Porsche 928 S4 Technical Specifications

Technical Data – Front Axle, Steering and Rear Axle

 

Front Axle

 

Wheel suspension

Independent suspension, double control arm with coil spring and internal damper

 

Springs

1 coil spring per wheel

 

Dampers

Double-action dampers

 

Stabilizers

Ř 28 x 4 mm (tubular stabilizer)

 

 

Steering

Rack and pinion power steering with tie rods

Steering wheelŘ

380 mm

 

Steering wheel ratio (in center position)

17.75:1

 

Turning circleŘ

11.5 m

 

Track circleŘ

9.6 m

 

No. of steering wheel turns from lock to lock

3.13

 

 

Rear Axle

 

Wheel suspension

Independent wheel suspension with lower diagonal suspension links and upper wishbones, coil springs and internal dampers

 

Springs

1 coil spring per wheel

 

Dampers

Double-action hydraulic dampers

 

Stabilizer

Ř 22.5 x 3.5 mm (tubular stabilizer)

 

 

 

Wheel Alignment Adjusting Values*

The following values apply to curbweight according to DIN 70020 (car with full fuel tank, spare wheel and tools)

 

 

Adjusting Value and Tolerance

Max. Difference Left to Right

Front Axle

 

 

Height setting:

From the contact surface to measuring point on rear link bearing

 

190 – 20 mm **

10 mm

Toe-in unpressed

 

+ 15’+5’

 

Track difference at 20° lock

-1°+20’

may only be affected by replacing steering arms

 

Camber

+30’+10’

10’

 

Caster

3°30’+30’

20’

 

 

Rear Axle

 

 

Height setting:

From tire contact surface to measuring point on cross member

173 + 10 mm**

10 mm

 

Toe-in per wheel

+10’+5’

10’

 

Camber

-40’+10’

10’

 

 

*The vehicle alignment settings are applicable to the actual vehicle ride height only (see repair manual pp. 44-1 etc.)

**The height setting values apply to new vehicles.  Used vehicles may be up to 10 mm lower, i.e. the tolerance may deviate by minus 10mm.  This must, however, be the same for both axles.

 

 

 

Technical Data – Braking System

Description

From Mod. 86

Specifications/

Remarks

Wear Limit

New brake disc thickness

front

rear

32 mm

24 mm

 

 

Brake discs – Min. thickness** after machining

front

rear

30.6 mm

22.6 mm

30.3/30 mm

18.6/22 mm

 

Thickness tolerance for brake disc max.

0.02 mm

 

 

Lateral runout for brake discs max.

0.05 mm

 

 

Lateral runout for installed brake discs max.

1.      mm

 

 

Max. surface finish after machining

0.006 mm

 

 

Play on brake pedal with brakes bled and engine stopped (footbrake arm without stop)

Approx. 10 mm determined by permanently set clearance at points inside braking unit

 

 

Parking brake*** (handbrake)

Drum brake applied mechanically on both rear wheels

 

 

Parking brake drum dia.

180 mm

181 mm

 

Brake shoe width

25 mm

 

 

Brake liner surface area per wheel

85 cm2

 

 

Brake liner thickness

4.5 mm

1 mm

 

 

* Fixed calipers with pistons of dia. 42/36 mm were installed in some cars (USA, Canada, Australia and Arabian countries) in the 1987 model year.

The front-axle brake calipers with 44/36 mm dia. Pistons can be retrofitted in 86 models only in pairs.

** Brake disks may only be machined symmetrically, i.e. evenly on both sides.

*** 87 models onward, parking brake liners made of asbestos-free material (Energit 559).  The liners can be retrofitted to vehicles earlier than the model year 87 (right-hand and left-hand sides).

 

Rims, Tires and Tire Pressure

Standard tires

 

Tires

Rims

ET**

87 mod. onward

928 S4

928 S4 Club Sport

 

front

rear

front

rear

225/50 VR 16

245/45 VR 16

225/50 VR 16

245/45 VR 16

(with 17 mm washer)

 

7 J x 16 H 2

8 J x 16 H 2

8 J x 16 H 2

9 J x 16 H 2

65

52.3

60

60

89 mod onward

928 GT

front

rear

225/50 ZR 16*

245/45 ZR 16*

(with 17 mm washer)

 

8 J x 16 H 2

9 J x 16 H 2

60

60

* “ZR” 89 model onward

  “VR” above 210 km/h, “ZR” above 240 km/h

** rim offset in mm

Tire Pressure in bar (Summer Tires)

Type

928 S4

928 S4 Club Sport

928 GT

Front axle

2.5 bar

2.5 bar

 

Rear axle

3.0 bar

3.0 bar

Collapsible spare tire until 85 models 2.2 bar, 86 models onward 2.5 bar

Winter tires front 2.5 bar, rear 3.0 bar

Checking wheel Rims

Refer to drawing for radial and lateral runout measuring points on inner and outer rim shoulders.

Max. permissible radial and lateral runout for light alloy rims = 1.0 mm.

Note:

Never straighten distorted wheel rims