In a sport where good tyres are essential, Dean Amos relies on four-year-old rubber that is past its best after just one kilometre of racing. A tyre shortage will be the biggest challenge for Amos as he bids for an 11th outright win – and possibly a lap record – at the 30th anniversary Historic Leyburn Sprints on 15-16 August. “None of us can get the correct tyres we need from Europe; they’re not making enough so we make do by swapping them arou…