Wheels and Tracks Go Head to Head

Wheeled excavators have historically been a mainstay in European and Asian equipment fleets. Yet they remain relatively unknown to many contractors in North America.

To understand why North American contractors view the role of the wheeled excavator differently than their counterparts in other areas of the world, Equipment Today arranged a test with the assistance of Caterpillar Inc., at Caterpillar’s Edwards Demonstration and Application Center near Peoria, IL. Four experienced hydraulic excavator operators, with no prior wheeled excavator experience, put a Caterpillar M316C wheeled excavator and a Caterpillar 315C tracked excavator through a series of four common tasks: lifting, grading behind a curb from a road, grading on a slope and trenching.

The two machines were equipped with identical excavation buckets.

While each machine was better suited to specific tasks, they were able to complete all of them with little difficulty. Note that these tests were performed on relatively flat terrain, with the exception of grading on a slope. The underfoot conditions were relatively firm and the digging was performed in moist, clay-loam.

Test 1: Lift and transport

For the lifting task, operators were instructed to transport a 36-in.-diameter concrete pipe across a jobsite. This task included negotiating a corner and setting the pipe in a trench where there was already another section of 36-in concrete pipe. The operators then lifted the pipe out of the trench and over the back and sides of the excavator to test stability on flat ground.

The wheeled excavator really excelled at transporting the pipe over the smooth hard pack. This is partially due to the 21-mph maximum travel speed. “Your ground speed is a lot greater and it is a lot smoother when you are moving pipe, or whatever you have to move,” says John Sigler, Ameren CILCO (Central Illinois Light Co.), a utility company based in Missouri. John is a 27-year veteran operator. “If you had a job where you had to move pipe back and forth, your production would probably go up.”

But Sigler was also quick to point out that the conditions on this test course were ideal for the wheeled excavator. “On a jobsite, about the second day you are there it starts raining,” he notes. Muddy jobsite conditions or uneven terrain may tilt the scales toward the tracked machines.

The main difference in this task between the wheeled and the tracked excavator was the ability to traverse the jobsite with the pipe, explains Jeff Litwiller, Wayne Litwiller and Son Excavating, Hopedale, IL. Jeff grew up in the family business and has been a full-time operator for the last 10 years. “The wheeled machine actually travelled a little easier. It handled very well,” he says, adding it was easier to negotiate turns with the load on the boom. “I was surprised how stable it was carrying the pipe and how much less that pipe was rocking back and forth — how much smoother it was.”

The steering function did require a bit of a learning curve. “When you have your house turned around, you have to think backwards with the steering. Once you get past that, it is not too bad,” says Litwiller.

He also praised the stability with the concrete pipe extended over the side of the machine. “With the outriggers down, the wheeled machine actually felt a little more stable than the tracked machine,” he says. “If I spent time in the machine, I would probably feel very comfortable lifting over the side without the outriggers.”

Several of the operators didn’t feel the outriggers were necessary for this task and didn’t use them. But without the stabilizers, they perceived a difference in stability between the wheeled and tracked machines. “I did not have the outriggers out, which would have made a difference,” admits Harold Powley, PIPCO Companies, Ltd. “So there was a little bit of movement. But it surprised me — it was stable for being on wheels. With what we were lifting today, I was comfortable. We were not lifting something that was at its max.”

Powley has more than 30 years of experience as an equipment operator. The company he works for, PIPCO (Peoria Industrial Piping), is a site utilities, excavating and mechanical contractor.

“As far as setting pipe, it was a smooth machine. It handled everything that you asked of it,” he adds.

Fred Monroe with R. Fred Monroe Excavating also felt the wheeled excavator really shined in this application, praising the ease to complete the task. Fred has 30 years of experience with residential, sewer and water and land-clearing work.

Monroe also lifted the load to full extension without lowering the outriggers. “You had a slight give to it, but that was no problem,” he says.

Test 2: Work on a road

The next task required operators to grade behind a curb from a finished gravel road surface. The operators then had to turn the machines around by rotating the undercarriage, while minimizing the impact on the finished surface.

“This is what this machine was designed for,” says Monroe of the wheeled excavator. “Maneuverability was excellent.” Turning the machine around on the finished surface resulted in minimal impact. “I made a wide, sweeping turn. If it was a cul-de-sac, like this, you could leave it with no marks. If it was tighter, you would leave marks, but they would just be marks.”

Litwiller also felt the wheeled machine was well-suited for working on finished surfaces. “Road work is a pretty good use for it,” he says.

Powley agrees, adding, “[The wheeled excavator] would be the machine I would use on a gravel base or a blacktop base.” The wheels prevent marring of the finished surface.

“I think in a new subdivision it would be just ideal,” says Sigler. “You could even go out before they had the blacktop in and you would not damage the road.” In addition, transport between jobs would be simplified. “Moving the piece of equipment would sure be a lot quicker.”

Test 3: Grade on a slope

For the next task, the operators drove the machines onto a 5:1 slope to perform a grading task. During this operation, they had to reposition the machine on the slope.

Powley tended to think the tracked machine was better suited for this type of work. “Being on rubber on a dirt slope, it may not be the right machine. It was stable. I just didn’t want to push it,” he says.

With the wheeled machine, the outriggers have to be raised to reposition the excavator. “Ease of positioning was a little bit of a hassle with those outriggers,” says Sigler. “On the slope, I think the tracked one just handled quite a bit better. You can just spin on a hillside with that tracked one.”

Fred Monroe says the wheeled excavator worked well in this application once it was in position. “With the outriggers, it is very stable,” he states. “Maybe with the addition of a tilting bucket, it would be ideal.”

But he also didn’t feel totally confident repositioning the wheeled excavator on a slope. “I didn’t feel totally comfortable moving it. There is just a little awkwardness on the slope,” he says. With the tracked excavator you can just creep forward or backwards and twist downhill.

Similarly, Litwiller felt more confident on the slope with the tracked excavator. “I’m sure the more you would run the [wheeled excavator], the more you would get used to it and you would get the feel of it. But going from the tracked excavator to the wheeled excavator [on the side slope], you can tell the difference on stability,” he says. “It is a little easier to track up and down there than it is to drive with that steering wheel. It is one thing to think backwards with the steering wheel when you are on flat ground, but it is another situation when you are on a slope. With tracks, you don’t even think there is a slope.”

Test 4: Trenching

Finally, the contractors were asked to dig a 4-ft.-deep trench that was approximately 30 ft. long. The depth of the trench had to fall within a tolerance of 1-in. vertically.

But the wheeled excavator proved to be a capable tool for this task as well. “I didn’t use the outriggers,” explains Powley. “I wanted to see how stable the rubber-tired excavator would be and it surprised me. It is stable.”

Monroe states that it is hard to beat a tracked machine for straight-line excavating. The wheeled machine was capable of accomplishing this task, but is was more of a challenge to reposition.

“It is not as easy as one thinks,” says Monroe. “It seems like a slight turn of the wheel and you are off of a straight line pretty easy. It moves easy, but straightness is the key.”

Litwiller used the outriggers on the wheeled excavator because he thought they resulted in increased accuracy by eliminating side to side movement. “If you are trying to dig fast and you have your outriggers up, that makes you wobble more off to the side when you are swinging back and forth real quick,” he explains. “But if you lower your outriggers every time, that is going to slow you down, too.

“A tracked excavator would be a lot quicker digging a trench like that,” he adds. “For trenching, you can move in and out a lot faster and you don’t have to lift and set the outriggers.”

A unique tool

As you can surmise from these contractors’ comments, the wheeled excavator is a unique tool that isn’t a replacement for a conventional tracked excavator. But it has attributes that allow it to operate in environments not well-suited to tracked machines, while still allowing you to occasionally perform the tasks traditionally handled by tracked excavators. It is a matter of choosing the tool that is most appropriate for your operation.

Underfoot conditions will influence your decision. “If you are going cross country, the track machine makes more sense,” says Sigler. “Being able to drive around town is sure a plus for the wheel machine. You don’t have to take it off and put it on a truck.”

Monroe adds, “To me, this machine was built for street work.” As proven by this test, the wheeled excavator also shines in lift and carry applications, especially in underfoot conditions that allow the wheeled machine to take full advantage of its increased speed.

And despite the outriggers, steering wheel, axle lock, etc., the wheeled excavator is relatively easy to operate. “It is operator friendly,” says Powley.