[Richard]

Synopsis: There is a way to adjust the caster on the non adjustable caster front end. Adding 1/2 degree of caster to my front end produced better straight line stability with 365 tires. It is my opinion the 365/70 tires require more caster than the DANA specifications call for due to their increased footprint.

The title is intentional to make searching for those terms easier. There are many of these front ends out there on other brands besides Newell, and I could not find in ten years of searching even ONE piece of info on increasing the caster. 

Why increase the caster? In theory an increased caster angle provides more force from the tires to self center. The downside is that too much caster can produce a shimmy or shopping cart wobble. It can also increase steering effort at slow speeds. 

As many of you gurus follow my OCD efforts to make the Newell drive like a BMW have read. I have touched everything and improved everything in the entire front end. New tie rod and drag link ends, new suspension bushings, new and bigger bearings in the steering column, new u joints in the steering, rebuilt steering gear box, and too many alignments by the ‘experts’ to count. Still I was not happy with the behavior at freeway speed. I was absolutely certain, and confirmed with dial indicators that there was very little slop in the steering system.

This is what I specifically was not happy with. I felt that a steering correction in one direction almost always resulted in an over correction because the steering wheel did not return to exactly dead center on its own. I was unconsciously having to move the wheel back to true center, and almost always would move it too far. I am talking about micro movements, but I was aware. Curiously enough, I found the straight line stability to be EXCELLENT under three conditions. One, a heavy road surface i.e a surface with a lot of drag on the tires. Two, a heavily crowned road that wanted to steer the coach to the left. Three, a consistent side wind from either side. 

As I drove for tens of thousands of miles, it became clear to me that in those cases either the rough surface or the side force moved the wheel to dead center on its own. 

I also noticed the worst behavior was on a flat glass smooth road with no wind. I was constantly making micro corrections. Things that make you go hmmmmmmmmmmm. 

Before we go any further. I am very aware of oversteering a bus where you sit in front of the front wheels. There are a number of people on the forum who have ridden with me, and I am pretty sure they would attest that I am not a steering wheel fighter. 

All of that to get to, I thought for years on how to increase the caster on this front end. All of the literature from the manufacturer says it is NOT adjustable. There is not an obvious way to adjust. I did take the coach to the most reputable alignment place in my area and they attempted to adjust the caster by placing shims in the vertical plane where the upper and lower A arms attach to the coach. A shim between the frame and suspension on the top A arm in the front, and a second shim on the lower A arm in the vertical plane at the back has the effect of twisting the A arms relative to one another, making the line between the A arms change it’s angle. It works on front ends that have ball joints at the A arms for the steering spindle. I hope my illustrations help my verbal descriptor.     

Except that DOES NOT work on this particular design and the photo illustrates why. The A arms are not attached to the spindle by ball joints at the top and bottom. The A arms are attached to the spindle with tapered roller bearings that are transverse to the spindle. The zero tolerance in those tapered roller bearings do not allow the A arms to twist relative to one another. This was not what I wanted to discover. 

However, during the replacement of the bushings in the A arms last year, I paid attention to how the overall suspension assembly was attached to the Newell frame. At the corner of each A arm, the straddle bushing is bolted to a right angle casting. The right angle casting is bolted to both a horizontal and vertical section of the main Newell frame. Two large bolts vertically and two large bolts horizontally hold the casting to the frame. One of the castings at each A arm end means there are four castings per side on suspension. 

Hmmmmmmmm. What if those castings were unbolted on the two rear points of the upper and lower A arm, and a shim inserted in the horizontal plane? Wouldn’t that tilt the A arms backwards more? And isn’t that going to tilt the spindle backwards increasing the caster? Yep. I did a little high school trig and calculated that a 1/8 shim on both A arm mounts in the back casting would increase the caster by almost 1/2 degree. 

So that’s what I did. I removed the castings, made the shims you see, elongated the vertical holes in the casting to allow it to move downward, and bolted it all back together. Adjusted the toe in to 1/16 and off for the test drive. 

Woo Hoo! That magic I had been searching for was now there. My hands were super still on the super slab. More research looking at the huge float tires that are on dump trucks, garbage trucks, and cranes says the wide tires require more caster. Except I could not find hard numbers. As best as I could measure with my backyard primitive techniques, I believe the caster to be a 5.25 degrees. That is way above the specification that Dana lists, way above the specs that alignment shops use. 

Some of you who monitor my antics are trying to reconcile this with selling the coach. The short answer is I completed all this just before I had any idea that I was buying a new coach and selling 512.

[[email protected]]

what tools do you use to measure toe in, caster?

[johnkosir]

I believe you have a ZF front end

[Richard]

You are going to chuckle at my redneck ways, but my numbers have been confirmed a number of times on high zoot alignment racks.

For toe in, I utilized the outside rain sipe on the Michelins 365 tires. It is just the width of mason’s twine. I have four plumb bobs. I back the coach up about 50 feet. Lower the suspension, and allow it to come to ride height. I drive forward onto my RV pad. I hang the four bobs front and back so they just clear the ground. I use two tape measures. I call this rolling toe, because it really represents what the tire sees rolling down the road as opposed to being on a turntable.

For camber, I use a digital level against the wheel face. I measure on a pad. I turn around and park on the pad the opposite direction and remeasure. I average the number. The reversal of the coach takes out any slope of the pad.

For caster, I have used the turn the wheel 20 degrees and use the digital level method easily found and explained on line. But in this case I hung a plumb bob, and measured distance from the vertical string to the pivot points at the top and bottom A arms. Tangent (caster angle) = difference in measurements / height between pivot points). Hard to trick gravity and a taut string!

[Latitude 28]

Richard,  i said this before...."you could run over a quarter in the middle of the road and tell if it's heads or tails" with all the work you've done on your suspension.  Your response was "running over a dime would be more of a challenge".  Well I take back what I said you have exceeded your challenge.  You can now run over a dime on a gravel road and tell if its heads or tails!  Great job and well documented!

[Richard]

Steve, you are far too kind.

[360]

I will cherish this post and use it anytime I attempt to describe the level of your knowledge on obviously not just a coach but frankly how stuff works. What a send off for 512!!!

[Jack Houpe]

You amaze me I would like to have been a fly on the wall watching this process. Did you have to roll the coach forward then backward before measurement? I see you snuck a picture of bus bay in there.

[Richard]

Backward first then forward to simulate what happens as you drive down the road. If you measure the toe after just backing up it is way different. It will be more toed in after backing up. As you roll down the road the forces on the tires want to move them to the outside. That is why they are toed in, so that rolling down the road they become neutral. If you back up, the forces on the tire are reversed causing them to move towards the center of the coach.

Trivia : Front wheel cars are usually toed out on the alignment rack because the pulling force of the drivetrain is higher than the rolling force of the tire. The pulling force of the drivetrain moves them to the center thus setting them up slightly toed out results in neutral toe while under power.

Bay pic was a fumble finger, and I don’t know how to edit it out. The remove button didn’t work for me.

[RussWhite]

Jack said, “I wish I was a fly on the wall to watch…..”

I was that fly!

Richard truly is amazing.
Sticking with the insect analogy, the bee will pollinate my lowly rig with a steering assessment tomorrow. I will report the results. Russ