Competition Wheel Spacers & Fixings
The old motorsport adage, “to finish first, first you
must finish”, is very true. The chances of crossing the finish line is much
higher if you have the full complement of wheels still attached to the car.
The importance of your wheels is often overlooked. I
mean, they’re there or they’re not, right? Competition
wheels are subjected to greater strain than typical car wheels and as such
you need to ensure that they’re fully secured before you take to the circuit.
The thing is, there are so many different wheel spacers and fixings available,
all designed to create the optimum setup, and it can be difficult to know which
ones you need. Until now that is.
Competition wheel fixing terminology
Wheel fixings are quite simple but there are pitfalls to
be wary of and some of the component’s names are often confused. The following
guide will clear up any confusion.
The wheel stud
protrudes from the wheel hub, with the wheel sitting over the studs and secured
by the wheel nuts. The wheel stud is externally threaded, typically M12 or M14,
and the thread pitch can vary so care must be taken to match the studs and
nuts. The wheel studs are fixed into the hub from the rear and are pressed or
drifted in place. The stud is splined to prevent it rotating when the nuts are
Some makes of car can have wheel studs that have the same
thread, but different splines. Mazda
is a good example. Sometimes the front and rear are different splines on the
same car. If fitting longer studs it is very important to select the correct
spline to suit the application.
bolt passes through the wheel and screws into the threaded hub. The hub
with the wheel removed will show female threaded holes. The bolt needs to be
the correct length: long enough that the thread length holds the wheel in
place, and not too long that it interferes with parts behind the hub. The wheel
bolt is normally externally threaded with a hexagon head, but can sometimes
have a splined
key head (normally where this very little space around bolt head.)
The bolt can have a 60-degree tapered seat, cone shaped
view from side on. This seating is used on most cars with original wheels and
99% of aftermarket wheels. The other common seating used is radius seating, which
are ball shaped from side on. This is typically used on VAG group cars like
Mercedes and Porsche OE alloy wheels. Wheel bolt threads are typically M12 or
M14 with various pitches, and another less common seating is a flat style used
on some Peugeot
or Citroen original equipment alloy wheels.
nut screws over the externally threaded wheel stud and tightens against the
wheel. The wheel nut can be 60-degree tapered seat, radius seat, or flat seat depending
on the application and wheels.
A wheel nut can be either open ended or closed end. Open
end is useful if the hub has long studs as there is no chance of the nut
bottoming on the stud. Some wheels on older cars can have what are known as sleeve
nuts which, as the name suggests, have a sleeve that goes inside the wheel
where the hole is much bigger than the wheel stud. The sleeve diameter needs to
match the size of the wheel hole. The seating at the top of the wheel hole can
be tapered or flat usually a washer slips over the sleeve nut and saves
damaging the wheel face.
Older Toyota and Nissan models, and some 1970’s Ford’s,
have sleeve nuts with flat seating. Newer Ford’s and some Rover’s can have
sleeve nuts with tapered seats. The tapered seats can be different angles so
care must be taken to ensure they match. The length of the sleeve nut is
measured from the base of the washer to the end. A sleeve nut should be almost
but not quite flush with the back of the wheel hole looking from the inside.
Cars that have wheel bolts as standard can be a problem
where fast wheel changes are required. A conversion
stud screws in to the hub and leaves a thread protruding. This means the
wheel can be slide over the thread like a car with studs and the wheel secured
by a nut.
The studs are measured end to end and can be anything
from 40mm long up to 100mm. It is common to use thread lock on the hub side of
the conversion stud. Most conversion studs are the same thread both ends but
some change the outer thread, useful if you have existing nuts or the nuts
required are a different thread from the existing thread. The conversion studs
normally have an unthreaded section or a small collar to allow the studs to be
tightened against the hub.
The wheel hub on modern cars has a locating spigot
(protruding nose) that the wheel locates on and transfers the weight of the
vehicle via the hub. This means the wheel fixings do not have to bear the load
and can just hold the wheel to the hub. The hub spigot prevents radial movement
of the wheel to correctly centre the wheel. Car manufacturers use many
different diameters, so some aftermarket wheels come with interchangeable
spigot or centre rings that match the spigot size. Some older cars with wheel
stud fixings do not have hub spigots though.
Many race cars have wheels secured by a large single nut.
The hub has a protruding thread and usually a spigot or taper seat to
centralise the wheel. The driving torque is transmitted by pegs in the hub that
locate in the wheel or the wheel and hub have corresponding splines. The
correct torque for the centre nut should always be observed.
The peg drive wheels normally have a locking pin to
retain the nut. The spline type is often right-hand or left-hand thread so they
will tighten on normal rotation. Some cars that have normal hubs can be
converted by bolt on centre lock adapters, these will be supplied with the
correct fixings to hold in place.
Wheel bolt or nut fitting guide
When fitting new wheels or new fixings the following
should be adhered to for safety:
- M12 x 1.25 or ½ “UNF 8 rotations of thread
- M12 x 1.5 or M12 x 1.75 6.5 rotations of thread
- M14 x 1.5 7.5 rotations of thread
- M14 x 1.25 9 rotations of thread
If this amount of rotations is not possible longer studs
or bolts will be required.
Competition wheel spacers
There are several types of wheel
spacers available, and the guide below shows each type. Wheel spacers can
be used to increase the track width for stability and looks, and can also be
used to correct the offset on wheels that otherwise would foul the brakes or
Spacer shim universal
These are simple spacers
typically 3, 5, or 6mm thick. The centre bore is large so will fit most cars.
They can be 3-hole, 4-hole, 4/5 hole and 5-hole type. The holes are generally
slotted so the spacer will fit many applications and are useful if increased brake
clearance is required.
They are very cost effective but do not locate on the hub
spigot so can be difficult to centralise. Care should be taken the wheel is
still located by the spigot and the bolts / studs are long enough.
Spacer shim car specific
These are as above but machined in the centre to locate
on the wheel hub, so no radial movement is possible. It is good policy to check
the depth of the hub spigot to ensure the wheel will still be centralised. If a
6mm spacer is chosen and the hub spigot is 6mm there will be no spigot
protrusion left for the wheel to locate on. (Please note many cars have
different depth spigots front and rear).
Hub centric wheel spacers
centric wheel spacer has a protruding nose to locate the wheel and a
corresponding machined hole at the rear to locate the spacer on the hub face.
This allows the weight of the vehicle to be transferred safely via the spacer.
This type of spacer can be 10mm per side right through to 50mm. The spacer kits
for cars with bolts up to around 30mm will use with longer bolts and the wider
versions will bolt to the hub with bolts provided and then have a set of tapped
holes in the spacer for the existing bolts. The spacer kits for cars with studs
up to 30mm will need longer studs, the wider versions will bolt to the hub
using wheel nuts in the kit. The spacer will have longer studs protruding from
the spacer outer face. These will fit the existing nuts.
The bolt on type spacer principle above can be used to
provide a new bolt pattern. The spacer
adapter will bolt to the hub and the different or new bolt pattern will be
in between these bolt holes ( either female tapped or studs protruding ) This
can be useful if the wheel required is not available in the standard hub P.C.D.
We hope you find the guide useful and you
finish your event all wheels present and correct. We have parts for just about
any application. If you are unable to find the required parts please do not
hesitate to get in touch with a member of the Demon Tweeks team.