MODIFYING VEHICLES WITH EPS
PSPA has issued a technical alert regarding Hi-Ride lift kit modifications vs OE Specifications
Power Steering Parts of Australia (PSPA) says that when modifying vehicles with Hi-Ride lift kits, problems are eventuating with how the Steering Rack Ends (Tie Rods/Inner Joints) are impacted by these modifications.
PSPA says the Rack End in most cases comes out of the Steering Rack Assembly on a horizontal plane to the Tie Rod End and then the Wheel Hub.
During normal driving of the vehicle, the wheels move up and down on the suspension and the Rack Ends, being a rod and ball assembly on a shaft fitted into a ball socket, allow the shaft to move off the horizontal plane. However, says PSPA, they are manufactured to only be able to move to a set angle that has been designed by the manufacturer as “standard suspension travel.”
With large changes in Hi-Ride lift kit applications as soon as the lift kit is fitted, PSPA says the Rack and Pinion assembly is raised and the Rack Ends (Inner Joints) are then operating downward at an angle close to maximum acceptable OE specifications.
As the vehicle suspension moves upwards, the downward angle of the Tie Rod becomes greater and in some cases exceeds the maximum OE spec, warns PSPA, which states that continuous moving up and down can then cause the tie rod shaft to come into contact with the ball socket which starts bruising the rod – over time, this becomes a weak point and can result in the shaft breaking.
PSPA reports evidence of this problem has been seen in some cases by the bruising on the metal shaft where it has been forced against the ball socket as well as being evident in broken shafts, with both OE and Aftermarket rods reported to have been susceptible to this damage.
This issue when reducing correct rack end ball articulation can also be made worse when the vehicle is fitted with long travel shock-absorbers that are commonly used by some 4WD enthusiasts, says PSPA, which states that Tail shafts and Constant Velocity units may also suffer from these modifications with some CV manufacturers now advertising units for Hi-Ride applications.
PSPA warns this has the potential to cause a very serious accident if it happens at speed, and advises mechanical workshops need to be aware when fitting these products and ask questions of their suppliers.
Figure one shows two sets of rack ends, demonstrating that one had broken on each set a short time after they were fitted to vehicles with Hi-Ride suspensions. PSPA notes these rack ends were manufactured by a very reputable company which has OE contracts and has been manufacturing rack ends for more than 30 years while complying to specific drawings, specifications and testing.
For more information from Power Steering Parts of Australia, visit www.pspa.com.au