© 1998-2005 Harald Pietschmann

How good is the ML320 spare tire off-road ?

The spare tire carrier of the M-Class is mounted in the rear under the vehicle.

The dimension of the spare ( 155 / 90 R18 ) makes it definitely a temporary spare for off-road use. It is too narrow to be of any use where the roads are rough and the high inflation ratio of 70 psi makes it very vulnerable to punctures ( picture a balloon that is pumped up really hard - a rough fingernail is enough to make it explode). The manual recommends even for pavement not to use the spare for long and only at moderate speeds. Therefore I strongly recommend to get the full size spare tire as offered in the M4 package if you intend to expose the ML to any rough roads on a regular basis.

The temp spare is extremely narrow compared to the stock tire.

The temp spare is mounted on a tubular frame which slides out from under the back of the M-Class. Unlocking of the frame is fairly easy - however, pulling the slide down was not an easy task when I needed the spare after a flat in the desert of Baja California in October of 1997 ( the vehicle had less than 10,000 miles). The pullout mechanism needed a few blows with a hammer to extend. I can only picture how the mechanism functions after it has been exposed to a few years of dirt and grime. After I got the tire carrier moving I had to find out that the M-Class had been designed for level roads only. On any well used dirt road or trail around the world the center is higher than the two tire tracks. The high trail center prevents the slide to come all the way out and allow access to the tire. Luckily I had a shovel on board and was able to dig enough dirt away to have the slide come down.

Unfortunately, the manual describes only how to unlock the spare tire slide but not how to unlock the tire from the carrier ( a plastic disk with bayonet lock needs to be pushed down and twisted with considerable force ). Especially women may need AAA assistance to free and unlock the spare.

After the job was done two more problems arose: The spare tire carrier did not want to slide back. I needed to use a BIG hammer to force it back into place. Since the carrier did not accomodate the regular tire I had to find room inside my vehicle which was stuffed with all kind of expedition gear. I could not find the plastic bag for the flat and had to load the tire as dirty as it was. Read on to find out how I managed to get home safely:

Alternative tire sizes to replace temp factory spare

After that experience I upgraded my ML320 to BFG 265/75R16 A/T tires

My personal opinion: BFGoodrich tires are unsurpassed off-road champions -