Standard Flow vs. High Flow Skid Steers: What Attachment Buyers Need to Know
If you are shopping for a hydraulic skid steer attachment, you have probably seen the terms standard flow and high flow.
Those two terms matter, but they can also cause confusion.
A skid steer does not become compatible with an attachment simply because both are described as standard flow or high flow. What actually matters is whether your machine can supply the hydraulic flow and pressure the attachment requires.
That means knowing your machine's GPM, understanding the attachment's operating range, and verifying any additional hydraulic requirements before buying.
Here is what attachment buyers need to know.
What Does Hydraulic Flow Mean?
Hydraulic flow is normally measured in gallons per minute, or GPM.
In simple terms, GPM tells you how much hydraulic oil the machine can move through the auxiliary hydraulic circuit in a given amount of time.
When you connect a powered attachment such as a brush cutter, auger, trencher, stump grinder, mulcher, or soil conditioner, hydraulic oil from the skid steer powers the attachment's hydraulic motor.
The attachment is designed to operate within a particular flow range.
For example, the CID brush cutter lineup currently available through JST Attachment Sales includes models ranging from 16 GPM on the low end to 48 GPM on the high end.
That is a huge range, and it is exactly why knowing your machine's actual hydraulic specifications is so important.
What Is Standard Flow on a Skid Steer?
There is no single GPM number that defines every standard flow skid steer.
Standard flow refers to the machine's normal auxiliary hydraulic circuit. The actual flow varies by manufacturer, model, and machine size.
A smaller skid steer may have considerably less auxiliary flow than a large compact track loader, even though both machines use what their manufacturers describe as standard flow hydraulics.
That is why shopping by the words standard flow alone can get you into trouble.
For example, JST currently carries the CID TR1626 Tree Reaper, which operates at 16 to 26 GPM, and the CID TR1730 Tree Reaper, which operates at 17 to 30 GPM.
Both are intended to work within hydraulic ranges commonly found on standard flow skid steers, but they clearly do not have identical hydraulic requirements. Always compare the actual numbers.
What Is High Flow?
High flow is an upgraded hydraulic system available on many skid steers and compact track loaders. It allows the machine to deliver more hydraulic oil through the auxiliary circuit than its standard hydraulic configuration.
That additional hydraulic capacity is useful for demanding powered attachments such as forestry cutters, mulchers, cold planers, stump grinders, trenchers, and other hydraulic tools designed to take advantage of the additional flow.
A good example is the CID XC3048 X-Treme High Flow Brush Cutter now available through JST Attachment Sales. The XC3048 operates at 30 to 48 GPM.
JST currently carries it in both 72 and 78 inch widths, with or without mulching teeth.
Shop the 72 Inch CID XC3048 X-Treme High Flow Brush Cutter
Shop the 78 Inch CID XC3048 X-Treme High Flow Brush Cutter
But there is an important distinction: Having high flow does not mean you should send maximum hydraulic flow to every attachment.
The attachment still has an operating range. If an attachment is rated for a maximum of 30 GPM, connecting it to a machine capable of substantially more flow does not mean the attachment should be operated at the machine's maximum output. The attachment manufacturer's limits still govern.
Standard Flow and High Flow Are Categories, Not Compatibility Specifications
This is probably the most important point in this article.
Think of standard flow and high flow as general categories. Think of GPM and PSI as specifications.
When determining compatibility, specifications matter more than the category name.
Before purchasing a hydraulic attachment, compare minimum and maximum hydraulic flow, hydraulic pressure requirements or limits, case drain requirements, coupler requirements, machine horsepower or size recommendations, attachment weight, and mounting system.
If those specifications are compatible, you can make a much more informed decision. If you only know that your machine is standard flow or high flow, you still need more information.
A Real Example: CID Brush Cutters From 16 to 48 GPM
The CID brush cutter lineup at JST Attachment Sales provides an excellent real-world example. We currently offer three different hydraulic ranges within this family of heavy land clearing cutters.
CID TR1626 Tree Reaper: 16 to 26 GPM
The CID TR1626 Tree Reaper operates at 16 to 26 GPM.
JST currently offers the TR1626 in 60, 72, 78, and 84 inch widths, with Mulching Teeth Yes/No options.
This provides an aggressive land clearing cutter option for machines operating within that hydraulic range.
60 Inch CID TR1626 Tree Reaper | 72 Inch | 78 Inch | 84 Inch
CID TR1730 Tree Reaper: 17 to 30 GPM
The next step is the CID TR1730 Tree Reaper, which operates at 17 to 30 GPM.
JST currently carries the TR1730 in 60, 72, 78, and 84 inch widths, again with Mulching Teeth Yes/No options.
The TR1730 uses a Parker bent-axis piston motor and extends the available operating range to machines capable of supplying up to 30 GPM.
60 Inch CID TR1730 Tree Reaper | 72 Inch | 78 Inch | 84 Inch
CID XC3048 X-Treme High Flow: 30 to 48 GPM
For machines equipped to supply considerably more hydraulic flow, JST now carries the CID XC3048 X-Treme High Flow Brush Cutter.
The XC3048 operates at 30 to 48 GPM and uses a Fluid Gear radial piston motor. JST currently offers the XC3048 in 72 and 78 inch widths, with Mulching Teeth Yes/No options.
This is where the difference between standard flow and high flow becomes much easier to visualize.
You could have a 72 inch CID cutter designed for 16 to 26 GPM, another 72 inch cutter designed for 17 to 30 GPM, and a third 72 inch cutter designed for 30 to 48 GPM.
They may have the same nominal cutting width, but they are intended for very different hydraulic systems.
That is why attachment width does not tell you the hydraulic requirements. Your machine's actual GPM does.
GPM and PSI Are Not the Same Thing
Hydraulic flow and hydraulic pressure work together, but they describe different things.
GPM is flow. It describes the volume of hydraulic oil moving through the system.
PSI is pressure. It describes the hydraulic pressure available to do work.
A simple way to think about it is that hydraulic power depends on both. More flow does not automatically mean more pressure, and more pressure does not automatically mean more flow.
That is why two machines with similar GPM ratings can still perform differently with the same attachment. When an attachment manufacturer specifies both a hydraulic flow range and a pressure limitation, both need to be respected.
Why Too Little Hydraulic Flow Is a Problem
An attachment designed for more hydraulic flow than the machine can supply may operate poorly.
Depending on the attachment, you may see reduced motor speed, lower cutting performance, slower cycle times, poor productivity, or an increased tendency to stall under load.
Consider the XC3048. Its operating range begins at 30 GPM.
A skid steer producing 24 GPM does not suddenly become suitable for the XC3048 simply because it can physically connect to the attachment or because the machine has enough lifting capacity to carry it.
The hydraulic system still does not meet the cutter's published minimum flow requirement. A TR1626 or TR1730 may be a more appropriate hydraulic match, depending on the rest of the machine specifications and intended use.
Why Too Much Hydraulic Flow Can Be a Bigger Problem
Too little flow usually results in poor performance. Too much flow can potentially damage components if the attachment or hydraulic system is not designed to accommodate it.
A hydraulic motor has operating limits. Running substantially beyond those limits can create excessive motor speed, heat, seal problems, and premature component failure.
For example, the TR1626 tops out at 26 GPM, while the XC3048 is specifically designed for 30 to 48 GPM.
Those are different hydraulic applications.
A high flow skid steer capable of producing 40 or 45 GPM should not automatically send that full output through an attachment rated for substantially less flow. Always stay within the attachment manufacturer's specified operating range.
A High Flow Machine Can Still Use Many Standard Flow Attachments
Owning a high flow skid steer does not mean every attachment you buy needs to be high flow.
Many high flow equipped machines can also operate attachments using their standard auxiliary hydraulic circuit or a lower flow operating mode.
That can make a high flow machine extremely versatile. You might use a lower flow auger for one job, a standard flow cutter for another, and then switch to a high flow attachment when you need the additional hydraulic capability.
The important part is knowing what flow the machine is actually supplying in the operating mode you select.
Consult the machine's operator manual and manufacturer specifications before assuming how a particular hydraulic mode behaves.
Hydraulic Flow Also Matters With Augers
Brush cutters provide an easy visual example, but the same principle applies to augers.
JST's Belltec lineup includes auger drives designed for different hydraulic ranges. The Belltec LC-150, for example, operates at 6 to 15 GPM. Other Belltec drives move progressively higher in hydraulic requirements as drive size and application change.
This allows the auger drive to be matched to the machine rather than assuming one drive fits every tractor, mini skid steer, skid steer, or compact track loader.
Shop Belltec Auger Drives at JST Attachment Sales
What About Case Drain?
Some hydraulic attachments require a case drain line.
A case drain provides a low pressure return path for internal leakage from certain hydraulic motors.
If an attachment requires a case drain and your machine does not have one installed, that needs to be addressed before operating the attachment.
Do not assume the two main hydraulic couplers are all that every attachment needs. Before purchasing a hydraulic attachment, check whether it requires pressure, return, and case drain connections.
That small compatibility check can prevent a very expensive mistake.
Coupler Size Does Not Tell You Hydraulic Flow
Another common misconception is assuming that hydraulic coupler size tells you whether a machine is standard flow or high flow. It does not.
Couplers are part of the hydraulic connection, but the physical coupler alone does not tell you the machine's actual auxiliary flow rate.
Two machines can have similar looking hydraulic connections and very different hydraulic performance. Likewise, two attachments may physically connect to the same machine while having very different hydraulic requirements.
Physical connection does not equal hydraulic compatibility.
How Do I Find My Skid Steer's Hydraulic Flow?
The easiest place to start is your operator's manual or the manufacturer's specifications for your exact machine model.
Look for terms such as auxiliary hydraulic flow, standard auxiliary flow, high flow auxiliary hydraulics, hydraulic system, or implement flow.
Be careful when searching online. Manufacturers sometimes offer the same skid steer model with multiple hydraulic packages. A specification found online may describe an optional high flow configuration rather than the machine sitting in your barn.
If your machine has selectable hydraulic modes, determine which modes are actually installed and how they are configured.
For a complete walkthrough, read How Do I Know My Skid Steer's Hydraulic Flow?
Do I Need High Flow?
For many skid steer owners, the answer is not necessarily.
There are a tremendous number of useful attachments that can operate within the hydraulic capabilities of standard flow machines.
Grapples, pallet forks, buckets, land planes, many augers, and numerous brush cutters can all be used without requiring a high flow hydraulic package.
High flow becomes important when the attachments you want to operate actually require the additional hydraulic capacity.
The XC3048 is a perfect example. If you specifically want to operate a cutter requiring 30 to 48 GPM, your machine needs a hydraulic system capable of satisfying that requirement.
If You're Buying a Skid Steer, Work Backward From the Attachment
This is particularly important for customers shopping for both a machine and attachments.
Do not simply decide that you want a high flow skid steer because high flow sounds better. Ask what you actually plan to run.
If your primary attachments will be a grapple, pallet forks, bucket, and an auger requiring 15 GPM, those attachments do not automatically justify buying a machine specifically for a much higher hydraulic output.
On the other hand, if you know you eventually want to operate an XC3048 requiring up to 48 GPM, hydraulic capability becomes a much more important part of your machine selection.
Start with the work. Identify the attachments needed to perform that work. Determine their hydraulic requirements. Then make sure the machine can properly operate them.
Before Buying a Hydraulic Attachment, Check These Six Things
- Your exact skid steer or compact track loader make and model
- Your machine's standard auxiliary flow in GPM
- Your machine's high flow output, if equipped
- Your machine's auxiliary hydraulic pressure
- Whether the machine has a case drain
- The hydraulic flow, pressure, and case drain requirements of the attachment
If those numbers are not available, find them before choosing the attachment.
A few minutes checking specifications can prevent purchasing an attachment that your machine cannot properly operate.
The Bottom Line
Standard flow versus high flow is useful terminology, but it should not be your final compatibility test.
The better question is: How many GPM does my machine actually produce, and what hydraulic flow does the attachment actually require?
The CID cutter lineup illustrates this extremely well:
TR1626: 16 to 26 GPM
TR1730: 17 to 30 GPM
XC3048: 30 to 48 GPM
Those three ranges take us from relatively modest standard auxiliary flow all the way into true high flow territory.
Once you know your machine's actual numbers, attachment selection becomes much easier.
A machine does not need high flow simply because you want to run hydraulic attachments. It needs enough flow and pressure for the specific attachment you intend to operate.
And if your machine does have high flow, that does not mean every attachment should be operated at maximum flow.
Match the attachment to the machine, stay within the manufacturer's operating specifications, and you will get better performance while protecting both pieces of equipment.
Not Sure Whether an Attachment Will Work With Your Machine?
Send JST Attachment Sales your machine make and model and tell us which attachment you are considering.
We can help compare your machine's hydraulic specifications with the attachment requirements before you buy.
That is especially useful for powered attachments such as brush cutters, augers, trenchers, stump grinders, mulchers, and other hydraulic tools.