"Why Do Semi Trucks..."

Google's Most Frequently Asked "Why Do Semi Trucks..." Questions

​Here at West Tech Mobile, we get asked a lot of questions about the vehicles we work on – everything from heavy industrial rigs to semi trucks and tractor-trailers. And we’re always more than happy to answer them! Since they are the most common, we decided to put our responses to some of Google's most frequently asked questions about semis all here in one place, for easy reference. Read on if you’ve been wondering these for yourself.

Why do semi trucks use diesel?

Mostly, it comes down to horsepower, as diesel engines create more horsepower than gasoline ones. Also, in the past, diesel was cheaper than gas, so it became popular as a more cost-effective alternative. And one more big reason is that truck drivers, who are constantly guiding top-heavy vehicles – and large tanks full of fuel – know that in the event of a rollover, diesel isn’t nearly as combustible as gasoline. If you’re always hauling large volumes of it in a tank underneath you, that makes a big difference.

Why do semi trucks drive in the middle lane?

It’s for safety. The truckers do it so that they have two options to quickly exit the lane if they have to. If they’re in an outside lane, their options are to swerve into the middle lane, or to hit the ditch – and both of those are basically guaranteed to cause further accidents and rollovers. Truck drivers have to be more aware of escape routes, because their vehicles take so much longer to stop than a car does.

Why do semi trucks have spikes on their tires?

This is actually a really common question. Sometimes, people are asking about the metal spikes on the wheel rims themselves – in which case, the answer varies, but it’s usually because the driver has personalized the truck to look like that. It’s their home away from home for long periods of time, so many drivers take pride in adding a bit of flair and personality to the truck, including the wheels.

Other times, people are asking about spikes on the rubber part of the tires, and those would be tire chains. They increase traction in snow and icy conditions, and sometimes even muddy terrain. It’s one more measure to ensure a huge truck doesn’t go out of control when the weather is less than ideal.

Why do semi trucks honk at me?

Contrary to what you might think, this isn’t usually because a young kid was doing the “honk” motion with their arm. More often, it’s because you are about to do, or have already done, something that could get you seriously injured! Semis, especially when fully loaded, are very heavy, and take hundreds of metres to stop when they are highway speed. If you cut one off, drift too close, or do another unsafe manoeuvre, this is the way for the truck driver to get your attention. Keep your eyes open, be alert, and prepare for an impact in a worst-case situation!

Why do semi trucks get weighed?

Most often, it’s to ensure that the load they are carrying is distributed evenly across all the axles. Each of the tires is only rated for a certain amount of weight, so piling up too much in one area of the trailer can result in a loss of control on the trailer and subsequently, the whole vehicle.  It could even cause a blowout, in extreme cases.

Another reason is that the weight affects the road. Too much weight on the axles, repeated hundreds of times a day for years, can damage the road surface by creating ruts or unevenly wearing the pavement.

And finally, some structures, like bridges and exit ramps, can only handle up to a certain weight at once. Weak embankments, shallow asphalt, and other material considerations have to be made around the road, too. That’s why it’s important for trucks to know how much they are hauling, in addition to their total size.

Why do semi trucks make loud noises?

Usually this question is referring to the squealing air release that happens when a truck stops at an intersection, or at the bottom of a hill.

The main air brakes are designed so that even if their operational system fails, their default position is to lock up and stop the truck. This is different from smaller car brakes, that need a mechanical force (like stomping on the brake pedal) to operate.

There are also engine retarder brakes, which heavy vehicles use when going down hills to reduce the friction on the brake system and prevent overheating during those times of continuous use. These are generally prohibited from use inside of city limits, though. Since the trucks are so large, there are many failsafes put in place to ensure runaway vehicles are extremely rare – the trade-off is that they are a bit noisier!

We hope this answered some of your FAQs about semi trucks. And if you have more that you need answered, or you’re a driver that has a heavy-duty vehicle in need of some expert TLC, we’re always ready to help at West Tech Mobile!