What Size Wrench Is Needed To Install The Curt 2" Hitch Ball?

Updated 01/30/2026 | Published 01/25/2026

Question:

Question is regarding the Curt C40004 - 2inch hitch ball. I know the nut requires a 1 1/2inch wrench or socket. What size wrench is needed for the wrench flats?

asked by: Kraig

Expert Reply:

Hey Kraig,

Along with the 1-1/2" wrench or socket, most installers use a 1-1/4" to 1-1/2" wrench on the flats, or a larger adjustable wrench for the flat portion while the nuts are being torqued on the # C40004.

What are you going to be using this to tow?

expert reply by: Nick S

Kraig

1/29/2026

Thank you for your response. I'm confused by your answer. How can it be a range of 1-1/4" to 1-1/2"? What is the specific size of the wrench flats? i,e, what size open end wrench is needed to hold the ball? Is it 1-14", 1-1/2, 1-5/8" or another size? I'd be using the ball to tow a small boat trailer.

Nick S.

1/29/2026

@Kraig I reached out to Curt for that exact size, a 1-11/16" should work for that flat.

Kraig

1/29/2026

@NickS Thank you

Daverhagen

1/29/2026

Now I am an old hardware guy, haveing owned a hardware store for most of 30 years. And I have a set of four pipe wrenches on one of the pegboards hanging above my bench. I use two of them, one of the nut and another of the flat and tug it snug. It's not rocket science. I DO use a torque wrench when mounting solar panels and assembly motor parts, but a two-inch hitch is a brute force pivot point between vehicle and load. Just make it tight. Works using pipe wrenches on my tractor and its hitch just as well as it does on my pickup truck that tows the camper. So, get er done and get on the road!

Wayne H.

1/30/2026

I put the hitch ball in a vise. I position it so the hitch ball mating surface is proud, or above the vise jaws so it mates with the hitch. Then I add the hitch, lock washer and nut, then tighten down the nut.