Faster #2 – Light Wheels

This time, we’ll talk about whether lighter wheels make you faster.  

This last summer, I upgrade from a set of Bontrager Race X Lite wheels (which run about 1900 grams) to a custom set from OddsAndEndos (which run around 1500 grams). That’s about 400 grams difference, which is about 0.9 lb.

The lighter weight will have two effects.

First, it’s going to give me less weight to climb. With me at about 165 pounds during the season and the bike overall weighing about 20 pounds, that means a drop of a pound will make me 184/185 or about 0.5% faster on climbs. On a 10 minute climb, that would be a savings of about 3 seconds.

Not really worth it for faster climbing (and you can probably guess what I’m going to say about light bikes in a future post)

So, what’s the big deal about lighter wheels? Well, it’s because they have a lighter rotational mass.

Whenever you start from a stop, you have to accelerate the bike and spin up all the rotating components of the bike. Because rotational inertia is proportional to the distance of the weight from the center of rotation, the weight of the rims + tires have the biggest effect. So, if you make them lighter, it takes less effort to do that.

This is especially important if you’re riding in pacelines or groups. Light wheels can reduce the amount of effort it takes to close gaps or grab onto the back of a paceline considerably, and those little efforts tire you out at a lot. If you ride by yourself at more of a constant speed, you probably aren’t doing as much accelerating, but it’s still a nice thing to do.

There are a few downsides of light wheels.

First, the lighter the wheel, the more expensive it is. My lighter wheels only cost about $500, but if you want to, you can easily spend $2000+ on a carbon wheelset.

Second, lightness may mean less durability, especially if you go for the really light stuff.

And finally, lighter wheels are a bit harder to control. Because there is less rotational inertia, it’s harder to hold a constant speed in a paceline, and the lower inertia also means that a given amount of force into the bars generates more lean angle. I notice this most on fast descents – I have to pay much more attention to keep the line that I want.

Speed Improvement: Medium to high (it may allow you to ride with a faster group where you couldn’t before)
Coolness factor: High
Cost effectiveness: Pretty good, if you look for some nice custom wheels.
Bonus benefit: You get to decide what hubs, spokes, colors, etc. if you go the custom route, and custom wheels are often tensioned better than machine-built wheels.

So, what do you think ?