For 17" wheels it's 36psi all round.

16" & 18" are 36psi at the front and 44psi on the rear.

Some owners prefer to run the rear tyres at a slightly lower pressure than this to improve ride quality.

For a narrow bodied car the limit is probably something like 10J with an offset of 47mm.

For a wide bodied car there is a little more clearance so 11J should be usable. For really extreme requirements a wide bodied car using narrow body trailing arms should be able to fit 12J wheels on the rear.

It depends on the make of the tyre.

Many tyre manufacturers recommend a minimum 7.5J wheels for a 225/45 tyre, others only a 7J. Many owners have confirmed that they use 225 tyres on a 7J rim with great success but we would recommend conforming to the advice of the tyre manufacturer.

Because of the unusual weight distribution of the 911 range of cars, Porsche go to extremes to ensure that the tyres that are approved for fitment comply with the strictest demands of construction and manufacturing in order to give the car the ultimate in grip, traction and wear rate whilst making the handling as safe as possible. Tyres are submitted by manufacturers on a regular basis for Porsche to approve and often significant changes are demanded to standard production tyres in order to comply with Porsche's requirements.

Additionally the owner is expected to comply with fitment and replacement criteria regarding axle matching and tread depth.

It is ultimately up to the owner whether to fit N-rated tyres but, if you choose not to, we would recommend that you check with your Insurance Company to ensure that a potential claim would not be rejected because of your choice.

During 2008 the Porsche engineers at Weissach conducted a series of tests on N-rated tyres and their suitability for many of the Classic models, including the 964. The results of those tests were published by Porsche and the 964-specific results can be found here.

The Carrera 2 and Carrera 4 came initially as standard with with Design 90 16 inch wheels. Both front and rear wheels have an offset of 52.3mm

All wide bodied cars (Turbos, Celebrations and wide bodied Coupes and Cabriolets) have a wider rear track implemented by using a different rear swinging arm. These cars use rear wheels with a 61mm offset. Bear in mind that ET61 wheels cannot be used on narrow bodied cars without using spacers of a sufficient size to reduce the offset to something around 47 - 50mm.

If wider wheels than standard are fitted you should be aware that the offset of the new wheels may have to be slightly less than the standard wheels (i.e. less than 52.3mm) in order to accomodate the additional rim width in gaining clearance from the chassis/suspension. There is also a vulnerable oil pipe in the wheel side of the right rear wheel arch which can be flattened if necessary to provide sufficient clearance.

Note that spacers can only be used to REDUCE the offset of a wheel, i.e. an ET61 wheel becomes ET48 with the addition of a 13mm spacer. Offsets CANNOT be increased.

The only models of the 964 which were factory approved for the fitment of 18 inch wheels were the 1991 Turbo S, the 1993 Turbo 3.6 and the 1994 Turbo 3.6 S. All these cars had the 18 inch Speedline for Porsche wheels fitted as standard. The fitment of 18 inch wheels to any other model has been prohibited by the factory and Technical Bulletin 9305 (here) refers.

However, many owners have fitted 18 inch wheels despite the warnings from Porsche. The original reasoning is largely lost but there are several theories, one being the close proximity of the exhaust heat shield to the rim on the rear left corner and another being the failure of stub axles in the Cup racing series when cars were using 18 inch wheels fitted with racing slicks. Neither scenario is considered relevant to road vehicles although it must be said that the cars on which 18 inch wheels were a standard fitment do have stronger stub axles fitted although incidents of stub axle failure on standard C2/C4 cars are rare in the extreme.

The correct torque to be used when tightening the wheel nuts is 130Nm (95.88 ft/lbs). It is important that you do NOT apply any lubricant (like Copperslip) to the taper on the nut although it is good practice to apply a small smear to the threads.

The weight of a wheel is an important factor in the performance of a car's suspension since it is a major contributor to the unsprung mass which the suspension is required to control.

Weights vary enormously between different designs and different materials.

A comprehensive list of many Porsche OEM wheels and other major brands can be found here, just click on "Felgengewichte".