Rear Bump Steer – What It Is & How To Fix It

If you buy a 4Runner with the intention of modifying it, a suspension lift is usually one of the first items on owners’ lists. A little research will highlight the importance of aftermarket upper control arms (UCAs) and general wheel alignment when lifting a vehicle. However, there’s an important aspect of the rear suspension geometry that changes and is often ignored—the positioning of the rear panhard bar.

This crucial rear suspension component keeps your axle aligned side-to-side during articulation and daily driving. Left unattended after lifting your 4Runner, it can’t perform as intended due to rear bump steer and potential tracking issues.

What Is Bump Steer?

Bump steer occurs when a vehicle’s wheels steer themselves without driver input as the suspension moves up and down. This can lead to unpredictable handling, especially on rough terrain or when hitting bumps at speed.

Rear bumper steer is primarily caused by the rear panhard bar sitting at an angle post-suspension lift rather than parallel to the ground (the factory spec). In short, it causes the rear axle to swing in a pendulum-like motion during articulation rather than vertically. As the suspension compresses over bumps, the altered geometry can cause the rear wheels to track slightly left or right, leading to instability.

General Effects On Driving

• When the suspension compresses or rebounds, the wheels can feel like they’re skipping side to side.
• Bump steer can cause the vehicle to pull unexpectedly at higher speeds or on uneven surfaces, requiring constant corrections and making the vehicle more difficult to control.
• Constantly adjusting the steering due to bump steer can make driving more tiring, especially on long trips.
• Excessive bump steer can contribute to premature wear on steering and suspension components.

Dr. KDSS B.O.T.C.K

The Dr. KDSS B.O.T.C.K (Bolt-On Trackbar Correction Kit) is designed to correct the track bar angle, which is the primary cause of rear bump steer in lifted Toyota 4Runners and Lexus GX models.

When a vehicle is lifted, the track bar (panhard bar) moves out of its ideal position, causing the axle to shift left and right instead of moving straight up and down. The B.O.T.C.K raises the pivot point to bring the track bar closer to parallel with the ground, restoring natural suspension movement.

By correcting the track bar angle, the kit eliminates the erratic steering inputs caused by bump steer and ensures the axle cycles vertically rather than shifting side to side. This makes the vehicle more predictable and stable on and off-road.

The kit comes in two variants: Shorty and Regular. The primary difference is that the former is intended for smaller lifts (under 2.5″ in the rear) or those wanting maximum articulation. However, keep in mind that you risk binding up your suspension with the latter option if all other components aren’t set up correctly.

The Regular version is a bit taller and adds a second mounting hole to level the trackbar for lifts greater than 2.5″. For example, my 5th Gen 4Runner has about a 3″ lift in the rear, and using the top mounting hole gets the trackbar pretty close to level. The kit is also KDSS-compatible.

Installation Overview

Tools Required

• 1/2″ Torque Wrench
• 18mm & 19mm Sockets & Ratchet
• 21mm Wrench
• Rubber Mallet
• Strap or Bungee Cord

Unlike traditional solutions that require welding, this kit is bolt-on, making it accessible for DIY installation with basic tools. All hardware is also included. This article won’t cover the installation in detail, but if needed, you can check that out here.

The installation should take about 30 minutes, depending on whether your trackbar bolts are seized and need more persuasion to break them loose. Removing your spare tire from the factory location isn’t required, but it will create significantly more working room. Once everything is installed, the torque spec is 125 ft/lbs. on all (4) bolts.

Note: If you’re not super strong and will install this with your truck on the ground, the lack of leverage can make it hard to hit the torque spec.

Final Thoughts

Whether tackling rough trails or highway driving, the corrected suspension geometry that the B.O.T.C.K. provides improves ride comfort and handling, making it a worthwhile investment for off-road enthusiasts. It doesn’t break the bank (at least regarding modifications) and features a simple bolt-on installation requiring only a couple of hand tools.

I didn’t think a simple bracket would improve the feel of my suspension, but it honestly has. The greater stability is most noticeable on corrugated roads where the suspension is cycling fast, or on big bumps. If you have a lift and haven’t already installed this kit, I highly recommend it!