Mounting Systems

Studs & nuts
Read the appropriate & general section before mounting Alcoa wheels:

  • Section A: when replacing studs and using standard nuts
  • Section B: when using standard studs and special sleeved cap nuts


SECTION A
Longer studs & standard wheel nut

  • 22.5” wheels for Heavy Duty trucks & trailers with 26 mm bolthole diameter
  • 19.5” wheels for Medium Duty trucks & trailers with 24 mm bolthole diameter
  • 17.5” wheels for Light Duty trucks with 21 mm bolthole diameter (6 on 245 only)
  • 17.5” wheels for trailers with 26 mm bolthole diameter


This wheel version requires longer studs than for steel wheels. The stud standout must be checked very carefully. The standout is measured from the surface that actually contacts to the wheel (steer or inner dual) to the outer end of the stud:

  • Single mounting
    Minimum stud standout = disc thickness Alcoa wheel
    + height of standard nut
  • Dual mounting
    Minimum stud standout = 2x disc thickness Alcoa wheel + height of standard nut


SECTION B
Standard studs & Alcoa sleeved cap nuts

  • 22.5” wheels for Heavy Duty trucks & trailers with 32 mm bolthole diameter
  • 19.5”wheels for Medium Duty trucks with 30 mm bolthole diameter
  • 19.5” wheels for trailers with 32 mm bolthole diameter
  • 17.5” wheels for Light Duty trucks with 26.5 mm bolthole diameter (6 on 245 only)


The standard wheel stud length can accommodate Alcoa wheels with more disc thickness when a special sleeved cap nut is used. The shank or sleeve of these nuts extends into the 32, 30 or 26.5 mm mounting holes and compensates the standard stud length or thread engagement. Only use wheels with appropriate stud hole diameter to allow the sleeve of the nut to easily pass through it.

Sleeved cap nuts are available for:

32 mm mounting system:    M22 x 1.5 (Metric), 7/8”-14 UNF (Volvo) and 7/8”-11 BSF (Scania)

30 mm mounting system:    M20 x 1.5 (Metric)

26.5 mm mounting system: M18 x 1.5 (Metric)

 

GENERAL

CAUTION! Applies to section A

Stud availability
Before purchasing Alcoa wheels always consult your truck or trailer OEM if longer studs are available in case of 26, 24 or 21 mm mounting system, i.e. longer studs & standard nuts

XL studs
Some trailer axle manufacturers offer axles with “combined” or extra long stud lengths, suitable for both thinner steel wheels and thicker aluminium wheels. In some cases Alcoa wheels can be mounted without modification of the studs or purchase of sleeved cap nuts. To determine correct & safe fitting follow the procedure as described above in section A.

CAUTION! Applies to section B

Centring with sleeved nuts
The shanks or sleeves of the special cap nut do NOT centre the
wheel(s); this mounting system still requires a hub piloting or hub centring axle.

Studs with unthreaded part / bottom
Studs that have an unthreaded part can cause incorrect or no clamping of the wheel(s) at all. Sleeved nuts may “bottom out” on the stud’s unthreaded part even before the wheels are clamped correctly.
Before mounting Alcoa wheels on hubs with such studs the space between the washer and the hubs mounting face must be determined. This space must be 2 mm less than the disc thickness of the Alcoa wheel to be accommodated. Determine this space when the nut is bottomed out at stud without a wheel mounted (picture / sketch).

 


This space (x) must be 2 mm less than the disc thickness of the Alcoa wheel to be accommodated.  Determine this space when the nut is bottomed out at stud without a wheel mounted.

CAUTION! Applies to section A & B

Spigot length
Before purchasing Alcoa wheels always consult your truck or trailer OEM:

  • The spigot length must be 3 mm or more for single mounting and 1x disc thickness + 3mm for dual mounting. Do not include bevelled edges on spigots. Always apply some ALgrease or non-water based lubricant on the spigots to reduce corrosion and make it easier to remove wheels for service


Thread engagement
The minimum recommended number of thread engagement between stud & nut is:

  • 13 full turns for M22 x 1.5 (Metric)
  • 12 full turns for M20 x 1.5 (Metric)
  • 11 full turns for M18 x 1.5 (Metric)
  • 11 full turns for 7/8”-14 UNF (Volvo)
  • 10 full turns for 7/8”-11 BSF (Scania)


Hidden valve design / disc brake axle application

  • All current produced 22.5” wheels have a hidden valve design that can be mounted on axles with disc brakes
  • Currently produced 19.5” x 7.50, 8.25 & 14.00 wheels have a hidden valve design, 19.5” x 6.75 wheels can be used on disc brake axles if the clearance between the calliper and the valve is 5 mm or more
  • All current 17.5” wheels do not have a hidden valve design and can be used on disc brake axles if the clearance between the calliper and the valve is 5 mm or more.

The shanks to not centre the wheel, the system still requires a hub-piloted axle.  Short and long sleeved cap nuts are available from Alcoa in thread sizes for all European vehicles.  The torque to obtain the correct clamping force is recommended by your truck/axle manufacturer.

 


Single wheels require sleeved nuts with a short shank.

 


For dual mounting wheels must be mounted with long shank nuts.