The company used its drive-over tyre pressure monitoring system to monitor vehicles arriving at the event, at the NEC, Birmingham.
More than one in 10 was under-inflated by 20% of more – with the worst measured at just 9psi.
The service was offered free of charge to CV Show visitors, with the equipment located at the NEC's East car park.
Motorists obtained their results by confirming their registration number on a touchscreen at the WheelRight stand and taking a print-out of their individual tyre readings.
Almost 1,500 vehicles were checked on the last day alone, with 500 in one hour.
A similar under-inflation of 10% in a heavy goods vehicle, says WheelRight, could cost £1,000 a year in additional fuel and unnecessary tyre wear.
"The data we have collected clearly highlights that tyre pressure remains an issue of concern," insists John Catling, WheelRight's chief executive.
"Indeed, the lowest tyre pressure read by our system during our CV Show demonstration revealed 9psi – a worryingly and extremely unsafe result."