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The Testers Manual

4.1 Tyres



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 eg 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.

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.
1a. 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 indentical 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. Type of structure, ie bias-belted, cross-ply or radial.
Note: Steel and fabric radial-ply tyres are to be regarded as the same structure type.
2. 
a. one tyre is of a different type of structure from another tyre on the same axle
b. a 3- or 4-wheeld 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 axle 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 300 mm 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
B. Load Index and Speed Rating (Applicable to Class 5 & 7 only)
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 Department of Transport plate (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.

B. Load Index and Speed Rating (Applicable to Class 5 & 7 only)

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. 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.
4.1 (Additional Information for Class 5 Only)
Restricted Speed Vehicle
A ‘Restricted Speed Vehicle’ is a vehicle displaying at its rear a ‘50’ plate as shown below (at least 150mm wide and 120mm high).

A vehicle displaying this plate is required to have tyres suitable for speeds up to 50mph, i.e. ‘F’ speed rating or greater.


Other Suitable Speed Ratings (Class 5 only)

Unless the vehicle is a ‘Restricted Speed Vehicle’ the tyres are required to be suitable for use up to the maximum prescribed speed limit of 70mph, ie ‘L’ speed rating. Tyres of the lower speed ratings of ‘J’ or ‘K’ however are acceptable for use at 70mph although the increase from the nominated speed rating imposes a reduction in the tyres’ carrying capacity

Note: This allowance is only applicable to the nominal service markings (Load Index/Speed Symbol).

This allows a tyre displaying a ‘J’ speed rating (suitable for a maximum of 62mph) to be used at the ‘L’ speed (suitable for a maximum of 70mph) at the penalty of reducing the tyres capacity by 7%.

In the case of a tyre displaying a ‘K’ speed rating (suitable for a maximum of 68mph) a reduction in capacity of 3% is imposed to allow use up to the ‘L’ speed.

e.g. 146/143K= 6000kg single/10900kg dual – at a maximum speed of 68mph

Less 3% = 5820kg single/10580kg dual – at a maximum speed of 70mph

This would allow a tyre displaying the speed rating ‘K’ to be used on a vehicle to which a maximum prescribed speed limit of 70mph applies, subject to it being suitable at the reduced capacity of 5820kg in single and 10580kg in dual formation, for the maximum permitted axle weight of the axle to which it is fitted (the GB maximum permitted weight as shown on the manufacturer’s plate).

If during an annual test a tyre of ‘J’ or ‘K’ speed rating is fitted to a vehicle subject to a maximum prescribed speed of 70mph and found to be below the weight capacity required, this is a Reason for Rejection.



C.   Speed Rating - Restricted Speed Vehicles (Applicable to Class 5 only)

1.    Check for a Speed Rating letter marked on the sidewall of each tyre.
1.  A tyre that is fitted to a ‘Restricted Speed Vehicle’ marked with one of the following Speed Rating letters - A, B, C, D or E
4.1 Tyres ( Condition)
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 with a six digit number, which may be preceded by 75R or similar marking (see example below).

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.

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.

The inspection of the tyre pressure monitoring system (TPMS) warning lamp only applies to passenger vehicles with:

. four or more wheels, and

. not more than 8 passenger seats excluding the driver’s seat, and

. first used on or after 1 January 2012

The check does not apply to quadricycles.

The TPMS warning lamp (as below) will generally illuminate and go off again when the ignition is switched on. If one or more tyre pressures are low, the lamp will remain illuminated.
In the event of a system malfunction, the lamp will flash a number of times and then remain on.

Vehicles must only be rejected if it is clear that the lamp indicates a system malfunction.

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.

 

4.
On vehicles fitted with a tyre pressure monitoring system, check that the warning lamp is operative and does not indicate a system malfunction.

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: A vehicle should only be rejected if the tyre is actually fouling a part of the vehicle. Evidence of fouling e.g. due to tyre flexing or suspension movement is not a Reason for Rejection.

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.

4.
A tyre pressure monitoring system warning lamp:

. inoperative

. indicating a system malfunction.
4.1 Tyres (Tread Pattern, Breadth and Depth)
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 1.6 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 3500 kg 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.

E. Tread Pattern Breadth and Depth
1.6 mm 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. 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 (ie. ‘bald’) and still meet the pass.  See diagram below
 
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.

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.
Issue Date: 01 January 2012