BRISTOL, Tenn. (AP) — NASCAR will try to run its first Cup Series race on dirt since 1970 on Monday after heavy rain swamped Bristol Motor Speedway. The converted track already was facing challenges before torrential overnight rain flooded the grounds surrounding the speedway. The Goodyear tire provided for the Cup cars doesn’t seem suited for the dirt surface and NASCAR is worried about multiple tire failures when the event finally goes green. The muddy track currently is too thick to avoid caking driver windshields. But the dirt has taken on enough water that thick dust may not be a problem Monday.