Are 29er’s Really Faster? The Physics Behind the Big Wheels

Some love them, others love to hate them, but hype aside, are 29er’s really faster? The simple answer is yes, but if you are the type who constantly wonders why, here is your explanation.

I hear a lot of talk about momentum whenever 29er’s come into discussion. It is in fact true that 29er’s carry momentum better than 26’s but for different reasons than you may think. Momentum is equal to mass times velocity. Let’s say we have a 26” bike and a 29” bike, both made of the same components. The 29er will naturally be a bit heavier due to the bigger frame to accommodate the wheels, as well as larger wheels, tires and tubes. If we look back to our momentum equation, if both bikes traveled at the same speed the 29” bike would carry more momentum because of the extra weight: However because of this extra weight more energy would be required to maintain the same speed as the 26” bike. In other words if a rider using the exact same effort rode each bike, the 29er would actually be slightly slower than the 26 because of the extra mass. But the big picture is not quite that simple…

Now to the core of the issue, the secret behind the big wheel; contact angle. Contact angle is simply the angle created by the tire and the ground. A 29” wheel has a lower contact angle to the ground than a 26” wheel because of the larger diameter.

Because of the lower contact angle the 29” wheel will cover bumps, rocks, ruts and other obstacles with ease. The 26” wheel has a harsh contact angle and will not climb over these obstacles as gradually as a 29” wheel. This more gradual climbing nature of a 29er means less energy lost to conquering terrain features. The larger wheel diameter also means that the 29er will not hit ever minor bump and rut. Now don’t confuse this with the contact angle principal; in this example the larger wheel simply skips over ruts and bumps.

Because the 29er can conquer technical terrain features more easily, less energy is lost to impact with the terrain, and more is preserved in the momentum. Also less energy is required to maintain a current speed, so less energy is required to maintain the level of momentum. All-in-all 29er’s do indeed carry there momentum better than 26’s in any technical terrain. 

Another consideration is momentum capacity. On the trail we have certain sections where we feel comfortable only riding at or below a maximum speed. For instance a very technical flat run with big exposure might cause us to dial down our speed even though we easily have the energy to go faster. Because a 29er is a bit heavier than its’ 26” equivalent, the momentum equation shows us that the 29er will carry more momentum than the 26” when they are both traveling at the same speed.