)

    • Frames the core question (why real-world testing matters)
    • Explains practical takeaways and guidance (smaller on hardpack, wider on rougher gravel)
    • Mentions equipment support (wheels loan, tire supplier) and promo code (BikeTiresDirect)

  • John Kerish (tire testing expert)

    • Explains the Chung method, what’s measured, and how variables are controlled
    • Provides key numeric results (e.g., ~206 W equal on hardpack, ~23 W win for 55mm on rough)
    • Discusses reliability/repeatability, limitations, and why straight-line rolling tests can diverge from handling needs

Original video