MORE than 8,000 cars have failed the NCT so far this year because their tyres were fitted the wrong way around.
Untrained and 'unscrupulous' fitters are being blamed for the dangerous mix-up which could mean a car takes much longer to stop in wet conditions.
Large numbers of modern tyres have treads with special grooves for better grip in wet and slippery conditions, to reduce stopping distances and avert accidents.
These 'directional tyres' are only supposed to be fitted in a specific direction, with an arrow on the tyre wall showing the direction it is designed to turn.
But more than 8,000 had the arrows facing in the opposite, incorrect direction when NCT tested, new research reveals.
Incorrect fitting heightens the risk of an accident because the tyres have substantially less grip on wet roads and a backward-fitted tyre leads to an NCT re-test.
Tyres are now the second most common reason for failing the NCT, after problems with front suspension.
For the first time, tyre outlets are being licensed as safety concerns grow, not just for 'backways' fittings but over the numbers of part-worn tyres being sold.
All staff of licensed retailers will be independently assessed and accredited.