Pull Behind Reel Mowers: Selection and Maintenance Guide

For property owners managing two or more acres of flat, high-visibility turf, standard rotary mowers leave behind a frayed, bruised grass blade that quickly turns brown at the tips. Pull behind reel mowers—often configured as multi-gang tow-behind units—solve this by employing a precise scissor-cutting action between a spinning helical reel and a stationary bedknife. According to turfgrass researchers at Purdue University, this clean cut significantly reduces moisture loss and disease susceptibility in high-stress turf environments. This guide details the mechanical differences between ground-driven and PTO-driven systems, provides a framework for selecting the correct cutting width, and outlines the exact tolerances required for professional-grade maintenance.

Ground-Driven vs. PTO-Driven Reel Systems

The primary decision when selecting pull behind reel mowers is the drive mechanism. The reel must spin at a specific RPM relative to the tractor's forward ground speed to achieve the correct "clip" (the distance the mower travels forward between each blade strike). If the clip is too long, the turf looks ribbed; if it's too short, the mower scalps the grass.

Ground-Driven Gang Mowers

Ground-driven units, such as the Tru-Turf RM56 or Greensleeves TR300, rely on a heavy traction drum that rolls on the turf. As the tractor pulls the mower forward, the drum turns a gearbox or chain drive that spins the reel. These models typically cost between $3,500 and $7,000. The major limitation is that reel speed is directly tied to tractor speed. If the operator slows down to navigate a slight incline or a damp patch of grass, the reel slows down proportionally, resulting in an inconsistent cut and potential turf tearing.

PTO-Driven (Power Take-Off) Mowers

PTO-driven mowers, like the John Deere 2653 or Toro Groundmaster series, connect to the tractor's 540-RPM PTO shaft. A hydraulic pump or mechanical drivetrain translates this constant PTO speed into a steady reel RPM, completely independent of the tractor's ground speed. PTO units are the industry standard for undulating terrain and sports fields, ensuring a uniform clip even when the tractor decelerates. Expect to invest $12,000 to $25,000+ for a new PTO-driven triplex or pull-behind gang configuration.

Sizing and Selecting the Right Gang Configuration

Pull behind reel mowers are rarely sold as single units; they are grouped into "gangs" (typically 3, 5, or 7 reels) mounted on a heavy-duty tow frame. Selecting the right width requires calculating your total acreage and factoring in a mandatory 2-to-3-inch overlap between adjacent reels to prevent uncut strips of grass.

Precision Maintenance: Backlapping and Bedknife Adjustment

Unlike rotary mowers where you simply unbolt and replace a dull blade, reel mowers require continuous micro-adjustments. The Golf Course Superintendents Association of America (GCSAA) emphasizes that daily backlapping and weekly bedknife adjustments are non-negotiable for maintaining a true scissor cut. If the bedknife and reel blade do not make uniform contact across the entire 20-inch width of the reel, the mower will tear the grass rather than slice it.

Step-by-Step Backlapping Procedure

Backlapping is the process of using an abrasive compound to wear the reel and bedknife into a perfect mating surface. Perform this weekly during peak growing season.

1. Apply Compound: Coat the stationary bedknife with a liberal layer of 80-grit silicon carbide paste (valve grinding compound). For severely dull reels, start with 60-grit and finish with 120-grit.
2. Engage Reverse: Connect a backlapping motor or use the mower's hydraulic reverse function to spin the reel backward. Never backlap with the reel spinning forward, as this will push the compound away from the cutting edge and ruin the blade geometry.
3. Run Time: Allow the reel to spin in reverse for 15 to 20 minutes per gang unit. You will hear the pitch of the metal-on-metal friction change from a harsh grinding sound to a smooth, high-pitched hiss.
4. Clean and Test: Thoroughly wash off all abrasive paste with a degreaser and water. Test the cut by sliding a standard piece of 20lb bond paper between the reel and bedknife. The paper should slice cleanly with zero resistance across the entire length of the blade.

Setting the Bedknife Clearance

After backlapping, the bedknife must be adjusted to maintain a microscopic gap. Using a brass feeler gauge, measure the clearance between the reel blade and the bedknife at three points: the left edge, the center, and the right edge. The target clearance is 0.002 to 0.004 inches. If the gap is wider, the grass will fold over the bedknife and tear. If the gap is zero (metal-on-metal contact), you will generate excessive heat, warp the bedknife, and prematurely destroy the reel bearings.

Annual Spin Grinding vs. Routine Backlapping

While backlapping maintains the cutting edge, it does not correct reel cylinder runout (wobble). Over a season of hitting hidden rocks, roots, and irrigation heads, the reel shaft can bend by fractions of a millimeter. Once a year, pull behind reel mowers must undergo spin grinding. This requires a specialized grinding machine (such as a Foley Belsaw) that spins the reel at operating speeds while a grinding stone shaves the outer cylinder perfectly concentric. Spin grinding removes approximately 0.010 inches of steel and restores the factory geometry. Expect to pay a specialized turf mechanic $150 to $250 per reel for this service, or invest $4,000+ in a commercial spin grinder if you maintain a large fleet.

Troubleshooting Common Cut Defects

When the turf quality degrades, the mower is almost always the culprit. Use this diagnostic framework to identify the failure mode:

• Washboarding (Ribbing): The turf looks like a washboard with distinct ridges. Cause: The reel RPM is too slow for the tractor's ground speed, resulting in a clip that is too long. Fix: Increase tractor PTO RPM or slow down your forward driving speed.
• Frayed or Brown Leaf Tips: The lawn looks greyish-brown a few hours after mowing. Cause: Dull blades are tearing the grass tissue instead of cutting it, causing the tips to desiccate. Fix: Perform an immediate backlapping session and verify bedknife clearance with a feeler gauge.
• Uncut Stripes (Step-cutting): Visible lines of taller grass left between the reel units. Cause: Insufficient overlap between adjacent gangs, or the tractor is drifting slightly off a straight line. Fix: Adjust the gang spacing on the tow frame to ensure a minimum 2-inch overlap and use GPS guidance or visual markers for straight passes.
• Scalping: The mower cuts into the soil or exposes the brown thatch layer. Cause: The front roller is set too low, or the traction drum is sinking into soft, wet soil. Fix: Raise the front roller height and avoid mowing when soil moisture exceeds field capacity.

Frequently Asked Questions

Can I use a pull behind reel mower on uneven or hilly terrain?

Reel mowers require a firm, relatively flat surface to maintain contact between the bedknife and the turf. On highly undulating or hilly terrain, the heavy traction drums will lose contact with the ground in the dips, causing the mower to scalp the high spots and miss the low spots. For slopes exceeding a 15% grade, a heavy-duty flail mower or a wide-area rotary mower is a much more effective choice.

How often should I grease the reel bearings?

Reel bearings endure high RPMs and constant exposure to moisture and grass clippings. You should inject a high-quality, lithium-based, water-resistant grease (such as Mobilgrease XHP 222) into the zerks every 25 hours of operation. Over-greasing can blow out the bearing seals, so apply just two to three pumps per fitting until you see a tiny bead of fresh grease purge from the seal edge.