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Pavement Problems

Pavement Problems

On my cross-country trip last summer, I was surprised to see that highways in general have deteriorated over the past several years. One major hazard I encountered was deep ruts in paved roads. And they were surprisingly hazardous. Crossing North Dakota on U.S. Highway 2, I encountered four distinct ruts matching the wheel tracks of heavy trucks for mile after mile. The left lane also had ruts, but they weren’t as bad as the right lane, so I’d move over into the left lane when traffic allowed. At one point, my front tire hooked on a rut and the bike headed for the right lane despite my attempts to hold it. One instant I was in the left lane — the next instant I was in the right lane. Fortunately, the right lane wasn’t occupied at the moment. But the unplanned lane change really got my attention. It was pretty unnerving at highway speed.

Road ruts
I’d already encountered bad ruts north of Toronto in Canada and on I-75 in Michigan, and I would find more ruts passing through the Spokane area in eastern Washington. Apparently, both heavy trucks and studded tires create ruts in the pavement, and road crews just aren’t able to repave as quickly as the ruts are generated. The ruts seem to be most prevalent in northern central states and Canadian provinces where the temperature varies widely between winter and summer.

Ruts are a special problem for motorcycles because of the steering dynamics. Ruts are also unnerving in a car, but they’re easier to control with four wheels and power steering. If you haven’t encountered serious road ruts yet, you may wonder what all the fuss is about. But once you’ve had the bike suddenly dart sideways in heavy traffic, you’ll be motivated to understand what’s happening and curious about managing such situations.

I’ve observed two different types of road ruts, which we’ll refer to as "truck” and "studded tire.” Truck ruts are four distinct grooves matching the location of the dual rear wheels on big commercial trucks. It appears that truck ruts are formed by heavy trucks gradually pounding and squeezing asphalt pavement into the rutted shape during the warm summer months rather than tires wearing away the surface. Studded tire ruts are more common near big cities where commuters regularly use studded tires during the winter months. The studs actually grind away the road surface in the tire track areas, creating two wider, more rounded ruts.

The problem for motorcyclists is that front-end geometry reacts in strange ways to the tire running in a rut. You may have the bike weaving from one side of the lane to the other, or suddenly steering itself in a new direction. And you’ll also get some curious steering feedback, such as the feeling that the front end is momentarily resisting your pressure on the grips. Let’s first think about why this occurs, and then we’ll make some suggestions for maintaining control.

Imagine a tire riding in the center of a deep rut. So long as the tire contacts the pavement in the center of the tread, the bike will steer straight ahead. But remember that with a two-wheeler, the front wheel constantly steers itself from one side to the other as it maintains the bike in a balanced state. It’s not much of a weave, but it’s a natural phenomenon with single track vehicles. The point is the bike won’t follow the center of a rut exactly. And when the bike drifts over toward the side of a rut, the contact ring also moves farther over to that side. As the contact ring moves toward the side of the tire, the tire will drag more and more on that side, steering the front wheel off center. For instance, the contact ring moving position to the right will tend to steer the front wheel to the right, out of the rut.

But remember that bikes tend to roll around the center of mass. So, the front wheel steering toward the right will actually countersteer the bike into a left lean. And in this situation, leaning left will point the machine back toward the rut. Now, with the bike steering itself back toward the rut, it probably won’t just center in the rut and rebalance again. If the bike continues across toward the opposite side of the rut, tire drag will again steer the contact ring out of the rut (toward the left), and that will countersteer the bike back toward the rut again.

All this off-center tire drag and leaning causes the bike to swerve around in the lane. The feeling at the handlebars can be startling because you might be resisting the swerve, but the bike moves over anyway. And if there are two ruts side by side, as with truck ruts, balance can get very twitchy as the rider fights to keep the bike pointed more or less straight down the lane. As a general rule, the geometry of the front end will tend to stabilize the bike after negotiating uneven pavement. But with continuous pavement ruts, the bike may not restore itself to a balanced condition until the tires are out of the ruts.

Potholes (also known as chuckholes) are formed when a small area of pavement begins to deteriorate and vehicle tires push the broken fragments out of the hole. The hole forms very quickly in wet conditions because tires slamming down into the hole force the water (and debris) out like a single shot from a powerful pressure washer. Potholes often form next to railroad tracks, creating a serious bike hazard. Potholes are dangerous for a motorcycle not only because the steep edge of a hole can push the tire sideways, but the sharp edge can bend or fracture a wheel rim.

Potholes are a fact of life every spring in and around northern cities. The road has to thaw before the maintenance crews can do any permanent repairs, and the only workable temporary fixes are to pack gravel into the holes or throw a steel plate over the hole, or both.

Frost heaves
Other road hazards in northern climates are frost heaves — big lumps of pavement pushed up into mounds by the freezing of the wet ground beneath the road. Frost heaves are common every spring on Canadian and Alaskan roads. Mounds up to a foot high can occur anywhere on the road, and you don’t want to hit one of these lumps at highway speed. If you’re heading for northern destinations in the spring, watch carefully and be prepared to swerve between the frost heaves.

As with potholes, the temporary fix for frost heaves is to scrape the pavement level, and apply a coat of gravel. On highways such as the Alcan, that means several gravel patches every mile, for thousands of miles. In rare instances, you’ll even get a sign. Crossing a short gravel patch isn’t a problem unless it happens to be in the middle of a turn, one reason to keep speed within sight distance when you’re off on an adventure in the wilderness.

Negotiating surface hazards
If it isn’t obvious, you need to maintain enough following distance behind other vehicles to be able to see surface hazards in time to change the bike’s line. But you know that in aggressive city traffic, leaving some space ahead of you is simply an invitation for someone to dive into it. The clever motorcycle commuter learns to search more aggressively, but must also accept the probability of bike damage as part of the deal. That’s why commuter bikes in northern climates tend to be beaters. The shiny bike stays home in the garage until the weather and roads settle down.

A big part of maintaining control when you encounter surface hazards such as ruts is to simply be aware of what’s happening. Let’s say you feel the bike start to waggle around, and you wonder whether it’s a bike problem or pavement problem. Ruts are most obvious when the sun is low on the horizon, casting shadows. And even if you can’t easily see the ruts, you know they are most likely to appear in the wheel track areas. Moving over to the center of the lane should confirm whether it’s a pavement rut problem or a bike problem.

You’ll find it easier to control the bike on a nasty surface if you’re in the habit of countersteering rather than just thinking "lean.” That is, to make the bike move left, force both grips toward the left. To make it move right, press both grips toward the right. Normally, it only takes a modest push on one grip to cause the bike to change direction. But when crossing a deep rut, or swerving between two potholes, it may require more powerful pushes and pulls on both grips. Focus on countersteering to make the bike hold its direction as the front wheel weaves its way into and out of the ruts.

Riding the ruts
Even on a severely rutted road, there are some areas of the lane that are typically smoother, including the center and the very edges of the lane. So, one option for riding badly rutted pavement is to stay in the center of the lane. Bear in mind that riding in the center of the lane isn’t hazard free. Debris tends to get kicked out of the tire track areas toward the center or sides of the lane. And the center of the lane also collects more slippery stuff, such as oil or antifreeze drippings. It can be a big shock when a tangle of truck tire tread, an AWOL muffler or a dribble of diesel oil suddenly appears ahead of you in the center of the lane, so remember to increase your following distance to allow more maneuvering room. That also helps make you more visible to other drivers.

And what do you do when you come up behind a slow-moving vehicle? You’ll have to slow down or pass. But passing on a deeply rutted road can be very unnerving, since the bike must wiggle its way through several different ruts, each causing some strange feedback. If you do decide to change lanes on a severely rutted road, try to cross the ruts at maximum angle, more like the tactics for crossing an edge trap or railroad track. Don’t try to ease over. Rather, steer away from the ruts slightly, then swing back and attack them.

The best tactic for negotiating broken pavement and pothole-laced roads is to watch the surface carefully and dodge between the holes. Cars and trucks may not be able to swerve around potholes, but a single-track motorcycle can often fit between the holes, which tend to be worse in the wheel tracks of other vehicles. All you need is a couple inches of level pavement between the bad areas.

How about bike modifications?
There really isn’t much you can do to improve the behavior of a motorcycle that’s trying to maintain balance on strangely shaped pavement. One thing you can do to improve your odds is to ensure your bike is well maintained. You might not notice a minor glitch on a straight, level road, but in an abnormal situation, even a minor problem can contribute to loss of control. For instance, cruising down the superslab you might not notice loose steering head bearings; but when you suddenly encounter ruts, the bike may weave all over the road. Worn bearings, loose fasteners, sagging shock springs, dry forks and under-inflated tires will all reduce stability.

The message is to keep your bike maintained, not so much for the everyday ride, but for those abnormal situations in which you expect it to perform at its limits. You already know to check your tire pressures before every ride. Don’t forget to check your wheel bearings, head bearings and swing arm bearings, and snug up critical fasteners such as the pinch bolts at the fork triple clamps and axles.

Once every year or two, drain and refill your front forks, or at least top off the fluid. Also, flush and bleed your brakes. And, if you’ve got more than 35,000 miles on your original shock absorbers, it’s probably time to replace them.

Changing routes
One primary tactic for badly damaged pavement is simply to find a different road — preferably one less used by commercial truck traffic. For instance, I’d been following U.S. Highway 2 across Minnesota and North Dakota, and my original plan was to stay on U.S. 2 across Montana. But it turned out to be a major truck route, and the pavement wasn’t tough enough for the job.

If I’d realized how bad the ruts would be on U.S. 2, I’d have turned off earlier. Finally, a few miles short of the Montana border, I diverted south to pick up U.S. 200, a delightful two-lane highway with only modest traffic. Since narrow U.S. 200 isn’t a favorite of the long-haul truckers, it hasn’t been pounded into ruts.

I wish I’d found an alternate route heading west from Spokane rather than staying on the interstate. I could have turned off onto U.S. 2 for a few miles then followed Washington 28 and 283, quiet little state highways with less traffic and less road damage. The state highways wouldn’t have added more than an hour to the day’s ride but would have been much more enjoyable on a motorcycle.

Aggressive traffic on interstates and major U.S. highways has already taken a lot of fun out of motorcycling. The older roads are looking better and better for motorcycling, not only because of less aggressive traffic, but also because of less pavement damage. If you encounter nasty traffic or road damage on your next trip, get the maps out and think about alternate routes.

  • 1 August 2014
  • Author: Army Safety
  • Number of views: 11022
  • Comments: 0