BMX Basics
The physics of humiliation, part 1.


I never thought I'd say this, but it's a real shame nobody listens to Iron Maiden anymore. For those of you who don't remember, Iron Maiden was an occasionally educational heavy-metal band famous for playing fifteen-minute songs based on literary classics. One of their songs, "The Rime of the Ancient Mariner", tells the story of a dude who's on his way to a wedding when some scummy-looking sailor "fixes him with his eye" and tells him a long, frightening story about accidentally causing a terrible catastrophe. After what seems like forever, he permits the wedding guest to continue in his way. The guest is relieved to be free, but he knows that he will not be able to view the wedding, or anything else, the same way again. The Ancient Mariner's words have forever changed his perspective.


There are times I feel like the Ancient Mariner of BMX---stopping you on your happy way through this paper and insisting that I will tell you the truth about our sport. It's a role I've been happy to take these past three years. Since everything comes to an end, however, even the longest of poems (or Iron Maiden songs), I am equally happy to note that "BMX Basics" will not continue into 1999. The website will remain open and be updated frequently, but my days in print will end this December. In the meantime, I will attempt to wrap up most of the "loose ends" we've come up with over the years and perhaps even tell a story or two, just like the Mariner himself. But enough of this. With apologies to our Hindu readers, I have a couple of sacred cows to cook up between now and then...


If I could snap my fingers and magically change the way things are in BMX, I'd start by eliminating what I call the "champion-chaser" mentality. I define "champion-chasing" as a belief that nothing in our sport means anything unless it is associated with victory. According to the champion-chasers in the BMX media, the only opinions that matter are those of "top experts" and "top pros". Never mind the fact that naturally gifted riders rarely have to learn racing techniques step-by-step, the way the rest of us do. Put aside the idea that it doesn't make any sense for a hundred-pound 13 Rookie to "train like a pro" or "ride like a pro". Most of all, don't even consider the concept of being a "nerd" and studying racing---if you can't "just do it", you shouldn't bother.
Champion-chasing drives me nuts, and I've devoted most of my writing career to fighting it in every way possible. I firmly believe that racing is as fulfilling for the less-than-perfect (the slow, the squidly, the untalented---in short, people like me) as it is for people like Patrick-Swayze look-alike and fellow BMX Today columnist Jeff Dein. I'm not likely to change my mind about this.
With the above I mind, let's talk about the physics of BMX. The champion-chasing mentality demands that I "dumb this down" and use photos of top riders doing impossible things to demonstrate my point. Instead we'll use humiliating incidents from my own racing career. The champions can laugh; the rest of us can, possibly, learn something.


We'll start with inertia. You've probably heard that "a body at rest wants to stay at rest, and a body in motion wants to stay in motion." If you've thought about it in a racing sense, you may have assumed that the "body" in question here is the bike/rider combination. That's only halfway right; in fact you and your bicycle are each "bodies", and each has a separate inertia.


Luckily for you, there are four "contact points" between your inertia and the bike's: your hands and feet. When you pedal the bike, it speeds up, and since you are holding on, you speed up too; when it slows down, you slow down as well.


The gate start is an example of inertia at work. The NBL rules state that you can't move your front tire over the dropping gate. This means that, no matter what you do, your bike has to come out of the gate slowly so as not to "jump the gate" when it drops. You could just resign yourself to this, or you could do what most people do and start moving your body before the gate drops. You can get your body moving early and, by using your contact points to pull the bike along, let it "catch up" with you after the gate hits the ground. That's why any photo of a Pro gate shows everyone shoving their hips into the handlebars out of the gate. You can't ride around like that, but you don't need to. All you have to do is get your body out fast, and your bike will follow after a while.
Why is it helpful to do this? It goes back to inertia. You outweigh your bike by quite a bit. It's much harder to move your body from a resting position than it is to move your bike from that same resting position. If you "roll the gate" then you have to accelerate your body by pedaling. If you "thrust" out of the gate, your body is already up to a certain speed and all you have to do is let your bike, which is much easier to accelerate, catch up.


The difference between body inertia and bike inertia can have disastrous consequences for the rider. Example: Fourteen years ago, I lined up on the gate for the very first moto of my very first race. Like most Rookies (then called Beginners), I was using the one-pedal start. Also like most Rookies, I was very, very nervous, so much so that I started my pedaling motion too early. My bike and I started rolling together, which was just fine, but soon after that, my front wheel hit the gate.
Remember, a body in motion wants to stay in motion. My bike had to stop because it had hit the gate, but does that necessarily mean that I had to stop? Only if my "contact points" were strong enough to slow me down. In my case, my feet weren't planted securely, so they slipped and my body kept moving.


I landed in a position known as the "top tube tango", which is where your hands are still on the bars, your feet are dragging on the ground behind the bike, and your, um, let's call it the "crotch area", has landed hard on the top tube pad. By this time the gate had actually dropped, so I rolled all the way down the starting hill in this position. Needless to say, I didn't win that moto.
That was a humiliating way to begin my racing career, but my luck improved after that and before I knew it I was doing the two-pedal start. We've already discussed how it's important to get your body moving early and bring your bike up to speed once the gate has dropped. Many riders pull their bikes forward so hard after leaving the gate that said bikes get ahead of them and they end up doing a "power-wheelie" down the starting hill. This is very impressive looking, but it isn't necessarily the best way to do things. Ideally, once you leave the gate your bike should be solidly planted and you should be using your power to move forward, not to keep the front wheel up.
I'm sure you won't blame me for not knowing this back in 1987, when I was struggling to make my way through the Ohio State Race Series. There I was, in the semi for 15 Novice at the West Chester track, and absolutely ready to do whatever it took to win. The gate dropped and I blasted out with all the feeble fury I could muster. I was so impressed with my start that I shoved the bike out and began power-wheelying to victory... and fell backwards off the bike.


At first glance, this seems like a balance problem, but it's really an inertia problem. I was letting my bike accelerate out from under me. Had I not made the mistake of bringing my bike too far forward, my "contact points" would have kept it under control and I would have been able to put whatever power I had into the bike without worrying about losing it. This isn't the same as falling off the back of a manual or sit-down wheelie; I had actually pedaled the bike away from my body. If you try it yourself you'll see what I mean, although I warn you it will hurt.


Inertia doesn't just help young riders make fools of themselves out of the gate---it works its magic everywhere. A body in motion wants to stay in motion, and that also means it doesn't want to change direction. Mrs. Boswell frequently complains about being tossed against the armrests and center console of my trusty Rover when we are traveling somewhere. "You're turning too hard!" she will say, usually while smacking me.


"I'm not turning too hard," I reply. "It's your stubborn inertia." If Mrs. Boswell didn't want to obey the laws of physics and keep traveling in the same direction, she wouldn't "travel" directly into the armrest when I hand a hard left. Explanations like this are what help keep a marriage together, and darn it, they also apply to BMX.


Once upon a time, at an indoor track in Hilliard, Ohio, yours truly was a real threat to win his main event. I'd won all three of my motos, stomped the comp in my quarter, and easily won my semi. I was on fire. This was going to be the day I triumphed over all my enemies. Why, then, did I let my enemies, who were also kind of my friends, talk me into leaving the indoor track and going riding in the snow?


We had a lot of fun getting our tires full of snow. We got back inside just in time for our main. I took a commanding lead and was four bikes ahead going into the second-to-last turn. Meanwhile, the snow in my tires had been melting and mixing with the dirt of the track, creating a slippery kind of mud. When I pointed my front wheel into the turn, I was surprised to notice that the bike didn't turn with it. The inertia of my straight-forward motion was too strong for the weakened turning force my slippery front wheel provided. I saw the disaster coming, but there was nothing I could do. The last thing I saw before plowing into the berm head-first was the triumphant grin of the dry-tired rider behind me.


Until next month, then, we'll leave my younger self chewing dirt in the berm. When we return, I'll discuss the other candidate for Most Likely to Humiliate a Racer---center of gravity. Until then, may The Force (of inertia) be with you.

 

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