You guys know how I feel about “weight-weeniness.” The obsession with the weight of bikes and their components is an expensive distraction from things that matter more, like how much fun you’re having. What follows comes from some of my other work, consulting for companies in the bike industry. That work often pushes me to do research I wouldn’t normally do. For example, I don’t care how much my wheels weigh, but part of my work with them required gaining an understanding of how wheels behave, out in the real world, when they’re not just sitting on a scale.
Based on my reading, here’s what’s true:
It takes fractionally more energy to carry a “heavy” wheel uphill than a lighter wheel. This difference in energy is extremely small, even with weight differences up to a pound. Once the wheel is spinning, most of its momentum is moving forward, not up, and so even on an incline, the energy of its momentum overcomes most of its weight disadvantages. There is an equation for this, but that’s for a white paper, not this venue.
Offsetting the slight climbing disadvantage of a heavier wheel is a descending advantage, since a heavier wheel takes longer to lose its momentum rolling downhill than a lighter wheel. The conserved energy isn’t exactly equal. It does take more energy to carry a heavier wheel up than it returns on descent, but the measured difference is vanishingly small.
The problem is, people tend to understand wheel weight as an absolute value, rather than a relative one. Lighter, by this way of thinking, will always be better. But that understanding misses some key points.
First, a low weight differential between two wheels, especially when the bulk of that weight difference is at the hub, leads to an imperceptible difference between the wheels in most climbing scenarios. In a blind test, most riders wouldn’t sense any difference at all related to weight. We’re just not that finely calibrated.
Second, other aspects of a wheel’s design, like the quality of bearings and the rims’ torsional stiffness, are more palpable. You may feel the smoothness of one wheel, or the immediacy of its power transfer, and assume those things are related to weight, when actually they’re just related to quality.
Third, to put this in some perspective, a full water bottle weights approximately one pound. Among “high end” wheels you will seldom run across a differential greater than a pound. In absolute terms, because that bottle has no rotational momentum, it actually costs you more energy on a climb than that same weight in a wheel’s hub, but again, the amount of energy we’re talking about is very small, beyond your capacity to perceive it, given all the other factors affecting you on a climb and descent.
I understand that what I’m telling you about wheel weight is counter intuitive.
Of course, heavier things take more energy to move uphill than lighter things. What I’m saying is that the relative difference between one wheelset and another, lighter pair of wheels is negligible, and the upsides to the heavier wheel are not insignificant. A heavier wheel will, more often than not, be more durable. It will be more stable on a fast descent, too. Also, when you’re evaluating wheels, it’s a mistake to capture one scenario, like climbing, and predicate your buying decision solely on that.
Wheel quality is a real factor in the way it feels to ride a bike, but that quality is seldom about weight. When I’m looking for new wheels I’m interested in bearings, hub engagement, and the rim’s torsional stiffness. If you choose a wheel that rates high in those three areas, you’ll be on something fast and smooth that handles well at all speeds, and that’s usually much more fun.
Truth.