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Old 09-24-2021, 04:52 PM   #1
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Lowering tire pressure for washboard dirt roads?

Lets say you have 10 miles of washboard gravel road you must travel- Class C, E-450. At 5mph it will destroy my coach by shaking it to pieces. How low can I lower the tire pressure on the front/rear without destroying the tires? 5 mph max. I have a 3/4 ram diesel/cabover that I lower to 35psi with no problems on the same road at 5mph. Les
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Old 09-24-2021, 05:23 PM   #2
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It depends on tire size and load on them. FWIW the vast majority (80%) of tire failures are the result of under-inflation or overloading.
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Old 09-25-2021, 08:46 AM   #3
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It depends on tire size and load on them. FWIW the vast majority (80%) of tire failures are the result of under-inflation or overloading.
What you say is absolutely true--- at normal highway speeds. 5 mph does not create the heat needed to destroy tires. Do you have anything to contribute that is relative to my question? How low is too low at 5 mph?
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Old 09-25-2021, 09:15 AM   #4
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Quote:
Originally Posted by Marine Les View Post
Lets say you have 10 miles of washboard gravel road you must travel- Class C, E-450. At 5mph it will destroy my coach by shaking it to pieces. How low can I lower the tire pressure on the front/rear without destroying the tires? 5 mph max. I have a 3/4 ram diesel/cabover that I lower to 35psi with no problems on the same road at 5mph. Les
Your tires have a recommended inflation pressure for the load they are required to cary. If you lower the pressure below that point, you risk damaging the tires. Low inflation leads to internal damage to the tire like belt separation. You can even see it from outside the tire so you'll only find out it's been damaged when it gives up while you're going down the highway. Certainly going slowly will limit any overheating but not overload damage to the tire.
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Old 09-25-2021, 12:20 PM   #5
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Lets say you have 10 miles of washboard gravel road you must travel- Class C, E-450. At 5mph it will destroy my coach by shaking it to pieces. How low can I lower the tire pressure on the front/rear without destroying the tires? 5 mph max. I have a 3/4 ram diesel/cabover that I lower to 35psi with no problems on the same road at 5mph. Les
Hmmm ... the longest washboard run to date in our 24 ft. E450 Class C has been around 25 miles each way on extreme washboard in and out of a remote place in the Oregon Outback.

We traveled 7-10 MPH the whole way and steered back and forth on that terrible road so as to keep the wheels on at least one side of the RV at any one time as much as possible on the smoother surfaces along the sides of the road out of the bumps. Our coach took it just fine this way ... but it did take about 2 1/2 hours or more going in and again coming out. It was worth it - to have all the comforts of home way out there on the far side of beyond.

I keep 75-80 lbs. of pressure in the rear duals and 65-70 lbs. of pressure in the front tires at all times in order to maximize tire life under all conditions. I've since then even installed larger diameter and narrower tires on our Class C to increase ground clearance, and widen spacing between the dual sets so as to improve cooling air flow around the inner wallls of the dual tires.
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Old 09-26-2021, 12:01 AM   #6
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I agree w/ RAYIN, LOW Pressure= Overload = Tires demise= worst enemy= INTERNAL, UNSEEN SIDEWALL DAMAGE= "ZIPPER FAILURE"/ BLOWOUT RISK; MIGHT BE CHEAPER TO BUY A PLOW ATTACHMENT AND PLOW/ GRATE/ GRADE/ FILL :-) AHEAD OF YOURSELF? :-)
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Old 09-26-2021, 08:57 AM   #7
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I agree w/ RAYIN, LOW Pressure= Overload = Tires demise= worst enemy= INTERNAL, UNSEEN SIDEWALL DAMAGE= "ZIPPER FAILURE"/ BLOWOUT RISK; MIGHT BE CHEAPER TO BUY A PLOW ATTACHMENT AND PLOW/ GRATE/ GRADE/ FILL :-) AHEAD OF YOURSELF? :-)
Yes, I agree that pressure too low will cause seperation and internal damage to the tire but at what point. 20 psi might destroy the tire fairly quickly but what about 30 psi? Also the rears are duallies and 30 psi on those for 10 miles may not cause any damage. 500 miles at 60 mph might destroy tires running 50 psi but not at 80. Static tire squish might be the indicater that is most telling. I made a mistake by not posting this thread in "Boondocking" as those class C drivers are most likely the ones who have experience with lowering the psi.
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Old 09-26-2021, 09:53 AM   #8
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I know I will probably catch some flack for this, but here goes . . .


SPEED UP!!! 5 mph is horrible on washboard. Of course this doesn't work on curvy mountain roads but open desert/plain type roads it makes a huge difference. Roads like Carrizo, Soda Lake in central California or roads 25 & 8A in northern Nevada 35-40 mph works great. Pay attention of any upcoming curves and scrub speed early. These beasts take a while to slow.



As far as tire pressure, I have put taller tires on and the manufactures chart says 62 lbs. for my weight. I run 64-65 lbs. regularly and when I have more than a few miles of rough stuff, I air down to about 50 psi. I think it takes the edge off and my duals don't touch in between



Remember, it's a big heavy, top-heavy vehicle, not a Baja race truck



Don't forget to air back up when you get to the pavement


Disclaimer: do this at your own risk
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Old 09-26-2021, 12:45 PM   #9
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I know I will probably catch some flack for this, but here goes . . .

SPEED UP!!! 5 mph is horrible on washboard. Of course this doesn't work on curvy mountain roads but open desert/plain type roads it makes a huge difference. Roads like Carrizo, Soda Lake in central California or roads 25 & 8A in northern Nevada 35-40 mph works great. Pay attention of any upcoming curves and scrub speed early. These beasts take a while to slow.

As far as tire pressure, I have put taller tires on and the manufactures chart says 62 lbs. for my weight. I run 64-65 lbs. regularly and when I have more than a few miles of rough stuff, I air down to about 50 psi. I think it takes the edge off and my duals don't touch in between

Remember, it's a big heavy, top-heavy vehicle, not a Baja race truck

Don't forget to air back up when you get to the pavement

Disclaimer: do this at your own risk
Ripping along a washboard road to smooth it out works for light weight PUs, jeeps, etc...

Sorry ... but no way am I going to rip along a road like this at 35-40 MPH in my ~12,000 lb. 24 ft. E450 Class C. I tried it a few seconds once, and it definitely did not work. Sloooow - with the right side tires of the RV off the main track as much as possible is the name of the game:

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Old 09-26-2021, 01:00 PM   #10
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As the low riders say, low and slow. I don't think airing down your tires for a few miles is going to hurt anything, unless you bottom the tire out on the rim. The reason that low pressure is the main cause of tire failure is that low pressure leads to heat build up which causes the belts in the tire to separate from the tread. At the speeds you are talking about there won't be any significant amount of heat generated so I don't think it will be an issue. If you're worried about heat build up stop a couple of miles or so in and see if the tires are hot, I don't think they will be. With all of that said I really don't know how much you will be gaining. Most of the problem with washboardy roads is the rocking back and forth not the up and down motion so I'm not sure your solution is going to solve much, but what the heck try it out.
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Old 09-26-2021, 06:18 PM   #11
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Ripping along a washboard road to smooth it out works for light weight PUs, jeeps, etc...

Sorry ... but no way am I going to rip along a road like this at 35-40 MPH in my ~12,000 lb. 24 ft. E450 Class C. I tried it a few seconds once, and it definitely did not work. Sloooow - with the right side tires of the RV off the main track as much as possible is the name of the game:

The flack I knew would come.


The time the dog got bit by the rattlesnake we were 20 miles off the end of the pavement. The road was pretty freshly graded gravel with not much washboard so I had not aired down. It is fairly flat with good sight lines.


Let's just say that 12,500 pounds will drift nicely at 60-70 mph if you keep your foot in it


the wife just looked up from the dog and said "just don't kill us"



I actually had to slow down when I got to the pavement between the dirt and the highway


35 mph doesn't seem like ripping to me.


The dog lived
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Old 09-26-2021, 06:22 PM   #12
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What you say is absolutely true--- at normal highway speeds. 5 mph does not create the heat needed to destroy tires. Do you have anything to contribute that is relative to my question? How low is too low at 5 mph?
So your acceptable risk at highway speed is to lower air pressure to get a comfortable ride on washboard dirt roads? PhilG told you how to drive washboard roads.
Well, yes. Years ago I had an 02 Chevy dually, when I bought new 16" LR E tires the tire shop had a bulletin on the wall stating "under no circumstances should tire pressure be less than 45 psi unloaded, or sidewall damage will occur."


This load/inflation table lists 35 psi and the absolute minimum to support the lowest load.
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Old 09-26-2021, 06:43 PM   #13
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‘Fraid I don’t have any relevant experience, but you might take your question to the folks on one of the various off-roader forums. They do it all the time with seemingly no ill effects, and may have useful insights for you.

I researched it for my Jeep JK over on Wrangler Forums (I think). Haven’t tried it yet though…


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Old 09-26-2021, 06:46 PM   #14
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Originally Posted by R Cabesa View Post
I know I will probably catch some flack for this, but here goes . . .


SPEED UP!!! 5 mph is horrible on washboard. Of course this doesn't work on curvy mountain roads but open desert/plain type roads it makes a huge difference. Roads like Carrizo, Soda Lake in central California or roads 25 & 8A in northern Nevada 35-40 mph works great. Pay attention of any upcoming curves and scrub speed early. These beasts take a while to slow.



As far as tire pressure, I have put taller tires on and the manufactures chart says 62 lbs. for my weight. I run 64-65 lbs. regularly and when I have more than a few miles of rough stuff, I air down to about 50 psi. I think it takes the edge off and my duals don't touch in between



Remember, it's a big heavy, top-heavy vehicle, not a Baja race truck



Don't forget to air back up when you get to the pavement


Disclaimer: do this at your own risk
No FLack here....I AGREE

Had to travel a wash board road Daily to/from house
5 mph....rattle your teeth
10 mph a bit smoother
15 mph...sweet spot

With just the right speed the SUSPENSION smooths out the wash boards


5 mph for 10 miles????
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