IIRC the maximum advised tow weight is approximately the same as the car. I
once towed in a broken down van weighing about 1.5x the weight of the car,
but this was a short run, the van had a driver to operate the brakes and you
could tell the auto was struggling on start up. The maximums should be in
the specification section of the manual. Also important is how much down
thrust there is on the hook, so you have to load the trailer to get this
right. The hook should weigh down, but not more than ~90kg, so if you can
just lift it, it is probably OK.
Any trailer but the very smallest should have over-run brakes.
The towing ball on the back of the 735i should be a proper BMW one, and
these cost $$$. Anything cludged on at your local 'shop may be anchored to
the wrong places and cause problems.
If the 735i is auto you want to try and get the rig up to 56mph* (90kmph) on
a long run so that the lock up clutch operates. Otherwise the torque
converter will be working very hard and the box will get hot. In a manual
it is pulling away that will burn the clutch, so try and avoid coming to a
complete halt (truck driver style).
* but this may not be legal in your jurisdiction.
The alternative of hiring a large van with a close coupled trailer and
towing the car on that is probably more sensible and secure, plus if you
haven't towed before and can't manoeuvre (in reverse) you can always drive
the car off, unhook and manhandle the empty trailer - try the same with a
One problem that is common to cars with a unibody construction is that there
is no place that is substantial enough to allow bolting a connection to the
trailer in place. You need to evaluate where the hitch needs to be
connected and if so whether that place has anything more substantial that
thin sheet metal.
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