General Assembly Information On Tires And Tubes

Always also use new tubes or rubber valve stems each time tiresj are replaced!

Tubes should only be used in "tubeless" tires in an emergency situation. It cannot be recommended to combine tires and tubes of different make. Tubes are not available for series 50 and 55 tires!

When mounting tubes with steel valve stems remember that valve core is screwed in only after inflation of the tire.

Eh careful not to turn the tire valve when tightening the nut. 1

"Tubeless" tires may only be mounted without tubes on rims with a double hump. If this type rim is not available, this tire must also be mounted with a pertinent tube. When necessary tubeless tires can be used on an axle with. tube tire as long as the make, size and type are identical.

Double hump rims (H2) were used on a general basis in the 1975 model year.

Original Porsche rims are identified by the Porsche part number in the wheel rim. Meaning of numbec 901.361. XXX. XX (rim without hump) or 911.361. XXX. XX (rim with double hump), where'by X = digit for internal designation of version and paint. j j

Diecast rims are not always sufficiently leak-proof because of the coarser grain structurej and consequently can only be used for tubeless tires when tested accordingly. Froml976 models on Porsche diecast rims are checked for leaks with a special fixture and therefore suitable for use with "tubeless" tires.

Part numbers; of these rims:

Rim Size Untested Diecast Tires Leak-proof Diecast Tires !

(tires with tubes) ("tubeless" tires) I

6 J X 15 (unpainted) 911.361.023.14

For cars, which have center pin wheel centering, we recommend always using rims with centering pins. Wheel nuts made of steel should be used on steel rims.

To prevent excessive loads on rubber tire valve stems (tube or tubeless version) caused by position of valve stem bore, 7" and 8" Porsche rims must be fitted with a valve stem support, Part No.

Porsche 964 Oil Leaks

7 J x 1 5 diecast rims (ATS) sometimes have a special cast boss in area of the valve stem bore, so that safe support can be guaranteed without a holding plate. On rims, which have this cast boss, the wall,thickness is so great at the valve stem hole that the 3 mm wide bead ring on the valve stem should not be pulled in when installing tubeless tire valves (as common on steel rims). Pulling in the valve stem bead would stretch the valve stem excessively.

Check sealing surfaces of tire and wheel rim for dirt and damage when mounting a tubeless tire. In conjunction with this point remember that the bead base of a tubeless tire provides the seal. If the bead flank is used for sealing, air could escape when driving aggressively.

Check flanges of aluminum wheel rims for wear (see page 4.1" 1/1).

Always coat tire beads with rubber lubricant when mounting.

Apply talcum powder inside of tire in tube type.

Inflate tubeless tires to about 4 bar/58 psi after mounting without valve core to guarantee proper fit on rim. With 3.3 bar/48 psi pressure the tire bead should jump over the rim hump. Screw in valve core and inflate tire to specified pressure.

Max. permissible radial and lateral runout of wheel (tire + rim) is 1.5 mm/0.59 in. If necessary, turn tire on rim 180 (uncontrolled matching) to reach an acceptable value.

Controlled matching: align highest point of rim (not marked on 911, determine) with green dot on side wall of tire.

New tires should be used on the front axle, since

1. the rear axle is more critical over stability and j

2. the front wheels must first make a track on wet roads, in which the rear wheels can follow.

(Not possible on cars with different size tires front and rear.) i

When replacing a defective tire, make sure difference in tread depth on one axle is notj greater than 30 "Jo, I

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