BMW M5 Wartungshandbuch PDF herunterladen (Seite 28)

Crankshaft/main bearings

The crankshaft is forged from a high-strength

steel 42CrMo4 and weighs 21.63 kg. After

grinding the bearing points, the shaft is

nitrocarburized.

The colour codes of the main bearing shells

are stamped on the crank web of the first main

bearing.

Connecting rods

The forged connecting rods of the S65 are

made from the material 70MnVS4 BY. As on

the S65, the large connecting rod eye of the

connecting rods used on the S85 is cracked,

thus achieving an unmistakable parting joint

with outstanding fit accuracy. As on the NG

engines, the small connecting rod eye is

trapezoidal, enabling it to support the force

over a large area. The connecting rods weigh

582 g and are produced to a tolerance of ±

2 g. No classification is necessary in view of

this very close tolerance range. When

assembling the connecting rods and pistons it

is important to bear in mind that the

connecting rod is asymmetrical and, in the

same way as the piston, must be specifically

installed with respect to forward direction.

The one-sided reduction of the thrust collar by

1.5 mm per connecting rod serves the

purpose of shortening the lateral offset by a

total of 3 mm and therefore reducing the total

length of the engine by 3 mm. The installation

direction is indicated by two elevations on the

connecting rod.

1 - Main bearing classification (G = green; Y = yellow; V = violet)

2 - Asymmetry of connecting

rod

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BMW M5 Wartungshandbuch Seite 28