Many customers neglect to ask for their shock-absorbers to be checked when they take their car in for a service. Oil, tyres, seat belts, brakes are checked but shocks are an essential part of the safety triangle of stopping, steering and stability.Here’s why...Most people are not aware of the danger inherent in worn shocks - particularly with increased loads that come with holiday travel.TRAVEL NAUSEAShock-absorbers are mostly associated with dampening a vehicle’s vertical wheel movement but they also keep the vehicle’s tyres in contact with the road. Over time, shocks can wear out – it’s a very gradual process so drivers are usually unaware of their diminished capability.Ineffective shocks greatly affect a car’s handling and braking, lateral drift and body roll through curves and corners. There’s also more chance of aquaplaning in rain. Almost unnoticed vibration can also cause travel nausea.Tiago Monteiro, official Monroe driver for the 2011 FIA World Touring Car championship and former Formula 1 driver for Jordan and Midland, tested the difference of new and worn shock absorbers and said:“It was really impressive to experience the effects of worn-out shock-absorbers. I was shocked by how much control of the car was reduced. The difference could be seen and felt, particularly in curves and braking.”Surveys indicate that one in four cars has worn shocks. In general Monroe recommends checking shocks every 20 000km and, if necessary, replacing both shocks on the same axle. The company’s Philip Lutz urges: “Car owners should have their shock-absorbers replaced every 100 000km for maximum performance and safety.”Vehicles that have done more than 150 000km should also have their suspension springs replaced, Lutz added.Some effects of worn shocks:• Increased braking distance.• Aquaplaning.• Increased tyre wear.• Failure of ABS/ESP.• Degraded road holding.• Headlight dazzle.• Car sickness.• Degraded towing capability.