Page 240 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CH AP TER 8 .1 Types of suspension and drive

Fig. 8.1-65 Hill-climbing capacity on a homogeneous surface with front, rear-wheel and four-wheel drive, and with locked centre
differential and a driving force distribution of 50%/50% on four-wheel drive. Of the cars studied, the front/rear axle load distribution
was (Fig. 8.1-36):
front-wheel drive 57%/43%;
rear-wheel drive 51%/49%;
four-wheel drive 52%/48%.

8.1.7.1 Advantages and disadvantages an increase in the drive-off and climbing capacity
regardless of load;
In summary, the advantages of passenger cars with per- better acceleration in low gear, especially with high
manent four-wheel drive over those with only one driven engine performance;
axle are:
reduced sensitivity to side wind;
better traction on surfaces in all road conditions, stability reserves when driving on slush and
especially in wet and wintry weather (Figs. 8.1-64– compacted snow tracks;
8.1-66); better aquaplaning behaviour;

Fig. 8.1-66 Influence of the type of drive and differential lock on the propulsion force with m split’, in other words, a slippery road
surface with m X,W ¼ 0.1/0.8 on one side only. 100% locking of the rear axle differential gives most benefits.
Some car manufacturers offer this option as ASR (or EDS ) or using a hydraulic manual selection clutch. However, only 25% to 40%
locking is provided on the multi-disc limited-slip differentials that have usually been fitted on vehicles to date.

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