A late fightback from Newcastle Diamonds kept them within two points of Glasgow in the KO Cup quarter-final - to set up a tight second leg on Monday night.
The Tigers had raced into a 10-point lead by heat 12 as they looked to be running out comfortable winners at the Peugeot Ashfield Stadium on Friday night.
But the visitors scored two 5-1s in the last two races to pull the gap back to just two points at 46-44.
The Diamonds may now go into the return leg as favourites to qualify - though Glasgow hope to welcome back more of their regular riders after having to rely on four guests due to injuries and fixture clashes.
Stewart Dickson's men suffered more bad luck pre-meeting when talented Englishman Kyle Newman - who was guesting for Nike Lunna - withdrew through illness, forcing the team boss to call in Tero Aarnio, who has had limited experience on the Ashfield circuit in recent years.
Overall it was a decent performance from the Tigers, barring the final two heats, with heatleaders Richie Worrall, Aaron Summers and Ricky Wells (guest) all bagging important wins - along with Aarnio and reserve guest Richard Hall.
But with Hall and fellow guest reserve Connor Coles having to race in heat 14, the stronger visiting pairing of Ludvig Lindgren and Ben Hopwood took a maximum, before the Tigers' suffered the same result in the last race.