Toe is the most critical alignment angle. It is also an angle that can change as the weight of the vehicle is transferred to the front or rear wheels. Engineers can tune the suspension geometry and toe to make the vehicle more stable under braking or initial turn in.
It is critical to remember that toe is not always zero or straight ahead. Some OEMs will specify a certain amount of positive or negative toe. These toe specifications could take into account bushing deformation as the tire is pushed rearward as speeds increase. Beyond that, a positive or negative total toe angle in the front or rear may make the vehicle more comfortable for the customer to drive.
It is critical to make sure that the tie rods are close to the same length after the toe adjustment is made. If one tie rod is longer than the other, it can indicate suspension damage, such as a bent steering arm or knuckle. Or, it could mean that when the total toe was adjusted, the alignment technician adjusted only one side to bring the vehicle into specification. It could also cause bump steer.
Inspecting Tie Rods
If the inner or outer tie rod for either a front or rear tie rod or toe link is bent, don’t adjust for it or try to bend the component back into shape. When a component is damaged, its strength and structure have been compromised. Any further bending or heating will only damage it further.
Excessive tie rod play is difficult for any driver to ignore. It may start with tire wear on the inner edge of the front tires. Next, there could be a slight knocking during braking or acceleration.
The No. 1 killer of steering tie rods is damage to the boots. Once a boot is damaged, the joint gets contaminated by dirt and debris that can wear the ball and socket. If you see a tie rod end with a damaged boot, recommend replacement of the tie rod.
The “dry park” method on a drive-on lift is the best method to check for worn tie rods. Tie rod wear on the ball and socket occurs in a defined range of motion. The wear typically occurs in an oval pattern versus a perfect circle. If the suspension is at full droop, the ball and socket may feel like it has no play.
During a dry park test, the inner tie rod ends on steering racks should be tested for excess wear by listening for a knocking or clicking noise as the steering wheel is turned. If the vehicle is on turn plates, have an assistant lock the steering and try to move the tire to detect any play. Remember that small amounts of wear in each tie rod end can add up to a major variation in toe angle.
If you use a pry bar and brute strength, your inspection could be influenced by the bushings in the control arms. If you use a set of “water pump pliers” to compress a tie rod, it will give you a false reading almost every time and is not a measure of wear for some types of tie rods. Even some new tie rods will compress.
If you find play at the inner tie rod, confirm that it’s the joint that is worn and not the rack bushings. If the rack boot allows it, squeeze the boot to feel that the joint is the problem and the rack isn’t loose and moving in the housing. This will also give you an indication if the rack boot needs to be replaced. It’s always a good practice to replace the boot, but you may find it’s easier to obtain a tie rod end.
Chances are you are seeing more aluminum knuckles and suspension components in your shop today. In order to secure the tie rod stud to the knuckle, it requires a different design than the conventional tapered stud. Most aluminum knuckles use torque-to-yield (TTY) studs. TTY tie rods are usually installed dry. Do not apply any oil, grease, assembly lube or sealer on the stud or tapered bore. Lubricants increase the torque load on the bolt or stud, which may overload and stretch a TTY bolt too far, causing it to break. If a TTY fastener is over-tightened, it can stretch beyond its limits and break. The increased torque can also cause the female part of the taper to crack if too much clamping force is applied.