IOP Conference Series: Materials Science and Engineering PAPER OPEN ACCESS Effect of plus sizing on driving comfort and safety of users To cite this article: I. Hetmaczyk 2018 IOP Conf. Ser.: Mater. Sci. Eng. 421 022013 View the article online for updates and enhancements. This content was downloaded from IP address 148.251.232.83 on 07/01/2019 at 06:52
Effect of plus sizing on driving comfort and safety of users I. Hetmańczyk 1 1 Opole University of Technology, Prószkowska 76, 45-758 Opole, Poland e-mail: i.hetmanczyk@po.opole.pl Abstract. This paper contains the results of a track test into the performance of tires manufactured by a leading brand applied on a surface with different conditions (dry and decreased friction). The research applied new tires in a common size (185/65R14), half-worn tires with the same size and replacement tires size 205/45R16. The tires were subjected to experiments involving stopping distance, average speed as well as maximum values of acceleration and deceleration. 1. Introduction Over the period of the last century and a half, the design of tires and rims has evolved to a considerable degree. The early vehicles had spoken wheels with large diameters, something that was came to vehicles from horse carriages. As a consequence of the increasing vehicle speeds, they were quickly replaced by pneumatic wheels, as the latter secured higher comfort coupled with longer service life of the vehicle chassis. Nevertheless, such designs still incorporated spoke wheels with a large diameter, e.g. 21 inch (Ford T) combined with small tire with and rim widths. In the successive years, considerable improvement of surface quality occurred and vehicles with greater weights were able to travel at greater speeds. This was also accompanied by the development of braking systems required to stop the faster than ever vehicles [3]. The drums followed by discs were installed in the wheel axles, and this change determined the further evolution of the wheel and tire design [7]. After World War 2, the nominal rim diameters gradually decreased. Table 1. Evolution of nominal rim diameter in successive generations of Astra hatchback. Generation Production year Axle base (mm) Rim diameter in the Alternative base model rim sizes Astra I (F) 1991 2517 13 14 Astra II (G) 1998 2614 14 15 Astra III (H) 2004 2700 15 16 Astra IV (J) 2009 2685 16 17 Astra V (K) 2015 2662 16 17, 18 In the 1960s and 1970s, a majority of passenger cars had wheels in which the nominal rim diameter was 13 inch, whereas Polish Fiat 126p had 12 inch wheels and in the Mini car the diameter was 10 inch. However, since that time, the nominal rim diameter started to increase again (Table 1) at the expense of the tire aspect ratio. This was mainly due to the need to increase the efficiency of the braking system by increasing diameters of brake discs. These design changes were initiated by car manufactures and have rational justification. The situation looks different for the case of tuning Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by Ltd 1
upgrades that are undertaken by the vehicle owners. These are guided by aesthetic considerations and the reasons are hardly ever associated with the improvement of safety characteristics. In most cases, the modifications involve replacing the wheels with ones having a greater width (Figure 1). Figure 1. Summary of tire sizes and nominal rim diameters for similar external wheel dimensions. This type of upgrade leads to an increase of rolling resistance and drag forces [6] as well as wheel s moment of inertia [2, 4], which is followed by an increase in fuel consumption [2]. However, it is not very common among car owners to take into account the aspects associated with tuning upgrades that can affect the safety of the driver and the passengers [1, 7]. In materials available online, we can find information regarding the reported reduction of stopping distance as a result of using larger sized wheels. This paper aims to verify some of such claims, as it contains the results of a comparative study involving tires with various widths (tire plus sizing) and in different condition in terms of wear pattern. The results were gained throughout track tests and the emphasis is put on the effect of these parameters on the safety of road users. 2. Initial claim This study adopted an initial statement in the following form: each tire size, whose use is permitted in a given vehicle, provides a similar level of safety and driving comfort. An attempt was made to verify this statement by performing tests on a track that applied standard size tires forming original equipment tire in a given model and a plus size substitution with the same tread design. In addition, the experiments additionally applied a tire with the standard size, whose level of wear was estimated at 50% on the basis of tread depth. The paper contains a summary of the results of road test conducted on a maneuver track with concrete surface, skidpad with a sprinkler system. 3. Research The measurements have been conducted by application of a passenger car carrying three people and measuring equipment and alternatively installing various tires in terms of size and wear. All the tires were the same brand and tread and were produced by a leading tire manufacturer. The equipment applied in the track tests included Datron DL-1 head for contactless surface measurements, DagBook 100 data acquisition unit and a portable computer. This use of this equipment provided the accurate measurements of the traveled distance, as well as speed and acceleration details registrations. The research was performed on a runway of a former airfield, on a concrete surface and on a special skidpad covered by epoxy paint to provide the conditions of reduced wet grip performance as a result of using a sprinkler system. The experiment applied produced by a leading tire manufacturer with a size 185/65R14 86H, and the same type of tire after 30 000 kilometers of service (they had 50% of original tread depth) and a substitute sized 205/45R16 87V (Figure 2). 2
185/65 R 14 86H (new) 185/65 R 14 86H (30 000 km) 205/45 R 16 87V (new) Figure 2. Tread pattern of investigated tires The following program of measurements was performed: on a dry surface: - starting - mean acceleration - braking from v=60 km/h - total stopping distance - slalom - average speed data gained on the course on a wet surface: - starting - mean acceleration - braking from v=60 km/h - stopping distance - braking in a curve from v=60 km/h - stopping distance - slalom - average speed data gained on the course Each trial was repeated six times, and only three results were taken for the analysis (the best and two worst results were rejected). A summary of the results is found in the tables below (Table 2, 3) and presented in a graphic form in Figure 3. Table 2. Comparison of the results of track tests. Dry surface Wet surface Braking Starting Slalom Braking Braking Starting Slalom Concrete Concrete Concrete Skidpad Skidpad, curve Skidpad Skidpad Tire size [m] [m/s 2 ] [m/s] [m] [m] [m/s 2 ] [m/s] 185/65R14 86H (new) 16.23 4.03 15.71 37.73 49.68 2.02 9.99 185/65R14 86H (30 000 km) 15.55 4.06 14.91 55.22 69.84 1.89 7.98 205/45R16 87V (new) 16.19 4.05 16.00 41.54 56.37 1.99 8.96 3
Table 3. Comparison of the results of track tests (in per cent). Dry surface Wet surface Mean Braking Starting Slalom Braking Braking Starting Slalom Concrete Concrete Concrete Skidpad Skidpad, curve Skidpad Skidpad Tire size % % % % % % % % 185/65R14 86H (new) 185/65R14 86H (30 000 km) 205/45R16 87V (new) 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 104.41 100.73 94.92 68.32 71.13 93.68 79.86 87.58 100.28 100.61 101.84 90.83 88.12 98.38 89.65 95.67 Figure 3. Comparison of results of the track test. 4. Conclusions On the basis of the above results (Table 2, 3), we can see that in terms of handling, a vehicle with wider tires does not demonstrate considerable advantages over the standard tires on a dry surface. Only during the slalom, an improvement of the recorded time on the course was nearly 2%. This confirms the common opinion regarding better handling characteristics of cars with wider tires in curves. For the case of the testes involving stopping and moving off, the results were nearly identical for both tire sizes. In the braking stopping test, the best result was obtained for the tires with the halfworn tread. This can be attributed to the greatest contact surface between this tire and the surface. However, the lack of a similar relation for the test of moving off from a stop comes as a surprise. For wet surface, the deterioration of the results was recorded for both the tires with a larger width and half- 4
worn tires. The result for the wider tires was average of more than 8% worse, whereas for the worndown tires, it was over 22%. It is clear that the tread depth of around 4 mm does not provide the sufficient capacity to channel away large volumes of water. It was also found that wider tires performed considerably worse in comparison to the standard wheel diameter despite having new treads with a depth of 8.5 mm. For the case of wider tires, the manufacturers need to find a comprise between tire-road interface, which decides on the stopping distance and the size of the circumferential and slanting grooves, which channel water away to maintain good traction. In this case, the manufacturer s design gave priority to the better grip, which resulted in the longer stopping distance on a wet road but provided a comparable braking distance to the standard sized tire on a dry surface. The results of the research do not confirm the initial statement made early in this paper that each of the tire sizes whose use is permitted by the vehicle manufacturer in a given model provides a comparable level of safety and driving comfort. The increase of the tire width can lead to the deterioration of some of the handling parameters of the vehicle to a various degree (depending on the geometrical pattern applied in the tire tread). References [1] Greibe P. 2007 Determination of breaking distance and driver behaviour bases on breaking trials. Trafitec, Danmark [2] Hetmańczyk I. 2002 Study into parameters deciding on the energy performance of a passenger car in driving cycles. Ph.D. thesis (in Polish), Opole. [3] Mitschke M. 1987 Dynamic car characteristics. Powertrain and braking systems (in Polish), WKiŁ, Warszawa. [4] Orzełowski S. 1995 Experimental study into cars and their assemblies (in Polish), WNT, Warszawa. [5] Rievaj V, Vrábel Jan, Hudák A. 2013 Tire inflation pressure influence on a vehicle stopping distances. International Journal of Traffic and Transportation Engineering, No 2 [6] Siłka W. 1997 Energy performance of car motion (in Polish), WNT Warszawa. [7] Wrzesiński T. 1978 Braking in automotive vehicles (in Polish), WKiŁ, Warszawa. 5