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"They need to know the hydraulic needs of the attachment, the GPM of attachment flow, and they need to match that up with the minimum flow put out by the skid steer," Zupancic says. "A high-flow capacity hydraulic option helps concrete and paving contractors run a planer, for example. That's a pretty robust attachment."

Fitzgerald agrees that planers require high-flow hydraulics for best planer performance. "People who are looking at planing as the function of the machine for a large percentage of use pick high flow," he says. "We do have planers that work with basic or standard machines but the planer performance won't be as fast. But you can still do it."

Other attachments that need high-flow hydraulics include cutting wheel, trenchers, and snow blowers. "Anything that really engages something requires high flow," Zupancic says. "It provides more rotation to whatever is engaging the material and provides more hydraulic horsepower."

Verdon says that in addition to the calculated hydraulic power number, it is also important to know what kind of pump the high-flow system is using. "Most high-flow systems are designed by adding a gear pump into the standard flow circuit to gain incremental flow at the same system pressure as the standard flow circuit. Although this will increase the available hydraulic power by increasing the speed of the work tool, it will not provide additional torque to the work tool," he says. Verdon says additional torque is achieved by providing higher system pressure in addition to higher flow, and that high-flow systems that utilize variable displacement piston pumps can provide this type of a benefit.

4. What type of surface will you be working on?

Most often the type of surface will determine whether contractors consider a skid steer, which runs on rubber tires, or a compact track loader (CTL), which moves on tracks. Verdon says the two types of machines have a lot in common but the applications for each type of machines are different.