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14.0 TYRE CLASSIFICATION
14.1 Standard wheels
A “standard wheel” is a car wheel with steel or alloy rim, with center hole, drop centre close to the external border of the
rim and a standard tyre (not RUN-FLAT nor LowProfile).
14.2 Low-profiled tyres (UHP) wheels
Low profile tyres (UHP) are those in which the height (H) and the width (C) have a ratio lower than 0.5 (i.e. low profile
series 45 stands for a ratio of H/C = 0.45).
For tyres to be considered as low profile (UHP), they must also have a maximum speed code of equal to and/or higher
than V.
Maximum speed codes
Q= to 160 km/h
R= to 170 km/h
S= to 180 km/h
T= to 190 km/h
14.3 RUN-FLAT tyres wheels
RUN-FLAT tyres are those which allow to continue to drive the vehicle for a preset number of miles and at a preset
speed, even if they have no internal pressure. These parameters change from one manufacturer to another.
The market currently offers 2 different types of RUN-FLAT tyres:
- Those with reinforced sidewall (self-supporting) where, thanks to a different mix and a reinforced structure, the shoulder
of the tyre can bear the weight of the vehicle even when the internal pressure of the tyre is zero.
- Those with internal support which have a ring inside the rim that bears the sidewall of the tyre when there is no pressure
inside it. The internal support may be made of plastic (Pax-Sistem) or of metal (Support-Ring).
All the tyres which do not correspond to the above mentioned descriptions have to be considered as “standard tyres”.
This Tyre-Changer is able to handle all types of wheels with “standard” tyres, LowProfile (UHP) and RUN-FLAT tyres
with reinforced side.
RUN-FLAT tyres with internal support (PAX System or Support-Ring type) mounting/demounting procedures need spe-
cial accessories to be used according precise dedicated instructions.
The mounting and demounting procedure is similar with “standard” tyre, LowProfile tyre (UHP) tyre or RUN-FLAT tyre
with reinforced side (self-supporting).
The bead-breaking procedure should be operated by shovel-blade bead-breaker with “standard” wheels – in order to
save time – while the rollers bead-breaking unit has to be used for all LowProfile (UHP) and RUN-FLAT tyres.
It is compulsory to follow the demounting/mounting instructions carefully, in order to avoid
tyre damages and the consequent risks for the vehicle and the passengers safety.
U= to 200 km/h
H= to 210 km/h
V= to 240 km/h
W= to 270 km/h
ZR= > 240 km/h
ZR(Y)= > 300 km/h
15.0 WDK RULES
WDK is a German certified body charged with the evaluation of tyre-changers functioning and their capability to perform
good and safe operations on RUN-FLAT and UHP tyres correctly, to avoid permanent and potentially dangerous dama-
ges to tyres.
In order to perform a correct demounting and mounting process, the following premises are strictly compulsory:
1. Guidelines knowledge - WDK literature provides all necessary guidelines for all tyre brands and models, including all
theoretical and practical instructions to avoid any possible damage to tyre, rim and pressure sensor.
2. Certified tyre-changer - This Tyre-Changer is WDK certified and fulfils all WDK requirements.
3. Qualified operator – The specific technical courses provide the operators with the necessary WDK guidelines and
service instructions. Dedicated WDK official courses are available to get the WDK diploma, when necessary.