• Explainer

The Explainer – Ch-ch-ch-chatter bumps

by Charles Pelkey

• September 30, 2009
• Comments Off

Champions, champions everywhere.

By Charles Pelkey

Dear Explainer,
My wife asked me on a ride out on the roads of North Boulder County “what causes washboards?” I promised her I’d pose the question to you; she’s gotten wise to my usual male “authoritative sounding but full of BS answers.”

I used to think washboards were caused by the braking action of cars but their presence on straight away sections makes me rethink that theory.

Dig deep, we need to know.
Brook Watts

Dear Brook,
I appreciate your question largely because as I get older I find myself enjoying quiet road-bike rides on isolated dirt roads more than I do on pavement, which seems to play host to increasingly large cars and trucks with their invariably distracted drivers.

You’re right in observing that if braking were the cause of washboards, it would be much more isolated and a rarity on long straight stretches of road. Now that we’re back in Southern Wyoming, our family spends a lot of time at a cabin that can best be reached by following 10 miles of dirt road.

One afternoon my son and I were riding down the road and hit a stretch of absolutely brutal washboards. Suffice it to say he was much, much happier on the fully suspended mountain bike, with the old Fox Terralogic fork, than I was on my rigid ‘cross bike. Whining as I was, we began to speculate about the cause. He suggested that even his nicely tuned suspension was adding to the problem.

“I don’t feel it, but there’s a lot of bouncing going on down there,” he said pointing to his wheels.

His was a reasonable point, but the effects of a 150-pound rider on a 24-pound bike would have to pale in comparison to those of a two-ton truck.

A few minutes later, we came upon a county employee taking a coffee break while resting on the giant wheel of a road grader. The county, he said, had to re-grade some portions of the road two or three times a year, significantly up from past years. He noted that a failure to regrade the surface makes the road almost impassable, because the severity of the washboard problem tends to increase exponentially, worsening at an ever-increasing rate.

The operator said he had long been under the impression that the washboards were the physical consequence of the vibrations created by a car’s suspension as wheels encounter anything but a perfectly smooth road surface.

“It’s your suspension,” he said. “Not the bike’s, of course, but your car’s.”

The theory is based on the idea that when a heavy vehicle encounters an irregularity on the road, the suspension bounces over, compacting the surface material around the original bump and causing another at the point where the wheel strikes the surface with greater force just after the initial encounter. After a while, you end up with another surface irregularity, which in turn creates another. Eventually, the washboarding effect can stretch on for miles.

Remarkably, however, more detailed studies suggest that the presence or absence of suspension or even size of the wheel in contact with the road surface actually play little role in the formation of washboards. Instead, the data suggests that washboarding is a natural consequence of any wheel’s interaction with an unstable material and that the problem begins long before there is a noticeable irregularity in the surface of the road.

A study by Jim McElwaine of Cambridge University, Nicolas Taberlet of the École Normale Supérieure de Lyon and Stephen Morris of the University of Toronto examined the factors that can contribute to the development of washboards, motivated by the dangers such damaged roads can pose to those that use them. The study, titled “The Dynamics of Granular Ripples Formed by Rolling Wheels” uses a simple model to simulate the effects of a wheel rolling over a granular surface.

The study concluded that the mass of the wheel interacting with the road surface has a profound effect. That may be why we’re seeing more washboarding these days than we did in years past. The average weight of the vehicles plying those dirt roads is considerably higher today than it was just a decade or two ago.

Indeed, the phenomenon can even be seen on poorly maintained, low-quality asphalt road surfaces, but it takes much more time to develop into a problem. On dirt roads, the only way to address the issue is to scrape off the surface, smooth it down and then wait for the washboards to return. And they will.

Of course, in an ideal world, we could follow the best strategy and just ban cars … everywhere, all the time, but I imagine that would encounter some sort of opposition in some quarters.

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Champions, champions everywhere

Good Morning Mr. Explainer,
Since the worlds are going on (as I type!), approximately how many current “world champions” are there at any given time?
John Pearson
Calgary, Canada

Dear John,
Well, simply put, there are a boatload of folks who’ve earned the right to wear a rainbow. In fact, there are so many that I’m not even going to attempt to come up with a definitive number, lest I open my front door and find the world 60-64 cycle-ball champions on my porch ready to kick my rear end for leaving them off the list. That said, let’s try to sort through all of the events and age categories in which the UCI hands out medals and jerseys.

Let’s start with road racing. There are, of course, the three titles awarded last weekend in Mendrisio: the elite men, the elite women and the U23 men. That automatically doubles when you factor in the time trial. So we’re already up to six.

The UCI also holds a separate world championship event for juniors. This year, that was contested in August in Moscow. With road and time trial events for both junior men and women, we add another four. We now have 10 world champions for two road events.

Beginning in 2002, the UCI also began awarding world championship titles in road and track events that fall under the auspices of the Para-Olympics. The road championships were held in Bogogno, Italy. The track events are scheduled for Manchester, England, in November.

The junior worlds are also host to track events, so we have a whole bunch of world junior titles awarded there. Those include:

• Sprint – Men and Women
• Individual pursuit – Men and Women
• Team pursuit – Men and Women
• 1km time trial – Men
• 500m time trial – Women
• Points race – Men and Women
• Keirin – Men and Women
• Team sprint – Men and Women
• Scratch race – Men and Women
• Omnium – Men and Women
• Madison – Men

Of course, at the elite level, the UCI also hosts a world championship for trackies and the jersey distribution is the same, with the exception of the women’s omnium, which is not yet contested at the elite level.

Then, to make the manufacturers of rainbow jerseys even happier, the UCI awards world titles to masters racers in age categories divided into groups separated by five-increments, starting with 30-34 and ending at 70+. (How someone 20 years my junior can qualify as a “master” is beyond me, but alas, I digress.)

So as far as road and track go, we think we have our bases covered. Now add the variety of mountain bike disciplines – both cross-country and gravity events – and for both men and women and then throw in all of the age categories from juniors to masters and we have another major shipment of jerseys headed to UCI headquarters in Aigle, Switzerland.

Then comes cyclocross, which offers jerseys to elite men, elite women, junior men and U23 (they have yet to offer a junior women’s event in ‘cross). As with all other disciplines, the UCI also plays host to a world masters championship, which will, of course, distribute rainbow jerseys to each winner in those age-graded categories.

Then there are world titles to be awarded in BMX, trials and the two “indoor cycling” events, known as Cycle-ball and Artistic Cycling.

It’s worth remembering that the designated world champions may only wear the jersey in the event in which they are reigning world champion. That’s why you will see Cadel Evans sporting the rainbow stripes in mass-start events next year, while Fabian Cancellara will have that honor whenever he’s in a race against the clock. Of course, that might get a bit confusing in your local cyclocross race, in which there’s a good chance that both the 40-44 and 40-49 world champions may be lumped into the masters category on a given day. You won’t, however, see the world’s artistic cycling champion sporting her jersey in that event, no matter how good of a ‘cross racer she is.

I am sure that if I tried to account for all of the officially sanctioned UCI rainbow jerseys awarded over the course of a single year, I’d certainly miss a few, so I’ll just revert to my original answer and say it’s “a boatload.” In fact, it would probably be a big boat. Maybe they should try that some time. It sure would make for an interesting cruise.

Email Charles Pelkey

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