Two 5-ton machines, two different answers to the same tight site.
A utility contractor in Denver bought a 5-ton mini excavator on a Thursday, ran it on a backyard sewer job on Friday, and called the dealer on Monday asking what the return policy was. He had done his homework on the numbers. The machine weighed about 12,000 pounds, so his trailer could haul it, and it dug to nearly 13 feet, so it could reach the sewer line. What he had not done was swing it. The first trench ran along a block wall, and every time he rotated the house to dump the bucket, the counterweight stuck out past the tracks by more than a foot and scraped the wall. By the end of the day the wall had a gouge the length of a truck bed, the homeowner was holding back $3,900, and the contractor was paying $550 a day for a rental that actually fit the site. He lost roughly $5,000 on that one job, and the machine was not the problem. The choice was.
That is the trap of the 5-ton class. On paper, every machine in this weight class looks nearly identical: around 12,000 pounds, around 37 to 50 horsepower, around 12 feet of dig depth, and a price tag in the same neighborhood. On a tight site, though, the differences that look trivial in a brochure decide whether you finish the job or spend the week fighting the machine. The Kobelco SK55 and the Kubota U55-4 are the two machines most buyers end up choosing between, and they solve the same problem in different ways. Kobelco brings a short-radius tail swing, a quieter cab, and deeper dig depth. Kubota brings a true zero tail swing, the strongest bucket breakout force in the class, and a dealer network that is hard to beat in most of the United States. This comparison walks through both machines the way a buyer should: specs first, then swing, digging power, cab comfort, running costs, and a decision test you can run in one afternoon.
Quick Answer: If your work is mostly backyards, urban lots, and jobs where the machine has to spin inside its own footprint, buy the Kubota U55-4 — its true zero tail swing and class-leading breakout force save more time than any other single feature. If your work is mostly open trenching, deeper utility digs, and long days where cab noise and fuel burn matter, buy the Kobelco SK55 — its deeper dig depth, quieter iNDr cooling system, and stronger arm force show up every hour. Both machines weigh about 12,000 pounds and dig to about 12 feet, so the decision is about the shape of your sites, not the size of your jobs.
1. The Specs That Actually Matter on a Tight Site
Brochure specs lie by omission, so start with the numbers that change how a day goes. Horsepower matters less than breakout force when the bucket hits clay, and dig depth matters less than tail swing when the fence is two feet behind you. Here is the head-to-head on current-model, standard-configuration figures, and the table is followed by what each number actually costs you on site.
| Specification | Kobelco SK55SRX | Kubota U55-4 |
|---|---|---|
| Operating weight (cab) | ~11,600 lb (5,262 kg) | ~12,115 lb (5,494 kg) |
| Engine | Yanmar 4TNV88C | Kubota V2607-CR-E4 |
| Net power | ~37.4 hp | ~47.1 hp |
| Bucket digging force | ~6,992 lbf (SAE) | 11,177 lbf |
| Arm crowding force | ~5,328 lbf (SAE) | 6,261 lbf |
| Max dig depth | 12.1 ft (3.69 m) | 11.8 ft (3.62 m) |
| Max reach at ground | ~20.5 ft (6.2 m) | ~19.6 ft (5.96 m) |
| Transport width | ~6 ft 5 in (1.96 m) | 6 ft 6 in (1.98 m) |
| Tail swing | Short radius, 4.2 ft radius | Zero tail swing, 41.1 in radius |
| Swing speed | 8.5 rpm | 9.3 rpm |
Two things jump out before you read a word further. First, the headline numbers do not tell the story: the Kubota has about ten more horsepower and nearly double the bucket digging force on paper, while the Kobelco digs about three inches deeper and reaches about a foot farther. Second, the two rows that decide jobs on a tight site are at the bottom of the table, not the top — tail swing and swing speed. That is why this comparison spends less time on the engine and more time on the footprint. Figures vary by model year, arm option, and counterweight, so confirm the exact build with your dealer before you sign anything.
2. Tail Swing: The Real Difference on a Tight Site
Tail swing is the one spec that can cost you a customer on the first day, and it is where these two machines genuinely differ. The Kubota U55-4 is a true zero tail swing machine. Its rear end stays inside the width of the tracks when the house rotates, with a minimum tail turning radius of about 41 inches, so you can spin against a wall, a fence, or a foundation without ever touching it. The Kobelco SK55 is a short-radius machine, not a zero tail swing machine. Its tail swing radius is about 4.2 feet, which is tight for its size and far better than a conventional machine, but the counterweight does swing out past the tracks by a few inches. On an open lot that difference means nothing. Against a block wall it means everything.
The practical test takes five minutes and no dealer will mind you running it. Set both machines beside a fence with the tracks parallel to it, swing the house 180 degrees, and watch the counterweight. The Kubota clears the fence with room to spare. The Kobelco needs a few extra inches, and on a job where the trench runs two feet from the wall, those inches are the difference between digging and repositioning the machine every few feet. If most of your work is in backyards, between houses, or inside a fenced utility easement, that is a decisive advantage for the Kubota.
There is a trade-off hiding behind the zero tail swing, and honest buyers should know it before they sign. A machine that keeps its counterweight inside the tracks gives up some of the counterweight mass that a conventional machine uses for stability, which is why the Kubota leans on its heavier operating weight to stay planted. The Kobelco, with its larger swing radius and heavy counterweight option, lifts more confidently over the side at full reach. Neither machine is unstable — both are rated for their class — but if your work involves setting pipe or lifting trench boxes over the side, run the lift test on both machines before you decide. For a deeper look at how tail swing changes what a machine can do on a cramped site, see our guide on zero tail swing excavators and the zero tail swing explained article.
3. Digging Power and Hydraulics
On paper, the Kubota wins the digging contest by a wide margin. Its bucket breakout force is rated at 11,177 lbf against the Kobelco's 6,992 lbf on the SAE measurement, and its arm force is 6,261 lbf against the Kobelco's 5,328 lbf. That gap is real, but it is smaller than the numbers suggest, because the two manufacturers measure bucket force differently. Kobelco quotes a two-pin bucket force of up to about 11,128 lbf for the SK55, measured at the bucket pins rather than at the cutting edge, while the SAE number is the conservative one. In practice, the Kubota fills a bucket faster in sticky clay and pries rock out of a cut more easily, while the Kobelco is no slouch — it just asks for a slightly slower, more deliberate crowd.
The Kobelco answers with hydraulics that feel like a bigger machine. Its Integrated Flow Pump System routes extra oil from the third pump to the arm and boom the moment digging starts, so the cycle stays quick even when you are crowding and lifting at the same time. The Kubota answers with a faster swing — 9.3 rpm against 8.5 — and a boom swing angle of 70 degrees to the left and 55 to the right, which matters more than it sounds when you are trenching along a wall and need the boom offset to keep the bucket in the trench. Both machines come thumb-ready with factory auxiliary hydraulics, so a hydraulic thumb, auger, or grapple bolts on without a field retrofit.
4. Cab, Controls and Daily Comfort
You will spend more hours in the cab than you will ever spend reading a spec sheet, so comfort is not a luxury feature on a machine you run every day. The Kobelco's calling card is its iNDr cooling system, which pulls air through a fine mesh and exhausts it in a way that keeps the engine bay clean and the cab noticeably quieter than most machines in the class. Operators who run the SK55 all day report less fatigue at the end of a shift, and the daily checks are all reachable from the ground, which means they actually get done.
The Kubota's cab is narrower but cleverly laid out, with the controls falling to hand the way Kubota operators expect and a seat that adjusts far enough for tall operators. Its air conditioning is strong, which matters on a 95-degree day in a glass box, and the pilot controls are smooth and predictable from the first hour. Where the Kubota loses a little ground is noise: the engine sits closer to the operator, and at full throttle the cab is louder than the Kobelco's. Neither cab is bad — both are a long way from the rattling steel boxes of a decade ago — but if you run ten-hour days, the Kobelco's quieter cab is worth real money in fatigue alone.
Best for: Kobelco SK55
- Deep utility trenching — the extra dig depth and long-arm option reach sewer and water lines the Kubota cannot touch.
- Long days in the cab — the iNDr system keeps noise down and the engine bay clean, so the operator finishes the day fresher.
- Open sites and farm work — where the short-radius tail swing is plenty tight and the deeper reach pays off.
- Side lifting — the heavier counterweight option gives the machine more confidence lifting over the side at full reach.
Best for: Kubota U55-4
- Backyards and fenced lots — true zero tail swing means the machine spins inside its own footprint, wall to wall.
- Hard digging and clay — the class-leading bucket breakout force fills the bucket faster and pries rock loose.
- Urban and road work — the fast swing and wide boom swing angle keep cycle times short in tight quarters.
- First-time buyers — the dealer network is the largest in the compact class, so parts and service are rarely more than a phone call away.
5. Running Costs, Dealer Support and Resale
The purchase price of the two machines lands in the same range, with new machines typically listed in the mid-$80,000s to just over $100,000 depending on cab, counterweight, and attachment package. The Kubota usually costs a little more up front, and it usually gives that money back at resale. Kubota's compact machines hold their value better than almost any other brand in the class, partly because the dealer network is so large that a used U55-4 is easy to sell anywhere in the country.
The Kobelco is the quieter value on running costs. Its Energy Conservation Mode and efficient Yanmar engine sip fuel on light work, and the iNDr cooling system keeps dust out of the radiator, which means fewer overheating shutdowns on dusty sites. Service intervals are straightforward, and the ground-level daily checks mean the machine actually gets its grease and fluid checks instead of skipping them. Kobelco's dealer network is smaller than Kubota's, so check the distance to your nearest dealer and the parts stock they actually carry before you buy. A machine that saves you $20 a day in fuel costs you far more than that if a failed final drive takes two weeks to get a part. For what a failed final drive actually costs when it goes, see our guide on excavator final drive failure.
6. Which One Should You Buy? Run This Test in One Afternoon
Spec sheets will not decide this for you, because the two machines are close enough that the right answer depends on your sites. The test below takes one afternoon, two demo machines, and the tightest job you have booked this month. Run it before you sign anything, and the machine will tell you which one it is.
Step 1: Measure your tightest site
Take a tape to the narrowest job you have coming up and measure the gap between the trench line and the nearest wall or fence. If the gap is under two feet, the Kubota's zero tail swing is worth more than any other feature on either machine. If the gap is over three feet, the Kobelco's short radius clears it comfortably and the tail swing question disappears.
Step 2: Dig your deepest trench on the demo
Ask each dealer to demo on a trench at the depth you actually dig — not a showroom dig in soft dirt. Time five bucket cycles in your hardest soil and watch whether the engine lugs. The Kubota's breakout force should show up in the first three buckets, and the Kobelco's deeper reach should show up when you check the trench floor with a tape.
Step 3: Swing against a wall
Park each machine with its tracks parallel to a wall, swing the house a full 180 degrees, and measure the clearance at the closest point. Write the number down for both machines. That number, more than any brochure figure, is the difference between finishing a backyard job and explaining a scratched wall to a homeowner.
Step 4: Sit in the cab for 20 minutes
Run each machine at working throttle for twenty minutes with the air conditioning on and the radio off. Notice the noise, the vibration through the seat, and whether the controls fall to your hands without reaching. A cab that feels fine for five minutes can feel cramped and loud by hour six, and you will live in this cab for thousands of hours.
Step 5: Call your nearest dealer for a part
Phone both dealers and ask for the price and availability of a hydraulic hose and a set of bucket teeth for the exact model you would buy. The dealer who answers quickly, stocks the part, and quotes a fair price is the dealer who will keep you working when something breaks on a Friday afternoon. That phone call is worth more than a $2,000 price difference between the machines.
Common Mistakes When Choosing a 5-Ton Mini
- Buying on horsepower alone — the Kubota's power advantage is real, but breakout force, tail swing, and cab comfort decide more jobs than the engine ever will.
- Ignoring the tail swing number — a short-radius machine is not a zero tail swing machine, and a few inches of counterweight overhang is enough to damage a wall on the first job.
- Skipping the lift test — if you set pipe or trench boxes, test the lift over the side at full reach on both machines before you buy, not after.
- Forgetting the trailer — both machines weigh about 12,000 pounds, so check your trailer and tow vehicle ratings before you buy, or the first haul becomes an expensive surprise.
- Choosing the cheaper machine without checking the dealer — a $3,000 saving disappears the first time a part takes two weeks to arrive while the machine sits idle.
The honest answer is that neither machine is a bad buy. The Kubota U55-4 is the better machine for the buyer whose sites are tight, fenced, and unforgiving, because its zero tail swing removes a whole category of expensive mistakes and its digging force is the strongest in the class. The Kobelco SK55 is the better machine for the buyer who digs deep, works long days, and values a quiet cab and low running costs, because its depth, reach, and fuel economy add up to real money over a year. Most buyers in this class work a mix of both kinds of sites, so the tiebreaker is usually the dealer: buy the machine whose dealer is closer, stocks parts, and answers the phone. Run the afternoon test, write down the numbers, and let the job decide.
If you are still weighing the wider mini excavator market, our comparison of the Volvo EC60E vs Bobcat E60 covers the 6-ton class, and our latest news page has the newest comparisons as they are published. Whichever machine you choose, measure the site first, demo both, and buy the one that fits the work you actually do.
