April 20, 2011
By Jim Kerr
I hope your neighbourhood streets are not like mine: A surplus of fall rain combined with the freeze/thaw cycles of winter have combined to make our streets look like the army used them for artillery practice.
Potholes deep enough to lose a small car are actually the easier ones to navigate. The tricky ones are the basketball-sized holes that you can’t see because they are filled with spring runoff water. Bounce through a few of these, and you will be lucky if your vehicle doesn’t need to go immediately to the repair shop.
The natural reaction is for drivers to hit the brakes and slow down when a pothole suddenly appears. Slow is good. Hitting the brakes while going through the pothole isn’t. If your foot is on the brake when the tire rolls into the hole, the wheel immediately stops turning. Then the tire slams into the far edge of the hole and this is when damage occurs.
A much better way to prevent damage is to slow down before the pothole and then release the brakes before hitting the rough stuff. This technique works on any kind of rough road, whether it is washboard gravel or a deep trench. The tire will continue to roll as it passes through the hole and tend to roll up the far side. Damage can still occur if the speed is too high or the hole edge too sharp, but it will be minimized. In most cases, you will be able to continue driving without any damage.
So what kind of damage occurs when you bounce through a pothole? Tire damage may be the first thing you think of but often the tire survives fine. The higher the tire sidewall, the more cushion the tire will have. For that reason, I prefer to install winter tires on wheels that are one-inch smaller in diameter than stock wheels and then install a tire with a higher sidewall so the overall tire diameters remain the same (known as “minus-sizing”). This gives more cushion for rough winter and spring roads. Of course, this is only possible if a smaller wheel will fit on your vehicle; the dealership or tire shop can help here, but most vehicles can use at least one size smaller. Low profile tires tend to sustain damage easier as the sidewalls are compressed against the wheel during an impact.
Wheels are probably the most commonly damaged parts. Steel wheels will bend, but so do alloy wheels. Manufacturers are making vehicles lighter so they get better fuel economy. One of the small ways they do this is to make the wheels thinner. A lighter wheel also gives a better ride but they can be damaged easier. A bent wheel may not be noticeable at first, but continuing to drive on it causes the wheel to flex and crack. A bent alloy wheel can often be repaired but a cracked one needs to be replaced, so if you have hit a pothole hard, it could save you money if you have the wheels checked for a bend at your local repair shop.
Suspension parts are very tough, but hard impacts can break a spring. You will notice this because the vehicle no longer sits level. Over the years I have seen almost any suspension part break, but more commonly, they will bend slightly or shift on the adjustment points when hit hard. Getting a wheel alignment is the best way to have the suspension checked. A technician looks for worn or damaged parts during the pre-alignment inspection and even if nothing is visible, the alignment readouts can show if suspension angles are incorrect and which parts may be damaged. Even if no parts are damaged, adjusting the alignment angles will minimize tire wear and help fuel economy.
Front suspensions take the brunt of an impact with a pothole. Rear suspensions and wheels can be damaged but the majority of weight is at the front of the vehicle, so those parts hit harder. If your streets are like mine, the only way to avoid hitting potholes is to stop driving. That’s not practical, so instead, drive slowly, keep some distance between you and a vehicle in front so you can see potholes in the road and steer around all that you can see. Hopefully with the proper driving techniques, your car will survive pothole season ‘til the street repair crews make their rounds.