Choosing a Weight Distribution Hitch for Your Enclosed Trailer

Neighbors Trailer

Feb 2, 2024
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7 min read
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An enclosed trailer is tall, flat-walled, and almost always heavier than the owner expects once it's loaded. Those three factors combine to make a weight distribution hitch (WDH) one of the most important upgrades an enclosed trailer owner can buy. This guide explains what a WDH does, when you actually need one, how to size the spring bars to your tongue weight, the difference between round-bar and trunnion-bar designs, and the installation details that separate a safe haul from a white-knuckle drive.

What a Weight Distribution Hitch Does

A WDH is a hitch system that uses two long steel spring bars to lever some of the trailer's tongue weight off the tow vehicle's rear axle and redistribute it forward to the front axle and backward to the trailer's axles. The result is a level tow vehicle, a level trailer, restored front-tire steering and braking authority, and significantly reduced sway potential. Without a WDH, a heavy enclosed trailer's tongue weight squats the rear of the tow vehicle, lifts the front, and turns the entire combination into a long, top-heavy, poorly braking unit.

WDHs are not a substitute for proper loading. You still need to follow tongue weight percentage rules (10 to 15 percent of GVW). A WDH simply manages the consequence of high tongue weight; it does not eliminate the need to balance the load. Our companion guide on cargo trailer weight distribution covers the loading side of the equation in full.

When You Actually Need a WDH

You need a weight distribution hitch when any of these conditions are true: (1) the trailer's loaded tongue weight exceeds 500 lbs, (2) the tongue weight exceeds 10 percent of the tow vehicle's GVWR, (3) the tow vehicle's owner's manual specifies WDH use above a certain trailer weight, or (4) the trailer manufacturer requires it. For most 7,000 lb and heavier enclosed trailers towed by half-ton or three-quarter ton trucks, all four conditions are true and a WDH is mandatory.

You can usually skip a WDH if your loaded tongue weight is under 400 lbs, the tow vehicle squats less than an inch when hitched, and you don't experience sway at highway speeds. Lighter single-axle enclosed cargo trailers (under 4,000 lbs GVW) often fall in this category.

Sizing Spring Bars to Tongue Weight

The most common mistake in WDH selection is sizing bars to the trailer's total weight instead of the tongue weight. Spring bars are rated by tongue weight capacity, not trailer weight. The general rule is to pick bars whose rated capacity is closest to your actual tongue weight without being lower than it. Oversized bars over-correct, lift the trailer's front excessively, and create a harsh ride. Undersized bars don't transfer enough weight to make a difference. The chart below shows typical tongue weight ratings by spring bar class.

Bar chart showing maximum tongue weight ratings for common weight distribution hitch spring bar classes: 400-600 lb bars up to 1500 lb bars

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Round Bar vs. Trunnion Bar Designs

Round Bar WDHs

The classic, lower-cost design. The spring bars hang below the trailer frame on chains that engage hooks bolted to the trailer's A-frame. Round bar systems are budget-friendly (often $250 to $400 for a complete kit), easy to hitch, and forgiving of slight misalignment. The downside is lower ground clearance and a slightly less aggressive weight transfer. Suitable for tongue weights up to 750 lbs and most light to medium enclosed trailers.

Trunnion Bar WDHs

The bars seat directly into the head of the hitch on rotating pins (trunnions) rather than hanging from chains. This puts the bars several inches higher off the ground, gives a slightly stiffer ride, and transfers weight more aggressively. Trunnion systems run $400 to $900 and are the preferred design for heavier enclosed cargo and race trailers above 700 lbs tongue weight. Most also accept integrated sway control friction bars or four-point sway brackets, which our sway control hitch guide covers in depth.

Integrated vs. Add-On Sway Control

Some WDHs include integrated four-point sway control (Equal-i-zer, ProPride, Hensley) that prevents sway from starting rather than just damping it after it begins. Others use a friction bar add-on (Reese Dual Cam, Curt) that resists sway through mechanical friction. For enclosed trailers above 6,000 lbs GVW or any trailer with a tall enclosed body shape, integrated sway control is worth the premium because the flat sides catch wind that round-profile boat trailers do not.

Spring Bar Sizing Reference

Use the table below as a starting point. Always check your tongue weight with a real scale before buying bars; estimates from the trailer's tongue-weight label rarely match a real-world loaded measurement.

Loaded Tongue Weight	Recommended Spring Bars	Typical Trailer GVW Range	Design Style
400-500 lbs	400-600 lb bars	4,000-5,000 lbs	Round or trunnion
500-700 lbs	600-800 lb bars	5,000-7,000 lbs	Round or trunnion
700-1000 lbs	1,000 lb bars	7,000-10,000 lbs	Trunnion preferred
1000-1200 lbs	1,200 lb bars	10,000-12,000 lbs	Trunnion only
1200+ lbs	1,500 lb bars	12,000+ lbs	Trunnion only

Installation Essentials

WDH installation requires a torque wrench, level ground, and patience. The shank height in the receiver must position the head so the spring bars sit roughly parallel to the trailer's A-frame when hitched and tensioned. Too high and the bars over-tension the front of the trailer; too low and they under-correct. Mount the lift brackets on the trailer's A-frame such that the chain reaches the head with three or four links of slack, then tension by lifting each bar with the supplied lift handle until the truck sits at its normal ride height. After the first short drive, re-check that nothing has shifted; bracket bolts can settle on a first heavy load.

Common Mistakes to Avoid

The two big WDH mistakes are oversizing bars and ignoring brake controller recalibration. Oversized bars give a tooth-jarring ride and put bending stress on the trailer A-frame. The fix is to weigh your actual tongue weight before purchase. Brake controller recalibration is necessary because the trailer now rides lower on its axles and the controller gain (and sometimes the load-sensing brake bias on newer trucks) needs to be re-set for the new weight distribution. Drive a quarter mile after first install and re-tune the controller in a parking lot. For a refresher on enclosed trailer brake controllers, see our brake controller setup guide.

Frequently Asked Questions

Will a WDH increase my tow vehicle's tow rating?

No. WDHs improve how the tow vehicle handles a given load; they do not raise the rated capacity. Some manufacturers do require WDH use above a certain trailer weight, in which case the rated capacity assumes you have one installed.

Can I use a WDH with a surge brake trailer?

Generally no, because the WDH pre-loads the coupler in a way that can interfere with surge brake actuation. Most WDH manufacturers explicitly prohibit surge brake use. Electric brakes are required for WDH use.

Do I need a special hitch ball?

Yes. WDH systems require a specific ball size and grade installed in the head's ball seat, not the receiver tongue. Use the ball the WDH manufacturer specifies; never substitute a standard receiver ball.

How often should I re-tension the spring bars?

Every hookup, every trip. The tension is set when you load the bars onto the lift brackets at the start of each tow. Never assume the previous trip's setup is valid for a new load.

Final Thoughts

A correctly sized weight distribution hitch is the difference between an enclosed trailer that tows like a sedan and one that fights you all the way to the destination. Measure your real-world tongue weight, match the spring bars to that number, pick trunnion bars if your tongue weight exceeds 700 lbs or your trailer is wind-catching tall, and integrate sway control if you're towing a heavy enclosed body. The total investment is typically $300 to $900, and it pays back in cleaner steering, better fuel economy, and dramatically improved safety on long hauls.

Content updated May 2026