When it comes to tire options, there are a lot. Here’s how to choose wisely.

By Whitney Allison

The purpose of any bike tire is to allow you to roll over terrain with as little rolling resistance and as much traction as possible. If you think about a road set up, the tires are skinny and smooth because the terrain is smooth. A mountain bike tire is fatter with a wider tread pattern (the little nodules all over the tire) to help you roll over rocks and roots with ease and have grip in loose, sweeping terrain. Gravel falls somewhere in the middle: you can have smooth gravel terrain or technical gravel terrain. Therefore, the gravel tire options also reflect the variety of terrain riders will tackle. Any gravel tire can likely get you down the road, but the “best” tire is going to be the one that can help you roll down your terrain of choice with the best balance of ease, efficiency and comfort. Let’s figure out what is best for your ride!

Initial questions to consider

What is your current set up?

Are you riding a road bike and want to put gravel tires on it? Or do you have a gravel bike? Many road bikes can accommodate gravel tires, but the issue is going to be clearance, or the ability of the tire to rotate without rubbing your frame. A typical road tire has a width of 25mm or 28mm. Many road frames can fit up to 28-20mm tires—it just really depends on your frame. This is a really wonderful way to get going on gravel if you aren’t ready to purchase a gravel bike. It’s always better to run what you brung than miss out on the fun! If you have a gravel bike, you likely have a lot of flexibility with tire width, but likely have an upper limit as well.

Do you have tubeless-ready wheels?

A tubeless-ready wheel allows you to use a tubeless tire. Special rim tape is placed around the rim of the wheel, the tire is placed on the rim, and tire sealant (a liquid-glue material) is added. When the tire is pumped up quickly the tire is able to seal to the rim and hold air. This is really, really ideal for gravel because bumpy terrain puts you at higher risk of pinch flatting (when the tube gets pinched by the rim and the ground). You don’t need to buy fancy tubeless-ready wheels, but they are 100 percent worth having if you can swing it. Although not essential, it is also helpful to know your internal wheel rim width. Just like how we all have an optimal helmet size, narrower wheels will fit a certain range of tires, but not a super fat tire well, and fatter wheels won’t fit a narrower tire well. This matters most if you are wanting a tire on the extreme—either as narrow or as fat as possible. Let’s assume that you will operate somewhere in the middle, and we can talk about the pros/cons of different width wheels another day.

What are you using the tire for?

A good tire for your gravel rides or your gravel event is the one that can get you through the hardest and most technical sections without blowing up! It’s that simple. For general riding, training, or events where you are participating but not competing where speed isn’t a top priority, opt a little beefier to give yourself more flexibility and comfort. If you are trying to choose a tire for a specific event that you are competing at or going for time, do some research and figure out what the terrain is like. If a majority of the course is pretty smooth, compact gravel, then you can get away with a narrower and smoother tire with less tread. This will be faster and more efficient. If it’s a super technical course, you’ll want something fatter with a lot of tread for traction and to avoid flatting.

Finally, if you are not a technical rider at all, you might find yourself more confident if you opt for a tire that is a little fatter with more tread in general. The gravel tire options have become so efficient in the last couple of years that even a fatter tire doesn't necessarily mean that it is a slower tire.

Determining the best tire for the job

When you are shopping for a tire in a shop or online, you’ll see something like 700x40 or 650x38. The 650b 27.5in and 700c refer to the diameter standard of the wheel not a physical measurement. If you have a “normal-sized” wheel, it is 700c. Although not super common, some very small women’s bikes come with 650c wheels. Some riders have taken to running 650 wheels on super technical terrain so they can fit a fatter tire on their bike (not something to worry about, it’s just something you may come across at some point).

The second number, 40mm or 38mm or 2.1 in, in this example, refers to the width of the tire. Most gravel tires will run between 28mm and 50mm. There are lots of tire companies out there, but let’s look at a few examples of companies that have a range of options (in no particular order): Maxxis, Donnelly and IRC. On the IRC link, about 2/3 down, there is a nice photo of all their tires lined up where you can see the range of widths and tire treads all next to each other. The more compact roads on your adventure, the more you can lean towards the left of width and tread. The more loose and rocky the adventure, the more you’ll want to lean right. The smoother treads and narrower tires will roll faster on compact surfaces but you’ll have to be more careful on technical sections and loose descents. The chunky treads provide more traction but do not roll as fast on smooth surfaces. It’s a balancing act and also why before purchasing a tire you need to think about what sort of riding you are doing with that tire.

For a practical example, I am 5’8, 140 lbs., live in Fort Collins, CO, and when I finally get to go to events this year, I will be racing. Because I like to incorporate adventure rides on questionable terrain and easier single track, I like to run a 700x40 Maxxis Rambler while training. It rolls pretty fast on smooth gravel, but gives me confidence and traction out in the mountains and on really hard terrain. I will probably run similar at Unbound Gravel and The Last Best Ride. For an event like BWR San Diego or SBT GRVL where there is either a lot of road or super smooth gravel, I would opt for something that isn’t as beefy and is narrower (like an 700x32 IRC Serac Sand) for faster rolling, but requiring me to be more careful in technical sections. For something like the FoCo Fondo, where it’s less compact than SBT GRVL but less chunky than Unbound, I’d probably run something like 700x40 Donnelly Strada Ush.

Tire pressure

So you’ve tracked down that perfect tire, but what do you pump it up to?! Skip the suggestions on the side of the tire. When we ride, there are three opposing forces: wind, drivetrain friction (i.e. your chain, cassette, etc) and rolling resistance. Tire pressure changes the contact patch of the tire on the ground. The bumps in the road providing resistance and an opposing force designates rolling resistance. It’s counterintuitive, but if you have too much tire pressure, the contact patch will be long and oval and have MORE rolling resistance than the optimal tire pressure for you, which will make the contact patch round and smaller, and therefore faster (and smoother!). If you run too low a tire pressure, you’ll be bouncing, deflecting the tire and causing more resistance and you may even hit a rock or root which can hit your rim through your tire. (Yes, you can pinch flat a tubeless tire; it’s just harder, and with the right tire pressure, more rare.)

Choosing a tire pressure takes into account your weight, your wheel rim width, and your tire width. The more narrow the tire, the more pressure you will need. ENVE Composites has a really amazing tire pressure chart that I keep on hand. It takes into account your weight, tire width, and although they use rim widths based on their wheels, it’s an excellent guide for any wheel you are using. If you are on really hard terrain, then you can opt low, and if you are on super smooth terrain, you can opt for a little more. Pumps do vary, so the chart should serve as a guide. Over time, get to know what these different pressures feel like when you push on the tire with your hand, and don’t be afraid to let some air out.

Putting it together

There are tons of gravel tires out there, but looking at what sort of equipment you have enables you to narrow down your choices. Evaluating what sorts of rides or events you want to do is a helpful way to narrow down your tire choices and find the best tire for the job. Pinning down optimal tire pressure will allow you to have the most confidence and best experience possible on that tire, no matter the width or tread.

Since 2013, Whitney Allison has raced on professional teams in the United States and Europe, constantly learning from and with incredible women, at both Women’s World Tour races and the local grassroots weekday time-trial. She owns and operates FoCo Fondo and Bike Sports in Fort Collins, Colorado.

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