The best and most effective upgrade on your bike? A perfect tire. With all of gravel riding’s intricacies, it is particularly important to have firm and safe contact with the ground. To help you find out which is the best gravel tire, we alternated between putting on our lab coats and putting in the miles on gravel roads, forest highways and flowing trails.

Gravel: seemingly omnipresent, and interpreted in many different ways. Broadly speaking, gravel tends to mean any kind of road bike riding that doesn’t involve asphalt. We asked ourselves how the cycling industry will respond to the diverse requirements of “gravel” if it isn’t even able to properly define the term. The gravel movement has risen from a niche existence to the mainstream, splitting itself into subgroups rich in nuance.

The Requirements

On an international level, gravel racers are at it every week, while mountain bikers blast their gravel bikes down trails on training rides, heavily loaded bike-packers crawl through the Gobi desert with 27.4 kg of baggage and a 5.7 L water tank. In the middle of these extremes, you’ve got average Joe – the weekend rider, the everyman-graveller. He bought a gravel bike because it doesn’t restrict him to asphalt, the riding position is more comfortable, the bike’s stability inspires him with confidence, and because it promises to be more durable and versatile than the sinfully expensive carbon machine he’s got standing in the garage. In the search for the best gravel tire, it was important to us to find the best all-rounder: a tire for Joe. This tire should cover as wide a range of applications as possible, offer puncture resistance, roll easily and offer loads of grip – in every situation.

Tyre dimensions

The available tire dimensions on the market are as varied as the gravel customer himself. It’s a good thing, allowing everyone to find the right tire to meet their particular requirements. The downside of it is that with increased choice comes increased confusion and indecision. The market for gravel tires, for example, includes 28″ (700 mm) and 27.5″ (650 mm) models in a wide range of widths ranging from 28 mm to 57 mm. To make the group test as accurate and fair as possible, we limited our test field to 700c tires with widths ranging from 37 mm to 43 mm.

What do the different tire dimensions mean?

Anyone who hasn’t yet gone down the rabbit hole that is tires will most likely be scratching their head over the various size classifications. In the pursuit of clarity, ETRTO (European Tyre and Rim Technical Organization) introduced the European tire and rim standard. For example, the ETRTO size classification “37-622” indicates the width (37 mm) and the inner diameter (622 mm) of the tire. Using this designation makes it easy to match the tire to the correct rim size.

The inch classification (e.g. 28 x 1.40) indicates the approximate outer diameter (28″) and tire width (1.40″). Using inches is neither precise nor clear. For example, tire diameters of 559 mm (MTB), 571 mm (triathlon) and 590 mm (Dutch touring bikes) are all labelled 26″. Tyres with diameters between 622 and 635 mm are both labelled 28″. Curiously, tires with an inner diameter of 630 mm, on the other hand, are labelled 27″. These classifications originate from the times of spoon or plunger brakes. At the time, the exact outer diameter of the wheel was determined by the brake. Depending on tire width, there were different standards for the inner diameter. A few years ago 27,5″ was added to the available sizes. 27.5″ tires have an inner diameter of 584 mm and are identical to the old French size 650B.

The French size specification (e.g. 700 x 35C) indicates the approximate outer diameter (700 mm) and tire width (35 mm). The letter at the end indicates the inside diameter of the tire. In this case, the C stands for 622 mm.

So far, so good. But what happens to all these standards once the tire is fitted? Due to the varying dimensions of different rim models, the width of the tire can actually vary according to the inner rim width. As a rule of thumb, as the inner rim width increases by 3 mm, the tire becomes 1 mm wider. Different tire designs can also lead to a more or less pronounced expansion of the tire with increasing air pressure. This means that the tire volume can vary depending on the model, even if the size classification is the same.

What are tires made of?

To help you navigate the jargon, the following diagram illustrates the basic components of a bicycle tire. Tyre construction varies from manufacturer to manufacturer and of course from model to model.

What is the perfect tire pressure?

Spoiler alert: unfortunately there is no such thing as THE perfect tire pressure. Due to a multitude of influencing factors, there’s no simple answer to this question. Manufacturers usually recommend a pressure range for their tires, but that only puts you in the ballpark. But your ideal pressure will then change depending on the tire model, its dimensions and the terrain you’re riding on. Our test has shown that it is worth experimenting with tire pressure on a known route and in some cases even to take the manufacturer’s recommendations with a grain of salt in order to find your ideal tire pressure.

In general, on a perfectly smooth surface, the higher the air pressure, the less the tire deforms and thus the lower the rolling resistance. On gravel and uneven surfaces it’s the other way round: the lower the air pressure, the lower the rolling resistance, up to a limit. This applies to gravel roads as well as soft forest floors and meadows. Why so? A tire with less air pressure can better adapt to irregularities. It doesn’t sink into the ground as much and it can roll ‘through’ bumps rather than having to ride over them.

Therefore our suggestion is: even if the tire manufacturer recommends at least 3.4 bar – start by inflating the tire with only 2.5 bar and see how that feels. The tire should be hard enough that it doesn’t squirm on compact surfaces. At the same time, it should be soft enough to deform and adapt to irregularities in the terrain. It is important to work out the sweet spot between too hard and uncomfortable and too soft and squirmy. As long as it doesn’t squirm when you’re on asphalt, less pressure simply means more comfort and less rolling resistance off-road. Attention: if you like riding up curbs, you should make sure that you have enough pressure in your tires to prevent damaging your precious rims.

It is also important to note that tires with less volume have more rolling resistance at the same pressure. A narrow tire has to deform more to support your weight than a larger volume tire: the tires flatten more, they become less round and more energy is wasted flexing the sidewalls. Wide tires, despite any cries to the contrary, roll more easily than narrow ones! This statement is often met with scepticism, but at the same air pressure the deformation effect is more pronounced on narrow tires and must, therefore, overcome more deformation.

To ensure consistent performance, we recommend checking your air pressure at least once a month. Even the best tubes or tubeless systems lose pressure over time, due to the fact that the air pressures in bicycle tires are much higher and the wall thicknesses much thinner compared to car tires. A pressure loss of 1 bar per month is considered normal.

The test field

Tyre Size Width1 Height1 + Rim2 Weight Price
Challenge Gravel Grinder Tubeless Ready 38-622 37.6 36,0 60.0 365 g € 45.90
Compass Barlow Pass Extralight TC 38-622 37.6 36.6 60.6 381 g € 84.00
Donnelly X’Plor MSO/ Tubeless Ready 40-622 38.9 36.7 60.7 569 g € 64.99
MAXXIS Rambler Silk Shield TR 40-622 38.0 36.5 60.5 426 g € 59.50
MAXXIS Ravager Silk Shield TR 40-622 37.8 37.5 61.5 523 g € 59.50
Panaracer GravelKing SK TLC 43-622 40.8 38.6 62.6 487 g € 42.90
Schwalbe G-One Bite Evo, MicroSkin, TLE 40-622 38.2 36.9 60.9 472 g € 59.90
Schwalbe G-One Allround Evo, V-Guard, Folding 40-622 38.8 36.5 60.5 440 g € 59.90
WTB Resolute TCS Light/Fast Rolling 42-622 41.8 39.7 63.7 457 g € 45.50
WTB Riddler TCS Light/Fast Rolling 37-622 35.9 33.4 57.4 431 g € 45.50

1 measured dimensions @2,5 Bar, in mm 2 tire height + test rim (24 mm), in mm

The test criteria

As already mentioned, our aim in this group test was to identify the best all-round gravel tire. To test factors such as the rolling resistance and puncture protection of each tire without riding hundreds of thousands of test kilometres, we accelerated the process somewhat and met with Schwalbe’s engineers in its tire laboratory. Isolated from the outside world, we measured, analysed and talked shop.

To determine the rolling resistance on compact surfaces, we mounted the tires on the same rim with the same pressure and tested them at 20 km/h on the test bench, one after the other. Next, we wanted to determine puncture resistance. We punctured both the central tread (next to the studs, i.e. at the thinnest point in the rubber) and the sidewall several times using different objects. In doing so we found out what amount of force is needed to puncture the tire and how deep an object would have to penetrate. These lab values are a good indicator for tire performance in a controlled environment, but since we’re “realists”, we placed more emphasis on the results of the practical test in our final evaluation – keep it real!

In the practical test, we considered a number of important factors. We focused on the amount of grip the tire was able to generate, which in combination with the handling indicates how much confidence you’ll have in a tire on different surfaces. Our test loop included asphalt roads, compact gravel roads, soft forest ground, and trail sections – uphill and downhill. Besides testing in sunny weather, we also braved the occasional late summer rains. We asked ourselves questions such as: how does the tire accelerate and brake? How well does it roll in a straight line? How does it corner? How much confidence does the tire convey?

Other important criteria were the damping and the comfort the tires provide. How much feedback do they give from the surface we’re riding on? How much “travel” does the tire offer over roots? How stable and secure does it feel on the trail?

To find out which tire best suited which kind of rider, our evaluation included factors such as how easy the tire is to mount, how it looks and value for money.

Tops und Flops


Tops

Fast
A tubeless system will save you an average of 10 % rolling resistance compared to a setup with tubes. Schwalbe has its manufacturing tolerances perfectly under control.
Safety First
The Donnelly’s puncture protection is excellent, making it a good choice for everyday commuters.
Almost as nice as flying
The Compass Barlow Pass offers superb levels of comfort with its large volume and supple casing. It’s also the fastest rolling tire in the test field.
Styles for Miles
The style award goes to the WTB Resolute: the tan sidewalls and the design of the profile are reminiscent of MTB tires from the good old days. And it’s very fast too.

Flops

Too much of a good thing
Oversized shoulder knobs like on the MAXXIS Ravager work well on loose and damp surfaces, but not anywhere else. On hard-packed ground, the insufficiently supported knobs squirm when cornering.
Under pressure
Tubeless ready design makes mounting more difficult and tubeless tires generally need much more tire-pressure than usual before they slip onto the bead of the rim. The Panaracer only seated at over 6 bar.
Generously dimensioned
The high manufacturing tolerances of the Challenge Gravel Grinder are clearly noticeable when mounting them to the rim.
Caution!
The Donnelly’s side wall detached from the tire bead during fitting. Fortunately, we weren’t able to replicate the problem.

Key findings of the test

  • Tubes are a thing of the past and have no business on a gravel bike. Compared to a setup with a tube, a tubeless system saves an average of 10 % rolling resistance – there is no easier and cheaper way of saving that amount of wattage. As a backup, we still recommend keeping a tube in your jersey pocket.
  • A tire primarily instills confidence and trust through predictable behaviour. A reliable tire is especially important on non-homogeneous surfaces such as those encountered on a gravel ride.
  • Tyre widths of 37mm to 40 mm are the preferred choice for all-round gravel tires as they provide the best compromise between off- and on-road performance.
  • Shallow tread patterns such as those featured on the WTB Riddler or the MAXXIS Rambler have proven to be outstanding all-rounders.
  • Even very minimal treads such as the diamond-file pattern on the Compass Barlow Pass are able to generate more grip than one would expect from looking at it. Finding the correct tire pressure is important here.
  • Precisely manufactured Tubeless-Ready tires are difficult to mount and sometimes require 6 bar before seating onto the rim bead. Unfortunately, ETRTO still hasn’t come up with a tubeless standard, meaning that some rim-tire combinations are more tricky than others. Before breaking a tire lever when trying to get the tire off, we recommend checking that the tire isn’t still seated on the bead at any point.
  • After 20 tire changes, the muscles in your hands start aching.
  • Tan-wall tires definitely go faster. Same as cool socks and beards!

Which is the best gravel tire?

A gravel tire will always be a compromise due to the varying requirements of the gravel segment. There are gravel tires that perform better on hard-packed surfaces, and others that are true trail kings. We were out to find the perfect all-rounder: a tire that inspires you with confidence on asphalt, hard-packed gravel roads and loose forest loam, leaving the rider to enjoy nature and the riding experience. The WTB Riddler TCS Light/Fast Rolling clearly deserves our best in test badge. Its qualities were able to convince all of our testers. Even if there were tires with better lab values, its all-round performance couldn’t be topped in real-world conditions – keep it real!

WTB Riddler TCS Light/Fast Rolling 700 x 37C

This article is from GRAN FONDO issue #010

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