DIY Front End Alignment

[Richard and Rhonda]

Ok, you guys are going to know that I have lost it.

For some time I have always set my own toe in on the rigs I've owned. It's a long story but I got tired of paying 100 to 200 to have someone set up the rig in an ill driving setup.

Setting the toe is really easy. Made a homemade trammel bar with a piece of 8 ft alumimnum tube. I used two short pieces of pvc pipe that I put sharpened nails for the indicators, and thumbscrews to hold it to the aluminum tube. Jack up the axle, spin the tire and paint a stripe with spray paint. Hold a nail or small screwdriver to the paint stripe and spin the tire again, that will give you a thin mark around the circumference of the tire. Let the coach down, back up twenty feet, and drive back forward twenty feet to let the alignment "set".
Set the nail points to hit the stripe on the front of both tires. Move the trammel bar to the back side of the tires, align the nail point with one stripe and measure how far the other is off. Obviously the back should be farther than the front to give toe in. I personally like a little more toe, so I tend to set at 2/32. Truck shops like to set at neutral or barely toed in, since it gives the longest tire life. However, neutral toe, or the slightest toe out can cause the coach to hunt all over the road.

If the toe needs adjustment, loosen the two clamps at each end of the tie rod, and twist the tie rod to move the toe in or out.

I also use two thin pieces of plywood with a layer of garbage bags between them to park the front tires on when I'm doing this. I found that if the tires are sitting on the pavement, that twisted the tie rod to adjust toe does nothing. Putting the tires on the home made rotation plates allows them to move when adjusting the tie rod bar.

Takes less than half hour after you have done it one time.

Here is where the real saga begins. My coach had a slight pull to the right. Really slight, but if you took your hand off the wheel, it would start drifting right. In a 100 to 150 feet it would pull the right tire over the white line. I know, I know, I'm OCD but I don't like that.

First I used a laser to make sure the thrust angles of the front and rear were aligned with the center line of the coach. They were, so that wasn't the culprit.

Camber and castor are two other key adjustables on front end. Camber is usually adjusted a little differently on the right and left to account for the crown of the road and prevent the drift I described. However, Newell specifically says NOT to bend the axle in order to adjust camber. OK, so that leaves castor. A little research revealed that some alignment guys will put just a little cross castor in a truck to combat road crown, while others think the castor should be exactly the same on both sides. I called Newell and the alignment guy confirmed that they actually use cross castor to correct drift. A ha ! As you know castor is the angle of the axle inclination in the front to back plane. More castor is more stable in a straight line. If the right and left have different castor, the front will pull to the side with the least castor. So, if it's pulling right, I need less castor in the left.

I went to three different aligment shops that work on busses around Fort Worth. All three gave me the "I really don't want to get into that routine" They were willing to set the toe, and thrust angles but that was it. Plus I figured that there would be some trial and error to the process, and I could easily drop 500 in shop labor seeking perfection. So, that, and previous negative experience with truck alignment shops convinced me I should work on it myself.

My coach has a double set of parallel arms that anchor the front axle to the frame. Two parallel arms on the right, and two on the left. The bolts that secure the arm to the frame are eccentric. If you turn the bolt you can actually move the arm relative to the frame just a little. Cool, that's how you can adjust castor. Move one arm relative to the other and you can change the tilt of the axle. Move both bolts together and in the same direction and you can actually move the axle forward or backward on that side.

Yeh well, it's not for the faint of heart. Those bolts are about 1 1/14 with 1 7/8 nuts on them. The book says 1100 foot pounds of torque. You have to remove the rear cover on the generator compartment to get to the nuts. My six foot cheater bar wasn't very effective at removing the nut, neither was my 1/2 inch impact wrench rated at 500 ft lbs. So, I HAD to go buy a 3/4 impact rated at 1400 ft lbs. One touch of the trigger was all it took. Sweet !!!

Now, the other end of the bolt has a washer the fits over the hex head, and that washer is spot welded to the frame. The purpose of that is prevent the eccentric from turning after you set the alignment. So, I used a combination of cutting torch and side grinder to bust that loose.

The homework recommmended about 0.5 degree of cross castor to correct for the typical freeway crown slope. Using a little basic trigonometry and a dial indicator I estimated how far I would have to move the upper pivot point to get that. So I moved the eccentric, tightened the nut down, removed all the jack stands, and went for test drive. Rats, better, but not perfect. It took a little iteration before I had it like I wanted. Once I was happy, I tack welded the washers back the bolt heads, hit the nuts one more time with the impact gun and put the cover back on the gennie.

I had to reset the toe, since any time you fool with castor or camber it moves the toe.

Ta Da !!! Now the steering wheel is straight and I don't feel like I am making a constant curve in the road.

Please don't send the men in white coats, I'm better now :-)

[fulltiming]

As always, I'm impressed Richard!! I had Newell check the alignment on my coach a couple of years ago and they had to do some eliminate the slight pull to the right. After replacing the front tires again (went to a larger size for more loading carrying capacity) it is again pulling a little. Don't have the equipment to attempt your solution but I will certainly save it for future reference.

[encantotom]

gotta love those air impact wrenches....btw, my 1/2" does 1000 foot pounds....AirCat 1000th http://www.aircat.com/Aircat.pdf

did you mean 1 1/4" and not 1 1/14"?

great work.

tom

[Richard and Rhonda]

yes 1 1/4 bolt

funny, the wrench I bought was the big brother NitroCat. That is one impressive piece of hardware.

[encantotom]

i couldnt tell any difference between the aircat and nitrocat that i cared about so i bought the aircat. i have a number of air impact wrenches and nothing compares to the aircat. i have even bought one for a mechanic buddy of mine as a gift and he is blown away.

hey, what can i say....we like good tools and newells.

tom

[chockwald]

I understand that a 12 step program is now available online at http://www.newellocd.org....LOL!!

Just joking, of course.....Richard you seriously impress me. That was quite an undertaking.