TO TYRE WEAR.
TO OPTIMISING TYRE SERVICE LIFE
All items on commercial airliners suffer
wear and tear. Tyres are no different. There
is no way to stop a tyre wearing but there
are practical things that airplane operators
can do to increase their service life.
perspective to tyre wear which is intended
to help aircraft operators, maintenance
staff and purchasers to understand a little
more about this critical component.
• General Information
• When and How Tyres Wear
• Identifying Wear Profiles
• Suggestions for Reducing Wear
Really Useful Guide to Optimising Tyre Service Life
In This Guide
An aircraft tyre is a pressure vessel. Its role is
to hold the gas that supports the load of the
aircraft. No other tyre has to deal with such high
loads and such high speeds as an airplane tyre.
For the purpose of this guide, we can consider
the tyres as being made up of three principle
elements, the tread, the beads and the casing.
This guide focuses on the tread and the casing.
Terms used in this Guide:
Tread The part of the tyre in contact with the
ground. Designed to resist abrasion.
Circumferential grooves displace water.
Bead Metal wire used to anchor the tyre to
the wheel and anchor the casing plies.
Shown in image one and two as blue
Casing For the purpose of this guide the casing
is considered as everything else that
makes a tyre. It is principally comprised
of fabric cords (ply cords) encapsulated
inside a rubber sheet (known as a ply)
and a number of other components
combined during final assembly. Multiple
plies are combined to form a pocket.
The ply cords provide strength. The
angle of the cords determine if the tire is
considered bias or radial.
Tread Life This refers to the landings per tread - the
metric with which operators are most
Casing Life This refers to the number of tread lives
(retreads) that a casing can have relative
to its design goal or total fatigue life.
FOD Acronym for Foreign Object Damage.
This is a significant cause of premature
tyre removal. FOD is not specifically
discussed in this guide.
Images one and two depict a rough
representation of an aircraft tyre with no load
and an aircraft tyre with load.
Images three and four show the components of
the tyre - the bit that nobody sees - under the
black. For more details see DM1172.
Unloaded Tyre (Image 1) Bias Tyre (Image 3)
Radial Tyre (Image 4)Loaded Tyre Showing Deflection (Image 2)
The full load and high speed is applied in a fraction of a second during
landing. During take off, the speed builds and the aircraft is typically
heavier than it is when it lands.
When Tyres Wear
Landing. A puff of smoke; the screech of tortured rubber. It’s always dramatic. But that’s not where most of the wear occurs. The graphic below
gives a rough indication of when, in the life-cycle, a tyre wears. For both casing and tread wear, heat is one of the most significant causes of
wear. Local factors and operating conditions or practices will determine the precise ratio between the various stages of the life-cycle.
How Aircraft Tyres Wear - Tread Life
The wear of the tread is caused by the abrasion of the tyre against the runway as the tyre progresses through its service life. Loading rubber
with a static and vertical force alone will not cause wear. Adding a dynamic force (the tyre rolling along the runway) certainly will! Factors that
increase heat such as hard braking and fast cornering will wear the tread of an aircraft tyre, just like it does the tread of a car tyre.
Load & Pressure: If the longitudinal force remains
constant a higher aircraft load and higher inflation
pressure will increase wear.
Tyre Shape: Certain profiles of tyre will wear
quicker due to the relationship of centre size and
Under Inflation: The footprint of the tyre on the
ground and the deflection on landing will be higher
than intended which means more wear.
Uneven Inflation: (On Multi Tyre Struts): The tyre
with correct inflation pressure will carry more of the
load which will increase wear of the tyre. Wear on
the under-inflated tyre will increase because of the
larger footprint and higher operating temperatures.
High Altitude Airports: The higher the airports
served the greater the tyre wear will be. This is
because air, at high altitude is less dense and
generates less lift. The aircraft needs to travel
both faster and further to take off.
Ambient Temperature: High temperatures cause
warm tyres. Heat is the enemy of all tyres and is
generated during ground operations. Furthermore,
as temperature increases the distance covered
before take-off increases because the air is less
dense which generates less lift. Again, increasing
Position of tyres on the airframe: Tyres fitted
to different positions of the aircraft will experience
different wear characteristics due to the interaction
of the tyre with the aircraft and the ground.
Camber: For landing gear or conditions which
induce a camber the footprint of the shoulder of
one side of the tyre will be greater than that on the
other side of the tyre. More camber causes more
wear. Too much negative camber will cause wear
to the inner shoulder. Too much positive camber
will cause wear of the outside shoulder.
Toe-In/ Toe-Out: If the tyre does not run straight,
i.e. there is toe-in/ toe-out, the tread will be
dragged down the runway at an uncomfortable
angle which will cause wear. Too much toe-in will
cause wear to the outside shoulder, too much toe-
out will cause wear to the inside shoulder.
Both tyres might look to be
the same but their inflation
pressure can be quite
different. The only way to be
sure is to measure with an
approved pressure gauge.
Flying from hot to cold?
Increase pressure before take
off in accordance with the
AMM. If flying from cold to
hot decrease the pressure in
accordance with the AMM.
See DM1172 for more
How Aircraft Tyres Wear - Casing Life
The fatigue (wear) of the casing is invisible and is mostly concerned with the impact on retreadability. A higher scrap rate at each retread level
will increase costs for the operator of the aircraft or, under certain conditions, the supplier of the tyre. Even so, conditions can lead to premature
scrapping in the interests of safety.
Heavy Landings will increase the deflection of the
tyre at the point of touch-down which can damage
the internal components of the tyre.
Fast and tight turns increase heat in the tyre and
combined with the high forces of fast and tight
cornering might cause separation of the internal
components. Such use increases tread wear,
Very slow and very tight turns where a tyre
remains broadly static or even moves backwards
can cause tearing of internal components.
Single engine operation induces a turning
force which is corrected with steering input. The
effect of the thrust on the ‘engine-off’ side makes
the tyre want to ‘crab’ which induces wear of the
internal components. The decision for the airline
is based upon the value of fuel savings compared
with increased tyre consumption.
Fast turnaround times leave heat in the tyre for
longer. Heat induces fatigue as it causes the bonds
between rubber components to break down. This
can cause voids to form in the tyre which will be
identified during the retread inspection process.
~12 cycles till failure.
~8 cycles till failure.
~2 cycles till failure.
Under-inflation is a significant cause of casing damage which
prevents a tyre reaching its full retread potential. At worst, a
catastrophic failure might occur as a result of under-inflation.
Under-inflation causes extra heat build up which can make
components separate from each other. Each phenomena on
this page is magnified by low pressure.
The wear of the casing is invisible and is mostly concerned with the impact on retreadability. A higher scrap rate at each retread level will
increase costs for the operator of the aircraft or, under certain conditions, the supplier of the tyre. Foreign Object Damage can force the
premature removal of the tyre in the interests of safety. See DM1172 or the Dunlop Pocket Guide for more information.
Wear of the Tread Wear of the Casing
When Dunlop receive a tyre to retread the external
characteristics of the tyre are visually inspected.
But it is the condition inside the tyre which is
To look inside the tyre to see if the casing is
damaged Dunlop use shearography.
A laser camera takes a photograph of a tyre in a
relaxed state and then another photograph of the
tyre is taken whilst a vacuum is induced. The two
images are combined and any areas where the
inside of the tyre is damaged are clearly shown.
Perfect - even wear across the tread and a
little life left to wear down to the bottom of the
This has stayed on wing a bit too long and has
worn below the grooves. It’s time to change if
fabric is visible.
This tyre has worn too much on one side of the
tyre. This wear profile is caused by camber or
Stepped wear is most prevalent on certain types
of tyre and is made worse by under-inflation.
This tyre has had a rough life. The
highlighted area indicates separation
within the tread. There is only one
separation - the software indicates
a double bulls-eye where the two
images are layered over each-other.
Even Wear across the tread. Excessively worn tyre
Asymmetric Wear Stepped Wear
Suggestions for Reducing Tyre Wear
As we have seen in this Really Useful Guide there are many different causes of tyre wear which affect different elements of the tyre. Friction will
damage the tread but certain operational practices may impact the integrity of the casing. So in other words, the tyre will wear and that is just
the way it is! But there are some things that operators can do.
Turn slow and wide: This will ensure that all
wheels rotate as the aircraft manoeuvres which
prevents the tyres being scrunched into the
asphalt. Starting all manoeuvres with wheels
straight ahead also helps.
Be cool: Heat is the enemy of all tyres. Slower turn
around times will reduce heat and thus prolong the
life of the tyre. Excessive heat can cause the joins
in the casing to breakdown.
Slow down the taxi: Fast taxiing causes more
heat to build up in the tyre which increases wear of
the tread and fatigue of the casing.
Maintain the Gear: Sometimes wear on landing
gear components can cause extra wear on the
tyre. Maintaining the gear well keeps everything
running in the correct tolerances.
Check out the tyre care data: Dunlop publication
DM1172 provides lots of information about tyre
phenomena and should be read with the AMM.
And Dunlop User Support Specialists are available
for you to provide bespoke training sessions at a
venue of your choosing.
Pump Up The
“If there is a silver bullet for increasing both
tread life and casing life then correct inflation
is it. Dunlop recommends 24hr checks.”
An over-inflated tyre wears more quickly on
the crown (top) of the tread and will be more
susceptible to FOD damage in this area. It will
be worn on the top but tread will remain on the
An under-inflated tyre deflects more than a
correctly inflated tyre for a given load. This can lead
to increased casing fatigue, reduced retreadability,
creep on the wheel or induce the wheel to pinch
the tyre or the wheel to strike the runway. The
tyre will also run hotter and will wear faster on the
shoulder than on the tread.
And finally, FOD free runways and ramps will guard
against costly early removals.
Under-inflated tyre: As
the load increases the
deflection of the tyre
increases more than
intended. Load will not be
tyre. The tyre
deflects in line with
the design and the
load is evenly shared.
Load % 100%
Dunlop Europe, Middle East & Africa
(44) 121 384 8800
Dunlop The Americas
Dunlop Asia Pacific
(86) 595 85931007