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Tyres and Tyre Structure
| Information |
Method
of Inspection |
Reason
for Rejection |
This
inspection applies to Tyres fitted to the road wheels only. The vehicle presenter
should be informed when it is noticed that there is a defective tyre on a spare
wheel
Identifying tyre size and type To identify the size and type of tyres,
it might be necessary to rotate the wheels or move the vehicle. Only one sidewall
of a tyre needs to be marked.
Section height-: section width ratio (aspect ratio) Unless marked otherwise,
“standard” car tyres have a nominal aspect ratio of 82%. Some tyres have an aspect
ratio of 80%. These have “/80” included in their size marking e.g. 165/80 R13.
Dual size marking of tyres Some tyre manufacturers are now dual marking certain
sizes of tyres. For example, a 185/75R14 tyre may be dual marked 185R14.
Where a tyre is found to be dual marked by the manufacturer on the side-wall,
either markings can be accepted.
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Permitted laden weight of an axle
This is the relevant axle weight in the column headed ‘WEIGHTS NOT TO BE EXCEEDED
IN GT BRITAIN’ (GB WEIGHTS) shown on the ‘Ministry’ plate fitted to the vehicle.
Vehicles not fitted with a ‘Ministry’ plate If a ‘Ministry’ plate is not
fitted to the vehicle, the relevant axle GB WEIGHT is that shown on the manufacturer’s
plate (See section 3.9).
Some vehicles first used before 1968, (Class 5 before 1982), might not
be fitted with a ‘Ministry’ plate or a manufacturer’s plate displaying axle weights.
The load capacity of tyres on such vehicles must be assumed suitable, unless
there is indisputable evidence to the contrary.
It is not possible to see every part of a tyre; in particular the tread contact
area, when twin wheels are fitted or when the body shrouds the tyres. The vehicle
must be moved to expose the hidden parts and the examination completed from under
the vehicle if necessary. |
A.
Type of Structure
On all the tyres fitted, check the 1. Nominal size and aspect ratio.
Note: It cannot be assumed that there is a difference in the nominal sizes of
tyres because either twin wheel is not in contact with the ground.
Note: A Class 3 or 4 vehicle tyre which appears to be of inadequate size, ply
or speed rating for the vehicle or its use is not a reason for rejection. However,
the vehicle presenter should be informed.
2. Type of structure, i.e. bias-belted, cross-ply or radial.
Note: Steel and fabric radial-ply tyres are to be regarded as the same structure
type.
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B. Load Index and Speed Rating (Applicable to Class 5 & 7 only)
1.
a. check for a load index (or ply rating and tyre size) marked on at least one
sidewall of each tyre. (See tables in Appendix D for the identification of tyre
load index, ply rating and tyre size) Note: A tyre not marked with a load index
or ply rating is assumed to have the lowest ‘load capacity’ of its size.
b. check the load index is adequate for the maximum laden weight of the axle.
2. Check for a speed rating letter marked on the sidewall of each tyre |
1.
a. One tyre is of a different nominal size or aspect ratio to any other on the
same axle.
b. special lightweight or space saving wheels and tyres fitted as road wheels
Note: Tyres with aspect ratios of 80% and 82% are almost identical in size and
can be safely mixed in any configuration on a vehicle. Where this is done, Reason
for Rejection 1 does not apply. In all other cases of mixed aspect ratios on the
same axle, rejection is justified.
2.
a. One tyre is of a different type of structure from another tyre on the same
axle
b. a 3- or 4-wheeled vehicle fitted with single wheels, and
(i) a cross-ply tyre or bias- belted tyre fitted on rear axle and radial-ply tyre
is fitted on front axle, or
(ii) a cross-ply tyre fitted on rear axle and a bias-belted tyre fitted on front
axle.
Note: Any tyre ‘type’ mix between different axles is acceptable for vehicles that
have
• 2 axles and ‘twin’ wheels on the rear axle
• 3 axles, one steering and one driving.
Note: This does not apply to vehicles with an axle fitted with tyres having a
road contact area at least 300mm wide.
c. a tyre of a different type of structure is fitted to a steerable axle from
that fitted to another steerable axle
d. In the case of non-steerable axles a tyre fitted to a driven axle is of a different
type of structure from that fitted to another driven axle
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1. a. a tyre not marked with its size on at least one sidewall. (See tables at
the end of this section)
b. a tyre that has a load index (or ply rating and tyre size) that is inadequate
for the permitted maximum laden weight of the axle to which it is fitted. (See
tables at the end of this section for the determination of tyre load capacity)
2. A tyre marked with one of the following speed rating letters: A, B, C, D, E,
F, G, J or K. Note: Some tyres are not marked with a ‘speed rating’ and the absence
of such a mark is not a Reason for Rejection. |
| Information |
Method
of Inspection |
Reason
for Rejection |
Inspecting
the tyres
Any areas
of the tyres that cannot be readily seen with the vehicle on hard standing should
be checked by rotating the wheel whilst the axle is jacked up during the under
vehicle inspection, or by moving the vehicle to expose the areas that could not
previously be seen.
Recut tyres
Recut tyres are permitted on
• a goods vehicle at least 2540kg unladen weight having at least 16 inch
(405mm) diameter wheels
• a vehicle with at least 8 passenger seats, excluding the driver’s seat,
and over 2540kg unladen weight
• a vehicle over 3050kg unladen weight Not for highway use Tyres with NHS,
Not for Highway Use
or similar markings should only be deemed acceptable if they display an ‘E’ marking
and a number contained within a circle. Adjacent to this circle, the sidewall
must also be marked 75R followed by a number
Note: Under-inflation
of a tyre is not in itself a reason for rejection. However,
• a brake test might be inadvisable, because of possible damage, or
• a headlight test might be affected, if the under-inflation is affecting
alignment.
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Tread
A tread pattern is the combination of plain surfaces and grooves extending across
the breadth of the tread and round the entire circumference.
The tread pattern excludes any tie- bars, tread wear indicators, or features designed
to wear out substantially before the remainder of the pattern, and other minor
features. Grooves that had not been cut as deep as those containing the wear indicators
when new, are not to be considered as part of the tread pattern
Breadth of tread
The part of the tyre which can contact the road under normal conditions of use
measured at 90 degrees to the peripheral line of the tread.
A 1.6mm minimum tread depth applies to
A vehicle first used after 2 January 1933 that is either
a. a passenger carrying vehicle (car, motor caravan etc) with not more than 8
passenger seats, excluding the driver’s, or
b. a goods vehicle or dual purpose vehicle not exceeding 3500kg maximum gross
weight.
Tricycle and quadricycle requirements are detailed at Section 9.4
A 1.0mm minimum tread depth applies to
• A passenger-carrying vehicle with more than 8 passenger seats excluding
the driver’s seat.
• A vehicle first used before 3 January 1933.
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D.
Condition of Tyres
1. Examine each tyre for
a. Cuts Note:It is permissible to check for exposed ply or cord by using a blunt
instrument to open a cut, taking care not to cause further damage.
b. lumps, bulges, tears, exposure of the ply or cord, or tread separation
Note: On radial ply tyres, care should be taken to distinguish between normal
undulations in the carcass, resulting from manufacturing, and lumps or bulges
caused by structural deterioration
c. recut tread
d. incorrect seating in the wheel rim
e. valve condition and alignment
f. correct fitting
2. Check tyres for fouling a part of the vehicle
3. Check tyres on twin wheels for wall contact.
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E. Tread - Pattern, Breadth and Depth
1.6mm tread depth
1. Check the tread pattern over the complete circumference of the tyre. Check
also that the tread depth meets the requirements using, as necessary, a depth
gauge accepted for MOT testing
1.0 mm tread depth
2. Check the tread pattern over the complete circumference of the tyre. Check
also that the tread depth meets the requirements using, as necessary, a depth
gauge accepted for MOT testing. |
1.
a. A tyre has a cut the length of which is in excess of 25 mm or 10% of section
width, whichever is greater, deep enough to reach the ply or cords
b. a tyre has
• a lump, bulge or tear caused by separation or partial failure of its structure.
This includes any lifting of the tread rubber
• any of its ply or cord exposed
c. a recut tyre fitted to a vehicle not permitted to be so equipped
d. a tyre incorrectly seated on the wheel rim
e. a seriously damaged or misaligned valve stem which could cause sudden deflation
of the tyre
f. a tyre not fitted in compliance with the manufacturers sidewall instruction,
e.g. an asymmetric with a sidewall marked ‘outer’ fitted with the marking to the
inner side of the wheel.
Note: Direction of rotation may be indicated by an arrow and/or words, but an
arrow by itself should not be taken to indicate direction of rotation.
2. A tyre fouling a part of the vehicle. Note: This does not apply to vehicles
designed to permit tyre contact with the chassis or frame e.g. steering lock stop
function
3. Tyres on twin wheels making wall contact due to under-inflation or incorrect
fitment. Note: Some tyres, e.g. radial ply tyres, with flexible side walls may
touch under load. Wall contact in these circumstances is not a reason for rejection.
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1. The grooves of the tread pattern are not at least 1.6mm throughout a continuous
band comprising
• the central three-quarters of the breadth of tread, and
• round the entire outer circumference of the tyre. Note: Each side of the
central band of the tyre can be devoid of tread (i.e. ‘bald’) and still meet the
pass standard. See diagram below.
2. A tyre with a tread pattern
a. not visible over the whole tread area, and
b. the depth of which is not at least 1mm throughout a single band
• round the entire outer circumference of the tyre
• of at least three-quarters of the breadth of tread.
Note: The 1.0mm tread depth requirement applies to the whole tread width if the
original tread pattern did not extend beyond three-quarters of the tyre width
when new.
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