New to the site, picking up my M soon, need help

[acmaui]

Aloha, recently moved to Gig Harbor on the Puget Sound and I'm picking up a 2008 M a week from Monday and I just got my hitch installed and I need to know what the ball size receptacle on the trailer is. Sorry if this is a no brainer, but I can't find it anywhere.

[Russ]

My 2008m uses a 2" hitchball

[seahouse]

Congrats on your purchase!

Note that when you determine the ball size, you also have to make sure the load rating for the ball you use is sufficient for the trailer. There are several different load ratings for each ball size.

- Brian.

[acmaui]

Thanks! 2" ball and I'll be good to go. I'll make sure it's in the right capacity range.

[acmaui]

Okay, I know it depends on hitch height of the tow vehicle, but in general are most people needing a ball height +/- their stock receiver? I'll be towing with a 2012 Mercedes ML350 Blue Tech Diesel (440+ foot pounds of torque I think).

[RobertB]

If I remember correctly, pick a hitch ball mount that positions the ball about 17 inches off the ground - should also take into account a couple of inches for compressing the suspention also. Recommend you do not remove decals and also not tighten the ball in the ball mount the first time you test, that way you can take back to teh store and exchange if it is not correct. In the end, you want the ball at a height that results in a level trailer.

Enjoy

[Tomfoolery]

Okay, I know it depends on hitch height of the tow vehicle, but in general are most people needing a ball height +/- their stock receiver? I'll be towing with a 2012 Mercedes ML350 Blue Tech Diesel (440+ foot pounds of torque I think).

You can't make any generalizations about rise/drop of the ball mount. It depends on the height of the receiver hitch, and the required ball height.

My likes to be at 18" above the ground to the center of the ball, loaded and ready to go. Ball height is higher without the trailer on it, of course, and my Highlander has softer suspension than heavier vehicles, so it's got about 2" of sag with a relatively light tongue load (dual-axle trailer, so I can keep the tongue weight light).

I thought I heard that standard trailers have a 20" coupler height, but that's probably to the top of the ball. I don't know why it's customary to use top of ball for height, since the flat on top can be at different points on the sphere, or non-existent, but that's what's used.

For ball mount (the part that plugs into the hitch) rise height, as shown in the label, you measure from the TOP of the 2" square tube to the TOP surface where the ball sits. Flip it over, and it's drop, but measured from the new TOP of the square tube when turned over to the new TOP of the surface the ball sits on.

To deterimine the required rise or drop of the ball mount, measure from the ground to the TOP of the inside of the receiver. Add the height of the ball, from the mounting flange to the top of the ball. The difference between what you have and what you need is the rise or drop of the ball mount, and don't forget that the ball will drop at least an inch when the tongue load is on it. Assuming 20" to the top of the ball is required, for talking sake, with a receiver height of 14" above the ground (top of the 2" opening), and a ball that's 2-1/2" high, you'd have 20" minus 16-1/2" so you'd need a ball mount with 3-1/2" rise. If you're not sure, just plop the ball into the ball mount, plug it into the receiver (hitch), and measure.

To determine the trailer's height, crank the landing gear up or down until the trailer frame is parallel to the ground. Measure from the ground to the trailer frame behind the axle, and also in front of the axle. The farther away from the axle, the better. When both measurements are the same, measure from the ground up to the top of the coupler where the ball goes. I prefer to eyeball where the center of the ball would be, and work everything from there, but whatever. Just be consistent. Allow sag in the tow vehicle when the tongue weight is on it (have a couple of 200 lb people stand or sit on the bumper to sag it, and use that as the loaded height of the hitch (top of the inside of the 2" receiver).

If you go to a trailer or hitch type place (like U-Haul), ask them to try a few combos of ball mount and ball until you get the right height by direct measurement - just plug the ball mount in, plop the ball onto the mount, and take a measurement from the ground. When you find the right ball mount and ball combo, you're there.

2" balls can be had with ratings as low as 2000 lb. I haven't seen any lately with a 1" shank (most common) and less than 6000 lb rating, so you shouldn't have any trouble there. Unless you have a very large wrench, or spend a few bucks for a hitch ball wrench (not a bad investment), you might be better off buying a pre-assembled unit, or going to U-Haul or a trailer place, and having them assemble it for you. It's a big nut, and you need to torque the crud out of it so it doesn't come undone.

[trdprotruck]

Okay, I know it depends on hitch height of the tow vehicle, but in general are most people needing a ball height +/- their stock receiver? I'll be towing with a 2012 Mercedes ML350 Blue Tech Diesel (440+ foot pounds of torque I think).

Wow that's a sweet tow rig. It's got tons of power, great mpg and it's awd. I was thinking about it getting rid of the truck and using the ml350 for a family vehicle and tow rig, but couldn't swing the price. I might get the 2012 used in a few years.

The ball height is going to be trial and error. Do you have the active supsension that lowers and raises your ride height at speed? I would probably just get an adjustable hitch.

[Tomfoolery]

I would probably just get an adjustable hitch.

There ya go.

The only reason I've never used one is because of the extra mechanical lash points, and that clunking is just annoying.

[trdprotruck]

I would probably just get an adjustable hitch.

There ya go.

The only reason I've never used one is because of the extra mechanical lash points, and that clunking is just annoying.

I hear ya, but I got used to it. I have a really steep drive way and the adjustable hitch is a lifesaver. It allows me to use the lowest drop setting to teeter totter the stern of my MAC higher so that it doesn't scrape when I back up. Once I am on flat ground, I set it back to normal ride height on flat ground.

FWIW I've been using this one: http://www.harborfreight.com/8-in-1-adj ... 95991.html It's cheap price wise, but its served me pretty well over the years.

-Randy

[Tomfoolery]

On sale for half price right now. Yikes! If I didn't already have half a dozen ball mounts laying around, I'd probably give it a try.

[u12fly]

I have 2009 AU trailer for my You need a standard 2" ball with an ideal height off the ground of 17" when loaded. From what the factory told me, the stock trailer with a stock boat puts about 300 lbs on the hitch. Don't forget the trailer plug. The MAC trailer needs a flat 5 pin plug, the wire comming off the vehicle needs to looks like this in order to mate with the trailer.

Also you probably need at least 1 foot of slack in your plug, as I recall when I got my trailer form the factory the wire was too short. My truck had a standard round connector. so I got an adapter to plug into it... however the stock wire on the trailer was about 5" too short to reach, so I had to cut and lengthen all the wires in the parking lot before I could tow it. Here is the addpater plug I used:

The signals needs for the trailer are Ground, Left Trun, Right Turn, Running Lights, and Reverse... there are no reverse lights on the trailer this signal is uses to block the trailer brakes from engaging when you back up. If you ever are just moving your boat around in the yard you need to plug it in (or install the manual brake block) otherwise she gets hard to push.


Chris.

[mastreb]

Okay, I know it depends on hitch height of the tow vehicle, but in general are most people needing a ball height +/- their stock receiver? I'll be towing with a 2012 Mercedes ML350 Blue Tech Diesel (440+ foot pounds of torque I think).

That's my tow vehicle as well. I just bought a typical off-the-shelf 2" ball + Hitch that was designed to put the ball exactly at receiver height with a drop tongue, and turned it over so that it adds about 2". That's been perfect for the ML.

The trailer assist breaking on the ML makes it really nice--you'll have zero towing issues. I've got the "blind spot assist" which gets turned off when you have a trailer plugged in.

You will need an adapter as in the post above to adapt to the 7-pin round connector on the ML. It's a stock off the shelf item. i got one with a 2' pigtail so it'll reach as the trailer connector is a bit under the ML.