How to choose the right weight distribution hitch

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Types of weight distribution hitches

Hayman Reese weight distribution hitches come in 5 basic weight classes. The first two, mini and intermediate, are designed for much lighter towing and mount underneath your towball. The other three sizes are 600lb, 800lbs and 1200lbs. Each one can take a greater load than the last and are designed to mount directly into a 50mm hitch receiver. The 600lb, 800lb and 1200lb kits are further divided into a Classic and Standard series. For reasons that will soon be explained, Classic series kits come with straight spring bars and standard series kits come with “L” shaped spring bars.

What does a weight distribution hitch do?

Weight distribution hitches transfer some of the weight from the ball to the front axle. This helps level the towing vehicle and caravan, which greatly improves handling. In the case of mid to large sized caravans a weight distribution hitch is often a necessity to tow with any degree of safety.

How do I know if I need one?

People often ask us this question. If you’ve already got the caravan and you’ve tried hooking it up then it’s simple, if you can see that the caravan weighs down the back of the vehicle enough for the front suspension to be raised, then you definitely need one.

Things get a little more tricky if the vehicle has harder rear suspension. In this situation the rear suspension may be taking the weight of the trailer, but if the weight at the ball is significant and you’re having problems with handling a weight distribution system may still help a great deal.

If you haven’t got the caravan yet and you’ve never towed with the vehicle it can be hard to know exactly how the vehicle will handle the weight. There are no hard and fast rules, so we recommend you start by asking the caravan manufacturer. Remember caravanning requires a new skill set, so there’s no replacement for doing your own thorough research before hooking up.

Choosing the right weight distribution system

1. Measure coupling and tow ball height

Start by parking your caravan on a level surface. Get the caravan level by measuring the front and rear, and adjust the jockey wheel as needed. Then measure the distance from the ground to the bottom edge of the coupling.

Next we measure the height of the hitch receiver on the vehicle. The hitch receiver is the 50mm square hole on the towbar that the ball mount is inserted into. Again, with the vehicle on a level surface, measure the distance from the ground to the center of the hitch receiver.

What we want to do is get the ball and the coupling at the same height – when everything is level – before we hook up our weight distribution bars. We achieve this by adjusting the height of the ball mount that comes with our weight distribution hitch.

Look at the height difference between the two measurements we just took, that’s the amount we need to raise, or lower the ball mount by to make them level. The 600lb, 800lb and 1200lb kits come with a standard drop shank in the box. Contrary to it’s name the standard drop shank does not actually offer any drop past center, but it can raise the height by 135mm.

Let’s do some examples. If after taking our measurements we find that the bottom edge of the coupling is already at the same height as the center of our hitch receiver we can go ahead and use the standard drop shank. If the bottom edge of the coupling is sitting 135mm above the center of the hitch receiver, we can take our standard shank and turn it so it points upward, this will allow a rise of 135mm. If we need more room for adjustment we can get either a 30, 95, or 160mm drop shank. These measurements refer to the drop below the standard shank. So going down it’s 30, 95, 160mm, but going up we add about 135mm to those figures.

If you are using the much smaller intermediate, or mini weight distributions hitch, chances are you’ll be towing a smaller caravan with a smaller car, so it’s less likely that you’ll need height adjustment. However if you do need height adjustment with these kits then you will need to purchase an adjustable ball mount kit separately, which uses the same standard, 30, 95 and 160mm shanks.

hayman reese drop shanks

Lets do an example. I’ve just measured the height of my coupling at 450mm and the center of the hitch receiver on my 4WD is at a whopping 675mm. That’s pretty high! I know the standard shank won’t be enough. I need to lower the ball by 225mm. The 95mm shank will give me about a 210mm drop, that’s pretty close, but I’ll need to try it out in store. If I’m wanting to get one shipped to me I could consider jumping up to the 160mm shank, but I might loose some ground clearance.

The above example shows that there are no hard, or fast rules when it comes selecting the right drop shank. That’s why we allow customers to test and exchange shanks that have not been used for towing.

 2. Measure the ball weight

Now that we’ve got the height right we need to measure the ball weight. The ball weight is the weight at the ball/coupling when the trailer is fully laden. This measurement is done by lowering the coupling onto a scale with the jockey wheel. There are proper ball weight scales made by Hayman Reese, which you can purchase through us. These scales are pretty cheap, especially if you tow regularly.

If it’s a small caravan and your in a pinch, you can use a bathroom scale and a block of wood, or if your really desperate a ball park figure can be had by resting the jockey wheel on a bathroom scale. This last method is really only safe for small vans and it becomes less accurate the further the jockey wheel is mounted from the coupling.

What if I haven’t picked up the Caravan yet?

The above information is great if you’re caravan is parked at home, but what if your going to pick up a brand spanking new one from the dealer? In this situation we can easily find out what the unladen ball weight of the caravan is by asking the caravan dealer. This information will also be included in the caravan owners manual.

Knowing the unladen ball weight still doesn’t tell us what the laden ball weight will ultimately be, but we can use it to make a reasonable estimate. To make the estimate as accurate as possible we need to factor in things like water tanks and gas bottles which are often mounted to the draw bars. You should also consider the weight of any gear you are storing inside the caravan. Remember, you can change the ball weight by shifting loads around.

Once you’ve done your calculations look at the diagram below.

weight distribution size chart

You can see that the weight distribution systems each cover a fairly wide weight range. If your estimates are very close, within 10-15kg of the next kit, it may be worth getting the next size up, because you can always add a little weight to the front end. Having said that, don’t just go for the biggest system to cover all bases. If you try to use a weight distribution hitch that is way too big for your caravan it won’t operate properly.

3. Measure draw bar depth

Most steel draw bars are either 4, or 6 inches deep. Alloy draw bars are often stacked to make a total depth of 8 – 10 inches.

The Classic series of Hayman Reese weight distribution hitches have spring bars that come straight out of the head unit. This means that the Classic series is better suited for use with 4 inch drawer bars. If you try to use a weight distribution hitch with straight bars on caravans with 6 inch or deeper drawer bars, they are likely to hit against the draw bar.



hayman reese classic series weight distribution hitch diagramhayman reese standard series weight distribution hitch diagram

The Hayman Reese Standard series, intermediate and mini kits are designed with 6 inch draw bars in mind. The spring bars on these are are “L” shaped and drop down from the head unit to allow extra draw bar clearance.

There are exceptions to these rules. Some deeper drawer bars have the coupling mounted underneath which greatly improves the clearance. There are some cases where ground clearance may need to be weighted up against draw bar clearance, although in these cases we suggest prioritizing draw bar clearance – you can always remove your bars to get up a steep gutter – for example. We suggest following the above 4 and 6 inch rule whenever purchasing a new kit.

Some draw bars taper along there length, making it difficult to determine the correct kit to use. In this case we suggest sending in an image of the draw bars either to ourselves, or Hayman Reese for advice. This is most common with alloy draw bars which can vary in depth along their length, with depth often doubling a third of the way back toward the caravan. So don’t hesitate to get in touch with us about alloy draw bars.

4. Measure draw bar length

We’re almost done! We just need to measure the usable length of the draw bars.

Consider this, we have two snap up brackets that clamp to the draw bar, from which our chains are hung. The chains must hang as close as possible to 90 degrees to the draw bar. The other ends of the chains attach to the spring bars. The spring bars come in 28 inch and 30 inch lengths. This means that if your drawer bar is shorter than 30 inches you will need to purchase a kit with 28 inch spring bars. 

You also need to be aware of objects mounted to the drawer bar. Things like gas bottle holders could interfere with the positioning of the snap up brackets and may need to be moved.

And we are done!

That was quite complicated, but remember, you don’t have to agonise over every measurement. Parts can be swapped and all most people need to get started is something that will allow them to drive their new caravan home from the dealer. Once you’ve got it at home you can play around to get things right.