Tires/Wheels - Summer Tire and Wheel Rim Summary
84porsche01Subject
Tires and Wheel Rims
Part Identifier N/A
Applies To 928, 928 S
Group
44
Key Points
Summer Tire and Wheel Rim Summary
C
Number
84-02
April 23, 1984
Tires tested by Porsche must fulfill a wide range of requirements.
For example:
^ service life
^ high speed strength
^ handling on wet and dry road surfaces
^ adaptation to vehicle design
^ comfort
^ rolling noise
^ wear
Listed below are tires and matching wheel rim sizes recommended by Porsche:
Other summer tires and wheel rim combinations are not approved by Porsche. Note Because of the large contact surface of 225/50 V R 16 and 215/60 V R 15 tires, suitability for winter use is limited. (See Product Circular, Group 44, No. 84-01)
Notes on Pirelli P 6 tires
Three different versions of P 6 tires have been produced:
A - no special markings B - cross in circle below size code 215/60 VR 15
C - five-pointed stars in circles, 215/60 VR 15 each side of size code
If different versions are used on the same vehicle, versions A and B are completely interchangeable.
Version C should be used on the front axle (preferably both tires at the same time) with any combination of A and B on the rear.
General installation instructions
Always use new rubber valves, Part No. 900.265.001.50, when replacing tires. Always coat tire beads with rubber lubricant when mounting tire on rim.
Work sequence
- install new valve stem and remove insert
- install tire on rim and inflate to 4.0 bar (60 psi)
- ensure tire is seated on rim
- install valve stem insert and inflate tire to correct pressure
Note
Use a tube with 215/60 VR 15 tires only in emergencies. Do not use tubes and tires of different makes.
Tubes are not available for series 50/55 tires.
New tire instructions
Always use tires of the same make, type and size.
Note
When changing tires of only one axle set, new tires should be mounted on wheels of front axle
^ rear axle is more critical to directional stability
^ on wet surfaces, front wheels contact water first while rear wheels follow in the produced track
If replacing only one tire of an axle set, the difference in tread depth between tires must not exceed 30%.
Matching tires with forged, perforated disc wheel rims, Part No. 928.361.021.05
Tires and perforated disc wheel rims are matched during vehicle assembly to minimize radial run-out.
Matching procedure
^ a machined depression on the rim well of the perforated disc wheel rim marks the point of highest radial run-out.
^ a red locating dot is pasted on the outside of the rim to mark the same point of highest radial run-out
^ tires are marked with a green dot
- align red and green dots when installing tire on rim
^ dots must be within 30 mm (1-3/16 in.) of each other
Note
If the red locating dot is missing, mark the location of machined depression with chalk or tape before installing tire.
Aluminum wheel nuts
Aluminum wheel nuts require special care. Before installing:
- lubricate threads and shoulders of aluminum nuts with Optimoly HT, Part No. 999.917.728.00 (Optimoly HT does not affect tightening torque)
- torque nuts to 130 N-m (96 ft. lbs.)
Note Tighten and loosen aluminum nuts with a socket that grabs the entire depth of nut.
CAUTION Other socket wrenches or wheel wrenches are not approved.
Never use impact tools.
Break-in time for new tires
New tires have a vulcanization skin that can cause poor vehicle handling. Handling characteristics improve measurably during the tire break-in period of 600 miles (1000 km).
Vehicle handling characteristics should not be evaluated immediately after tire replacement.
Driving conservatively during the first 600 miles (1000 km) will help to maximize tire life.
After the break-in period, check wheel balance.
Obtain even tire wear by rotating tires after 3000 miles (5000 km).
Tire pressures Measure tire pressure only when tires are cold. Air pressure increases as tires get hotter and must not be decreased.
Note
Underinflation can cause tire damage that is not immediately noticeable.
Conditions leading to slow air loss or structural damage
^ damage to bead during installation
^ installation damage from excessive expansion of bead core; tire could part from rim
^ installation damage to inside of tire; could cause loss of air or ply separation
^ punctures from foreign objects (nails, glass, rocks, etc.); moisture can cause rust at puncture
^ squeezing damage (from driving over potholes, curbs, or similar objects)
^ sidewall damage (from rubbing against curb or slipping off road shoulders)
^ cuts in tire (especially sidewalls) damage from underinflation
CAUTION Porsche recommends replacing a tire if there is damage to the tread or sidewall and any possibility of structural deterioration exists.
Note
Repairing tires with pressurized sealants or tubes is not acceptable.
Retreading tires is not acceptable.
Damage that impairs true-running of wheels
^ Flat spots from standing. Under high temperature conditions, tires may develop flat spots on the contact surfaces during long periods of standing. Driving the car should correct this condition.
^ Uneven wear from damaged suspension parts or misalignment. Checking/correcting wheel alignment is necessary along with the replacing of damaged parts.
^ Uneven wear from improper balancing. Correct balancing must be performed before damage occurs.
^ Flat spots from locked wheels while braking. This damage usually remains noticeable and cannot be repaired.
When checking tire pressure, also check condition of tires. Look for uneven tire wear, damage to tires and rims and damage to suspension parts.
Porsche recommends checking wheel alignment following the first 600 miles (1000 km) of driving, or after any repairs to the suspension system.
Wear
Excessive, rapid tire wear is usually attributed to driving habits.
Almost all tires have tread wear indicators specified for the U. S.
The tread wear indicator is a ridge across the tread base at 6 points on the circumference of the tire.
Tread wear indicators
The ridge has a height of 1.6 mm. When tread wear reaches this point, the ridges become visible. The appearance of the wear indicators signals the need for tire replacement.
Storing tires
Rubber ages and is sensitive to certain substances. Ozone, fuels, oils, greases and solvents have a damaging effect.
Storage information
^ store tires indoors where cool and dry. Temperatures between -10~C and +20~C (44~F and 68~F)
^ clean tires with water before storing
^ store tires in a dark room
^ store tires on rims and inflate to higher pressures
^ do not store tires near heat radiators, electrical equipment, fuels, lubricants, solvents or chemicals
^ do not store tires in direct sunlight or under constant fluorescent lighting. Avoid blue light protection paint on windows.
^ do not store tires by suspending on hooks or in stacks
Note
The assumption that tires are more wear resistant after aging is not valid. VR rated tires should not be used if older than 6 years.
Age can be determined by the last three digits of the DOT code on the tire sidewall. For example:
If the last three digits are 193, the tire was manufactured in the 19th week of 1983.