Suspension/Ride/Tires

Last Edited: July 23, 2017 // by TruckerScape, Inc.

Suspension and Ride

The ride in my truck is an additional, if not primary, factor for me to deal with when driving.

When cruising on a new, smooth highway, I enjoy a ride that approaches that in a nice sedan.  Unfortunately most roads have at least some imperfections and wear and tear that markedly roughen the ride.   At the other end of the spectrum are conditions that cause the ride to resemble off-road driving.

My truck’s suspension has to be stiff to support the freight loaded on it.  And tires are inflated to over 100 psi (pounds per square inch).  In spite of the latest features for driver seating comfort, I feel every bump, hole, repair patch, joint and seam in the road.  I tell friends, especially those with horses that I ride an iron horse.  And I am only half joking when I tell them that it bucks and heaves, rocks and rolls, shakes and rattles and creaks and groans.  (NOTE:  It is true that the new trucks I have driven have been tight and quiet, with better suspension and smoother rides, but after 200,000 to 300,000 miles of driving they all have begun to loosen up and ride more roughly.)

I almost wince when driving over the worst potholes and bumps and try to miss them when possible.  Some road conditions cause my truck to shake like a berserk vibrating lounger.  Vibration can tire me and make me drowsy if it lasts for a long time.  Actually, trucks are responsible for some of these rough surfaces.  Their weight aids formation of and worsens potholes and troughs.  Particularly on acceleration/deceleration lanes for entering or exiting highways and on hill climbing lanes, they wear concrete into washboarded surfaces.  Luckily many of the most offensive stretches of interstate and other major highways in past years have been repaired.

In the midrange of the ride spectrum, typical motions in the cab are gentler rocking forward and backward and side to side, vibration from stretches of older concrete surfaces and occasional bouncing from pounding over such objects as potholes and bridge joints.  Rocking occurs as my tractor rides over bumps and depressions and also from pushing and pulling and twisting forces exerted on the tractor by the trailer as its wheels trail over the same surface irregularities.  Many back roads have surfaces more uneven and demanding than those of the interstates and main surface streets, requiring significantly more steering correction.  Cross breezes and gusts contribute to side rocking, and other weather-related factors may also affect ride.

Ride is also affected by weight and distribution of freight in the trailer.  When deadheading (towing an empty trailer) the truck accelerates best, but has a springier, bouncier ride.  When towing the heaviest loads, the truck cushions less severe bumps and holes but pounds hard over the worst ones.  Heavy loads and loads stacked high in the trailer cause more cornering lean. I feel the ride is most comfortable in the midrange of legal capacity (around 20,000 pounds), when bouncing is dampened without too much leaning or lugging down.  Over all weight ranges, freight that is well distributed in the trailer improves the truck’s ride, handling and tire wear.

Tires

I am amazed that the steer tires, front suspension and steering mechanism can stand up under the pounding for so many miles.  The two steer tires are designed for extra strength and durability.  Each of them must support one and a half times the maximum weight on each of my truck’s drive and trailer tires.   (Specialized steer tires on heavy haulers support significantly more weight.)  Safe steer tires are critical to the safe operation of the truck.  Only new steer tires are ever mounted on the steer wheels—no used tires or re-caps are permitted.

Thick-treaded snow or all weather tires are commonly mounted on the truck’s drive wheels.  They provide some extra traction in mud, snow and ice, but are not as effective as you might imagine–on mountain passes in snowy and/or icy conditions, chains on at least some drive tires and trailer tires are often required.  Drive tires wear longer than trailer tires.  Trailer tires generally have a smoother tread.  They are the tires that wear and/or blow out most frequently and are often replaced with less expensive re-caps.

A truck can usually be guided to a safe stop on the side of the road when a trailer tire or drive tire blows out.  However, if a steer tire blows, all bets are off—the truck is much more difficult to control.  Hence a lot of scrutiny and care is devoted to steers.

Blowouts hurl chunks of steel-reinforced rubber with destructive force.  Blown trailer tires often damage other trailer components such as mud flaps and their metal hangers and air bags (which help suspend and cushion the ride of trailers and trucks).  A fragment thrown sideways could injure or even kill a person riding alongside in a personal vehicle with a window open.  This is one of several reasons not to dawdle in certain areas around my truck that I describe in the Risk Zones and Caution Zones chapters.

Takeaway

Whenever practical, safe and lawful, stay out of risk zones alongside a truck, to avoid shrapnel if a tractor or trailer tire blows, among other safety reasons.

A blown steer tire can not only hurl shrapnel but result in a serious tractor control problem for the driver.

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