The forum members asked URD some time ago to develop a traction bar for the XRunner. At the time there was not anything available for our application.
Doing research I looked at many traction bar designs and picked out what I thought was good from each and identifying was would not be good for the XRunner.
What I wanted was a traction bar that would stop all axle twist in the leaf springs, but that the same time would not cause any binding of the suspension or limit the differential articulation from side to side of the rear suspension. This is when one side is extended all the way down while the other is all the way up in the bump stop.
What I found that was most ideal for the XRunner was the torque bar used on the Camero of years past. This had a lever arm that was rigidly attached to the axle housing and ran along the propeller shaft to a forward frame mount. This is the configuration I wanted to go with.
Right after this decision was made I attended a national off road event in Pennsylvania and spent some time 4 wheeling with my good friend Bud. I told him of my traction bar idea and he asked if he could make them for URD as our contract manufacturer. I was happy to give him the business as his build quality is second to none.
I later traveled to his house in North Carolina and we got to work. It would have been nice if all the very same parts could be used for the XRunner traction bar, but as it turned out it had all be redone from scratch with basically no common parts.
The diff bracket he was using at the time would not work on the XRunner because it would smash the EVAP canister installed above the differential. A new one was developed for the XRunner. The main torque bar was totally different, and then the front mount was developed just for the XRunner.
What we ended up with was a completely new design with basically no common parts from his existing bar, it was uniquely an XRunner traction bar.
What I think makes the URD bar better than the other traction bars that have come along since is pretty simple. It works better and does so without binding the suspension in any way.
As the rear suspension goes through its natural range of motion it moves forward and rearward pivoting on the forward spring mount and it moves in an arc with the forward spring mount as its anchor. You will notice that the rear spring mount allows for back and forth movement of the spring assembly.
When an under the spring type bar is solidly mounted to the frame forward of the spring mount it will want to have a different arc path as the suspension goes through is normal range of motion. If some mechanism is not used to allow for the differential arc path there will be binding in the suspension. This can lead to high stress on the suspension components.
URD compensates for this by using a slip mount bushing that allows the nose of the torque bar to slide in and out of the front mount so the bar can change lengths as needed when the suspension moves up and down and through it arc of motion.
Next is the differential side to side articulation of the rear suspension, when one side is compressed and the other is dropped. This natural twisting motion has to be allowed without causing binding in the suspension. If an under the spring bar is used with a fixed hard mount in the front it can’t allow for one side wanting to be longer while the other side wanting to be shorter. This can cause binding and a lot of stress on the system and all the parts are fighting each other.
The URD bar compensates for this by allowing the nose of the torque bar to twist in the nose bushing without any resistance.
The URD bar allows for the rear suspension to move through its entire range and arc of motion without and allows the axle to move back and forth in its arc of motion without binding and inducing any stress on the system.
Now I will speak about preventing twist of the axle in the springs. This is the simple part, it is all about leverage. The torque, lever, or moment arm of the URD bar is very long and as a result has an impressive ability to arrest axle twist.
You would be shocked at how easy it is to twist the axle in the springs by simply applying pressure on the end of the URD torque arm when not attached to the front mount. With just a couple of fingers you and push up and pull down on the torque arm and wrap that axle up in the springs with surprisingly little effort.
The length of the moment arm is very important and you must understand what the moment arm really is and what it is not. If you look at the Cal-Trac (which is a good setup) bar you will see the moment arm as the part that sticks down from under the axle and the link bar attaches to. The moment arm is the distance from the center of the axle to the attachment point of the link arm and only that distance that is at right angle to the frame of the truck. There is one on each side so you will have to double it to get the total moment arm.
There are a couple of other designs out there that have the link bar attachment point right under the spring just forward of the spring perch. If you draw a line from the center of the axle straight down to ground to the point level with link bar attachment point you will get the length of the moment arm and you can double it. In these examples we are talking, I am guessing 14” for one and maybe 6” or so for the other compared to the URD that is something like 5 feet or so.
You cannot count the length of the link bars that travel under the springs as they are not the moment arm. If you undo the front of those link bars they will drop right down to the street and you cannot stop rotation with a hinge. The link bar is what the moment arm pushes against as the axle twists.
The URD moment or torque arm solidly attaches above and below the axle center for a very positive way of preventing axle twist with a VERY LARGE amount of leverage.
In all these years there has not been one report of a URD bar breaking, bending or coming apart and they still sell for a good price used.
The URD Traction bar is compatible with all the current suspension upgrades for the XRunner and lowering kits, even the DJM one. There is not any ground clearance issues with it either.
In summary, the URD bar is uniquely different than other traction bars out there, it is designed specifically for the XRunner, it does not bind the suspension in any way, and it has the most leverage to arrest axle from twisting in the springs. It was developed and offered to the XRunner community at your request.
The downsides to the URD bar that I see are few. Cost is a big one. Next is it maybe a little more involved to install then other designs, and it may have the lowest BLING factor since it is mostly tucked up out of sight.
There are a few other designs out there. Feel free pick from the many different options and it is for you to decide which if any is best for you and your truck.
Gadget
