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HOW TO: Re-Index Your Torsion Bars: Further Explained

7846 Views 3 Replies 2 Participants Last post by  robcarync
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There is already a how to on re-indexing the torsion bars, which is correct, but I aim to fill in some gaps as far as why this needs to be done and what is happening at a conceptual level, and answer some commonly asked questions. I hope I am not stepping on anyone's toes by covering the same material. The original How To is found:

I really try to go into the conceptual level of what is going on here, assuming little to no knowledge of a torsion bar suspension system. There is a LOT to read, but there are also a LOT of questions asked on this topic.


I am a firm believer in the philosophy of not doing anything to your car unless you truly understand what it is you are doing. That is why I am often times longwinded and over think things at times. That is also why I have these prerequisites that I suggest you understand before you touch a wrench to your torsion bar adjusters.

Before going into the actual process of re-indexing, or re-phasing, an Xterra torsion bar, you really need to understand how these things works on a conceptual level. This how to article is written to completely encompass everything involved with adjusting the torsion bars on a first gen Xterra independent front suspension.

Firstly, the torsion bar is located under the car and runs from the lower control arm (LCA) under the front tire all the way to a cross member, which is located near the rear of the front doors. A torsion bar is a steel bar with splines on the ends, which is anchored into the lower control arm on the front, and an adjuster lever inside the cross member. Both of these anchors stick out to the sides in opposite directions, which act as a lever arm. The following diagram shows the overall schematic and location of the torsion bar’s function.

Now, a torsion bar is a spring. Most people think of a spring as a standard coil spring…you push down on it, it pushes straight back at you. A standard coil spring has a direct relationship with how far it is compressed. For instance, if you push down 1 inch, the spring pushes back with 5 pounds force. A torsion bar uses the inherent stiffness of the material to resist motion. Instead of a linear distance, a torsion bar has an angular displacement and a resulting torque. The same direct relationship applies for a torsion bar. For instance, if you twist the bar by 1 degree, the bar twists back with 5 foot pounds of torque. (Force displacement numbers are made up)

What is the point of this? When you adjust your torsion bars, you are NOT TIGHTENING the bar. The bar will have the same angular displacement because it is holding up the same amount of weight! You may crank the adjuster bolt upwards into the cross member, but the result is the lower control arm mount is pointed down, which lowers the tire and raises your ride height. This results in the same internal force in the bar, and the same angular displacement or twist in the bar. Adjusting your torsion bars will not stiffen the front suspension. The ride quality will not be changed, except for needing an alignment and the possibility of hitting the bump stops on the upper control arms (UCA).

Now, let’s take a look at the bump stops in the front. The UCA will hit this black rubber dome bump stop when the tire droops too low (or the frame bounces too high). Whenever you are adjusting ride height, you need to ensure that you have at least 0.5 inch gap. It is important to note that the physical gap is not what is important. The bump stop is just the easiest place to measure. The issue is with aligning the front tires. If the control arms are too low, or ride height too high, the tires can’t be properly aligned. This means that low profile bump stops can help improve tire droop, but raising the suspension further will compromise your alignment and tire wear.

Secondly, if the bump stop gap is too small, or nonexistent, the ride quality will be quite harsh. Now wait a minute you may say…The UCA contacts the bump stop when the tire droops down...doesn’t that mean the car would be off the ground for it to hit the bump stop? Not necessarily. It all goes back to the concept of a spring. When you push a spring down and let it go, it does not simply go back to the original free position. It snaps back and forth until a damping force will resist this motion. That is where your shock comes in, but no vehicle vibration will be perfectly damped; there will always be a little bit of back and forth motion. So if you hit a bump in the road, and your tire snaps upwards, the torsion bar snaps it back down. Depending on how good your shocks are, the UCA will travel below the original ride height or static position and can hit this bump stop. It may not lift the car off the ground, but it is something you can feel. I feel it on a daily basis.

Moral of the story: Always leave at least 0.5 inch gap between your UCAs and your stock bump stop, even if you have aftermarket UCAs or low profile bump stops. Your tires and passengers will thank you. Even with re-indexing, you must always stop lifting once you have a 0.5 inch gap, measured at the stock bump stop.

Introduction to Re-Indexing

Re-indexing your torsion bars is the process of removing the torsion bar from at least one of the anchors, rotating the bars position in the anchor either direction (typically 1-4 splines), and reinstalling. This process changes the position of the adjuster finger for a specific ride height.

This process is used to solve two specific situations:

1) You have more than 0.5 inches between your stock bump stop and your UCA, you want to raise your adjuster, but the adjuster lever is too deep in the cross member and can’t go any further. You need to remove the adjuster bolt, remove the torsion bar from one of the anchors, and rotate the bar so the adjuster lever is further away from the cross member. This allows the adjuster more room to lift the vehicle.

2) You are at your desired ride height, you have your correct bump stop gap, but your adjuster is hanging down below the cross member. You need to remove the adjuster bolt, remove the torsion bar from one of the anchors, and rotate the bar so the adjuster lever is closer to the cross member. This will allow the adjuster lever to be inside the cross member when you readjust to your desired ride height.
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How to Re-Index

Ensure your tire pressure is even on all four corners. Ideally you want even tread wear across all of your tires. You are adjusting to ride height, which should be measured at the seams below the doors; the seam that would be parallel to the floor boards of the truck. Ideally, you want a 1-1.5 inch rake with the front being lower.

Here is my truck. I have aftermarket UCAs from [url="]4x4 Parts[/url] to allow for 3 inches of front lift. I have a large bump stop gap, but my adjusters are maxed out, hitting the top of the cross member.

Using a floor jack, support the front of the vehicle under the differential. This supports the weight of the vehicle so the torsion bars don’t have to. The torsion bar adjust lever is located around the middle of the truck. There is a long bolt pointing upwards, through the adjuster lever, and through a hole in the cross member. There are two nuts on the top side of the cross member. Using a 19mm open end wrench, loosen the top nut just barely. If you are good, you can use one wrench, hold both of the nuts on the top, and use a socket wrench to remove the adjuster bolt from below (counter clockwise rotation while laying on your back, looking up at car).

Once the bolt is almost falling out, note the position of the adjuster lever in comparison to the cross member. I want to rotate my adjuster away from the cross member so I have more room to lift my X. Starting further away from the cross member means the adjust lever will hit the cross member after more threads are turned, which means a higher ride height.

Completely remove the adjuster bolt and associated hardware. Take a wire brush to it to clean it up some. Have anti-seize ready for when you reinstall the hardware.

Use a hammer and hit the adjuster finger towards the rear of the vehicle. If you are good, a few hits will knock the torsion bar forward and out of the LCA anchor. You may have to lower the front end of the truck a little bit with the jack to let the adjuster droop below the cross member so you can hit it.

Rotate the bar with the adjuster lever still attached to the torsion bar. Use anti seize on the torsion bar splines before you re-insert the bar into the anchor. This makes it much easier the next time you remove the torsion bar. It is difficult to guess the right position the first time around! Note that the position when I reinsert the torsion bar is so that the adjuster lever is farther away from the cross member. This comparison is for the no load position of the bar when I first removed the bar. Make sure both anchors are securely in place with a few taps on the end of the bar with a hammer.

Reinsert the hardware and crank the bolt so that the adjuster finger is inside the cross member. Check your ride height at the seams and make any finely tuned adjustments so the ride height is even on each side. Make sure you still have a 0.5 inch bump stop gap. Hopefully, you got the anchors set at the perfect spline and you won’t have to take them out again.

Note the front end lift on my truck now. The adjuster lever is barely inside the cross member, when it used to be maxed out, hitting the cross member. Keep in mind that I can only adjust up to a 0.5 inch bump stop gap in the UCA, regardless of adjuster lever position. Reindexing did not directly give me the lift, it allowed me to adjust to the lift that my bump stop gap would allow me.

If your adjuster levers are not inside the cross member, you rotated too far and have to repeat the process to make the levers closer to the cross member. If your adjuster levers hit the back of the cross member, and you still have more than 0.5 inch bump stop gap, and you want a higher ride height, you need to repeat the process and move the adjuster further away from the cross member.

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I really wish you lived closer to me. I could learn alot.
Hahaha well thank you! You can learn a lot reading too. There are a LOT of smart Xterra owners around here and we are always happy to help!
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