The basic process: bump the head, unwind, and reload

To replace the string on a Ryobi 18V cordless trimmer, you tap the bump head against the ground while the trimmer is running, which automatically feeds fresh string from the spool inside. If the string is completely gone or too short to bump-feed, you'll need to open the trimmer head, remove the old spool, wind new string onto it by hand, and reinstall it. Most Ryobi 18V models use the same head design, so the process is nearly identical across their lineup.

The bump-feed method works when you still have a stub of string left. The automatic feed method works only while the trimmer is running and the head is spinning. If you've run completely out of string or the spool is damaged, manual winding is your only option.

Key Takeaways

  • Ryobi 18V trimmers use a bump-feed head that automatically extends string when you tap it against the ground while the trimmer is running.
  • If string remains on the spool, bump the head to feed more; if the spool is empty, you must manually wind new string onto the spool and reinstall it.
  • Replacement string for Ryobi 18V trimmers is sold as pre-wound spools or as bulk line that you wind yourself, both available at hardware stores and online.
  • The entire manual winding and reinstallation process takes 10 to 15 minutes and requires no tools beyond what comes in the trimmer's box.

When to use the bump-feed method

If you still see string protruding from the trimmer head—even just a short length—use the bump-feed method first. Stop the trimmer, let it come to a complete stop, then restart it. Once it's running at full speed, tap the bottom of the head gently against the ground or a hard surface. The impact triggers the automatic feed mechanism inside the head, which releases a measured length of new string from the spool.

You may need to bump it several times to get enough string to extend from both sides of the head. Each bump typically feeds 2 to 3 inches of string. If after five or six bumps you're not seeing new string appear, the spool is likely empty and you'll need to manually rewind it.

Opening the trimmer head and removing the old spool

To access the spool, you need to open the trimmer head. Most Ryobi 18V models have a head that unscrews by hand—no tools required. Hold the shaft of the trimmer steady with one hand and turn the head counterclockwise with the other. It will unscrew and come free in your hand.

Once the head is off, you'll see the spool inside. It's a plastic bobbin that sits in the center of the head. Lift it straight out. Some models have a small spring underneath the spool; if you see one, note its position so you can replace it correctly. Set the old spool aside—you can discard it or keep it as a spare if it's still intact.

Winding new string onto the spool

Ryobi sells replacement string in two forms: pre-wound spools that you straightforward drop in, or bulk string that you wind yourself. Pre-wound spools are faster and more reliable, especially if you're new to this. Bulk string is cheaper per foot but requires hand-winding.

If you're using bulk string, cut a length of approximately 20 feet. Insert one end into the small notch or hole on the edge of the spool—this is the anchor point where the string starts. Wind the string tightly around the spool in the direction indicated by the arrow molded into the plastic (usually counterclockwise when looking at the spool from above). Keep the string under tension as you wind so it sits flat and doesn't bunch up. Wind until you've used most of the 20 feet, leaving about 6 inches free. Tuck the free end into the slot or notch on the opposite side of the spool to hold it in place.

If you're using a pre-wound spool, straightforward remove it from its packaging and skip to the next section.

Reinstalling the spool and closing the head

Place the spool back into the trimmer head, making sure it sits flat and centered. If there was a spring underneath, place it back in position first. The two ends of string should be pointing outward toward the openings on either side of the head where the string exits.

Thread each end of the string through the small eyelets or slots on the sides of the head. These guide the string outward as it spins. Screw the head back onto the trimmer shaft by turning it clockwise by hand until it's snug. Don't over-tighten—hand-tight is sufficient.

Trimming the string to the correct length

Before you use the trimmer, the string needs to be cut to the right length. The trimmer head has a cutting blade or guard on the front that shows you where the string should end. Start the trimmer and let it run at full speed. The spinning string will naturally wear down and break at the guard, self-trimming to the correct length. This usually happens within a few seconds.

If the string doesn't trim itself, carefully guide the spinning head toward a hard surface like a concrete step or driveway, allowing the string to make contact and break. Never force the string against the surface—let the spinning motion do the work. Once both sides are trimmed to the same length, you're ready to use the trimmer.

Choosing the right replacement string

Ryobi 18V trimmers typically use 0.065-inch diameter string, though some models use 0.080-inch. Check your trimmer's manual or the label on the head itself to confirm the diameter before you buy. Using the wrong size can cause feeding problems or poor cutting performance.

String is sold by the spool, by the pound, or in bulk spools at hardware stores, home centers, and online retailers. Pre-wound spools cost more per foot but save you the time and effort of winding. Bulk string is economical if you trim frequently. Both work equally well once installed correctly.

Frequently Asked Questions

Can I use string from a different brand in my Ryobi trimmer?

Yes, as long as it's the correct diameter (usually 0.065-inch for Ryobi 18V models). The string itself is generic—the brand doesn't matter. What matters is the diameter matching your trimmer head's specifications.

Why isn't the bump-feed working?

The spool is likely empty. Bump-feed only works if there's string left on the spool to release. If you've bumped five or six times and nothing appears, you need to manually wind and install a new spool. Also make sure the trimmer is running at full speed when you bump—the mechanism won't trigger if the head isn't spinning.

How often do I need to replace the string?

It depends on how much you trim and what you're cutting. Thick weeds and brush wear string faster than light grass. Most homeowners refill the spool every few weeks during the growing season. You'll know it's time when the trimmer stops cutting cleanly or the string becomes noticeably short.

Do I need to remove the battery before opening the head?

No, but it's a good habit to remove it anyway for safety. The trimmer won't start without the battery installed, so as long as the battery is out, you can't accidentally set up it while your hands are near the head.

What if the spool is cracked or damaged?

You'll need to replace the entire head assembly, not just the spool. Ryobi sells replacement heads separately. Order the correct model number for your trimmer and follow the same unscrew-and-replace process. A damaged spool won't feed string reliably and can't be repaired.