MG Tech – Part Worn Tyres


In these days of austerity you have only to walk into any commercial motor car servicing and maintenance operation to overhear hardened motor trade professionals talking of the decline in Mondeo man’s call upon their services, or a back and forth banter about the growing propensity for the average motorist to resort to d.i.y maintenance to keep down the cost of running personal transport.

Whenever the averagely prudent motorist is compelled by the attractiveness of price to consider replacement of a no longer serviceable tyre with a part worn substitute, apparently knowing very little about the technicalities of tyre construction, he or she will likely require that only two criteria be met when first setting eyes on the tyre – is it aesthetically pleasing in that it seems to be fashionably squat or low profile, and does it still have ‘plenty of meat’ or an abundant depth to its remaining tread?

A consequence of this trend for the lay public to shy away from the service and maintenance professional when the personal exchequer maybe is getting a little depleted, is the burgeoning growth of commercial outlets specialising in the retail supply of part worn tyres at something like 50% or even 25% of the likely cost of new.

Recent research with which the author of this article has been connected, examined a core sample of ten part worn tyres purchased from commercial tyre dealer and vehicle part recycling sources within one English county. A careful examination of the core sample tyres immediately after purchase, revealed a widespread ignorance, or a blatant disregard of consumer protection legislation among the suppliers of the part worn tyres. (The Motor Vehicle Tyre Safety Regulations 1984) These Regulations were specifically promulgated to protect the unquestionably naive average motorist from the commercial supplier of motor vehicle tyres who might be shall we say, a little less than scrupulous about the merchantable quality of the goods he purveys .

A significant requirement of consumer protection legislation protecting you, the average motorist, when you purchase a part worn tyre from any commercial enterprise (the stated legislation does not apply to sale by a private individual) is that the words ‘PART WORN TYRE’ must be indelibly and durably marked on second hand tyres in characters four millimetres or more in height. The characters must not be scratched or etched into the tyre’s composite rubber, it is best that they are embossed on a composite rubber label vulcanised to the tyre.

Of the ten core sample tyres purchased in the recent research exercise not one was clearly marked to inform the consumer the tyre they were about to buy was part worn. Sixty percent of the core sample tyres had one or more unsealed penetrations of the tread area, some reaching to the tyre’s chords and/or plies. An unsealed penetration reaching chord or ply allows road surface water ingress to the very fabric of the tyre. Steel plies rust, textile chords decay, leading to ply separation which then manifests as a lump or bulge in the tread area and a breakdown of the tyre’s concentricity – an uncomfortable ride and a potential time bomb just waiting to go off.

Ten per cent of the sample tyres had visible kerb impact cuts and tears up to six millimetres in length in the outer sidewall, albeit they did not in subject instance expose the sidewall chords or plies. Kerb impacts may often visibly damage the air retentive layer, that is, the inner soft rubber composite lining of the tyre, and yet remain unseen on the outer sidewall – so be sure to scrutinise the inside of the offered tyre at very least as carefully as you check the outside. If you see something resembling a ‘snake bite’ marking – reject it. Air seepage via a damaged inner air retentive layer may sometimes manifest as a ‘blister’ in the outside of the sidewall when the tyre is inflated. A sidewall blister isn’t a plaything like bubble wrap, which you might like to poke with your finger, it’s an instantaneous deflation disaster just waiting to happen.

Two of the test sample tyres purchased after advising the seller source that both were to be fitted to the steered axle of a certain make and model of motor car, exhibited differing load index and speed rating. (An explanation of load index and speed rating follows)

So, should you be about to purchase one or even a set of part worn tyres, maybe you should first ask yourself and make your own decisions:- is the practice intrinsically safe? Are the tyres on offer entirely suitable for your vehicle? Has any one of them even a slight defect that may in time let you down?

Inspect the tyres offered you intensively. First, look for a sidewall marking indicating the tyre’s authorisation for use in any member state of the European Union. This will normally be a circumscribed capital letter E followed by one or two numbers within the circle, and up to a seven digit number outside of the circle to the right side. This coding does not indicate the country of the tyre’s manufacture. For example a circumscribed code of E11 means the tyre may have been manufactured anywhere in the world, but authorised by the United Kingdom for use in Europe. Probably the majority of budget range new tyres available in the UK now originate from China, and are authorised for use in Europe mainly by an embossed E4 symbol. The E4 code applies to the European member state of Holland. Old tyres manufactured in non EU countries, or even made under licence in an EU country will often pop up in the second hand market. The moral of the story being told is therefore should you be offered for purchase in the UK any new or part worn tyre which does not have an E symbol marked upon it, you’re best advised not to buy it.

Next, check the tyre size correct for your car. No matter what the cost to your image or to your street credibility, you’d do best to avoid the temptation to fit oversized or very low profile tyres to standard or narrow bead seat wheel rims. Realise that if you buy for the fashionable look, you will be unwittingly altering your car’s steering and suspension geometry, its sprung weight balance about centre of mass, and you almost certainly will detract from your car’s handling stability and ride comfort.

Let us now for sizing explanation sake, take a tyre sized 195/65/R 15. The first three digits of this example – ’195’ indicate the width of the tyre expressed in millimetres and measured outside sidewall to outside sidewall, they do not express tread width shoulder to shoulder. The next two digits, in subject example ‘65’ represent the aspect ratio, or the relationship of the tyre’s height (measured bead heel to tread cap) to the tyre’s width, (sidewall to sidewall) expressed as a percentage. In other words in subject example, the tyre’s height at circa 127mm, is 65% of the tyre’s width of 195mm. The tyre is thus said to posses a 65% profile. Next the letter R represents a Radial type of construction. Nowadays one is unlikely to want cross ply or bias belted tyres on anything other than vintage or very old classic and American cars, and then probably only for sake of originality. Finally, the digits 15 in the sizing represent an Imperial measurement of the diameter of the wheel rim onto which the tyre should be fitted, expressed in inches, and measured bead seat to bead seat diametrically across the rim.

Now let us consider and explain in down to earth terms, the complexities of load index and speed rating. What do they mean, and why is either relevant? When looking to buy new or second hand tyres authorised for use in any member state of Europe, look to the right side of the size markings on the sidewall, you will usually see a series of two or three numerals followed by one or two letters.

The combined alphanumeric code indicates tyre load index and speed symbol. The load index part of the code, starting from the left – the first two or three numbers, is an escalating numeric code which correlates with the maximum load a tyre can carry at the maximum speed indicated by its alphabetical speed symbol when the tyre is inflated to manufacturer recommended pressure.. The Speed symbol part of the code is alphabetical, and is represented by the final one or two letters. If you are fitting replacement tyres to your vehicle, be they new or part worn, make sure there is no load rating or speed symbol mismatch between tyres you’re about to fit or incompatibility with your vehicle manufacturer’s precise specification.

Strictly controlled repairs to damage and penetrations of a part worn tyre are permissible, but only within certain confines of the tyre’s dimensions, and the repair method must conform with British Standard Automobile Series Standard (BS AU). As a rule of thumb, should the tyre offered you show sign of repair in the area of either tread shoulder or either sidewall, reject it. Unless you can recognise BS AU conformity in any repair showing elsewhere, remembering to inspect both inside and outside of the tyre, reject repairs in that area too. Check minutely the soft pliable rubber layer which lines both beads of the tyre between heel and toe of the bead and which makes the air retentive seal with the wheel rim. Any cut, snag, tear, or break in the rubber inflicted during demount or remount of the tyre on a wheel rim will ruin the seal utterly, if fitted none the less, the tyre will when first inflated appear to hold air satisfactorily, but inevitably will slowly deflate with the passage of time. Do not ever accept a supplier’s assurance, that to fit a tube within a tubeless tyre to overcome air loss via a point of penetration or damage is acceptable practice. It isn’t, even should he offer to supply and fit the tube for free.

The sidewalls of tyres which are ‘run flat’, used excessively overloaded, or excessively under inflated flex and ripple greatly between hinge points at tread shoulder and bead seat as they rotate.. This produces visible circumferential marbling or chafing on sidewalls both inside and outside the tyre, but it often first appears only inside the tyre. If you see any such marks on any part worn tyre offered you, you can be sure the tyre has been ill used and abused during a very hard previous life.

So, who then polices these commercial part worn tyre supply organisations? Strangely enough not the overstretched British Police Service; what meagre traffic patrol resource the Police Service is now left with has its work cut out enforcing the Motor Vehicles (Construction & Use) Regulations 1986, as far as those regulations address the use of defective tyres on public roads. The sting in the tail which results from focus of Police on enforcement of criminal law and not so much focus on consumer law, means that it is you the car owner, and you the car driver who is at risk of Police prosecution. The question of whether the tyre was supplied you in the defective condition in which the Police Officer found it, is hardly ever followed through.

No, the enforcement of consumer protection legislation relating to the supply of part worn tyres now falls firmly in the lap of the equally overstretched and under resourced Trading Standards Offices throughout the country. Across the board consumer protection officers are acutely aware of the disturbing trend of the less well off motorist to resort to second hand tyre supply outlets instead of fitting his car with new as and when tyres wear out. Consumer protection officers are indeed actively addressing the issue, but in all probability it has now grown in times of austerity to overwhelming proportion. So in the meantime of the paucity of public service assistance, what defence you have to your buying a pig in a poke should you think fitting second hand tyres will save you a pretty penny, rests fairly and squarely in your own hands. Am I suggesting you should not buy part worn tyres no matter how strong the economic compulsion? No I am not. Just be very, very sure you know what you’re about when it comes to looking them over before buying.


Wayman Consultancy Ltd 1st September 2011.