Originally Posted by tomv
I can feel high winds and trucks passing and can live with this.
This is where a rear trac bar would do wonders due to the long overhangs of our gas'rs in crosswinds and with the passage of large trucks.
But when the winds are relatively calm and I am all by myself on the road I find the coach does not want to stay straight requiring minor steering adjustments. It feel like the steering gear has a bit too much play. (feels like and old 70's era car with a front end going bad) Is this common
Mike hit this one on the head! This is where adding tapered shims between the front axle and leaf springs to increase positive caster FIRST would help. Positive caster (an imaginary plane centered vertically that tilts aft at the top of the wheel~that's positive), gives the vehicle it's ability to track in a straight line. If a front end is set at or near a "0" degree of caster and/or there is excessive toe out (or 'incorrect toe'), the vehicle will display 'wondering' or an inability to maintain directional stability.
So you can see why if one installs self centering/true tracking devices that you may be covering up symptoms caused by the lack of positive caster. If after the vehicle still displays wondering due to lane depressions/ridges, then those self centering devices would be beneficial and not just a cover-up.
On our coach, we had excessive porpoising at bridge expansion joints and road sections, a lot of 'tail wag' in crosswinds and passing trucks and a little of the wondering on flat roads w/no wind. Had I known better(and it cost me two front tires) I would have had the alignment done first w/ the 5 degree shims(pos. caster increase)installed. As it was, I installed new Koni FSDs and added a BlueOx rear trac bar...what improvements... and I thought I was done. We then went on a 10K mile trip.
During the last 2500 miles, I was noticing some vibration and our front TV started to oscillate slightly and the wondering was getting worse. Turns out I did not notice any prior vibrations because the front end had almost 3/4 of an inch toe out and that had a 'damping' effect. The front tires did not show that kind of severe toe out. Also, the front end only had 1/2 of a degree pos. caster on the right and 3/8 of a degree pos. caster on the left. Josam's of Orlando installed the 5 degree shims to increase the caster, aligned the front end and I had the coach 4 corner weighed. Even with a safety margin of 5 PSI, I had been running 10 psi too much pressure in both the front and rear tires for the weight we were running.
The point of all this is I should have straighten out the front end problems before I added any other upgrades...I was lucky(except for ruining two tires) the two upgrades I did install turned out to be just the ticket. The coach now handles so well I feel we don't need to go any further...