Groad Trip: Tire-pressure and gear lessons from racing gravel

Rewind exactly one year: I had just made my privateer debut and raced the muddy Low Gap Grasshopper. In dramatic fashion, Geoff Kabush had overturned a 3-minute time deficit on the final descent, and literally caught me on the line. I was disappointed to have my gravel coming out party spoiled, and it came down to two things. First, I had mentally checked out, I was far enough ahead that I believed the ‘W’ was in the bag and I just had to cruise down, not taking any risks on an open road. The recurring reminder that it ain’t over til it’s over. Second, my tire pressure was way too much for the slip-sliding final descent.

In talking with Geoff — a known master of tech — over post-race beers, I realized I had chosen a whopping 45 psi to his 27 psi (with Cush Core inserts) on the half tarmac, half dirt course. Add that to the fact he is a much heavier rider than I and the difference was alarming. We had each played our strengths: I had chosen a firm “roadie” pressure to maximize my advantage on pavement and planned to hold on when we were on the dirt and he played the exact opposite card, putting everything into the dirt and the descent. The end result was thrilling and more importantly, a very valuable lesson.

This incident was, in hindsight, probably the best thing that could have happened. I dove deep down the rabbit hole of tech: Gearing, tire pressure, chain efficiency, and more. In my WorldTour roadie years, I had mostly just geeked out on weight (body and bike) and wheel depth, and never really concerned myself with the finer points of gear. Let the mechanics deal with the bike and I’ll focus on my body.

Recently, I called up Nick Legan and asked him to take me to school. Nick is currently head of all things road and gravel at Shimano North America, one of my biggest sponsors. But he is also a gravel OG, he’s written a book about gravel, done most of the gravel events across the country at some point or another, oh and he was a ProTour Mechanic in an earlier life. He’s quickly become my gravel guru from anything about the best place to stay before an event to which marginal gains to implement for an FKT.

With the new season fast approaching for many of us, now is the time for trial and error rides. The time to spend a few rides testing psi and thinking about gear choices. Legs aren’t everything in gravel and a little homework goes a long way when your goal is an ultra-endurance test of body and equipment. When I called up Nick and asked him to share some wisdom for the masses, he laughed. And then he proceeded to share some valuable wisdom, which I’ll pass on here.

For starters, Nick said now is absolutely the time for gravel racers to experiment with gear, including dialing in tire pressure.

“We’re all getting a break from our races and our travel, so it’s a good time to experiment in general,” Nick said. “One of the easiest and cheapest ways to improve your performance is by optimizing your tire pressure, and most of us are over-inflating and running too much pressure. When you and I first spoke you were telling me some of the ranges you were in and I thought they were a little high. I thought you were probably giving up some speed and efficiency.”

Tire Pressure: The Bracketing Test

Bracketing is where you take a series of photos with the same subject and you change the exposure and the aperture. The idea is by systematically going higher or lower you can narrow in on what looks and feels good.

“This is the same idea with tire pressure. A lot of this is really just dialing in what feels good for you and it can be highly personal. If you’re going to play with tire pressure I recommend you do this when this is the only thing you’re doing and the only thing you’re paying attention to. Go on a ride dedicated solely to testing tire pressure,” he said. “Incrementally take air out of the tire and notice how it feels. If you’re really paying attention, when your pressure gets low you’ll start to feel it squirm in a gentle corner — in other words, you’ll feel the casing fold and that is going to start to happen before you actually burp the tire, so that means it’s a little too low. Put a couple of PSI back in.”

“Nobody’s going to be the same, it is so personal but generally you want to get as low as you can go. In off-road instances you want to get as low as you can go without hitting the rim, pinch flatting, or breaking the wheel, and then work your way back up from there,” he said. “In gravel specifically there is a lot more pavement so you might want to be a little higher than, say, cyclocross.”

Remember, a smoother ride will equate to a faster ride due to it softening the impact on your body. The tire will envelop the stone rather than bouncing off it vertically.

Here is Shimano’s recommendation for gravel tire pressure, based on body weight and tire size.

Gearing: 1x vs 2x, and chain line

I get a lot of questions on what gears I am using and as Nick explains below, it’s way too personal. Mimicking the top pros is actually the worst thing you can do.

“To say there is an ideal gravel gear is a silly statement,” Nick said. “You should be thinking about your speed and the course. The biggest thing to consider is this: Proportionally you spent a lot more time on any given course going uphill than downhill. You are the motor, you are what propels the bicycle forward, so if you’re not optimizing for your output then you are leaving a lot on the table.”

“Your small climbing gears are actually the most important because you’re going to spend more time there than in the fast downhill gears. I would always err on the side of lower gear than you may think you need, getting bogged down and wasting strength leads to faster fatigue. If you expect a whole lot of mud, the simplicity of a 1x may have an advantage. If you want smaller steps and there’s a wide range of terrain then GRX also comes in a 2x and might be a better option to cover all your bases. Everyone wants a simple answer, but in the end, it’s a complicated question because individuals are just that.”

“You, Pete, being a stronger rider and a climber, have the ability to push a low gear that’s significantly higher than what many can push. That’s why it doesn’t make sense to always look at what the pros are running; it’s about customizing it to your motor. Small gains in efficiency adds up to tons of time over 6-20 hours.”

My personal homework

Having Nick on the phone, I couldn’t resist asking how this can pertain to me as we plan our 2021 campaign.

“For you at the pointy end of the race where things come down to sprint finishes, we are looking at every little watt we can save. We actually start to consider the drivetrain efficiency,” he said. “One of the easiest ways to do that first and foremost, and applies to everyone, is we’re going to make sure your drivetrain is really clean going into these events. You can’t show up with gunk on your pulleys and it sounds obvious [insert WorldTour roadie joke here] but that is all upwards of five to ten watts just in drivetrain efficiency. We’re going to make sure your chains are really clean and really well lubed.”

“Then we will focus on gears: I want you to run the biggest chainrings you can get away with. We’ve got to make sure you’re optimized where you think you’re going to spend a majority of your time in particular. We want to make sure that chain is as straight as possible and for your Shimano 2x, that’s probably somewhere in that third or fourth position from the smallest cog.”

Since last January, I have steadily lowered my tire pressure both on gravel and road, it’s truly something I wish I’d done in my WorldTour road years. This is also a case for some of those low cadence drills, not only will you get stronger but if you handle a bigger ring you can also gain efficiency. Lastly, in the words of my gravel guru and as a friendly PSA from Shimano: Clean your damn chain!