Does tire pressure drastically affect crosswind stability?

[gperky]

One of the biggest spoilers of our travelling enjoyment is the spooky handling of our moho in the southwestern desert winds. Gusts of crosswinds can literally make it change lanes if they are strong. It doesn't lean much, but it moves sideways. I run the tire pressure on our 30ft. gasser A at 75 to 80 psi for a smoother and quieter ride. Do you know if increasing the pressure by 10 or 20 psi would make a big improvement in the stability? The tires are 245 70R 19.5.

[RCtime]

#1 Get a 4 corner weight-After You are sure your alignment is proper.
A laser alignment,loaded to traveling weight, fuel-water etc.
#2 Look for your tires (whatever brand) presuure chart for your 4 corner weight distribution.
#3 Adhere to charts recommendations.
You will be at your best, winds or not.

[wolfe10]

Words of clarification:

Those who recommend maximum PSI on the sidewall may (HOPEFULLY AREN'T) be correct.

They are correct (and only correct in this instance) IF, repeat IF you are at the maximum carrying capacity of the tire.

Stated another way, your chassis/coach maker made the TIRES the WEAK LINK to save money. I would read that as not a good thing. And if I considered a coach with that issue, would research upgrading tire size/load range so that I had a comfortable RESERVE on tire capacity.

[4x4van]

Different rig, but my old Class C handled horribly with higher pressures. I finally weighed it, dropped the pressure to what the table recommended, and the handling improved tenfold. DO NOT simply air to the max printed on the sidewalls; there's a reason it says "max" rather than "recommended" or "correct".

[Effy]

gperky wrote:
It's an 04 F-53 with the long wheel base and very short rear overhang. I haven't weighed it but, I'm sure it is well under the ratings for the chassis and the tires, so, I'm not concerned about underinflation. It has never wagged tne tail, so, I doubt that a track bar whould help much. I guess I'll just start by taking the pressure up twenty pounds and then go from there. I'll let you know the results. Thanx for the suggestions and experiences.

Sorry but it seems like you asked the question only to hear what you wanted to hear and support what you had planned on doing in the first place. If you haven't weighed it then you can't be sure of anything relative to psi. Increasing PSI errs on the side of caution but that does not mean its technically the right thing to do. Why wouldn't you want to weigh it and know for sure if you have it set right rather than guess? It's a couple bucks at the most and can be done at just about any truck stop.

The CHF which adjusts the sway bars will have a huge impact on wind push and is totally free and takes about 20 mins. Simply moves the front sway bar connections to a tighter setting. The F53 comes with 2 settings on the front and the factory default is on the softer setting.

[gperky]

It's an 04 F-53 with the long wheel base and very short rear overhang. I haven't weighed it but, I'm sure it is well under the ratings for the chassis and the tires, so, I'm not concerned about underinflation. It has never wagged tne tail, so, I doubt that a track bar whould help much. I guess I'll just start by taking the pressure up twenty pounds and then go from there. I'll let you know the results. Thanx for the suggestions and experiences.

[Effy]

djgarcia wrote:

gperky wrote:
One of the biggest spoilers of our travelling enjoyment is the spooky handling of our moho in the southwestern desert winds. Gusts of crosswinds can literally make it change lanes if they are strong. It doesn't lean much, but it moves sideways. I run the tire pressure on our 30ft. gasser A at 75 to 80 psi for a smoother and quieter ride. Do you know if increasing the pressure by 10 or 20 psi would make a big improvement in the stability? The tires are 245 70R 19.5.

Look on the side of your tires for "max pressure" psi the tire is designed for. Then air the tires to the max. I run my Good Year "G" rated tires at 110 psi.

Do NOT do this. This advice may be ok for a trailer, it's bad advice for a MH. Weigh your rig and adjust PSI according to the manufacturers chart based on the loaded weight. Max on the sidewall is a warning - not a recommendation. That is the maximum psi you can put for the max weight your rig can carry. Without weighing your MH this is a blind assumption and if after weighing the chart tells you to put them at max then your tires are inadequate.

[Cloud_Dancer]

It's complicated. And, much more information is needed in order to respond.

[Dale_Traveling]

Ductape wrote:
Have you weighed it?

I have experimented with pressures from 75 to 100 and get the most stability at 80. Same tire size. Load inflation chart says 75 for my weight.

Lower pressure it slows the response to steering inputs. Higher gets more reactive to road imperfections and skittish as the contact patch shrinks.

YMMV

Same experience with the same size tires but I air to 85. I played around increasing pressure. Once I hit 90-95 PSI it took a lot of concentration just to keep the coach in the lane on calm days in addition to the increasingly harsh ride of over inflated tires.

What has helped the most for me was adding a rear track bar in addition to the CHF of the Ford chassis. I still get pushed some during heavy wind events but the steering response to such and the speed coach reacts to steering inputs has improved greatly. I get little if any movement from passing vehicles.

The geometry of various rigs (wheel base to overall coach length), loading and balance of the load, towing, road conditions and such may effect how coach A drives as compared to coach B. In other words what worked for me might not solve your problem or concern.

[rgatijnet1]

I travel out West all through the Great Plains and we are accustomed to the high winds. I installed four corner air bags that I pump up to about 80PSI on windy days. This stabilizes the box on the chassis. I do not adjust my tire air pressure and I find that it makes no difference. It is the leaning of the box on the chassis that causes the problem. My air bags are controlled by an on board 12 volt compressor that I can control from the dash to increase pressure in high winds and lower the pressure after the winds have passed.

[kalynzoo]

We drive the SoCal gusty winds all the time. Gusts can often exceed 60mph. There are plenty of photos of big rigs on their side on the Cajon Pass. I've driven on a head wind that made my awning vibrate on the rig. The answer is not in tire pressure, it is speed. Just slow down. Sometime you might have to drop you speed to the 40-45mph range. Think back to high school physics, you have the vectors of your speed plus the angular velocity of the wind.( or something like that, it's been a long time since high school physics). Anyway, slow down and enjoy the drive.

[MarkTwain]

gperky wrote:
One of the biggest spoilers of our travelling enjoyment is the spooky handling of our moho in the southwestern desert winds. Gusts of crosswinds can literally make it change lanes if they are strong. It doesn't lean much, but it moves sideways. I run the tire pressure on our 30ft. gasser A at 75 to 80 psi for a smoother and quieter ride. Do you know if increasing the pressure by 10 or 20 psi would make a big improvement in the stability? The tires are 245 70R 19.5.

Look on the side of your tires for "max pressure" psi the tire is designed for. Then air the tires to the max. I run my Good Year "G" rated tires at 110 psi.

[naturist]

I've no experience with your rig, so can't answer directly. But back in my youth I raced sports cars, and I know that tire pressure makes all the difference in the world with how a vehicle handles, with under inflated tires causing just the problem you discribe. I also know this from driving a truck full of firewood that I borrowed from a friend. On the way to get the firewood, it handled fine. On the way back with the wood aboard, we were all over the road until I stopped at a gas station to pump up the tires. Then we were fine again.

[old_guy]

how fast are you driving?

[Effy]

You don't mention what kind of RV you have. Is it on the F53 and if so have you done the CHF? That will help sway a lot. Secondly, have you weighed your rig and adjusted PSI properly? I wouldn't play with PSI unless you had weights to justify it. In the end, there are some things you can do but you are driving a billboard. Wind will push it. More wind you need to travel at lower speed to reduce the impact on steering.