While automotive manufacturing has become increasingly standardized, strong country flavors remain, and this often requires the need for special tools.
American cars often use SAE (Society of Automotive Engineers) measurements based on the English system of inches, while German cars are all metric. Beyond this basic difference, each manufacturer tends to gravitate to certain fasteners and fabrication methods.
Volkswagen favors hex key (Allen), torx (6-point star), and triple-square XZN (12-point star) fasteners.
The 12-pointed internal star shape of the triple-square superficially resembles a “double hex” fastener head, but points have a 90° angle (derived from a square) rather than the 120° angle of a hexagon.
In practice, hex drivers forced into a triple-square fastener may work for low torque (and non-critical) applications but in general the correct triple-square should always be used.
Common sizes — M4 through M18 — seem identical to metric bolts/nuts specifications but there is no correlation between triple-square names and the fastener dimension! Triple-square drives are also labeled in a XZN1nn format where nn is the numerical size. For example, M6 would be called XZN106.
Due to the inherent strength of their design, triple-square fasteners are typically found where high-torque is required, like engine head and drive train components. Common sizes used by VW are M6, M8, M10, and M12. Drives can be purchased individually, but a set may make more economic sense.
The 6-point star-shaped torx is a trademarked drive developed fifty years ago and subsequently standardized under ISO 10664. Torx screws are advertised as more tamper-resistant (because Torx drives are less available) with better torque robustness than common Phillips or slot heads.
Torx head sizes start with the capital letter “T” followed by a number ranging from 1 to 100. Only the correct driver can fit into a specific head size without risk of damaging the fastener.
Volkswagen frequently used sizes are T20, T25, T30, and T40. In addition to a socket set, a collection of long, short, and micro length Torx bits will make various tight-spot jobs go more smoothly.
The Allen name is trademarked so many mechanics refer to this shape generically as a hex key. This simple 6-sided shape has been used in mechanical applications for over 150 years.
Hex key metric sizes are defined in ISO 2936 and Volkswagen commonly uses 4mm, 5mm, 6mm, 7mm, 8mm, and 10mm.
Useful hex keys include stubby, medium, and long lengths as well as ball end variants (these help for different tool angles in tight spaces).
The New Beetle axle hub is secured with a 24mm 12-point one-time use nut (N90587602 front and N90654502 rear) and requires a 24mm 12-point socket for removal.
A 1/2 drive socket is recommended due to the torque requirements of this nut. It must be first tightened to 148 ft-lb, then loosened a half turn, tightened to 37 ft-lb, and finally turned an additional 60 degrees (best measured by the distance of two points on the nut).