It may be out of sight, but it should never be out of mind. The undercarriage of the average track loader or crawler contributes to 20 percent of the machine's purchase price and can eat up close to 50 percent of its maintenance budget.

Proper maintenance is an essential task for slowing normal wear and tear. One of the most important ways to avoid undercarriage damage is to keep a close eye on track tension. In fact, track-chain tension is probably the most controllable element in reducing undercarriage wear.

Too loose? Too tight?

When no one is regularly checking or staying on top of adjusting track tension, a lot can go wrong. Acceptable track sag for conventional crawlers is usually about 2 inches. A track that has more slack than that and is too loose is likely to come off and damage the undercarriage.

"All it takes is an uneven surface or a slope and you can walk your machine right out of its track," says Gregg Zupancic, marketing product manager for skid-steers and compact track loaders at John Deere. "When you detrack, you're going to damage undercarriage components, which could include the frame itself, three to five small rollers, two big rollers or idlers, the sprocket that moves the track around the idler and rollers, and the rubber around the track."

Track tension that is too loose also allows rocks and other debris to get between the rollers and damage undercarriage components.

While tracks will wear out faster if too loose versus too tight, a tight track can also increase roller, idler and track wear by up to 50 percent. A tight track increases load, resulting in more wear on the track bushings-to-sprocket-teeth contact areas and the track-link-to-idler and roller contact areas. The track-link-to-idler contact point and track-link-to-roller contact points are affected by the added load and will wear faster, too.

An 80 hp crawler with track sag that falls within recommended parameters might have about 800 pounds of tension at the track adjuster. But too-tight track sag on the same machine can create up to 5,600 pounds of tension. That much tension robs horsepower from the machine, requiring it to burn more fuel. It also creates heat buildup that contributes to premature wear.

The impact on operating and maintenance costs is clear. The cost of track replacement is something to avoid as long as possible, given that today's new tracks can run as much as $2,000 for each track/side.

Measure or eyeball?

While some OEMs recommend special tools to check track tension, others say visual inspection is adequate. "At John Deere, we believe ensuring you have the right track tension should be your number one priority," says Zupancic. John Deere, which does not require any measuring device, recommends visual inspection in most cases to assess if there is too much looseness in the track.

"You will most often see slop or sag at the top of the track plane between the idler and the high sprocket in the back of the track," Zupancic says. "If taking an actual measurement, measure the distance between the lowest part of the sag and the top of the track." Whether taking actual measurements or eyeballing the track, there are a few ways to make sure you're accurately measuring slack or looseness.

When and where

Some service organizations advise checking track tension only on the job site, because a track properly tensioned in the shop may become too tight when packed with mud out on the job.

To check tension on site, Zupancic advises putting the loader arm or boom all the way down, then tilting the bucket, curling it slightly downward. This should lift the front of the machine slightly off the ground.

"Deere machines have four rollers in the middle of the track, but no matter how many, we recommend picking one on the bottom edge," he says. "If you only see about a 1-inch gap between the roller and where the track would tend to sag, you're good to go. You can even just use the width of your thumb to eye it up."

If the gap is as wide as 2 to 3 inches, there's a high likelihood of walking the machine out of the track when trying to turn or when moving on a slope where the tracks naturally fight against each other. But when there is less than a 1/2-inch to 1-inch gap, Zupancic cautions, tension may be too tight.

Add grease carefully

Track tension adjustments are made by pumping or draining grease through the track adjuster, located just behind the front idler. Grease pumped into the zerk fitting expands a cylinder that then tensions out undercarriage or track components away from each other. Add grease slowly, as even small adjustments in track sag can have a big impact on tension. You should also inspect the adjuster valve itself periodically for leakage, another cause of tension loss and greater wear.

The tension cylinder should expand well beyond the life of the track itself, says Zupancic. "In most cases, when the cylinder won't expand any further and you've added as much grease as it will take, it's probably a sign that those tracks need replacing." Another indication that tracks are ready for replacing is when steel becomes visible under the rubber, and the ride gets rougher.

Breaking in a new track

New tracks tend to be stiff to start; most stretching will occur during the first 50 to 100 hours of operation. Checking track tension daily is important during break-in. After that, weekly checks are probably adequate.

However, significant temperature swings on the job site – such as below-freezing mornings that become warmer afternoons – can be a red flag that suggests checking the tension more often, Zupancic says. Tracks that are rigid and tight in the morning can become looser as the weather warms up. Black tracks will absorb heat on sunny days, so even at 50 degrees ambient temperature, some stretching can occur.

"It pays to stop and check the tension mid-job to make sure you don't walk out of the track," Zupancic says. "And always refer to the operator's manual for information on how to adjust track tension for your specific machine."