Not too many people know it - but when ww 2 started there was only so much latex in the country - and ALL tires were made of natural latex. But we were cut off from our source of that in SE Asia once the Japanese war got going. 
So ALL tires needed to be carefully conserved - and during the war you couldn't get tires for anything much - nor vacuum tubes for your radio either. 
We could have easily lost that war just based on not having latex for our rolling stock.