Fisher: Can LT tires handle ‘electric' reality of trucking industry?

The trucking industry is in the throes of great change with new trucks and shorter deliver areas.

As a result of the growth in e-commerce and the "Amazon effect" on shipping, logistics itself is changing.

Decentralized and regional distribution networks that locate inventory near customers and local, last-mile fulfillment centers are popping up like Starbucks, in order to shorten delivery times.

The end result is that instead of freight being hauled an average of 800 miles 20 years ago, the average length of a haul today is only 500 miles The industry's focus is on last-mile deliveries.

Last-mile deliveries (from the distribution center to the customer) have burgeoned and are now being made not only by Class 3-6 vans and medium-duty trucks but also by Class 1 and 2 vehicles; something you never used to see.

In addition, truck types are changing to operate more efficiently in the new environment. The new low cab-forward, cab-over trucks are a direct response to the demands of the growing last-mile market.

And this market continues to surge.

This change in vehicle usage is impacting the tire market. While these vehicles normally would run on light truck tires in 16-, 17.5- and 19.5-inch wheel diameters, standard LT tires will not survive in the commercial delivery environment. Not only are final-mile delivery trucks traveling shorter distances, but they are operating in more urban environments with more frequent starts and stops.

New commercial light truck tires must be able to handle the additional stresses and strains of heavier loads, withstand curbing with stronger and more durable sidewalls, defend against impacts and punctures, absorb a higher degree of scrubbing and chipping, provide more traction year-round in addition to wet braking in high-stress applications, have superior fuel economy and retreadability, and operate at higher speeds.

Oh, and don't forget, fleets require that they have better tread life, too.

One of the biggest changes happening in the light- and medium-duty markets is the switch from internal combustion engines to electric motors in last-mile delivery trucks and vans. These vehicles have the ability to accelerate at far greater rates than conventional trucks. Electric motors can hit maximum torque at 0 RPM at startup. (Compare this with standard internal combustion engines, where torque rises as RPM increases.)

Since clutches, drive shafts, axles and other drive-train components, as well as tires, are affected by this instant high-torque, limiting torque to levels similar to conventional power-train vehicles is a must.

Depending upon how a vehicle's system is tuned using software, it could perform like an electric car that has quick get-up-and-go or be throttled back to prevent trucks from "laying a patch" every time the traffic light turns green.

Therefore, electric trucks must have software or other on-board electronics to limit acceleration rates and protect drive-line components from being overstressed and tires from being worn prematurely.

It's unknown what types of irregular wear are going to pop up in these applications, but I'm sure there will be some. High torque normally results in chipping/flaking/chunking tread, heel/toe wear, alternate lug wear and overall fast wear — all of which reduce tread mileage.

High torque also produces diagonal cracking and lug-base cracking, which can shorten a tire's life. Therefore, electric vehicles are creating a need for tires that can handle higher torque and the accompanying scrubbing and faster tread wear than tires normally found on gas or diesel-powered trucks.

Tread patterns will have to be designed specifically to eliminate much of this irregular wear.

Since it still is early in the development of electric trucks, and only small numbers of these vehicles have been placed in service to date, there is limited data and anecdotal reports about the effects these new power-trains have on tires. (I heard one fleet reported a 40% reduction in tread mileage when using its normal tires on their electric trucks.)

Keep in mind that commercial radial truck and bus tires used on vehicles with gas or diesel engines have evolved over the last four decades to be long-lasting, cost effective, retreadable and fuel efficient. Their tread designs have been engineered for specific axle positions as have their retread patterns.

They also are designed for specific types of operations: long-haul, super regional, regional, vocational and urban pick-up and delivery.

These tires are designed to deliver optimum performance under acceleration, braking, cornering and other wear forces they experience in the environments in which they operate.

However, electric vehicles may change the magnitudes and distribution significantly of these forces that we have traditionally come to expect, and therefore tires have to be designed specifically for them.

Since range (a.k.a., miles per charge) is a major concern with electric vehicles, their designers are working on maximizing the number of miles a vehicle can travel on one charge.

When they look at tires, they have to select the tires with the lowest rolling resistance available for each wheel position. They can't simply use low rolling- resistance, long-haul tires on an electric vehicle intended for urban pickup-and-delivery applications since irregular wear issues will develop quickly.

In addition, it's common knowledge that fuel-efficient, low rolling-resistance tires traditionally have not performed well under high torque. So the challenge for tire makers is to design tires for electric vehicles that do provide fuel efficiency despite the torque that is being applied to them.

Another capability that almost all electric vehicles have is that they use regenerative braking to maintain battery life. Regenerative braking uses an electric vehicle's motor as a generator to recover the kinetic energy dissipated as heat during braking and convert it into stored energy in the vehicle's battery.

Then, the next time the vehicle accelerates, it uses much of the energy previously stored from regenerative braking instead of tapping in further to its own energy reserves. This helps to extend the range of the electric vehicle by up to 25%.

So far these systems are used only on drive axles and tires to supplement the traditional service brakes, a situation that changes the normal distribution of braking forces by axle.

As a result, some users have reported noticeable increases in drive-tire wear rates. Therefore tire designers need to make changes in drive tires to provide longer treadwear while still assuring other tire performance characteristics including traction, resistance to irregular wear, cornering ability and casing longevity are maintained.

One of the first things I learned about tires back in the late 1970s was that tires should never be stored near electric motors, battery chargers, generators, welding equipment or other ozone-generating sources.

Everyone knows that ozone creates weathering/ozone cracking in rubber. So, the big question remains: What effect will electric motors have on tires that are mounted right next to them if the motors are located on the axle ends or even some feet away?

If ozone is created by these motors, will it be enough to age tires prematurely? No one knows yet, but if the answer is 'yes,' tire rubber compounders will have to come up with a solution.

Another characteristic of electric motors on trucks and vans is that they are very quiet, especially when compared to internal combustion engines. Therefore, the noise generated by tires rolling down the road will be much more noticeable which could become a concern that tire designers may need to address.

On the other side of the coin, the fact that pedestrians and other motorists can't hear an electric vehicle coming could be a problem as well, and some noise generation would be a good thing.

As you can see, there are a lot of challenges and some unknowns regarding electric vehicles, their impact on tires and what can be done to re-engineer them for this application.

Who knew when Jeff Bezos sold his first book on Amazon in 1994 that he would change trucking, tires and perhaps the world?