Tire Pressure Questions

[ciret7]

I’ve read a bunch of posts here and other places and I’m still not clear on what to do.
Tire pressure data:
- sticker in cab says 82psi (2017 ACE 29.4)
- tires are Roadmaster RM170+ 245/70R19.5 Load range G
- Thor axle weights Front 7000, Rear 12000 (I’m well within that 6180/10620)
- calc’d tire load plus 5%
Front 3675 (Front axle weight/2 X 1.05 = Weight to look up in single wheel chart.)
Rear 3150 (Rear axle weight/4 x1.05 = Weight to look up in dual wheel chart.)
- Max pressure 110psi
- Cooper/Roadmaster Load Inflation table says
Front/single 85psi
Rear/dual 75psi
I’ve also read that you should never go below 80% of Max, which would be 88psi
I’ve been running at 90-94.
Think I’d have a smoother more comfortable ride at 88, or do you think I can go lower, even if it’s below that 80% of Max? Should I stick with 90-94 and deal with the rough ride? We were on I-55 Chicago to St Louis and man, rattle the teeth out of my head in spots.
Let me know what you think and what you do.

Thanks,,
==>Eric

[dkoldman]

How did you get to be running at 90-94 PSI?

Sticker says 82 psi
Tire Mfg says Front/single 85psi & Rear/dual 75psi

Also; if you care to follow to the tire Mfg (your choice) then you can't accept parts of what they say, if they says 75psi to 110 psi is the range so be it.

If you go by the yellow sticker ( I do) then it is 82 for all tires. That is with in reasonable statistical tolerance to not make significant difference.

I have 29' RV too, and my Steer was just under 6,000 and and my drive is 11,180. My tires ( Goodyear) minimum is 80 psi ( 14 ply G rated). I use 82 to set my tire pressure when cold. It goes up and down from there.

I read hundreds of posts on this topic and even a few Tire Specialist Consultants or professed Engineers. You are not along with be confused. It is Sugar Pill for those that desire if you ask me.

If it were me, and based on what study you have done. For your tires and weight, I would run my Steer Tires at 82 and Drive Tires at 78 and call it day.

[Lt Keefer]

I would say that running your tires in the 90s is probably over kill. I would go by the manufacturers yellow sticker. Your ride and handling will probably improve at the lower psi.

[ciret7]

90 was where they were and what a friend with an ACE 30.4 runs his at.

I’ll probably drop them down a bit and see how it feels and handles.

[ciret7]

There is a lot of information and opinions out there

I’m new to the class A, so lots of investigating and learning. We’ve done 3 trips, 250 - 400 miles one way, about 2100 miles so far. Did the CHF before this trip and seemed to be an improvement, however the wind conditions were a lot better, so who knows lol. I-55 Chicago to St. Louis was REALLY rough, so I went back to looking at tire pressures. Like I said above, I’ll drop the pressures. Probably go 85psi on the steer tires and 82psi on the drive. That puts me on the tire manufacturer and chassis specs.

[dkoldman]

Originally Posted by Lt Keefer

I would say that running your tires in the 90s is probably over kill. I would go by the manufacturers yellow sticker. Your ride and handling will probably improve at the lower psi.

Question for you or thoughts from anyone...

I am a 100% yellow sticker guy, I figure I am not going to question Ford, TMC or WBGO Engineering because they may actually know my tire application needs better than Goodyear or a tire Mfg that has a specification that is written to cover every possible application.

But with that said, I recently bought a new spare. It is not mounted on a wheel, but a just in case spare tire if needed. I bought specs better than what came with the coach. It is H Rated 16 ply, and can handle 81 mph with max pressure of 120 psi versus Goodyear G670s which as G rated 14 ply and can handle 75 mph with 110 as max psi.

I intend to run those at 82 psi as well. Does that make sense?

[16ACE27]

Originally Posted by ciret7

I’ve read a bunch of posts here and other places and I’m still not clear on what to do.
Tire pressure data:
- sticker in cab says 82psi (2017 ACE 29.4)
- tires are Roadmaster RM170+ 245/70R19.5 Load range G
- Thor axle weights Front 7000, Rear 12000 (I’m well within that 6180/10620)
- calc’d tire load plus 5%
Front 3675 (Front axle weight/2 X 1.05 = Weight to look up in single wheel chart.)
Rear 3150 (Rear axle weight/4 x1.05 = Weight to look up in dual wheel chart.)
- Max pressure 110psi
- Cooper/Roadmaster Load Inflation table says
Front/single 85psi
Rear/dual 75psi
I’ve also read that you should never go below 80% of Max, which would be 88psi
I’ve been running at 90-94.
Think I’d have a smoother more comfortable ride at 88, or do you think I can go lower, even if it’s below that 80% of Max? Should I stick with 90-94 and deal with the rough ride? We were on I-55 Chicago to St Louis and man, rattle the teeth out of my head in spots.
Let me know what you think and what you do.

Thanks,,
==>Eric

Where did you read that?

Ford put those tires on the chassis to handle the Chassis; GVWR.
The 82 PSI is for when the chassis is loaded to GVWR per the TIRE MANUFACTURER'S LOAD CHART which may go even lower than 82 psi.

Doesn't lend much merit to your 80% rumor.

[ducksface]

That 80% max is a new one.
But the op did say he was a bit confused.

I'm sloppy, and lazy, but I couldn't get Google to even recognize
80% of maximum tire pressure
As a search.
And I got it to use xxyrdgjtf as a search.

Please;
No one, ever, should follow that advice.

It should be stricken, as were some other posts here, so Mrs Inane Smurf© doesn't misread and follow.

[happy]

There are so many opinions that you are going to have to chose who you ignore.

With the inflation tables from the tire makers being based on actual load range of your vehicle, I would recommend following that. I follow the Cooper (who I believe makes Roadmaster) inflation tables.


There is no need to run higher PSI as that will give a rougher ride. But, it is not a good idea to run less than the tables show. At highway speed that is dangerous.

[Scubawise]

Originally Posted by Lt Keefer

I would say that running your tires in the 90s is probably over kill. I would go by the manufacturers yellow sticker. Your ride and handling will probably improve at the lower psi.

Appreciate.
Previous posts mention this.
For me Sticker 80 rear 75 front.
3 years. 25k miles no issues

[Scubawise]

Originally Posted by happy

There are so many opinions that you are going to have to chose who you ignore.

With the inflation tables from the tire makers being based on actual load range of your vehicle, I would recommend following that. I follow the Cooper (who I believe makes Roadmaster) inflation tables.


There is no need to run higher PSI as that will give a rougher ride. But, it is not a good idea to run less than the tables show. At highway speed that is dangerous.

Thanks will print and review

[dkoldman]

One of the easiest things in life to do, is to gather proof that something The Ace and The Damn Duck both say is true.

So I go to my Goodyear Tire & Rubber Table, and I can see the scale for a sample of tires call for the low psi to be as low as 72% of it's maximum psi rating.

So it looks like Goodyear did not get the 80% email

Lighter loads on a tire is a good thing, and same for higher speed rating. Not that you need to drive that fast, but you can improve your margin of safety. You can also fill up with air faster. KISS principles applies, Keep it Simple... I just make sure all tires are at 82 psi and my head does not hurt.

[Lt Keefer]

Originally Posted by dkoldman

Question for you or thoughts from anyone...

I am a 100% yellow sticker guy, I figure I am not going to question Ford, TMC or WBGO Engineering because they may actually know my tire application needs better than Goodyear or a tire Mfg that has a specification that is written to cover every possible application.

But with that said, I recently bought a new spare. It is not mounted on a wheel, but a just in case spare tire if needed. I bought specs better than what came with the coach. It is H Rated 16 ply, and can handle 81 mph with max pressure of 120 psi versus Goodyear G670s which as G rated 14 ply and can handle 75 mph with 110 as max psi.

I intend to run those at 82 psi as well. Does that make sense?

When I bought my current coach I loaded it for travel, to include full water and fuel, then weighed the coach at a CAT scale. I then adjusted the tire pressures based on the Goodyear tables. Those pressures were a tad below the yellow sticker rating. That, and folks I trust on this forum, tells me that the yellow stickers are accurate. So I just recommend the yellow stickers. For my coach, I just inflate to 80 psi which splits the difference from the higher rating yellow sticker and the Goodyear weight table for my tires. The Goodyear tables also informed me that my tires have a speed rating of 75 MPH.

[MLP]

The posted sticker in an RV like a car is for the maximum weight the vehicle is rated for. Depending on just how you load your vehicle, it maybe over kill or under inflated. CAT scale is the same problem for some. If you are heaver on one side, then you will be under inflated. I add ten psi to the CAT scale weigh use on the tire manufacture load/pressure chart. Four point weighing is the only sure way to be sure. Each time I was four point weighted, the psi added to the required CAT scale weight was actually spot on. If you are equal weigh on both sides, then the CAT weigh is perfect.

[ciret7]

Thanks for the interesting and lively discussion ��

The 80% of Max was my mistake, it’s 80% of recommended pressure. Only “official” reference to that was from OSHA ¯\_(ツ)_/¯

I’m gonna go with 85 steer and 82 drive based on Cooper Load Inflation chart for the steer/85 and coach sticker for the drive/82.

I also understand it’s a small class A on a truck chassis, it’s gonna ride like a truck Glad my daily driver is a Jeep Wrangler, that definitely rides like a truck lol

The other thing is the road makes a huge difference, on the well maintained tollway ride was smooth and surprisingly quiet.

[dkoldman]

Originally Posted by Lt Keefer

When I bought my current coach I loaded it for travel, to include full water and fuel, then weighed the coach at a CAT scale. I then adjusted the tire pressures based on the Goodyear tables. Those pressures were a tad below the yellow sticker rating. That, and folks I trust on this forum, tells me that the yellow stickers are accurate. So I just recommend the yellow stickers. For my coach, I just inflate to 80 psi which splits the difference from the higher rating yellow sticker and the Goodyear weight table for my tires. The Goodyear tables also informed me that my tires have a speed rating of 75 MPH.

I have gone 4 years 100% yellow sticker. I finally did a weigh or two a few months back but it was only for GCVWR for new toad.

Per Goodyear 80 psi is the lowest possible setting for my tires. I would have to grossly exceed the GVWR to ever have need to increase the pressure. That will never happen.

But my question is given that I have all of my Goodyear tires at 82 psi and I have bought a new spare tire from different Mfg; It is H Rated 16 ply, and can handle 81 mph with max pressure of 120 psi versus Goodyear G670s which is G rated 14 ply and can handle 75 mph with 110 as max psi.

Am I good with keeping the better rated tires at 82 psi? I assume that my new tire can handle more load, speed etc and still perform at 82 psi?

[happy]

If Goodyear shows that 80 psi of a specific Goodyear tire handles the weight of your vehicle it should be perfect.
Adding a few extra psi should not hurt. The sticker placed on your vehicle is for the tires the factory put on your vehicle when they made it. The factory sticker does not apply for any changes you make to your tires ...... if those changes affect the load carrying ability of the the tires.


You can get the same size tire in different weight carrying abilities. 285/70/17 with a C rating or an E rating. Service index of 110 or 112 etc...
With an Axis many use Commercial C rated tires and need to increase the PSI to get the higher weight carrying ability. All without changing the size of the tire.
If you stayed with the factory sticker PSI you probably not be correct.

[dkoldman]

Originally Posted by happy

If Goodyear shows that 80 psi of a specific Goodyear tire handles the weight of your vehicle it should be perfect.
Adding a few extra psi should not hurt. The sticker placed on your vehicle is for the tires the factory put on your vehicle when they made it. The factory sticker does not apply for any changes you make to your tires ...... if those changes affect the load carrying ability of the the tires.


You can get the same size tire in different weight carrying abilities. 285/70/17 with a C rating or an E rating. Service index of 110 or 112 etc...
With an Axis many use Commercial C rated tires and need to increase the PSI to get the higher weight carrying ability. All without changing the size of the tire.
If you stayed with the factory sticker PSI you probably not be correct.

I don't think my question is clear. I am all set for 4 years running using 82 psi on all OEM tires from Goodyear.

My question is that I recently bought a brand new spare, it is spare not mounted and not even on a wheel. I bought the tire because it has better specifications than Goodyear (forget air pressure for a moment). It is a Goodride CR960A = H Rated 16 ply, and can handle 81 mph with max pressure of 120 psi versus Goodyear G670s which is G rated 14 ply and can handle 75 mph with 110 as max psi.

So now the tire pressure question, given I have a stronger and better tire, shouldn't it be able to run on or at least what the Goodyear could do which is 82 psi? My thinking is I have same requirement for my Coach, I just bought a better tire than what Ford put on.

[MLP]

It depends on what the manufacture says. Get their load/pressure chart. That will tell you the correct answer.

[ducksface]

Look up
Tire chaulking.
Ignore the 'other' tire chaulking cops do.

Chaulking is the only way to determine psi with any reason to believe, on any tire, at any temperature, of any size, on any vehicle, at any weight, ever.

Everything else, bar none, is legalese or preference.

Consider doing it right.
The guesses are guesses, the tales are preferences.