Good news indeed.5.2.3. Tyres
You only need to inspect the tyres fitted to the road wheels at the time of the inspection. If you notice a defect on a spare tyre, you should advise the vehicle presenter.
Size
The aspect ratio of a tyre is included in the size marking. For example, a 215/55R15 has an aspect ratio of 55%.
‘Standard’ car tyres have a nominal aspect ratio of 82% (unless marked otherwise) and these are almost identical in size to tyres with an aspect ratio of 80%. They can be safely mixed in any configuration on a vehicle.
Some tyres may be marked with two sizes. For example, a 185/75R14 tyre may be dual marked 185R14. In such cases, you can accept either marking.
Load rating - Classes 5 and 7 only
A tyre load rating table is in Appendix B.
Make sure the tyre load rating is suitable for the axle weight.
You can find the permitted maximum laden weight of an axle on the manufacturer’s plate.
If axle weights are not displayed on the manufacturer’s plate, you must assume that the load capacity of the tyres are suitable, unless there’s indisputable evidence to suggest otherwise.
If a goods vehicle has a ‘Ministry’ plate showing lower axle weights not to be exceeded in Great Britain, you must use those instead of the ones on the manufacturer’s plate.
Speed rating - Classes 5 and 7 only
A tyre’s speed rating is shown on the sidewall as a letter and usually precedes or follows the load rating. Speed ratings from A to K are unacceptable, with the exception of H.
If no speed rating is shown it must be assumed that the minimum requirements are met.
Load ratings for low speed rated tyres - Class 5 vehicles only
Tyres must be suitable for use up to 70mph (L speed rating) unless the vehicle is a ‘restricted speed vehicle’.
If the tyre can carry the maximum permitted axle weight of the vehicle, these vehicles can use tyres with a lower speed rating tyres up to 70mph as follows:
K speed rating – but the tyre’s carrying capacity is reduced by 3%
J speed rating – but the tyre’s carrying capacity is reduced by 7%
For example, K speed rating tyres can be used at 70mph if the load is reduced as follows: 146/143K = 6,000kg single or 10,900kg dual - less 3% = 5,820kg single or 10,580kg dual
You must not accept a tyre load rating that’s less than the maximum permitted axle weight.
Structure
Tyres of different types of structure, such as radial-ply and cross-ply, must not be mixed on the same axle.
Steel and fabric radial-ply tyres are considered to be the same structure.
Run flat and conventional tyres can be mixed on the same axle, although this is not recommended.
Condition and fitment
Evidence of a tyre contacting a part of the vehicle, such as due to tyre flexing or suspension movement, is not considered to be a defect. A vehicle should only be rejected if the tyre is fouling a part of the vehicle at the time of test.
Some vehicles have lock stops comprising rubbing pads on the body that the front tyres may contact on a full lock. These are acceptable if they are properly maintained so that they do not damage the tyres.
When assessing cuts in a tyre, it is permissible to check whether a cut is deep enough to reach the ply or cord by using a blunt instrument to open the cut taking care not to cause further damage.
The following criteria should be used when assessing a cut in a tyre:
any ply or cord that can be seen without touching the tyre - fail
if by folding back rubber or opening a cut with a blunt instrument, so as not to cause further damage, exposed ply or cord can be seen irrespective of the size of the cut - fail
if a cut which is more than 25mm or 10% of the section width whichever is the greater, is opened with a blunt instrument and cords can be felt but not seen - fail
Before failing a cut, you must make sure it’s the cords that you can feel not a foreign object. If you’re not sure, then you should pass and advise.
When assessing lumps or bulges in a radial ply tyre, care should be taken to distinguish between normal undulations in the carcass, resulting from manufacturing, and lumps or bulges caused by structural deterioration.
Take extra care with stretched tyres because they’re more prone to sidewall damage.
Recut tyres are only permitted on:
vehicles over 3,050kg ULW
goods vehicles with an ULW of at least 2,540kg having at least 16 inch (405mm) diameter wheels
passenger vehicles with an ULW of at least 2,540kg having 8 or more passenger seats
You should only accept tyres with NHS, Not for Highway Use or similar markings if they have 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).
Example tyre marking
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.
Asymmetric tyres are marked with correct fitment information on the sidewall, such as ‘outside’. However, if an asymmetric tyre is fitted the wrong way around it is not to be considered a reason for rejection. The presenter should be advised.
Tread depth
A tread pattern is the combination of plain surfaces and grooves extending across the breadth of the tread and round the entire circumference. It excludes any tie-bars, tread wear indicators, or features designed to wear out substantially before the remainder of the pattern, and other minor features.
In simple terms, grooves containing tread wear indicators (TWI) or grooves cut as deep as those containing the wear indicators when new, are considered to be primary grooves. Other grooves or sipes that are not cut as deep as the primary grooves are secondary grooves and are not to be considered when assessing tread depth.
The ‘breadth of tread’ is 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.
Different vehicles require different tread depths.
The following vehicles first used on or after 3 January 1933 need 1.6mm tread depth:
passenger vehicles with a maximum of 8 passenger seats, excluding the driver’s seat
goods vehicles or dual-purpose vehicles not exceeding 3,500kg DGW
tricycles with an ULW more than 410kg and all quadricycles
The primary grooves of the tread pattern must be at least 1.6mm deep within the central three-quarters of the breadth of tread and around the entire outer circumference of the tyre (see diagram 1).
Either side of the central three-quarters of the tyre can be devoid of tread (‘bald’).
Diagram 1. Primary and secondary grooves in tyre tread pattern
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The following vehicles must have 1.0mm tread depth:
vehicles first used before 3 January 1933
passenger vehicles with more than 8 passenger seats excluding the driver’s seat
tricycles with an ULW not exceeding 410kg with an engine capacity greater than 50cc
tricycles with an ULW not exceeding 410kg which are electrically powered
The tread pattern must be visible over the whole tread area (see diagram 2), and have a depth of at least 1.0mm throughout a single band of at least three-quarters over any section of the breadth of tread round the entire outer circumference of the tyre.
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.
Tricycles with an ULW not exceeding 410kg with an engine capacity not greater than 50cc do not need to have 1mm of tread. However, they must have a visible tread pattern around the entire circumference and across the whole breadth of the tread.
Diagram 2. Tread pattern visibility
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Tyre age
The check of tyre age applies to all vehicles with more than 8 passenger seats, other than vehicles of historical interest.
Tyre age is determined by the date code on the sidewall and will be a three or four-digit code. Tyres with a three-digit code will be more than 10 years old.
The code is usually located in a ‘window’ on the sidewall and may or may not be located at the end of the DOT number (see image below).
example image of a date code on a tyre sidewall
The first two digits of the code represent the week of manufacture of the tyre and the second two digits represent the year of manufacture. In the example above, the tyre was manufactured in week 35 of 2016.
Tyres over ten years old at the time of test must be failed if they are on:
any front steered axle
any rear axle of a minibus with a single wheel fitment.
Tyres not displaying a date code must also be failed. However, date codes are only required to be marked on one side of the tyre so it may not be possible to see the date code on twin wheel fitments. Under these circumstances you should advise the presenter and assume the date code is present and the tyre age is acceptable.
On tyres where the date code is illegible, for example, due to kerbing or deliberate tampering, a major or minor defect must be recorded, depending on the location of the tyre.
Retreaded tyres
Remoulded/retreaded tyres may have two date codes. One being the original code and the other being the date of retreading. In this case the most recent date code must be used.
example image of a date code on a remoulded tyre
The appearance of the date code on retreaded tyres may be different from the original date code and may be branded rather than moulded.
- If I understand correctly, an early 911 is neither Class 5 nor Class 7
No mention of E marking
Tyres of different types of structure, such as radial-ply and cross-ply, must not be mixed on the same axle
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