Any Alignment Gurus Out There?

[travelite]

Folks,

I was at the Prevost Service Center in Nashville, TN. Had some steering rod-ends replaced and an alignment done. They use Hunter equipment model R811 which helps in centering the steering wheel. I believe Hunter uses the drive axle as a reference point. After setting caster, camber, and toe, the techs centered the steering wheel by unbolting the u-joint connection at the steering box and reattaching the column a spline or two over. If the steering wheel isn't centered and is removed to re-center can't this lead to the chassis dog-tracking down the street.

Maybe this is much ado about nothing because my rear axle thrust angle is spot on.

Thoughts? Any gurus on Hunter and alignment out there?

[travelite]

BTW, this MCI document (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http%3A%2F%2Fwww.mcicoach.com%2Fservice-support%2FtechnicalTrainingWebinar%2FsteeringAlign ment082411%2FsteeringAlignment082411.pdf&ei=GoWJVegPjZ_IBMjukuAN&usg=AFQjCNFfUm6H1wQEJxPN2rUvYl7ADZzoAA) covers it, page 22. It says:

"All steering gearboxes have a center point which must be maintained before, during, and after alignment.

Performing a complete alignment to the coach, or even adjusting the toe-in setting and the re-aligning the steering wheel on the column defeats this center point feature and can lead to complaints from operator about coach steering or ‘pulling’ to one side or the other."

[dale farley]

David, I think I would call another Prevost shop and see if they do the same thing. I agree with you that something doesn't sound right.

[Mikee]

The correct way to do a 4 wheel alignment is to first verify the thrust angle via the front end machine, then center the steering wheel and secure it. After that set the toe-in on each front wheel at 1/2 the total toe in. This maintains the steering gear center point and wheel. Changing the steering shaft is not the way to do it. It is actually more work than doing it correctly.

Mikee

[coreygrubb]

David, refer to PC forum under chassis on page 2 Post H-45 IFS alignment dated 6/5/15. Geo.

[Gil_J]

George, too funny.

David, the MCI reference makes perfect sense. The Provost procedure, as you described it seems flawed.

It seems to me that the logical procedure would be to first make sure the steering box is centered. The next step would be to align the steering wheel as you described. This should never have to be done more than once. The next step would be to follow the common automotive practice Mikee described. Using the automotive procedure will ensure the steering wheel is perfectly centered and the steering box is as close to center as possible while the steering wheel is straight. The spline adjustment on the steering column will likely still result in the wheel being slightly off center given there is x degrees between each spline.


If you really want a great alignment I recommend Josams in Orlando. Not only are they great at doing an all axle alignment, they are the manufacturer of the equipment.

[Donnie Myers]

Second vote for JOSAMS in Orlando! Call and ask for Barry, tell him Donnie sent you! They are the best! If you have a trailer, take it also and let them do it all.

[Grizz]

Steering wheel centering should only be accomplished by adjusting tie rods (setting toe in). Moving the steering wheel off top dead center of the steering gears causes other serious problems. Only a lazy or incompetent tech would take the gears off top dead center for any reason when the vehicle is going straight.

Josam in Orlando has my vote and has been doing my vehicles for over 15 years.

[travelite]

Thanks guys,

I've used Josam's before and I know they're a top notch shop.

Well, I just completed my 300 mile trip home from Prevost's Service Center in Goodlettesville, TN, and all I can say is WOW! The coach handles and tracks better than ever. Any doubts I had over the shop's method of finding the steering box center are erased. They use their Hunter R811 to find center and as far as I'm concerned the result is either spot on or negligibly off. I can take my hands of the steering wheel at speed and the bus tracks straight for an unimaginable distance. My records show that my bus had an alignment performed back in 2007 at Mira Loma, I can't vouch that the steering wheel was left in it's factory set position. There's magic going on in the Hunter equipment which I'd love to uncover, but for now I just have to accept the fact that as the operator sweeps the wheel thru it's turning range the Hunter system finds center sufficiently close such that anything better is probably picking nits. My coach's steering wheel has no perceptible play when driving straight down the highway and it tracks unbelievably straight. I also had Prevost replace the dogbone sway bar bushings on the drive axle. Again, another phenomenal difference. If you're coach is ten years or older and these bushings haven't been replaced, by all means do it. Passing trucks are a non-event! Turns are razor sharp. In short, Prevost TN worked wonders on my suspension and steering and Kyle is very, very good at what he does! Thanks Kyle!

BTW, the trip home includes I-40 East thru the Cherokee Mountain Range on my way to Asheville, NC. I put the coach thru one of the best slalom road circuits you're every likely to encounter in your Prevost and it just ate it up! :)

[Gil_J]

David, thanks for sharing your service results. I seldom hear a complaint about service.

[travelite]

Absolutely Gil,

My advice to folks is just go to Nashville, let them do their alignment job, and don't question it! :) The results speak volumes. They base the front off the drive. If the drive's thrust angle is on then the front will be on and the Hunter R811 will find center, and if you want they'll pull the steering column to center the steering wheel. If you wish you can always skip this step.

[Mikee]

It sounds like what you are saying is the steering gear was not centered to start with and they centered the steering gear first then did the alignment. That is a good way to do it. Earlier you stated they moved the steering shaft to center the wheel. From what you said above they centered the gear then aligned the coach.

Mikee

[travelite]

Sorry for the confusion.

They don't center the steering gear by visually lining up sector shaft marks with gear box housing marks. They use the Hunter system to derive or calculate the center. How the Hunter system does this exactly I don't know; I was hoping for a Hunter System expert to explain it to us. The steering wheel isn't swept thru its entire range of motion its moved slowing to the left then slowly to the right thru a portion of its range. The screen then shows what you might call a derived center. (Having searched thru a handful of Hunter patents it's becoming clear that they found a method for detecting steering system play, so they are able to find the window of least play).

Because my coach was aligned in 2007 at Mira Loma I can't vouch for the steering wheel being centered with respect to the marks on the gear housing; in fact, I have to conclude that it wasn't because I now know that it is. From my experience and from posts on another forum I do know that unbolting and rotating the steering column is almost always the last step in Prevost's centering of the steering wheel. I stood there and watched a brand new Volvo 9700 being aligned with the last step being the unbolting and repositioning of the steering column. I sure hope the steering angle sensor learns its new zero position! I'm sure it does after a few miles of driving.

What Grizz is saying is true, the sector shaft is eccentric and is setup for zero play only when the steering gear is centered. Go online, look at the Prevost manuals for your coach, specifically the steering section and you'll find a good explanation of this for the ZF-Servocom steering gear box. There's a zero play zone that's probably some number of degrees wide and the Hunter system finds it. I'm convinced after putting on 300 miles and testing it thru the Great Smokey Mts on I-40.

[Joe Camper]

On a straight axle front axle the steering wheel is only centered if the front ride height is spot on. If the ride height is set a bit low wheel is a bit left. Height bit too high wheel is right. Cant recall if IFS is the same easy enough to see just dump the suspension air and see if the wheel turns.

The ride height linkage on IFS is attatched to the sway bar and if sway bar bushings go bad front ride height is affected.