What is a motor grader and how do you choose the right one?

1. What a motor grader is and what it does

It is a wheeled machine with a long blade mounted between the front axle and the rear tandem. The blade rotates, tilts and shifts sideways, which lets it cut, move and spread material in thin, precise layers.

It is measured by the surface it leaves, not the cubic metres it moves. That is why it is the machine that finishes the work the excavator and dozer started:

• Road construction: cutting and finishing subgrade, base and slopes.
• Maintenance of dirt and gravel roads: shaping and crowning the road.
• Ditches and drainage channels.
• Spreading and mixing material in layers.
• Industrial pads, airstrips and mine haul roads.

2. Define the job before the size

Maintaining a rural road several times a year is not the same as building a highway, nor as keeping a mine haul road, where the machine works long shifts on abrasive material and availability matters more than finish. Add the jobs nobody mentions when quoting and that then show up daily: ditches, slopes, ripping and mixing material. Real use defines the model.

3. The four Komatsu models, from municipal to mining

The GD535-5 (15.1 t, 145 HP, 3.7 m blade) is the municipal and rural road machine, with economy and power modes and an anti-stall system that keeps the engine from dying. The GD555-5 (15.8 t) delivers 158 to 193 HP and takes a 12 to 14 ft blade: it adapts to the job. The GD675-5 (19.3 t, up to 218 HP, 4.3 m blade) is the high-production step for highways and pads. The GD705-5 (22.2 t, up to 250 HP) is the heavy one for mining and large road projects. Figures from Komatsu datasheets.

4. Blade width, variable power and tyres

Blade width sets how many passes you make to cover the road: going from 12 ft (3.7 m) to 14 ft (4.3 m) is where output is won or lost on highways and large pads. On narrow roads or around obstacles, the shorter blade maneuvers better.

Variable power delivers high power only in the gears that need it, so you do not pay fuel for the reserve while shaping. And tyres are not a detail: 14.00 R24 on the GD535-5, 17.5 R25 on the GD555-5 and GD675-5, and 20.5 R25 on the GD705-5, which is what holds it on a mine ramp loaded with material.

5. What decides the finish: chassis, blade and visibility

Three functions separate a flat surface from a wavy one. Travel: moving at the right speed and holding a straight line with the blade working. Blade control: limiting its vertical movement even as the chassis rides up and down, holding it in any position and adjusting it finely. Visibility: the operator can see the blade while working; the GD555-5, for example, has a low front end for that.

Wheelbase and frame design control how much chassis movement reaches the blade. A machine that copies every undulation leaves it in the surface. That is why it is not compared on power and blade length alone.

6. If tolerance governs: 3D guidance with Smart Construction

In paving, canals with guaranteed grade or road work paid by surface, the conversation moves from the machine to the control. Komatsu Smart Construction offers two automatic systems for motor graders. 3D GPS: GNSS antenna, slope and rotation sensors and a control box; centimetre accuracy and a blade governed by the design, with no stakes or string lines. 3D LPS: a robotic total station tracks a prism mounted on the machine; it goes from 20 down to 5 mm and needs no open sky, so it works in tunnels and dense urban sites.

Per Komatsu, guidance can cut working time by up to 50 %, and nobody has to stand next to the blade giving references.

7. How to read the model code (and order parts right)

In GD555-5, the letters indicate the machine type, the figures the size and class, and the number after the dash the generation, which advances with each modification. There may be extra codes for configuration and emissions version.

Parts change between generations. To quote parts, give the full code and the serial number from the data plate: it is what stops a cutting edge or filter that does not fit from arriving.

8. Where to buy a motor grader and who backs you

Grupo ConstruMarket is an authorized Komatsu dealer in El Salvador (Zaragoza, Antiguo Cuscatlán, San Miguel), Guatemala as CMARKET (Mixco, Río Hondo, Xela), Nicaragua (Managua) and Panama (Panama City); all four models are offered in all four countries.

They all carry KOMTRAX, included at no cost to the customer per Komatsu. Komatsu Warranty Pro applies to GD motor graders and extends coverage up to 60 months or 12,000 hours, and Komatsu service contracts come in 5 levels. For the blade there are genuine Komatsu cutting edges and end bits in all four countries and Hensley edges in Nicaragua and Panama. Financing through credit or leasing, subject to approval.