Bump Steer? How To Fix: Measure Your Drag Link and Track Bar to Make them Parallel
Bump-steer Solutions and Causes, by Kevin from KOR
Cause: The Drag Link and Track Bar on a coil-sprung vehicle are out-of-parallel. (affects some coil-sprung Dodge, Jeep, and Ford models)
Result: You hit a bump, and the steering wheel moves first one direction, then the other direction. The steering wheel will also pull out of your hands when you hit the brakes, sometimes DIVING into the next lane over. Scary stuff!
Solution: You need to make the Track Bar and the Drag Link parallel to each other....but it's not quite that simple.
Explanation: When a coil-sprung vehicle's front suspension compresses, like during heavy braking, or over speedbumps, the front axle is forced to move in the arc that the track bar pushes or pulls it in. The track bar is a solid chunk of steel, and it's not compressing or stretching very far, lol, so the axle moves laterally (left/right) following the arc of the track bar. From the factory, the Track Bar upper mount and lower mount were more or less parallel with the pavement. When you hit a bump, VERY little side-to-side movement happens, because the TB is nearly parallel with the pavement. However, when you lift a vehicle, the axle is moved away from the body/chassis. This moves the track bar mounting points further away from each other, and moves the UPPER track bar mount further upward, and as a result, out-of-parallel with the pavement. As long as the drag link's (also known as a "steering link" or, incorrectly labeled sometimes as a "tie-rod"...) upper mount is moved *the same* distance upward (typically when installing a lift, both would move the same amount upward) as the upper mount on the track bar, the bars are kept parallel...(though they WILL both need to be lengthened slightly). End result: very little, if any, bumpsteer. All good! However, old ideas never die...and some folks think that a dropped Pitman arm (the steering arm that the drag link attaches to at one end, and which attaches to the splined shaft on the steering gear at the other end) should be added when lifting EVERY vehicle. On a leaf-sprung vehicle...this makes perfect sense! You WANT the drag link as parallel to the factory setting (parallel with the pavement) because the axle cycles upward and townward following the leaf spring mounts, which is perfectly straight up and down. However, on a coil-sprung vehicle, the axle follows the arc of the track bar, so adding a drop pitman arm is one of the worst things you can do...because it CREATES bumpsteer! Remember, you want the track bar and the drag link to be nearly parallel. Here's how you do that... Tools needed: Tape measure, a print-out of this article, and a pen What you want to do to resolve bump steer on a coil-sprung vehicle is make the amount of DROP the same amount on both bars. If the drag link drops 4" from left to right, then the track bar should drop 4" from left to right. Measure from the pavement up to the pivot point of each, and fill in the numbers here: Lower (Pass. Side) Track Bar mounting bolt to pavement: Upper (Driver Side) Track Bar mounting bolt to pavement: Lower (Pass. Side) Tie Rod End CENTER on Drag Link to pavement: Upper (Driver Side) Tie Rod End CENTER on Drag Link to pavement: [caption id="attachment_5203" align="aligncenter" width="1024"]
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Great info…super interresting….real pro…😉
great article thank you for your information. Will measure my set up soon and see how off it is. I know it’s off I installed a 4 in lift pitman arm with no track bar offset. It’s OFF !!!!
The theory of this is correct but is kind of misleading. Parallel is not the best verbage and the picture is very misleading due to the crossover setup instead of the y link style and the fact I can’t see the track bar in this picture. The closer you can make the track bar and drag link be on the same plane is what you’re shooting for, not to make them parallel. That’s why for Tj’s, a high steer bracket for the axle is the best way to go to fine tune the track bar angle and position.