By: Bruce Lin

Nothing looks faster than a triathlon bike with a solid rear disc wheel. You’ve probably seen many top triathletes racing on disc rear wheels, too. They don’t just look fast, they are fast too. A disc is the most aerodynamic rear wheel option available, and for the right athlete on the right course, it will deliver real, measurable speed gains. But discs are not for everyone.

If you’re considering ordering your next bike with a rear disc, upgrading your current bike, or buying a disc wheel to have on hand, it’s a good idea to understand the trade-offs. Here’s what you need to know.

Why a Rear Disc Wheel Is So Fast

As a general rule, the deeper a rim gets, the more aerodynamic it is. The smaller the hole in the center, the less turbulence there is from the rim and spokes passing through the air. A rear disc wheel takes this to the maximum by eliminating the hole and the spokes entirely. 

With a solid surface, a disc rear wheel passes through the air more cleanly, reducing drag. On a flat, straight course with steady wind conditions, the savings can be huge. In our wind tunnel tests, we’ve seen a disc rear wheel reduce drag by up to 25 watts at 40 km/h over a stock box-section rim, which can equate to a gain of 1-2 seconds per kilometer. These gains, of course, will be less when compared to a deep-section carbon aero wheel, but there’s no denying that a disc rear wheel is the fastest option. If you are trying to smash your PRs or achieve a dream result, choosing a rear disc is almost always the answer.

There’s also a less obvious benefit that we’ve heard described by some of our pro triathletes. A disc rear wheel is more affected by wind than a shallower wheel, but we’ve found that a rear disc remains relatively easy to handle in windy conditions, as long as the winds are steady. The disc can actually help stabilize the bike by shifting the pressure from the wind rearward, away from the front wheel, which is much more sensitive. 

Many of our Quintana Roo pros feel confident racing on a disc in windy conditions, and besides the drag reduction, this is actually a reason why so many of our pros choose a disc. That said, there is a point when the winds will become too much for a disc. 

The Downsides of a Rear Disc Wheel

When there are high, gusting crosswinds, a disc can become a liability. This is the biggest downside of rear disc wheels, and it’s why disc wheels are prohibited at events like the World Championship in Kona, where riders are exposed to gusty winds while riding along the coastline. If you plan on running a disc, always check that it’s allowed at your particular event! 

Weight is the other major downside. Discs are often significantly heavier (generally around 150-250 grams more) than deep-section aero wheels. Does this extra weight matter, though? On flat courses, the aerodynamic savings more than offset the added weight. But on hilly courses, you’ll feel that extra weight on every climb. 

Then there’s the handling. Modern disc wheels on well-designed triathlon bikes are quite easy for most riders to handle, even without exceptional bike handling skills. But when facing gusty or unpredictable crosswinds, a disc rear wheel will require more active management from the rider. Experienced athletes might be okay, but less experienced riders will probably find it unsettling. 

Cost is another downside. A quality disc wheel is a significant investment and often more expensive than a standard deep-section wheelset. The high price tag makes it harder to justify as your only rear wheel option.

Finally, consider versatility. Unlike a standard aero wheelset, a rear disc is a specialized tool. Many athletes wouldn’t want to train on a disc regularly, and it’s not the right choice for every event or course.

When Should You Choose a Rear Disc?

A rear disc makes the most sense when:

• You’re racing on a flatter and less technical course. With long, open roads and minimal turns and climbing, you can achieve higher average speeds. These are the kind of courses where a rear disc will thrive. 
• Wind conditions are predictable. Calm or consistent tail/headwind conditions favor a disc. Variable, gusty crosswinds do not. 
• You’re an experienced, competitive athlete chasing every last marginal gain for a specific target race. Are you on the edge of World Championship qualification? Are you chasing a podium result? A disc can give you a better chance at success. 

Discs make less sense when courses are hilly or technical, conditions are unpredictable, or you’re still building confidence on the bike.

As a general rule, the faster you are, the more a disc is worth using. Quintana Roo pro, Kristian Høgenhaug, for example, almost always chooses a rear disc because he averages well over 30 km/h on the bike at every event. At the World Championship in Nice, which featured over 1,000 meters of climbing, he still chose a disc wheel because he expected to average over 38 km/h. At that speed, the drag reduction outweighed the weight penalty. Regular riders averaging less than 30 km/h, however, will likely benefit more from a lighter wheel when a course features significant elevation gain. 

The Bottom Line

Here’s my advice: for the vast majority of triathletes, a quality set of deep-section aero wheels in the 60-80mm range is the more versatile choice. They’re faster than standard wheels, easier to handle in varied conditions, lighter on climbs, and more useful across a much wider range of courses and weather. If you’re using the same set of wheels for racing and training, this versatility can be extremely important. That said, I do know a few athletes who like to run a disc on their triathlon bike at all times, and they just live with it every day, no matter what. They’re seriously committed! 

The ideal scenario, if your budget allows it, is to own both options: a disc for your flat, fast target races and a deep-section wheelset for everything else. That kind of course-specific optimization is exactly what our pros do, and it’s what lets you maximize your potential race day.