"Extra safety in critical situations is guaranteed if the towing vehicle is equipped with ESP." Continental-Teves

For towing the frame based W163 M-Class may be preferable over the unit-body W164, using the frame rails for towing instead of the body.

Towing Capacity

Mercedes-Benz model

towing capacity incl. drawbar load
(zulässige Anhängelast inklusive Stützlast)

maximum drawbar load
(zulässige Stützlast)

speed limit

USA

ML320 (W163)
ML350
ML430
ML500
ML55 AMG
ML350 (W164)
ML500
ML320 CDI
ML63 AMG
ML550

5000 lbs Class III
Starting MY2008:
7200 lbs Class III 		500 lbs

55 MPH - 88 km/h

applies to all vehicles with trailers in CA
VC 22406

G500 (W463)
G55 AMG

7000 lbs Class IV 700 lbs

GL450 (X164)
GL320 CDI
GL550

7500 lbs Class III + IV 750 lbs

Germany

A-Class L

2205 lbs - 1000 kg1

at least 4% of
trailer weight

50 MPH
80 km/h
applies to all vehicles
with trailers

62 MPH
100 km/h
applies to tow vehicles with
4 wheel ABS

W114
W115
SL (R107) 1975
S-Class (W116)
W201

2650 lbs - 1200 kg

190E
C-Class (W202)
CLK
W123
SL (R107) 1983
SL (R129)
S-Class (W126)

3305 lbs - 1500 kg 165 lbs - 75 kg to
220 lbs - 100 kg

CL
E-Class (W124)
E-Class (W124) T-model stick
E-Class (W210)
E-Class (W211)
S-Class (W126)2
S-Class (W140) stick

 4190 lbs - 1900 kg 167 lbs - 76 kg

V-Class

4410 lbs - 2000 kg

E-Class (W124) T-model auto
E-Class (W210) 2
S-Class (W140) auto
S-Class L (V220)
S-Class (W221)
R280 CDI (W251)
R320 CDI
R350
R500
R63 AMG

4630 lbs - 2100 kg

G270 CDI (W463)
G400 CDI
G320
G500

2850 kg - 3360 kg 140 kg

ML230

6615 lbs - 3000 kg 275 lbs - 125 kg

ML270 CDI (W163)
ML320
ML350
ML430
ML500
ML400 CDI
ML55 AMG
ML280 CDI (W164)
ML320 CDI
ML420 CDI
ML350
ML500
ML63 AMG
GL320 CDI (X164)
GL420 CDI
GL450
GL500

7715 lbs - 3500 kg 300 lbs - 135 kg
1 trailer brakes required over 880 lbs or 400 kg
2 with special permit (meaning it's fine for the occasional horse trailer, but not for every day use)

Trailer brakes are required above 1655 lbs or 750 kg. Electric trailer brakes require a brake controller.
Many boat trailers have surge brakes, not requiring electric controllers.

Tow hooks for the W163 M-Class
W163 M-Class (1998 to 2005) OEM Hitch (made by Oris) and harness install instructions (1.3 MB pdf) Mercedes part number Q6-31-0002

Draw Tite Hitch for W163 M-Class (1998 to 2005) install instructions (305 kB pdf)
All pdf files provided by Charles Alt. Thanks!

The wiring harness plugs into the connector in the M-Class.
Q-6-54-0013 harness with three inbound plugs
Q-6-54-0014 PCB Assembly connects to 2 of those
Q-6-54-0015 outside Pollak Plug
Q-6-84-0033 bracket for outside plug
Part numbers provided by Peter in Arizona

If you also want to install a brake controller, follow these instructions:
W163 M-Class (1998 to 2005) Brake Controller Wiring (104 kB, pdf)

Pollak USA trailer plug 

pink    right turn signal
gray    backup lamp
red     + power fuse 18
white   taillamp
orange  stop lamp; or brake controller
brown   - ground
green   left turn signal

Trailer Hitch Installation info on off-road.com

Oris Automotive
They build the factory hitches for the M-Class.


Brenderup Real Trailers
"The World's Easiest handling Full Sized One and Two-Horse Trailers. Available in the United States since 1982."

Advanced Accessory Systems / Brink

Champion Trailers/Classic Mfg

New M-Class (W164) with Trailer Stability Assist (TSA)
The factory-fitted package of measures will in future include the new Mercedes-Benz Trailer Stability Assist (TSA). This is an extra function incorporated into the ESP® Electronic Stability Program that is designed to offer drivers even greater safety when towing a trailer. TSA is capable of detecting the dreaded fishtailing motion swiftly and nipping it in the bud effectively. To do this, it uses the ESP® program's own sensory system and initiates precision brake applications at the front left and right wheels individually and alternately to stabilise the car/trailer outfit. TSA will be added to the specification of the M-Class from late August 2005.
from a Mercedes press release dated July 7, 2005.

Trailer Brake Controller Installation in new ML, R and GL
A dealer technical bulletin (DTB) dated Mar 9, 2007 with number T-B-31.19/07d describes how to install an Electric Trailer Brake Controller. The bulletin is for the new W164 M-Class and X164 GL, but might also work for the W251 R-Class.
Four wires are required to operate the electric brake controller. These four wires can be found on a plug tie wrapped to the harness leading to the diagnostic plug under the dash. On early production vehicles the plug was stuffed behind the rear SAM and sometimes difficult to locate.

rameder Anhängerkupplung (Germany) kupplung.de
They have a tow hook for the new W164 M-Class.

Hidden Hitch makes a trailer hitch for the R-Class with 3500 lbs capacity. Part number 87413.

Draw-Tite model 75470 for the R-Class also has a 3500 lbs capacity.

shoptalk

Schleppen macht den Kohl fett.

Wolfgang's ML Page