Is that why BMW driver training went to Bridgestone in this case? A couple of racing categories had a deal with Kumho and after a few cars went into the wall with tyre failures, one went to Bridgestone and the other to Dunlop. Either marketing deals or tyre issues can result in a brand change.
There is a Kumho V8 racing series....There is also another category that runs Kumho race tyres too...Can't remember the name but they are open wheelers
The super 2 V8 supercar series run Dunlops from memory..
Bridgestone not sure who runs them...
The 2 v8 series running the different brands I think is based around the limited testing policy for the main game to prevent an unfair advantage tp the really big cashed up teams....If you notice the super 2 cars are the older generation cars, whilst the Kumho series is older again...Call it the series that runs out of date race cars....
I am sure some marketting deal is done to run particular brands as well...It is also possible tyre failures have resulted in the brand changes...
As to why BMW went to bridgestone....If the test drivers are sponsored by Bridgestone, BMW will switch...Or it might be possible BMW have done a deal with Bridgestone to supply tyres for their cars...
The tyre industry, like all industries will try different ploys to get the consumer to buy their product...