DIY: How to Fit a Weight Distribution Hitch
Our friends at the RV Repair Centre step us through the overview of fitting a Hayman Reece Weight Distribution Hitch.
A weight distribution hitch (WDH) is a potential solution for a tow vehicle that is experiencing handling problems associated with a ‘light front end’. A heavy load imparted by the caravan on the rear of the tow vehicle will cause the rear to lower. It will also cause the front of the car to lift as the car chassis pivots around the rear axle. The result is less downforce being imparted on the tow vehicle's front tyres, reducing their contact patch with the ground. This can cause less precise steering and diminished braking performance. It will also set up altered dynamics, with the car and van more likely to pitch up and down. Another side effect can be your headlights pointing up, shining into oncoming traffic rather than directing at the road.
A WDH shifts some of the load imparted by the caravan off the rear axle and back onto the front axle. A correctly rated and fitted WDH can return the car to sit in a level position. The important thing, however, is that the returned load to the front axle means you have restored the front tyre contact patch for improved steering and braking. Restoring the balance between the front and rear loads can also stabilise the bouncing effect described above. Plus, your headlights should now be pointing where they are supposed to.
In principle, WDHs use levers to put upward force on the tow bar. This causes the chassis to rotate around the rear axle, lifting the rear of the car (reducing the load on the rear axle) and lowering the front of the car (increasing the load on the front axle). This is achieved by part of the load being lifted off the rear of the car now hanging off the A-frame.
Our friends at the RV Repair Centre step us through the overview of fitting a Hayman Reece WDH. This should only be treated as an incomplete guide and the detailed instructions provided by Hayman Reece, including safety information, should be carefully followed. WDHs involve springs under high tension and should be treated with extreme caution at all times.
Preparation
The front and rear ride height of the tow vehicle unhitched is used as a benchmark for achieving a level ride once the WDH is fitted. The van should also sit level once the WDH is fitted. Therefore, the following preparation is required:
- Load the tow vehicle and caravan as they would be for normal travel.
- Position the tow vehicle and caravan aligned in a straight line on flat even ground with at least 3 metres of clear area in front of the vehicle.
- Unhitch the caravan from the tow vehicle.
- Use the jockey wheel to level the caravan. Measure and record a point at the front and rear of the van on a common plane.
- Measure and record the height from the ground to the underside of the coupling.
- Measure and record the front and rear vehicle height from the ground up to the wheel arches.
Drop Shank and Weight Distribution Head Assembly
1. Insert the adjustable drop shank into the hitch receiver on the tow vehicle
2. Secure the drop shank with the receiver pin
3. Slide the ball mount head over the shank
4. Position to achieve the same coupling height recorded
5. Insert the 115mm long bottom bolt in the nearest hole and fit the spring washer and nut
6. Insert the 127mm top bolt into one of the cams against the bolt head
7. Slide the 127mm top bolt through the ball mount head and the shank, orienting the cam so the top plate is horizontal
8. Attach the second cam with the same orientation and fit the spring washer and nut on the other side
9. Ensure the towball is correctly rated for your application
10. Fit the towball to the top plate of the weight distribution head with the spring washer and nut
11. Tighten the towball nut
Springbar and Snap Up Bracket Assembly
1. Attach the chain to each spring bar using the ‘U’ bolts and locking nuts
2. Tighten the locking nuts evenly until there is a minimum of 5mm thread exposed and the chain can still pivot freely in all directions
3. The spring bar is ‘keyed’ to engage into the weight distribution head
4. Note the notch in the weight distribution head
5. With the van coupled to the tow vehicle, insert the spring bar at right angles to the tow vehicle
6. Pivot the spring bar to run parallel to the A-frame
7. Fit the set screw to the snap up bracket
8. Place the snap up bracket on the A-frame
9. Position the snap up bracket so that the chain will hang vertically when connected
10. Finger-tighten the set screw against the inside of the A-frame
11. Then tighten a further full turn
12. Repeat the process for the second spring bar and snap up bracket
Connecting Spring Bars to Snap Up Bracket
Use the jockey wheel to raise the coupling until the caravan is roughly level or slightly above.
1. Position the snap bracket pivoting arm level to the ground, hold the chain vertically and connect the nearest chain link onto the pivoting arm hook
2. Slide the lifting handle over the end of the pivoting arm
3. Raise the handle to allow the pivoting arm to go over centre
4. Hold the lifting handle under tension until the safety pin is fully in place
Adjustment and Fine Tuning
- Raise the jockey wheel so all of the van’s front load is now sitting on the coupling.
- Remeasure the front and rear tow vehicle height from the ground up to the wheel arches.
- Compare these measurements against the original ‘uncoupled’ measurements.
- Ideally, the tow vehicle front and rear ride heights should have lowered by equal amounts (around 15mm).
- Remeasure the front and rear of the van to check for a level ride.
- Raising the tow vehicle front can be achieved by:
- Lengthening the chain
- Or if there are not enough links available, adjusting the cams to change the angle of the towball towards the vehicle
- Raising the tow vehicle rear can be achieved by:
- Shortening the chain*
- If the chain can't be shortened (as per below), adjust the cams to change the angle of the towball away from the vehicle
- If the above tuning does not level the tow vehicle, more macro adjustments can be achieved by readjustment of the ball mount head.
*A minimum of four working links is required (working links do not include those attached to the U bolt or snap up bracket)
IF IN DOUBT, CONSULT A PROFESSIONAL
Improper maintenance can lead to injury, death or property damage. Maintenance work of this nature should only be undertaken by people with suitable competence. Information provided is general in nature, not comprehensive and should only be taken as a guide. Individual discretion must be exercised and persons undertaking described tasks do so completely at their own risk. Publishers and creators of this content accept no responsibility for loss or damage.
Thanks to Andrew Phillips and the team from the RV Repair Centre for their assistance.