Ball Mount Basics: How to Measure for Trailer Hitch Drop

What are Rise and Drop?


For safe and comfortable towing, your trailer should always be as level as possible. A level trailer handles well, promotes even tire wear, and minimizes strain on both the trailer and tow vehicle. However, with the many different tow vehicles and trailers out there, it's rare that any vehicle and trailer line up perfectly for towing. This is why ball mounts are made in a variety of sizes and come with what's known as rise and drop—to compensate for the height difference between your trailer and vehicle and allow for safe, level towing.



Ball Mount Rise
Rise is the distance from the top of the shank to the top of the ball platform when the ball mount is oriented for greater coupler height.

Ball mount Drop
Drop is the distance from the top of the shank to the top of the ball platform when the ball mount is oriented for lower coupler height.





How Do I Measure for Rise and Drop?


To choose a ball mount with the correct rise and drop, you'll first need to take two measurements: your hitch height (Measurement A) and coupler height (Measurement B). The difference between them will be your rise or drop.

Step 1: Find your hitch height

Measuring Hitch Height
With the tow vehicle parked on level ground, measure from the ground to the top of your hitch receiver opening.
Step 2: Find your coupler height

Measuring Coupler Height
With the trailer level, measure from the ground to the bottom of the coupler.
Step 3: Find the difference

Infographic-Rise and Drop
Determine which has a greater height—your hitch or coupler—and find the difference between the two measurements.

If your hitch height is greater, use a ball mount with a drop.

Hitch Height (A) - Coupler Height (B) = Drop (C)


If your coupler height is greater, use a ball mount with a rise.

Coupler Height (B) - Hitch Height (A) = Rise (D)


Select a ball mount with a drop (C) or rise (D) measurement that is closest to the difference between your hitch and coupler heights. For instance, if your hitch height is 15 inches and your coupler height is 10 inches, you'll need a ball mount with a 5-inch drop.


Measurement A (15") - Measurement B (10") = C (5" Drop).


If your hitch height is 12 inches and your coupler height is 13 inches, you'll need a ball mount with a 1-inch rise.


Measurement B (13") - Measurement A (12") = D (1" Rise).

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What If I Tow Multiple Trailers?

Adjustable Ball Mount

If you need to tow multiple trailers, you should consider an adjustable ball mount. While fixed ball mounts have a set rise and drop, the rise and drop on adjustable ball mounts can be altered to accommodate different coupler heights. Adjustable models can save you the trouble and expense of using a separate ball mount for each trailer. Simply slide the ball mount platform up or down the shank and secure it in place with the locking pin to achieve the necessary rise or drop.


How Do I Choose an Adjustable Ball Mount?


To choose the best adjustable ball mount for your towing needs, first you'll need to determine the tongue weight of the heaviest trailer you want to tow. Make sure your adjustable ball mount has the weight capacity to support the loaded weight of the trailer. Also make sure the ball mount you choose has the correct size shank to fit your hitch's receiver (for instance, use a 2-inch ball mount with a 2-inch hitch receiver). Next, determine the tallest rise and deepest drop you'll need using the guidelines above—this will be the range you'll need in your ball mount. Finally, determine which hitch ball diameter you will need. Adjustable ball mounts usually come with at least one ball, and most come with two or three balls of different sizes for towing different trailers.


Watch a Video Review of an Adjustable Ball Mount ►

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Written by: Amber S.

Updated on: 12/20/2017





Questions and Comments about this Article

Jc

Where is the best spot to place the level on the trailer’s towing frame when taking the coupler height measurement? I get slightly different ‘ground to coupler’ measurements when placing the level at different locations on the central bar of the towing frame. With the level right behind the coupler, the measurement from the ground to the bottom of the coupler is 12.5”, closest to the front of the camper body—11.5”, and about half way in between those two points—10.75” Seems odd to me that the middle location has the lowest measurement but did measure everything twice and central bar does not appear wonky in any way. Advice appreciated. Thank you in advance! 95206

Reply from Chris R.

When determining coupler height for choosing the right ball mount, you'll want to measure right under the center of the trailer coupler itself, not further up the A-frame. Just take a single measurement from the ground up to the bottom of the coupler. 70374

Pete

What if the trailer hitch is 18” and the top of the truck ( Ford F-150) is 18-1/2? What hitch do I need? 94450

Reply from Chris R.

This is a good thing! That means you're just about level with the trailer without a rise/drop even needed. You can always expect at least a little sag/drop at the rear end of your truck when hooked up to the trailer, so since the hitch receiver sits 1/2" taller than the coupler, going with a very small rise like the 1" Rise Curt # C45030 or a zero rise like with the Curt # C45002 will work great. 69971

Steve D.

I have an Equalizer EQ 4 weight dist/sway control hitch that I reinstalling on a 2019 Ram 4x4. The receiver is 20.25 inch high, trailer coupler sets at 16.25 inch. The shank that came with the hitch does not allow adequate drop. What adjustment do I make to the hitch/coupler formula to calculate the drop I need. The standard formula does not factor in the massive hitch hardware. 81610

Reply from Chris R.

The process the drop you need will actually be pretty much the same as a standard ball mount, as described above. For a larger drop, the Equal-i-zer Shank # EQ90-02-4400 should be sufficient. 67099

Kevin C.

I had a hitch and ball mount installed on my 2018 Volvo XC60 at the dealership today. It is a foldaway one, that's the only tow package they offered. It's a Class I hitch rated at 3500 lbs trailer weight and 350 lbs tongue weight. The ball mount that comes with the hitch is a bit too low though at about 16 inches. I am looking in to some trailers that are 18-19 inches in tongue height. So I want to get an extra 2-3 inches of rise. But according to the manual "The ball mount must fall within the geometric limits for the towbar" with respect to height and distance from the hitch pin. I notice the current ball mount is already at the limit in both distance and height from the hitch pin and to get another 2-3 inches of rise I would have to go outside the geometric limits a few inches (both in distance and height). Is this safe? Does it just lower the trailer and tongue weight limits perhaps? Please advise. 80456

Reply from Chris R.

Those limits that are on some vehicles like your Volvo are a bit confusing. I can't really tell you to go against what the owner's manual says, but it's also not ideal to pull a trailer that's not level. I would honestly try talking to a local Volvo dealer to see if they can offer any more insight (such as whether or not going outside those parameters will decrease capacity and by how much, etc). 66306

Warren E.

I have just purchased a 2020 Mercedes 350 GLE SUV. The Trailer Hitch set up only has a receiver and does not have the 4 pin outlet to plug in my boat trailer. I trailer a 17.1’ Mako Center Console boat. Do you have a recommendation for the best ball mount and wiring harness to work with the MB 350 GLE 4 Matic Hitch Assembly? Any assistance you can provide would be greatly appreciated. 77177

Reply from Chris R.

For a trailer wiring harness I recommend the Tekonsha # 119190KIT . This is a hardwire kit that you'll use to tap into the signal light wires on your Mercedes to provide you with the needed 4-Way. There isn't a plug-and-play harness available for your GLE350. The right ball mount will depend both on the hitch height of your Mercedes and the coupler height of your boat trailer. You'll just need to take a couple measurements as described above to find the best option. 62875

Blaine W.

This is generally great advice however, when I connect my boat to my SUV, there is sufficient sag so it is now lower than the recommended height. I know it would be hard to determine how much sag from each vehicle, but considering mine was 1.25 inches, would it not be prudent to consider this in the calculation?Thanks 75547

Reply from Chris R.

I completely agree with you here. Like you mentioned though, it's hard to calculate something like this beforehand - as both the actual tongue weight and tow vehicle type are going to have huge effects on sag. Because of that big variance, it's not something we try to add into the "how to choose a ball mount" procedure, but it's also really good to keep in mind. If the measurement you come up with ends up being between various rise and drops, it's always better to go with the higher option. 61700

Richard S.

Question: Id prefer to avoid an adjustable mount and get something that works with most trailers. I have a 2001 Yukon XL 2500 - the top of the receiver hole is at 20.5”. I’m likely to be towing an enclosed car hauler weighing between 6-7000 lb. The rear suspension is quite stiff the ¾ ton has leaf springs and is rated to tow 12k, I’m guessing no more than a half inch drop with 700lb of tongue weight but I’m not sure. I’d like to get set up to tow so that I can go trailer shopping. Trailer will likely be a 24’ double axle car hauler if it makes a difference. It seems that 17-18” is standard for coupler heights. Would a 2” or a 3” be appropriate here? 74248

Reply from Chris R.

Thanks for all of the info! I do think a 2-3" drop is a pretty safe bet for any trailer you plan on towing with your Yukon. Even with a strong rear suspension setup you will still get SOME sag, so a 2" drop is probably your best option. I linked our full selection of 2" drop ball mounts below that you can look through. 60409

Dave

The Expert Jacob states to measure from ground to top of coupler for Hitch Height. The link provided states to measure to the bottom of the Coupler. Which is correct? 72321

Reply from Chris R.

When measuring for the right ball mount, you will want to measure from the ground to the BOTTOM of the trailer coupler. You'll measure to the inside top of the trailer hitch receiver on your vehicle. I'm sorry for the confusion! 59271

Mike J.

Can you suggest a good ball mount that holds up to salt water? 64146

Reply from Jacob H.

Your safest option is going to be an aluminum ball mount with a stainless steel ball. I will provide a link below! 54447

Nick H.

How do I know what height hitch I need for my trailer? Thanks! 64139

Reply from Jacob H.

We have some helpful links available I will link them below. You will want to make sure that your trailer is as level as possible and you will measure from the ground to the top of your coupler where your ball would hook to and that will be the amount of rise or drop ball mount that you will want to haul your trailer level. 54440



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