Skid Steer Attachment Compatibility Guide: Hydraulic Flow and Machine Sizing

The most expensive mistake in the attachment world is not buying the wrong width. It is buying an attachment your machine cannot actually drive. A rotary cutter built for high-flow hydraulics will bolt onto a standard-flow skid steer perfectly well, mount up, look right, and then simply refuse to do the work it was bought for. The plate fits. The hydraulics do not.

This page is a reference chart, not a sales pitch. Every figure below is taken from the published specifications of the 143 Top Dog attachments we currently stock. Where a specification is not published for a given attachment, this guide says so plainly rather than filling in an industry average. Hydraulic figures are not something to guess at, and we would rather send you to your operator manual than to a number we cannot stand behind.

Start Here: The Three Compatibility Checks

Before any attachment purchase, three things have to line up. In order of how often they get people:

1. Hydraulic flow class. Does the attachment need low, standard, or high flow, and is that what your machine produces? This is the one that costs money when it is wrong.
2. Machine class and size. A skid steer, a compact track loader, a compact tractor, a sub-compact tractor, and a mini skid steer are five different machines with different mounting plates and very different lift capacities.
3. Working width and weight. The attachment should be at least as wide as your machine's tracks or tires, and well within your machine's rated operating capacity once loaded.

Understanding Hydraulic Flow Classes

Loaders are sold in auxiliary hydraulic output classes, commonly labeled low flow, standard flow, and high flow. The class describes how much hydraulic oil the machine can push to an attachment. An attachment with a hydraulic motor, such as a rotary brush cutter, is engineered around a particular class.

Two things follow from that, and both matter:

• Under-flowing an attachment starves it. Run a high-flow cutter on a standard-flow machine and the rotor turns slowly, bogs in material it should handle, and the job takes far longer than it should.
• Flow class is a property of your specific machine, not of your machine's brand or category. Two loaders from the same manufacturer, the same size class, and the same model year can ship with different auxiliary hydraulic packages, because high flow is very often a factory option rather than standard equipment.

Table 1: Flow Class and Machine Class by Attachment Type

This is the primary lookup. The middle column reports the flow class stated in our own product listings for that attachment type. Where it reads Not stated, that means exactly what it says: we have not published a flow class for those models, so confirm the requirement with us or with the manufacturer's documentation before ordering. It does not mean the attachment has no hydraulic requirement.

The right-hand column lists the machine classes named in the listings themselves, which is the most reliable fitment signal we can give you from our own data.

A useful pattern falls out of that table. Across all 143 attachments we stock, the models that carry an explicitly stated hydraulic flow class are the brush cutters. That is worth knowing, because the brush cutter is also the attachment where getting flow wrong is most immediately obvious in the field.

Table 2: Brush Cutter Flow Requirements in Detail

Because these are the models with a published flow class, they deserve their own table. Every entry here is taken directly from the model's own specification.

Read across that table and the buying logic becomes clear. The same 72 inch and 78 inch cutters are built in more than one flow class, so the width you want is generally available for the machine you already own. Identify your machine's flow class first, then choose the width. Doing it the other way around is how people end up with a starved cutter.

One further distinction worth understanding: closed front models are offered in low and standard flow, while open front direct drive models are offered in standard and high flow. If your machine is a low-flow unit, the closed front 42, 66, 72 and 78 inch models are the ones built for it.

Table 3: Available Widths by Attachment Type

Sizing rule of thumb: the attachment should be at least as wide as your machine so the loader is not driving over unworked ground or material it has already passed. Below is every width we carry, by type.

Note how the widths cluster by machine class. The 36 and 48 inch soil conditioners are Dingo style for mini skid steers, while the 72 and 84 inch versions are skid steer style. Same attachment, two entirely different machines.

Table 4: Rock Bucket Tine Spacing, 3 Inch vs 6 Inch

This is the second most common question we get after flow, and it has a clean answer. Tine spacing is the gap between the tines on the bucket floor. Material narrower than the gap falls through; material wider than the gap is retained. That is geometry, not marketing, and it is the whole decision.

We carry rock buckets in both spacings across the same four widths, so you can pick the spacing on its merits without giving up the size you need.

Choosing between them comes down to what you want left on the ground. A 6 inch spacing lets far more soil and small stone drop back, so you lift mostly large rock and root. A 3 inch spacing holds on to smaller debris, which means more material collected per pass but more soil carried with it.

Outside those two lines we also carry light duty rock buckets at 60 and 72 inches for sub-compact tractors, a 42 inch for Toro Dingo and mini skid steers, and a 54 inch for MT85 mini skid steers. Tine spacing is not published for those four models, so if spacing is the deciding factor for your job, ask us before ordering rather than assuming they match the skid steer lines.

Table 5: Bucket Capacity by Width

Capacity in cubic yards, as published per model. A dash means we do not carry that type in that width.

Two things stand out. Screened snow buckets hold considerably more per inch of width than dirt buckets, which is what you would expect from a bucket built for light material rather than soil. And the dirt bucket and tough tooth bucket share identical capacities at every width, since the tough tooth is the same shell with a toothed cutting edge.

Capacity matters for a practical reason: a bucket rated in cubic yards tells you volume, not weight. A cubic yard of snow and a cubic yard of wet soil are very different loads on the same machine. Size the bucket to your loader's rated operating capacity with the heaviest material you actually move.

Machine Classes, Defined

Our listings name specific machine classes, and the terms are not interchangeable. Here is what each means in practice:

• Skid steer: The standard wheeled loader with a universal quick-attach plate. The largest share of our range is built for this class.
• Compact track loader: Tracked rather than wheeled, and generally sharing the skid steer mounting standard. Our root grapples name this class explicitly.
• Compact tractor: A tractor with a front loader, typically using a Euro or global mount or a manufacturer-specific mount such as John Deere. Our granite grapples are offered in both a standard and a John Deere mount version for exactly this reason.
• Sub-compact tractor: Smaller and lower lift capacity again. Our light duty rock buckets and standard firewood buckets are the models built for this class.
• Mini skid steer and Toro Dingo: Walk-behind or stand-on machines with their own smaller mounting plate. The 36 and 48 inch soil conditioners, the 42 inch brush cutter, the 42 and 54 inch rock buckets and the 48 inch buckets are built for these.
• MT85: A specific mini skid steer mounting pattern named directly in two of our listings.

Frequently Asked Questions

What size skid steer do I need for a brush cutter?

The more useful question is what flow class your machine produces, because that is what determines whether the cutter will work. We carry brush cutters from 42 to 78 inches across low, standard and high flow classes. Check your operator manual for your machine's auxiliary hydraulic rating, then pick the cutter built for that class in the width that suits your machine.

What is the difference between standard flow and high flow?

They are different auxiliary hydraulic output classes on the loader itself. High flow moves more oil to the attachment than standard flow does. High flow is frequently a factory option rather than standard equipment, so two otherwise identical machines can differ. Your operator manual and machine specification plate are the authority on which one you have.

Will a high flow attachment work on a standard flow machine?

It may physically mount and it may turn, but it will not perform as designed, because it is not receiving the hydraulic flow it was built around. In our range the same 72 and 78 inch cutter widths are built in more than one flow class, so match the attachment to your machine rather than compromising.

How much hydraulic flow does a rock bucket need?

Our rock bucket listings do not state a hydraulic flow requirement. If you are looking at a rock bucket with a hydraulic grapple attached, that grapple has its own requirement, and we would rather confirm it for your specific model than have you work from a general figure.

What tine spacing should I choose on a rock bucket?

Pick by what you want to leave behind. A 6 inch spacing drops more soil and small stone back to the ground and lifts mostly large rock and root. A 3 inch spacing retains smaller material. We stock both spacings at 62, 68, 75 and 82 inches.

Are mini skid steer attachments interchangeable with skid steer attachments?

No. They use different mounting plates and are engineered for very different lift capacities. Our listings name the machine class for each model, and mini skid steer, Toro Dingo, and MT85 models are identified as such.

How wide should my attachment be?

As a general rule, at least as wide as your machine, so you are not driving over ground the attachment has not worked. Balance that against your loader's rated operating capacity, since a wider attachment is both heavier empty and carries more material when loaded.