How to Measure a Hydraulic Cylinder (Bore, Stroke, Rod and Pin Size)

A step-by-step guide from the FIMIC Implement team

Ordering a replacement hydraulic cylinder should be simple. But one wrong measurement, a stroke that's 2" short or a pin that won't go through the clevis, and you're stuck with a cylinder that doesn't fit and a machine that's down for another week.

Most of the cylinder returns we see come down to the same few mistakes: measuring the outside of the tube instead of the bore, measuring the whole rod instead of the stroke, or forgetting to check the ports. The good news is that you can avoid all of them with a tape measure, a set of calipers and about fifteen minutes.

This guide walks you through each measurement in order, shows a real example, and gives you a worksheet to fill in before you order.

Why accurate measurement matters

A hydraulic cylinder has to fit three ways at once: it has to fit between the mounting points, push or pull the right distance, and connect to your hoses. If any one of those is off, the cylinder won't work.

• Wrong retracted length: the cylinder won't pin in, or the implement can't fully lower or raise.

• Wrong stroke: the implement doesn't travel far enough, or the cylinder bottoms out and strains the mounts.

• Wrong bore: the cylinder is too weak to lift the load, or it moves faster or slower than the other cylinders in the system.

• Wrong pin or ports: it doesn't bolt on, or your hoses won't connect.

Safety first

• Lower the implement to the ground or block it securely before you touch the cylinder. Never rely on the hydraulics to hold a load while you work.

• Shut off the tractor and move the control lever back and forth to relieve pressure in the lines.

• Loosen fittings slowly and keep your hands away from any spray. High-pressure hydraulic fluid can inject through skin and needs emergency medical care.

• Wear gloves and eye protection, and have rags and a drain pan ready.

Tools you will need

• Tape measure

• Calipers (a basic dial or digital set is fine)

• Thread pitch gauge, or a known fitting to test the ports

• Marker and the worksheet at the end of this post

• Your phone, to take photos of the cylinder, ports and any tags

Step 1: Check for a tag or stamp first

Before you measure anything, wipe the cylinder clean and look for a tag, a stamped number or a decal on the tube or end caps. Many cylinders list the bore and stroke right there, for example "2 x 10" or "2.5 x 8". Some also list a part number you can search.

Even if you find a tag, measure anyway. Tags wear off, and cylinders get swapped over the years.

Step 2: Measure the bore

The bore is the inside diameter of the tube, which is the size of the piston. It's the most important measurement because it sets how much force the cylinder makes.

You can't measure the bore directly without taking the cylinder apart, so here's how to get it from the outside:

1. Measure the outside diameter of the tube with calipers.

2. Estimate the wall thickness. On most farm cylinders it's around 1/4", but check at the end of the tube or a port hole if you can see the wall.

3. Subtract the wall thickness twice from the outside diameter.

Example: a tube that measures 2-1/2" on the outside with a 1/4" wall has a 2" bore (2.5 - 0.25 - 0.25 = 2.0).

Bores come in standard sizes, such as 2", 2.5", 3", 3.5" and 4". If your number lands close to one of those, that's almost always your bore. If you're between sizes, call us before ordering.

Step 3: Measure the stroke

The stroke is how far the rod travels from fully retracted to fully extended. It is not the total length of the rod.

The most reliable way:

1. Measure the pin-to-pin length with the cylinder fully retracted (Step 5 below).

2. Measure the pin-to-pin length again with the cylinder fully extended.

3. Subtract the retracted length from the extended length. That difference is the stroke.

If the cylinder is off the machine and you can't extend it, measure the exposed chrome rod with the cylinder fully extended, from the face of the gland (where the rod comes out) to the shoulder of the rod end. Don't count the threaded or clevis part of the rod.

Common strokes are 4", 6", 8", 10", 12", 16", 20", 24" and longer.

Step 4: Measure the rod diameter

Use calipers on the shiny chrome part of the rod. Common rod sizes on farm cylinders are 1-1/8" (1.125") and 1-1/4" (1.25").

While you're there, look at the chrome. Pitting, scratches or a bent rod mean the cylinder needs replacing, not just new seals.

Step 5: Measure the retracted pin-to-pin length

This is the measurement people skip, and it causes the most returns. Two cylinders can have the same bore and stroke but different overall lengths.

With the cylinder fully retracted, measure from the center of the pin hole on one end to the center of the pin hole on the other end. Don't measure from the outside edges of the clevises.

Write down the extended pin-to-pin length too. It's how you double-check the stroke.

Step 6: Measure the pin and clevis

Measure the pin itself with calipers, not the hole. Holes are slightly larger than the pin and wear oval over time, so a hole measurement can make a 1" pin look like 1-1/16".

Then measure the clevis:

• Clevis width (gap): the opening between the two clevis ears. The mounting tab on your machine has to fit inside it.

• Clevis depth: from the center of the pin hole to the bottom of the slot.

Also note the mounting style: clevis on both ends (common on tie-rod cylinders), a cross tube, or an eye. The cylinder you order has to mount the same way.

Step 7: Identify the ports

Ports are where the hoses connect. Check two things: how many there are, and what size and thread they use.

• Two ports means a double-acting cylinder (pushes and pulls with oil). One port usually means single-acting.

• Port type: the two most common are NPT (tapered pipe thread) and SAE O-ring (straight thread with an O-ring seal). They're not interchangeable without an adapter.

Here's a real example from the Spartan® line: the 2500 PSI 2" x 10" cylinder uses 3/8" NPT ports, while the 3000 PSI 2" x 10" cylinder uses 3/4-16 UNF ports. Same bore and stroke, different fittings. If you're unsure, take a fitting off the old cylinder and bring it to a hydraulic shop, or send us a clear photo.

Note where the ports face relative to the clevis, too. If the ports point the wrong way on the new cylinder, the hoses may rub or kink.

Step 8: Check the pressure rating

The new cylinder's pressure rating should be equal to or higher than your tractor's hydraulic relief pressure. Check your owner's manual for the system pressure. If your system runs above 2,500 PSI, or the cylinder takes shock loads, choose a 3000 PSI cylinder. Our guide on 2500 PSI vs. 3000 PSI hydraulic cylinders explains the difference in detail.

Common mistakes that lead to returns

• Measuring the outside of the tube as the bore. A 2-1/2" tube is usually a 2" bore, not a 2.5" bore.

• Measuring the whole rod as the stroke. Stroke is travel only, not rod length.

• Skipping the retracted length. Same bore and stroke doesn't guarantee the same pin-to-pin length.

• Measuring the pin hole instead of the pin. Worn holes read larger than the pin.

• Ignoring port type. NPT and SAE O-ring fittings don't mix without adapters.

• Measuring the edges instead of pin centers. Always measure center to center.

• Mixing inches and millimeters. Metric cylinders exist, especially on some imported equipment. If your numbers don't line up with standard inch sizes, measure in millimeters and call us.

Find your replacement

Once you have your numbers, match them to a Spartan® cylinder:

• Spartan® 2500 PSI tie-rod cylinders: 2" to 5" bores in a wide range of strokes, for systems at or below 2,500 PSI.

• Spartan® 3000 PSI tie-rod cylinders: for higher-pressure systems and shock loads.

• Spartan® 3000 PSI welded clevis cylinders and welded tube cylinders: more compact options for tight spaces.

• ASAE implement cylinders, such as the 2" x 8" ASAE (2500 PSI) and 2" x 8" ASAE (3000 PSI), for standard pull-type implement lifts.

• Hydraulic cylinder seal kits, when the rod is good and only the seals are leaking.

Every Spartan® product page lists the retracted length, extended length, pin size and port size, so you can compare your numbers line by line before you order.

Your measurement worksheet

Print this, fill it in at the machine, and keep it with your order.

Hydraulic cylinder measuring FAQs

What's the difference between bore and rod diameter?

The bore is the inside diameter of the tube, which is the piston size. The rod diameter is the size of the chrome rod that comes out of the cylinder. The bore is always larger.

How do I find the stroke if the cylinder is stuck?

Measure the retracted pin-to-pin length, then look up that length with your bore size. If you can't extend the cylinder, send us the bore, rod, retracted length and photos, and we'll help you narrow it down.

Does the retracted length have to match exactly?

It should be as close as possible. A small difference may fit if your mounts have adjustment, but too long and it won't pin in, too short and the implement won't reach full travel.

Can I use a cylinder with a different bore?

Sometimes, but it changes the force and speed. A bigger bore pushes harder and moves slower with the same oil flow. If the cylinder works with others in the same circuit, such as on a batwing, keep the bores matched.

What if my ports don't match?

You can use adapters to go from one port type to another. Order them with the cylinder so you can finish the job in one trip.

Final checklist before you order

• Bore and rod diameter confirmed

• Stroke checked against extended minus retracted length

• Retracted pin-to-pin length recorded

• Pin size and clevis width measured

• Port size, type and count noted

• Pressure rating matched to your tractor

• Photos of the old cylinder, ports and mounts saved

Still not sure? Call our cylinder line at 865-755-1101, or the main office at 601-342-5178, 7 days a week. Send us your measurements and a few photos, and we'll help you find the right Spartan® cylinder the first time. FIMIC orders dispatch the next business day.