This piece set out to be about front center, and then I realized if you care about front center, I’ve probably already got you in my contacts. We nerds stick together. Put another way, there’s little reason to care about an aspect of bike design that means next to nothing on its own, but does reflect an occasional irritant: toe overlap.
Toe overlap is the phenomenon where a rider’s toe touches the back of their front wheel. Before we go any further, I’m going say something that may surprise some readers: Toe overlap is no big deal.
That said, we are going to talk a bit about front center; it may be the single weirdest dimension of a bicycle frame. It’s weird because unlike top tube length and chainstay length, it doesn’t relate to the length of a particular tube. So what is it?
Front center is the distance between the center of the bottom bracket and the center of the front dropout, measured in a straight line. Toe overlap happens due to an interplay of front center, crank arm length, cleat position, shoe size and tire size. Which is to say, there’s no easy way to predict when a rider might encounter it.
Not to worry
So why did I say toe overlap is no big deal? Easy. When you are traveling any faster than a walking speed, you are unlikely to turn your front wheel enough for the tire to rub your shoe. The solution is relatively easy: At low speeds, if you are going to make a sharp turn, just make sure to keep the outside pedal down.
I encounter toe overlap on occasion when I’ve been stopped on the bike and need to make a sharp turn to get rolling again. I will also get it on rare occasions when racing cyclocross or riding singletrack on a gravel bike in which I’m both pedaling and making a sharp turn.
Why does it happen?
More diminutive riders tend to have toe overlap issues due to the short top tubes of their bikes. In making a smaller bike, the distance between the front wheel and the bottom bracket—front center—decreases. Bike designers have ways to work around this and I’ll cover that in a piece about how size affects geometry.
Toe overlap is not just a phenomenon of small bikes, though. It is more of an issue than it was than it was 25 years ago because bike fitters now advocate positioning the cleat behind the ball of the foot rather directly beneath the ball of the foot. This change in fitting came about because people are naturally inclined to center their foot over a flat pedal, rather than placing the ball of their foot over the pedal axle.
For many riders, this change improved their sense of poise on the bike; it also decreased calf fatigue for most riders.
But.
I always seem to do that, don’t I?
In moving the cleat toward the midfoot, that moved the front of the shoe closer to the front wheel. That change in cleat position means that, to use me as an example, while I never used to have toe overlap issues, it means that I can run into toe overlap on any bike with tires larger than 28mm in width. If I’m on a gravel bike, I have toe overlap. End of story.
The when
Toe overlap won’t always happen on a given bike. Unlike head tube angle or fork rake, which are set in stone when a frameset is built, toe overlap is arises from a number of factors that can be changed: cleat position, crank arm length, shoe size and tire size will all affect it. Bigger shoes, longer crank arms and wider tires are typical suspects. As most riders can’t just choose to wear a smaller shoe, and changing crank length is rather expensive, if the problem is truly worrying to a rider, the easiest way to address it is by installing a narrower tire. Honestly, that’s a pretty bad solution as well.
It’s important to understand that toe overlap can’t happen on road and gravel bikes once you are moving fast enough to need to lean the bike to turn. Once you are leaning the bike over to turn you are countersteering and if you are countersteering, you won’t be turning the bar enough to make contact between shoe and tire.
Because toe overlap can’t happen at speed, that means it can only happen at low speeds. That should be reassuring in that it guarantees it can’t cause a high-speed crash. Not that you can’t get hurt at low speeds, but if you’re going at least 10 mph, it’ll never happen. And when going slow? Just try to remember that as you turn, you need to keep your outside pedal down, which is a practice that hopefully everyone rides by.