Racers and tuners will often focus on the rear of a race car for anything suspension related since it holds the key to creating the best passes possible. While the rear suspension is vital in drag racing, the front suspension, specifically the rod ends, need their fair share of attention, too. Making sure your tie rods are functioning properly can not only help you lower your E.T., but it will also keep you safe on the track.
If you’ve ever driven or ridden in a street car that has tie rod end issues you know it can cause the car to not track straight, have stability issues, or emit awful vibrations. All of these problems are annoying and can become a safety issue in a street car, but in a racing environment tie rod concerns can bring about some dangerous conditions.
John McCrory from Aurora Bearing Company puts things into perspective when it comes to what kinds of problems worn tie rod ends can cause in drag racing.
“Think of this: looking for that last fraction of a tenth, you set a perfect front end alignment to minimize tire scrubbed caused by front toe. Yet, that perfect static alignment is spoiled by dynamic toe change from sloppy rod ends. Another aspect of worn steering rod ends you need to think about is top end control of the car on deceleration. You want a car to launch straight and often focus on the rear suspension to ensure the car launches this way. What about when you’re slowing the car at the top end, especially if you rely on brakes to bring the speed down? Again, the car should track true, and not dart. Worn tie rods can cause your road car to dart under braking, and they also cause it at the track,” McCrory explains.
Regular inspection of tie rod ends is the best defense against a part that is beginning to wear too much. The two main types of tie rod ends that are used in a suspension are PTFE-lined rod ends and metal-on-metal joints. You can tell when it’s time to replace a PTFE lined joint because they begin to develop play and don’t feel as tight. Metal joints can be a little more difficult to diagnose as needing to be replaced.
“Good non-lined joints should have a maximum of about .004-inches end play when new. If you use metal-on-metal joints, it’s up to you to determine when a greater clearance becomes an issue. Certainly, the car can tell you if you let it. Do you feel play in the steering, either statically, or at speed? Do you see evidence of tire scrub or wear? The same alignment and component wear that influence tire wear on a road car happen on a drag car, just at much shorter intervals of driving distance,” McCrory says.
Another point to keep in mind when trying to ensure the health of your tie rod ends is the level of stress they are put under. A tie rod end isn’t designed to be the travel limiter for your front suspension and should never be subjected to that level of stress. This is why rod end misalignment and travel is important to take into consideration when you’re selecting parts.
“Once you reach the joint’s limit of travel, you start applying a bending load to the part. Rod ends are designed to be best used with radial loads, or loads along the direction of the shank. Using them beyond their misalignment or travel limits places a bending load on the parts. In a severe case of bending overload, a part can break. In lesser cases, you can create stress risers that can hasten breakage by fatigue down the road. So a bent tie rod end can be one sign of over misalignment. Another is a distortion of the race or a dent in the race from the impact of a fastener with the bearing race,” McCrory says.
McCrory explains how you can deal with the situation if you find yourself run out of rod end misalignment when building a front suspension tie rod ends.
“You can use a rod end with increased misalignment capabilities. There are rod ends that are considered high misalignment rod ends. These will have balls with extensions and a head width that is narrower than conventional joints. However, these also feature a shank or thread size that is bigger than the hole or bore size. If your car uses a rod end that is 3/8- x 3/8-inch size, a high misalignment 3/8-inch joint with a 7/16-inch shank will require new tie rods or related components.”
You do have some choices in the type of rod end you use for the front suspension. A rod end takes the form of a three-piece joint that’s commonly referred to as an aircraft joint. These joints consist of a body, ball, and a race. The alternative is a two-piece body that has the race-way formed into the body of the joint.
“The two-piece joints have a narrower body width than a three-piece — this allows a greater ball misalignment. For the last decade or so, many manufacturers have been offering two-piece joints with heat-treated alloy steel bodies. As such, they are of similar strength to three-piece alloy body aircraft joints. Additionally, they are widely available with zero clearance self-lubricating PTFE liners. The reason to consider this style of joint is that they normally offer about 8- to 10-degrees more total misalignment than an equivalent three-piece joint,” McCrory explains.
Making sure you’re managing the wear of your tie rod ends can ensure you’re getting the maximum performance possible out of your suspension. By replacing worn tie rod ends you will help your racecar handle better and be safer in every section of the dragstrip.