When the tender was answered and won in 2009 Kumho put forward the V70A as the specified tarmac tyre for the one and only tarmac round. At that time Kumho was not aware that a/ the V70A was not load rated for the Eva 10 Lancer and that b/ there would be any Evo 10s running in the ARC section at Rally Tasmania. When Kumho became aware of the entry of two Evo 10s it was flagged that they require a 95 load rated competition tyre. Kumho Australia immediately contacted Kumho motor sport engineers in Korea to ascertain whether the V70A could be used with Evo 10 and the engineers told them that the tyre was not load rated for Evo 10.
As such, with a relatively short time to the Tasmanian round, it was then necessary to find a tyre that would be suitable for all cars including the two Evo 10s. The CO3 was chosen; this is a tyre that has won rounds of the Irish Rally Championship and the British Tarmac Rally Championship.
As it was a short lead-time and there was only a small number of CO3s in stock here it was decided to airfreight sufficient numbers in from Korea. Korea did not have enough stock and the shortfall was made up with stock from the UK. Here was where the major problem arose, a difference in nomenclature meant that in Korea the B compound is the hard compound, in the UK the B compound is the medium hard compound, so while B compound was specified for all the tyres Kumho received hard compounds from Korea and medium hard from the UK. It was a human error exacerbated by the short lead times and pressure to have enough tyres here on time for the critical open round, again we emphasize the only tarmac round in the title.
The problem was only identified on the Friday, one week ahead of the Rally Tasmanian round, Kumho requested stock from Korea which could have been air freighted over the weekend, however there was simply no stock available and air freighting all medium hard compound from the UK would not have arrived here in time.
As a result of this Kumho Australia and the ARC has put in place a system to ensure that this situation does not arise again with a number of checks and balances now in place. Off the record, if the tarmac round had been the final round of the year then this problem would not have occurred, that is not an excuse that is the reality.
2. Why did Honda have tyre failures?
There were two key issues relating to the tyre failures on the Honda, firstly there was no time to test on those tyres before the rally and if that had been possible Kumho would have ascertained that the Honda needed a hard compound not the medium hard.
Secondly, the Honda was not set up for the Kumho CO3 initially. The Kumho CO3 has a very square shoulder and needs very little negative camber. The problems were with blistering on the inside edge of the tyre. Once this was identified the Honda engineers were able to pull some negative camber out of the front end of the Honda. Once this was done the situation was greatly improved. The blistering only occurred on the inside 30 to 40mm of the tyre when the geometry was changed the blistering stopped.
3. Why did some competitors have a tyre failure? Â
Difficult to answer since the punctured tyres were driven on while deflated and badly damaged and because one or two competitors would not allow Kumho motorsport coordinator John Mills to take the tyre off the rim to inspect, it is hard to see what causes a tyre to puncture without this analysis. Simon Evans had a tyre fail on Sunday and allowed the tyre to be taken off the rim and there was some evidence of an impact on the inside of the casing. Other drivers reported there were some rocks on the road and the edges. Short answer, we think some of the punctures were caused as a result of drivers dropping a wheel off the tarmac on to a broken edge or striking a rock damaging the tyre. This is only speculation because as we said some drivers would not allow Kumho to take the tyre off the rim for inspection.
4. Why were some tyres dated more than 18 months old?
Kumho motorsport tyres have a shelf life of up to 3 years. The tyres had to be sourced at short notice from two different global locations as we said and Kumho was not expecting old stock, but that is what we received. While they were still serviceable and usable under Kumho guidelines, to ensure customers are not disgruntled by older manufacturing dates on tyres, Kumho Australia has put a process in place to make sure it doesn't happen again. This was another factor that slipped through the cracks in the short lead time available.
Summary
Kumho Australia is committed to making the tyre contract with the ARC work and is working hard to ensure that none of the problems at the opening round arise again.
For the remaining five rounds of the ARC on gravel there are sufficient stocks of the three different gravel tyres available for all cars for all rounds, testing has been carried out and Kumho is confident that the challenges encountered in Tasmania will not be encountered at any of the remaining rounds.
This is not to say that drivers will not have punctures and damage tyres, that is an unavoidable possibility particularly in competition on loose surfaces
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