19.5 versus 22.5 tires

America's highway are in the worst condition ever. I don't know a single vehicle that likes to track straight when the lane is dished out into ruts.

Try driving with two wheels near the white line. and stay out of the ruts.

When was it last aligned and did the caster get set to at least 4-1/2 degrees?

I added steering stabilizer and rear trac bar on my coach with 19.5 wheels and 22. Made a nice difference on both. Thanks for the post as it reminds me I need to get it aligned.

What part do the tires play.. likely none but.

First are the tires properly inflated, But this I do not mean the pressure molded into the side wall, nor the pressure on the sticker inside the RV NOR the pressure the dealer put in.

I mean scale the rig, each corner. so you know the load on the tire, then inflate each tire to the pressure specified for the load it is carrying (or that pressure plus 5 PSI, some folks (myself included) like to add 5 PSI)

Then you have 3 chassis issues that may need adjustment.

Sway "SIde to side rocking of the RV like fans swaying to the music at a rock concert while holding up their BICs) Sway bars control this, MANY RVs the factory sway bar is a bit anemic.

Wag: LEAF SPRING suspension allows the body to move side to side over the axles only a little bit,, but.. If the rear moves one way while the front moves the other and then they swap (Which they will) you think you are going down the road like this ~~~~~~~~~~~~~~~ so you try to compensat and as a result really do.. Had you not compensated you would have been going ============

TRAC bars stop this 100% completely control it (2 of them) just one may be enough I mean it makes a BIG difference

Steering stabilizers like the Blue-Ox True Center of the Safe-t-steer does a great job of assisting you in keeping to the straight and narrow. (And trust me when you are driving a vehicle that is 8'6" wide "NARROW" applies.. Only one other vehicle is allowed on the freeway (Save during construction) that size.. A flat bed tow truck (Ag Machinery which may be on Rual roads can be much wider but may NOT go down the freeway without special permits)

My Rig had decent Sway control but let me tell you a trac bar and stablizer made a BIG and I mean BIG difference.

My last class A had 19.5's on a 35 foot coach and now I have 22.5's on a 36 foot coach. I noticed very little difference other than maybe the larger tires ride smoother. I have anti-sway bars front and rear and the coach rides just fine, even in a heavy side wind. Like others have said, alignment is one of the best ways to cure that side to side wheel correction. Inexpensively.

Your front end needs to be aligned! Try that before spending any money for add ons. All 5 of my motor homes needed an alignment to make them go straight down the road. Do this before anything else!

No we don't tow a car.

MURPHY55347? Do you tow a car? And if so, do you notice any difference when towing and not towing? We notice much less "wander" when towing. It seems like our toad acts like a stabilizing anchor. Not that it would be a practical solution but I'm curious if other people have noticed the same thing.
And, on a previous rig with severe "wander" problems, after trying several remedies, a front steering stabilizer turned out to be the answer. At that time, more brands were available than just the Safe-T-plus at a much cheaper price. Safe-T-plus seems to be the only one sold currently, and they do a great job according to people who have installed them, but they're a little pricey.

Get the front end aligned. That was the best money I ever spent. Have it done by a shop that does commercial truck alignments. Probably will need to have the caster adjusted, and that means unbolting the axle from the springs and inserting shims. Before ours took constant correction. Afterward you can stay on track easily unless you have to apply heavier pressure in which case we have the gearbox slop below.

Re the CHF- After extensive trialing different settings both drivers agree we get the best handling with the rear antiroll bar in the inner holes (most stiff) and the front antiroll in the outer holes (less stiff). Stiffening up the front antiroll made the coach more sensitive and less inclined to track straight. Probably not true for all coaches.

I installed a rear track bar. Honestly felt no change from that.

Next issue to address is the steering gear box has some free play in it. If the direction of the road crown changes or the wind and you have to go from holding left to holding right then there is 2-3" of play at the rim of the steering wheel before the gear takes up the slack. I'm going back to Ford for that and insisting on a new steering gear.

I also find directional stability is better at 90 psi in the tires. That's what Newmar recommends. Following the usual advice to weigh and then air accordingly we ran a lot of miles at 80 psi. At 80 it rides more smoothly but has less stability. I'm going to try it one time with 100 in the rears just to see what the difference is. There is a clear tradeoff between smoothness and stability when it comes to pressure.

YMMV. Good luck!

My motorhomes all had the 19.5 inch tires and I thought that if I traded I might go to the larger tires. then I priced the difference and decided against it.
bumpy