Bike Shorts: Stop Cycling Glasses From Fogging Up While Biking

Summer is fading away, and with it go those comfortable, warm rides. As the days shorten and cool, cyclists have to start digging out that cold-weather cycling gear so they can keep riding through the chilly fall and winter months ahead. 

But there’s another problem that starts to pop up for cyclists during cooler months, and it’s not just uncomfortable—it’s downright dangerous. The culprit? Foggy glasses.

When you’re in the middle of a ride, your vision is your most important asset. So, when your sunglasses fog over, it’s immediately disorienting. If you’re racing downhill at 30 miles an hour, this could be disastrous. You need to quickly stop your cycling glasses from fogging up so you can see the road and stay safe. As always, our good friend Coach Darryl MacKenzie has some tips.

What Causes Foggy Glasses When Cycling?

The reason foggy lenses happen on cooler bike rides lies in simple chemistry. The temperature difference between the back of your lenses and the front of your lenses causes a phase change in the moisture that’s in the air.

Here’s how it works: The back of your lenses is near your face, absorbing heat from your body and your breath. The harder you’re working, the more warm air you’re breathing onto your glasses. The front of your lenses, on the other hand, is under a constant flow of cold air, which rapidly cools them down. The moisture in the warm air on the back side quickly condenses onto your cool lenses, causing them to fog up.

The same thing can happen when you enter a warm indoor space after being in cold outdoor air. The warm air hits your cold glasses and — Voila! — condensation. A moment like that can send you stumbling down the entryway stairs. Isn’t science fun?

Don’t Take Off Your Glasses

“The knee-jerk reaction is to take the glasses off,” says Coach Darryl. “And that’s really not the right thing to do because the glasses protect the eyes.”

When you’re speeding along on your bike, your face is subjected to steady winds. These can cause your eyes to tear up with moisture, which restricts your visibility. The wind also brings dirt, dust and debris. Your glasses protect you from all of these hazards.

There’s also the obvious fact that you wear sunglasses to shield you from harsh UV rays. On a bright, sunny day, the glare from the sun reflecting off the road, cars and other objects can be even worse than direct sunlight itself. So, keep those glasses on. Because glasses protect you from potential harm, removing them is not a good way to stop your cycling glasses from fogging up. 

The (Surprisingly Simple) Solution 

The real solution to this problem is so simple it’s easy to miss.

“It took me 15 years or so to figure this out,” says Darryl. “I bet 90% of cyclists don’t know this one.”

What do you do, then? Simply nudge your glasses down your nose, slightly farther from your face. You don’t want to move them so far that they’re ineffective — just far enough to allow more cool air to get around the back and cool the backside of your lenses down. In Darryl’s experience, this stops your cycling glasses from fogging up—while still biking—within 10 seconds. 

If you consistently experience foggy glasses when cycling, you can also get fog-resistant lenses and sprays to help prevent it from happening. But, in a pinch, moving your glasses down your nose is the simplest way to defog them.

A Note on Masks and Foggy Glasses

In today’s pandemic-inverted world, many cyclists face another fog-inducing situation: riding with a mask. If you find yourself close to other cyclists and need to pull up your mask, this can instantly cause fogging by sending your hot breath directly toward your eyes. This can also happen when you wear a balaclava on frigid winter rides.

There are a few ways to deal with your face mask fogging your glasses. First, wear a mask that fits snugly around your nose, allowing minimal upward air escape. You can also try pushing the mask down toward the tip of your nose to let more air escape before it gets close to your glasses.

Whatever you do, be sure you know how to stop your cycling glasses from fogging up before you get on the bike. When it happens, you need to react quickly to clear it up.

Look for more insights from Coach Darryl over at his website.