[Richard]

Not that I needed any more inducement on my OCD tendencies relative to coach steering, BUT I just drove a rental 26 ft box truck for almost 3000 miles. I drove it empty and completely at it's max GVW, and the steering was relatively precise. No wandering, no slop, and no trouble to run side by side with other trucks. The truck was not new, it had 200K miles on it. 

Now the engine was a dog, and it rode awful, but the steering was sweet. I don't see semi drivers fidgeting with the wheel either. 

So, that makes me wonder. What is different about a motorhome or bus. I've had three, and none had the steering this truck had. 

Straight axle and leaf springs in the front, with a TRW steering box. 


If you have any insight will you share it with me.

[Trainer]

Just got new tires and new front end alignment. The folks at Big Truck Alignment in Huntington, Tx, do a good job on straight axle trucks and motorhomes. So the alignment is dead on.

Now after driving for a while and having to correct it a bunch, I added more toe-in buy turning the tie-rod one turn to add more toe. Great improvement in drivability.

So I recommend adding to the toe setting. I can not wear the tire out so what little scrub I might have added does not concern me.

[HoosierDaddy]

My amateur thoughts...Leaf spring holds the front axle in place better than the air suspension. I'm thinking I saw a discussion once regarding castor setting....Maybe Newell didn't recommend as much castor as some who are knowledgeable about front suspension thought was best. More castor (to a point) would improve straight line stability except for side loads.
I believe Volvo class A trucks run air on the front but I don't know if they use the parallel link or not.

[Guy]

Not that I needed any more inducement on my OCD tendencies relative to coach steering, BUT I just drove a rental 26 ft box truck for almost 3000 miles. I drove it empty and completely at it's max GVW, and the steering was relatively precise. No wandering, no slop, and no trouble to run side by side with other trucks. The truck was not new, it had 200K miles on it. 

Now the engine was a dog, and it rode awful, but the steering was sweet. I don't see semi drivers fidgeting with the wheel either. 

So, that makes me wonder. What is different about a motorhome or bus. I've had three, and none had the steering this truck had. 

Straight axle and leaf springs in the front, with a TRW steering box. 


If you have any insight will you share it with me.

Richard, if there was one thing I could change is this 1984, steering would be it I love  all aspects of this 30 year old coach, but this one thing. I say change, not correct, because I believe they roll out of Miami like this.Todd Flickema , the previous owner  spent time and money on the steering box adjustment on this coach. On the interstate , I have been passed by Darwin Award winners in semis, on the cell phone, one hand on the wheel , with no worries. I'm thinking the semi driver is in effect dragging his trailer around and does not feel the issues of his trailer wandering. As to why a box truck is immune from the wander and slop,could it be that it has a are bones system, with fewer components?

I must say that this old coach steers 100 percent better than a previous class A Winnebago i had.

Has anyone tried the steering dampers on the market? I suspect that they would just mask the issue, but I am just a rookie at this point!

 Me , I going to by an old UHAUL and frankenst
en a steering system out of it. ( Not)

[HoosierDaddy]

I have to say that I have no complaints concerning my 1993's steering... The worst thing is if there is an abrupt change in the road such as a severe dip on one track I have to correct for that, but I think that is common to solid axle front suspensions.

[jcus]

No facts to back it up, but think it is the combination of steering geometry, [fact that steering box is so far forward of axle with a lot of pieces to move for a reaction] air bag suspension, long wheelbase, and big tires with sidewalls made more for comfort that turning precision. 
I have had a couple of old class C's that steered better than any of the bus's I have had. 
Meet an old bus nut one time, and I asked him why the old intercity buses had such poor brakes, he told me Greyhound did not want the passengers falling out of their seats, if the driver jammed on the brakes.
Jim

[Richard]

Thank you all for the comments.

I do agree that toe in has a huge effect.

I wonder how much effect sitting in front of the front wheels has versus sitting behind them in terms of the seat of the pants reaction to steering movement. Anything in front of the wheels is going to move further for a given steering input than anything behind the wheels. That's the reason we learn not to over steer.

I also wonder if the airspring suspension in front contributes to the vague steering. The straight axle coaches have a panhard bar to keep the coach from moving side to side over the air bags and the IFS coaches don't need one, but relative to steering stability I can't tell any difference between the straight axle and the IFS.

It does make me jones for a drive in one of the toterhome style rigs like a Renegade built on a Class 8 chassis.

[bikestuff]

When I was at the Prevost shop, I asked them to look at my front brakes since the hubs had gotten really hot. They did not find any problem with brakes, but did find a problem with steering.

What they did was to take off the front tires, and then grab the rotors at 9 and 3 o'clock positions and then tried to quickly turn the wheel left and right. One wheel did not have any play, but the other one had probably half an inch play in it. That problem is still to be diagnosed but if your wheels are not always going straight, I suspect that will introduce a lot of wobble and steering drift.

They also found a bushing for the front sway bar that was deteriorated.

The coach had been driving like normal with no more wander than normal.

So, my point is that if you feel your coach is not keeping down the straight and narrow, you might have something to repair on front end. I will keep you posted when I get that looked at.

[HoosierDaddy]

Positive caster tends to straighten the wheel when the vehicle is traveling forward, and thus is used to enhance straight-line stability. The mechanism that causes this tendency is clearly illustrated by the castering front wheels of a shopping cart (above). The steering axis of a shopping cart wheel is set forward of where the wheel contacts the ground. As the cart is pushed forward, the steering axis pulls the wheel along, and since the wheel drags along the ground, it falls directly in line behind the steering axis. The force that causes the wheel to follow the steering axis is proportional to the distance between the steering axis and the wheel-to-ground contact patch-the greater the distance, the greater the force. This distance is referred to as "trail."

pasted from:
http://www.ozebiz.com.au/racetech/theory/align.html

[Chester Stone]

I agree with Rudy, changing my toe to 3/16" made a major difference in reducing over-steering.