Product Quality and Performance

3.1 Product Quality Regulation - Generic Considerations

3.1.1 The public perception of the safety of retreaded tyres has been highlighted by a number of studies as one of the major market barriers.1, 2
These preconceptions arise from the early development of retreaded tyres when some examples were less reliable than new tyres. Legislation and regulation now dictate the industry must produce to a good quality level. In these safety-related products, this history has had major repercussions. Since the first of January 1995, however, it has been illegal for anybody to supply retread tyres which do not conform to BS AU 144e.1, 3
This standard requires that a percentage of retreaders products undergo the same type of rolling drum tests which new tyres must undergo From January 2004, amendments to the Motor Vehicle Tyres Safety Regulations (1994) make it compulsory for retreaded tyres to meet UNECE regulations 108 and 109.4, 5, 6
The Used Tyre Working Group (UTWG) considers that these 'tougher regulations can only improve retreading's negative public image'.2

3.1.2 The specification for retreaded tyres for cars and commercial vehicles has been clearly defined by these two regulations ECE 108 (private cars)4 and ECE 1095 (commercial vehicles). These regulations not only define the process of retreading and tyre structure but also the specifications for their use and the testing procedures to ensure constituent safe use.

3.1.3 The regulations are highly specific about the dimensions of the tyre and their specifications in terms of load and speed ratings. These specifications must be clearly identified by a series of markings on the sidewall of the tyre. Both the retread company and its range of products must be approved by an independent authority which also tests the tyres. In order to comply with production standards and product quality a representative selection of tyres must be tested.
For each type of tyre a sample equivalent to 0.01% of total annual production or a minimum of 5 tyres has to be tested. These stringent requirements are further enforced by random selection. Each regulation also defines the rolling test procedures that must be followed for each tyre's speed and load ratings. The adherence to a highly prescriptive testing regime ensures consistency and an authoritive endorsement of retread quality that is not required for new tyres, where in-house testing is allowed.

3.1.4 There have been some practical concerns raised over the adapatability of the testing process given that retreaders produce much shorter runs of tyres with a wider range of different sizes than Original Equipment Manufacturers (OEM's) 7. There have also been concerns in other Europe states over the lack of testing facilities available. The UK, however, already works to standards at or above those proposed by the EU.

3.1.5 Standardised drum rolling tests have been proposed as an effective method for assessing tyre quality for both new and retreaded products for comparable applications.

3.1.6 Despite the adoption of existing standards and impending legislation, the overall image of retreads amongst potential adopters is still extremely poor. One procurement consultant within Government made the following points:
· He was not aware that retreads are tested to the same standards as new tyres
· Even when he was told that they meet the same standards, he indicated that surely they must have suffered some loss in strength due to their first lifetime
· It was up to the vehicle suppliers to stake their name and insurance liabilities against the quality of retreads, not the end purchaser. He was also not aware that retreaded tyres for commercial vehicles are supplied as Original Equipment on some new vehicles with specific requirements.

3.2 Testing & Quality Assurance - Commercial vehicle Tyres

3.2.1 It is accepted that commercial vehicle tyres are purchased with hard economics dictating the purchase decision. Within this economic structure will also be details which will not have escaped the notice of the more professional logistics outfits. A good corporate purchaser will already be looking at:
· Fuel costs per mile
· Cost of wear per mile
· Insurance costs per mile
· Related issues such as CSR, ISO14001 (see later)

3.2.2 All of these parameters would be adversely affected if retreaded tyres were of poor quality. Running costs would rise and well-run logistics outfits would consequently not use retreads. The fact that commercial vehicle retreads consistently pass economic and operational tests is good evidence that they can meet high quality standards. Commercial vehicle tyre retreaders sometimes downgrade the speed rating of their tyres from casing to remould, this is due to the long lifetime which they predict for their product.

3.2.3 Despite the good market for retreads in commercial vehicle tyres, there is still a market demand for single use economy imported tyres. This highlights that even for commercial vehicle operators there are still some operators who lack awareness of the real economic benefits of managing tyres as investments rather than one-shot consumables.

3.3 Testing & Quality Assurance - Car Tyres

3.3.1 Although the same economic arguments that apply to the commercial sector can work in favour of retreading car tyres, these tyres are often purchased solely on a distress or boutique basis. Long-term economics are not encapsulated in the process. In the case of the distress purchase, a subjective judgement is made, combining price, perceived quality, performance and availability.
For many purchasers this decision assumes that safety and quality are a given, and price and the recommendations of the tyre dealer influence the decision. In the case of the boutique purchase, brand and image perception dictate acquisition.
Further back in the hierarchy of information, but informing the decision making process, is the speed rating and the producer's marketing information on issues such as grip, wear, and fuel economy. This information is presented in a marketing context, and is frequently not given with supporting test data and measurement standards. It should be stressed that all tyres (new and retreads) are supplied with relevant technical markings such as speed ratings. It is, however, taken as reliable by the tyre seller, simplifying the job of selling to the customer, and the buyer takes such information on trust.

3.3.2 Comparison with the energy efficiency rating system for some white and brown goods (including fridges, washing machines and dishwashers) offers a useful example of how measurement standards can be applied. The consumer products have to comply with the European Union Energy Label if an Energy Label has been established for the product group in question. An official committee, comprised of civil servants, industry, test houses and CEN the European test standard body, works with stakeholders (including consumer groups) to decide the specification for the performance rating category (A, B, etc). Once the ratings have been agreed products have to be tested and the results are put on the publicised Energy Label.
Manufacturers are obliged to hold the information. The information is provided to the Commission through trade associations who aggregate the data so that progress with overall improvement can be monitored.

3.3.3 Car retreaders retread for one life cycle only, and do maintain the speed rating if the customer requires it. This is a positive point for their products.

3.3.4 It should also be stressed that all retread manufacturers are subject to stringent independent testing authorities (e.g. RAPRA) who test their products for quality and performance. In one case the tyres which are selected at random for this testing are also subjected to further analysis, including rolling resistance and tread depth. In addition, car retread companies claim that only a few tyres are returned because of user dissatisfaction. Data is not available from new tyre manufacturers, although recalls of new tyre batches are not unknown.

3.3.5 One key fact that should be emphasised is that the use of retreaded tyres is not discriminated against by insurance actuaries on UK vehicle insurance policies. The degree of detail with which insurance is calculated to avoid risk is well known, which supports the good circumstantial evidence from retail suppliers and retread companies that retreads present no safety threat to consumers.

3.3.6 Despite these positive properties of retread tyres the perception of quality amongst most consumers remains poor. This can be attributed to several different reasons:
· For retreaded car tyres the image battle dates from years ago, and must be rejuvenated to increase market share.
· For non-adopters who are responsible for tyre procurement there is likely to be questions asked of them if commercial and environmental benefits are ignored, leading some managers to a predetermination not to adopt.
· Some tyre retail chains do not stock or actively promote retreaded tyres and may inadvertently appear to endorse their negative image.

3.3.7 The basis for addressing all of these issues is hard evidence. However, there is limited information available, very little of what can be found is presented in sufficient detail to be analysed. In addition there is little funding available for filling in the knowledge gaps. It is noted that all passenger car tyres sold in the USA require a Uniform Tyre Quality Grading System rating to be marked on the tyre wall. Although not perfect, this system indicates a way forward for clarifying the quality issues in tyres sold in the UK.

3.4 Driver experience and related generic issues

3.4.1 The two service quality features which a driver might immediately notice for a tyre are handling and road noise.

3.4.2 Handling is associated with the structural response of the tyre casing, and the mechanical/friction properties of the tread compound. As there is no technical basis to expect changes in the tyre structure during retreading, and as retread compounds duplicate those of new tyres, handling behaviour for retreads should be similar to new tyres. There is in fact no information anywhere on claims, spurious or otherwise, to the effect that retreads handle any differently from new tyres.

3.4.3 Road noise is of increasing concern as traffic volumes continue to rise, degrading quality of life near roads. As most noise from a vehicle is due to tyres at speeds above about 50 kph, the noise generation characteristics of tyres are of significant interest to legislators.
The question of whether retreading raises the intrinsic noise properties of tyres is therefore an important one. Experts agree that there is no reason why retread tyres should handle and grip any less well than the corresponding new tyre. The structure of the tyre is not altered in any way by the retreading process, and any claim to that effect is not made on a firm basis. This comment also applies to claims made concerning the emission of noise from tyres. In fact most mentions of noise from tyres on the internet refer to the importance of a "low noise pattern" rather than any special compound related issues.
A recent study at Cambridge University identifies for the first time the mechanisms for tyre noise, showing the importance of the tread pattern and dynamic response of elements of the tyre structure. This probably forms a good basis for arguing parity in noise levels between retreads and new tyres.

3.4.4 There are few studies which have provided actual test data on noise performance, but where data has been collected there are conflicting results.8 One independent study, carried out by the Swedish national Road and Transport Research Institute and the University of Gdansk, performed a series of laboratory drum tests on retreaded tyres from Swedish retreaders and 58 new tyres of similar models. These tests showed that there are no significant differences in noise production and rolling resistance for summer car tyres (H, S, and V rated)

1. 3.5 Rolling Resistance & vehicle fuel economy for Commercial Vehicles

3.5.1 The rolling resistance coefficient depends on several factors, including:
· Tread material formulation (grip of the tyre material to the road)
· Tyre inflation pressure
· Speed
· Weight of the vehicle (load)
· Surface roughness of the road
· Thermal effects and ambient temperature
· Overall tyre design.

3.5.2 Data from a quality retread manufacturer (Bandvulc Tyres) indicates that fuel economy figures for commercial vehicle tyres may not be easily compared across brands.

3.5.3 A study by RAPRA quoted several studies which indicated the importance of tyre flexion in rolling energy loss, and how lower profile tyres therefore have an advantage in this respect. Clearly the retreading process only changes the rubber in the tread area of the tyre, which accounts for 33% of the rolling resistance of the tyre. Therefore if materials were to blame, increases in overall rolling resistance would need to increase the loss rate in the tread compound exponentially. It is felt that this would be unlikely from a materials point of view.

3.5.4 An interesting dichotomy emerges for commercial vehicle tyres, as there are claims that commercial vehicle tyre retreading will not increase rolling resistance because commercial vehicle tyres are constructed to fulfil different performance requirements than car tyres. This infers, albeit indirectly, that it is the casing structure which has the largest influence on energy loss, rather than the material in the tread.

3.5.5 This conclusion has implications for the argument that the stresses induced by retreading cause "damage", which leads to increases in the energy absorption in tyre structures. As there is no radical difference in commercial vehicle tyre construction, which would render them more immune to energy induced damage during retreading, it can be inferred that such changes do not take place for any tyre. The cost and construction of a premium new commercial vehicle tyre casing makes it ideal for retreading, a feature which has been promoted for many decades. In fact some manufacturers base their whole sales philosophy on the assumption that their new truck tyres will be retreaded as a matter of course.

3.5.6 It should also be noted that not all new tyres use silica and only a relatively small percentage of new tyres, especially in the commercial vehicle sector, are low rolling resistance tyres. In the commercial vehicle market many operators have reached the conclusion that the increased cost of "energy" type tyres is unproven when compared with any fuel saving. Driver actions and aerodynamics of the vehicle play a bigger part than tyres.
The views of the US retread industry are notably pertinent on this question. Their response, when informed that new tyre manufacturers in Europe hold that retreading increases rolling resistance, is that "This has never been an issue in the States. Its nonsensical to suggest that retreading intrinsically alters the rolling resistance of a tyre". 3.6 Wear in Commercial Vehicle Tyres

3.6.1 The key environmental advantage of retreading is that it prolongs the life of a tyre and therefore saves the energy and resources required to produce a new tyre. A truck tyre can be retreaded up to four times which prolongs its life to almost 600,000 kilometres (375,000 miles). There have been no formal studies comparing the lifetime of a retreaded tyre with a new tyre. The European Association of the Rubber Industry, however, used the assumption in their life cycle analysis that a retreaded tyre was equivalent to a new tyre being produced.8

3.6.2 In engineering terms there is no plausible reason why the retreading process should change the intrinsic wear behaviour of a tyre. The main structure remains the same, and the tread compound can be exactly matched to the original material. Commercial vehicle tyre retreaders do admit that sometimes their tyres do not last quite as long as new tyres. This increase in wear rates is thought to be less than 5-10%.
However, there are also indications that sometimes retreaded tyres last longer than new examples. The confusion probably relates to different use, different position on a vehicle, axle set-ups and the designs of the OEM specification tyres. Modern vehicles have axle set-ups which are designed with a strong input from the manufacturer of the chosen tyres for that vehicle.
These specification issues affect the wear, and probably other aspects of tyre performance. A retread built on a casing which is not made to this precisely tailored design will behave slightly differently. This is an area where more information from OEMs would help retreaders, and where a larger population of tyres entering the retreading process would ease the logistics of casing matching.

3.6.3 Again, if increased wear were a real issue, astute fleet operators would have ceased using retreads on economic grounds where wear rates meant that the initial purchase cost advantage of retreads no longer applied.

3.7 Maintenance Issues: Commercial Vehicles

3.7.1 There are no studies directly comparing the effect of maintenance in new and retread tyres. There is no published information to indicate that good quality retreaded tyres are more fragile than good quality new tyres. As has been stated previously, tyres are intrinsically extremely fatigue resistant structures, and if care is taken to remove operationally damaged articles from the raw casing stream, the resulting raw material for retread should be as structurally sound as new casings.

3.7.2 In general however, maintenance is acknowledged to have a major impact on the performance of tyres. Of key significance is the necessity to ensure correct air pressures and regular checks. One of the main reasons reported for tyre failures in commercial vehicles is under or over inflation, particularly for tyres in a dual configuration.9 Tyre pressure can also have a major impact on fuel use with a 7 psi decrease in tyre pressure resulting in up to a 5% increase in fuel use.1

3.7.3 The importance of good tyre maintenance, and therefore longevity, is widely recognised by large commercial fleet operators. However, one RMA member who services small-scale hauliers, has commented that they in particular do not generally recognise the importance of tyre pressure or other maintenance procedures.

3.7.4 The TRL study (1992) has indicated that tyres are frequently run in an over-inflated condition, due to operators playing safe when carrying variable loads. This is at variance with observations from some retreaders, who indicate that under inflation is the largest problem faced by a tyre in service.

3.7.5 Most failures in service are certainly shown to result from running flat or heavily under-inflated. This can arise from under-inflation, a slow puncture or fitting/valve defect, or a catastrophic puncture, the first two of which could be confused in inspection. The frequency of tyre pressure checks and the accuracy of pressure gauges will also contribute to the variability of tyre pressure.

3.7.6 Overall, results indicate that most tyre failures in service are due to inflation failure, independent of tyre type.

3.7.7 The highly visible sight of tyre debris on roadsides is one of the factors that is felt to have led to the negative image of retreads held by the public. In 1992, the Transport Research Laboratory carried out a study to verify whether this view had any real basis. The study involved a survey of the HGV tyre debris on the M4 Motorway and required complex analysis in an attempt to remove experimental bias.10 Due to the nature of the problem, the report could not draw strong conclusions, however a detailed analysis of the debris carried out by Transport Research Laboratory and the Vehicle Inspectorate was supportive of the assertion that "retreaded tyres are as safe as new tyres".

3.7.8 The study found that retreaded tyres were over-represented in the tyre failure debris found by the side of the road. This was assessed against the types of tyres found on vehicles, the axle positions of different types of tyres, and the numbers of vehicles observed. The analysis was able to give strong reasons why the over representation of retreads in the debris could be accounted for by factors other than any quality issues.

3.7.9 Of all the debris found, almost 75% was emitted from tyres which had deflated under load. Of these deflated tyres, 56% had clearly deflated because of penetration damage, 28% had deflated for other reasons, and 11% because of poor puncture repairs. Insufficient data is present in the report to allow a proper consideration of the mechanics of the tyre debris analysis procedure, but in-service damage was clearly a major controlling issue.

3.7.10 The gaps in the data were however significant, and the retreading population was an extremely old one (1991). Significant improvements in retreading quality and the reduction in commercial vehicle speeds (now restricted to 56 mph) will have changed any failure rates, and this work should therefore be repeated, possibly utilising different data sources and routines. These could include independent audits of tyres taken off fleets of cars and commercial vehicles, and of those received at retreaders.

3.8 Rolling Resistance & vehicle fuel economy for Cars

3.8.1 During its life an average car tyre requires about 200 litres of fuel to overcome its rolling resistance. This relates to approximately 15% of the total fuel consumption1,2. To try and reduce the impact this has on the environment, tyre manufacturers have developed energy efficient tyres, which can reduce rolling resistance by 10% or more1, 11 These efficient tyres are marketed on this benefit being produced using a combination of silica and carbon black in the tread compound rather than just carbon black.

3.8.2 One reason for the difficulty in assessing the relative fuel performance of new and retreaded tyres is the problem of comparing tyres of comparable specification and profile. Testing tyres of comparative quality and tread contact shape is likely to remain contentious as there are a number of variables that can affect changes in the tyre shape and performance during use.12 There is also some debate over how well testing methods replicate road conditions.7

3.8.3 Investigations during the BLIC study found that the average European retreading technology in 2000/2001 did not include retreading with silica technology.8 This led to their concern over whether the materials and energy saving environmental benefits of retreaded tyres are cancelled out by their higher rolling resistance during use. The break-even analysis carried out by the authors (Pré Consultants) showed that if retreading causes rolling resistance to be 8% higher, then this cancels out any benefits from using retreads.

3.8.4 The BLIC study also notes that: "A worn car tyre induces less fuel consumption than a new one, in a similar way for both kinds of treads (Carbon black & silica). The maximum reduction of the rolling resistance coefficient is 20% for a totally worn car tyre compared to a new one". This is probably due to the reduction in flexed volume of the worn tyre, reducing hysteresis losses.
Discussions during this study have highlighted the importance of this issue of the tyre volume under stress. There is some suspicion that the lower rolling resistance of some tyres derives more from their lighter structures than from use of any "magic bullet" compounds. However, it should be noted that it is probably easier to convince purchasers of a materials choice benefit as opposed to a benefit derived from more obscure engineering design changes.

3.8.5 This perception further highlights the need for careful comparison of rolling resistance between retreads and new car tyres.

3.8.6 Findings from the audit visits also showed that there was no reason why silica formulations could not be used for retreading if this was what the market desired, negating some of the conclusions drawn by the BLIC study. There are differing views within the RMA on its significance and the benefits offered. It should be noted that one car tyre retreader does employ silica compounds in certain specifications of retreaded tyres. However, silica compounds tend to lead to production difficulties because of wear induced by their relative hardness.

3.8.7 The conflict between reports, and the lack of a thorough methodology or referencing, means it is not yet possible to prove the effect that retreading has on the performance of car tyres. This is especially important given the use of economy data for marketing. However overall issues which emerge include:
· Tyres need to be tested under exactly repeatable conditions.
· Tyres under test need to be representative of that tyre during its lifetime (i.e. properly run-in).
· Tests need to be defined against a standard both for the test procedure itself, and the selection process for the tyres under test.

3.9 Wear in Car Tyres

3.9.1 There is no practical data available on wear of car tyres, but Colway Tyres, for example, have never had a complaint that a retreaded car tyre has been returned due to wearing quality. It should be stated that possible differences in basic tyre wear rates of 5-10% are fairly small in comparison to the effects of driver behaviour. Despite this, in marketing terms higher wear rates would be detrimental, and the issue does need to be properly bounded.

3.9.2 Again, the commercial vehicle and car tyre markets will differ in response to the wear issue. However, the market conditions for car tyres mean that an image of more rapid wear would be damaging to an already muddied economic case.

3.10 Conclusions: