Tire Pressure?

[mikemc53]

2022 Gulfstream Conquest 6280 on a Ford E350 chassis. The tire pressure recommended on the driver door tag says 75 psi front and 65 psi rear (drw). Last year I had a young tire tech tell me that they should all be at 80 psi, which I thought might be a bit high.

I run about 80-85% weight capacity and I was wondering if the door tag is accurate. The reason I ask is that the door tags are likely put on before the vehicle is modified to become a motorhome. Would that change the recommended tire pressure?

Thanks in advance.

[4x4van]

Obviously the best option is to weigh the coach, preferably 4 corner, but at least each axle. Then use the tire manufacturer's load tables to set your pressure. The 2nd best option is to use the Federally mandated sticker on the driver's door that specifies tire pressures needed for the chassis's max GVWR. NEVER should you simply use the max psi listed on the tire (which is likely what the young "tire tech" was going by); it has no relevance to any specific rig.

[PatJ]

My personal opinion you have two good options: 1) Weigh each corner fully loaded for a trip and inflate accordingly per the tire manufacturer's inflation tables (personally I add 5psi as was previously mentioned.) 2) Inflate to max, which is 80 psi for 16" LRE tires.

I use option 1 which lined up with the "yellow tag," then added 5 psi for my own neurosis. I use option 2 when I am towing with no ill effects. When in doubt, always go with the higher pressure. For LRE tires you can't go wrong with 80 psi all around (ride/handling may be affected, but load safety will not.) Again my opinion

[pianotuna]

I run the maximum (80) on the rear. Front feels much better at 65 lb

[Cruisineasy]

way2roll wrote:

Grit dog wrote:

way2roll wrote:

Cruisineasy wrote:
I have a 2011 31' Jayco Greyhawk. I used to set the tire pressure at 80psi all around. The front always felt like it was drifting. Not much fun to drive. I lowered the front to 75psi. Made a world of difference.

Was this adjustment made on any determining facts or just from the hip? Without weighing the rig and comparing against the tire manufacturers charts, it's just a guess. Personally I find advice based on a guess is a bad idea.

Or think about it the old fashioned practical way. What % of passenger vehicles or even commercial vehicles are out there pounding the pavement every day with totally unknown tire pressures? The answer is a shat load of them. And aside from the extremes like driving on a half flat tire, how many end up on the side of the road with a low pressure blowout? Objectively, very very few. A very minuscule fraction of 1% at best.

Given that TPMS has been mandatory on all vehicles (including commercial buses) for over 20 years I doubt there are many vehicles at all where the car doesn't at least know it's own psi and issues warnings if it's too far out of a safe range. The car won't let you guess. On my wife's CRV that range is very narrow as a drop in ambient temp usually trips the low psi warning. Oddly enough and to the point, RV's are one of the few vehicles on the road that are not required to have a TPMS and thereby must be managed manually. So adjusting on the fly in a MH really is a guess and there's no system to tell you you're wrong. Unless you have an after market TPMS, And if you are diligent enough to have one of those, you probably take the time to set the psi properly.

I ride a Harley and saw a truck tire blow out and it was pretty violent. Needless to say, I don't ride next to trucks.
Not that scientific. I check the tires and the pressure every time I roll out. I lowered the front tires 2psi and drove the rig and it felt better. Dropped it another 2psi and it was great!

[Grit_dog]

Well TPMS hasn’t been mandatory for over 20 years. But it has been since 08 IIrC. And only for under 10k gvw vehicles. Although I think within the last year it is or will be mandatory for larger vehicles and trailers.
Now many light/med duty vehicles over the last 15 years do have tire pressure monitors motoring but no warnings and thresholds. Like a class C rv
So to your point yes many vehicles have some sort of tire monitoring capabilities whether operable or not. So whatever.
Heck I have only 2 out of 9 vehicles/trailers that even have tpms capability and 1 of the 2 can’t use the TPMS because it’s preset way too high. I actually had to delete the monitor screen from the display to keep from clearing the low pressure warning every time the ignition is cycled.
My point had nothing to do with Tpms anyway though. But good re-direct, albeit wholly inapplicable to the discussion since knowing pressure in no way ensures it’s the right pressure, or even close, in all vehicles like class 2-3-4 trucks and vans.

[CWilson]

Second Chance wrote:
On what was the "young tire tech" basing his recommendations

Perhaps his years of personal experience driving his 3rd hand Kia daily to Wendys when he had a previous position as a burger tech.

[way2roll]

Grit dog wrote:

way2roll wrote:

Cruisineasy wrote:
I have a 2011 31' Jayco Greyhawk. I used to set the tire pressure at 80psi all around. The front always felt like it was drifting. Not much fun to drive. I lowered the front to 75psi. Made a world of difference.

Was this adjustment made on any determining facts or just from the hip? Without weighing the rig and comparing against the tire manufacturers charts, it's just a guess. Personally I find advice based on a guess is a bad idea.

Or think about it the old fashioned practical way. What % of passenger vehicles or even commercial vehicles are out there pounding the pavement every day with totally unknown tire pressures? The answer is a shat load of them. And aside from the extremes like driving on a half flat tire, how many end up on the side of the road with a low pressure blowout? Objectively, very very few. A very minuscule fraction of 1% at best.

Given that TPMS has been mandatory on all vehicles (including commercial buses) for over 20 years I doubt there are many vehicles at all where the car doesn't at least know it's own psi and issues warnings if it's too far out of a safe range. The car won't let you guess. On my wife's CRV that range is very narrow as a drop in ambient temp usually trips the low psi warning. Oddly enough and to the point, RV's are one of the few vehicles on the road that are not required to have a TPMS and thereby must be managed manually. So adjusting on the fly in a MH really is a guess and there's no system to tell you you're wrong. Unless you have an after market TPMS, And if you are diligent enough to have one of those, you probably take the time to set the psi properly.

[Grit_dog]

way2roll wrote:

Cruisineasy wrote:
I have a 2011 31' Jayco Greyhawk. I used to set the tire pressure at 80psi all around. The front always felt like it was drifting. Not much fun to drive. I lowered the front to 75psi. Made a world of difference.

Was this adjustment made on any determining facts or just from the hip? Without weighing the rig and comparing against the tire manufacturers charts, it's just a guess. Personally I find advice based on a guess is a bad idea.

Yet it’s of almost no significance because if 75 psi cold is too low and makes a discernible negative difference in steering then 80 is likely overloaded as well. And 75 cold is close to 80 with tire heat and over 80 if ambient is warmer as well.
So it’s not a “bad” idea. A bad idea might be thinking a much lower pressure is appropriate without at least knowing a ball park weight.
It’s not rocket surgery. And load/inflation tables are merely a starting point for the min safe pressure vs weight for ALL conditions. There’s acceptable adjustability each way depending on actual conditions.
OP was/is nowhere near shooting himself in the foot by shooting from the hip….except maybe in the minds of some rvnet members.

Or think about it the old fashioned practical way. What % of passenger vehicles or even commercial vehicles are out there pounding the pavement every day with totally unknown tire pressures? The answer is a shat load of them. And aside from the extremes like driving on a half flat tire, how many end up on the side of the road with a low pressure blowout? Objectively, very very few. A very minuscule fraction of 1% at best.

Now is it better to be informed and diligent? Absolutely. But there’s a huge range of acceptability between being super diligent and obtusely negligent.
And the feller who consciously adjusted his tire pressure a small amount and knows and checks pressure (obviously) is real close to the super diligent end of the spectrum.
Saying it’s a bad idea as a sort of blanket statement is just over reacting.

[way2roll]

Cruisineasy wrote:
I have a 2011 31' Jayco Greyhawk. I used to set the tire pressure at 80psi all around. The front always felt like it was drifting. Not much fun to drive. I lowered the front to 75psi. Made a world of difference.

Was this adjustment made on any determining facts or just from the hip? Without weighing the rig and comparing against the tire manufacturers charts, it's just a guess. Personally I find advice based on a guess is a bad idea.

[Grit_dog]

Or literally just know your weight (approximately is ok) and know how to read a tire pressure chart.
It’s one thing for someone who understands absolutely nothing about vehicles to drive a little car around. It’s another if you’re responsible for operating a large vehicle.
Just because the govt doesn’t mandate training or licensing to try to ensure operators aren’t totally ignorant to the basics isn’t an excuse for not being knowledgeable enough to do basic pre trip inspections and have basic knowledge about particularly safety items like tire pressure.

[Matt_Colie]

When someone says "tires" near me, I always ask if said person has heard of Roger Marble.

Roger is a very interesting guy. I know I captured him for a bunch of answers to some of my "Forever Questions" about tires one afternoon at an FMCA Rally.

So, if you want to know what really matters, look up what he has written and take it to the bank.

Matt_C

[Cruisineasy]

I have a 2011 31' Jayco Greyhawk. I used to set the tire pressure at 80psi all around. The front always felt like it was drifting. Not much fun to drive. I lowered the front to 75psi. Made a world of difference.

[Desert_Captain]

enblethen wrote:
first thing you need to do is weigh the rig ready for the road. Gear on board, fresh water and the like.
Then go to the tire manufacturer website and get the inflation chart.
Inflate the tires according to that.
I run five pounds over chart indicated pressure!

Winner,Winner, Winner! Ding, Ding, Ding! It is just that simple. :S

For the record I have 24' E-350 Class C, GVWR 11,500# and run at or very near that often towing a 2,500# Cargo trailer. 60 psi for the fronts and 65 for the rears gives me a 5 - 10 percent fudge factor and a very smooth /stable ride.

The folks who place the door tags have no clue how you are going to load/use your coach. The kid who recommended 80 psi is an idiot as that will guaranty a horrible ride. Over inflating the fronts will make the steering loosey/goosey as it reduces the contact patch.

Opinions vary as to when but tires time out, often long before they wear out. Had a tire grenade doing $4,181 in damage {it blew the wheel well right up through the bottom the coach}. It was less than 6 years old and had been inspected by Discount tire the previous day, had 6/32" of tread, looked great and was aired for the load carried. I now replace my RV 's tires at no more than 5.5 years and yes I live in Arizona which is a "challenging" environment {to say the least} for tires.

Folks who actually use their RV's on a regular basis will often approach wearing them out {5.5 years for us is easily 40,000+ miles}. I just replaced all 4 of my duallies with Michelin Agillis Cross Climates {my front tires and spare are all Agillis CC's and just a little over 2 years old}.

As noted,... Opinions and YMMV.

:C

[Grit_dog]

Golden_HVAC wrote:
Ford put the same sticker on every E-350 they produce, and they know it will be put into a RV chassis, and should be close to the maximum GVWR. So if Ford says 65 PSI, that will give the most comfortable ride. 80 PSI and it will feel more bumps in the road. The tires should last 7 years - and you normally do not wear them out in that time.

You really should not keep the tires once they are 7 years old.

Fred.

Well, fortunately the OPs rig won’t have 7 year old tires for like 5 more years likely. But the “when to replace my tires?” recent threads could maybe use your advice, but not this one.