UPDATE - NEW INFO - Tire pressure recommendation - 1999 Diplomat - new Hankook tires

[Kuhlbreeze]

MODERATOR's EDIT.

Brian @Kuhlbreeze just PM'ed me with his 1999 Diplomat Tire Data Plate.  Based on the Hankook Inflation Table and his 10K Front and his 19K rear Axle, he will be OK at 90's or so.  BUT, if he weighs and gets a LOWER inflation MOST folks would advise NOT TO GO BELOW 90...based on all the comments from folks and knowledgeable folks, most experts and our members say not to go below 90 for a MH tire.  Therefore 90 all the way around will be fine for his Axle ratings I have attached the Photo to clear things up.  Thanks to Brian for sending it to me...END of EDIT

I have new Hankook tires 275/70R22.5 load range J  in our 99 diplomat wondering  what tire pressures you guys like I was running 100psi in all seems like a slight harsher ride 

[DavidL]

Weigh your rig front / back / tag and set YOUR pressure to your tire specifications.

Doesn't make any difference what others are doing.

[Rikadoo]

Hey brian i bought the hankook ah37 tires your right they are a little harsh. That said, untill i can get my axels weighed im just using the TP stated on the sticker next to the driver. Mine states 115 front an 100 in the rear.

Im really wanting to weigh each corner so hopefully be able to know if i need more or less.

[Ivan K]

I would imagine load range J to be a bit stiffer no matter what since it is 18 ply.

[klcdenver]

I have hankook tires and they ride rougher than Michelins, especially the 16 ply front tires. 

[Dr4Film]

As others have stated, each coach is different no matter what type of tire it has installed. The only way to get the correct psi's for your tires is to first get your corner weights. Then using the tire make and model inflation charts you can determine the psi for each axle.

There are web sites with calculation sheets available. Plug in the numbers and do the math.

Until you are able to complete that task, you can use the manufactures recommendation for inflation.

Edited August 8, 2023 by Dr4Film

[Tom Cherry]

On 8/8/2023 at 3:27 PM, Kuhlbreeze said:

I have new Hankook tires 275/70R22.5 load range J  in our 99 diplomat wondering  what tire pressures you guys like I was running 100psi in all seems like a slight harsher ride 

Edited after Brian PM'ed me the data plate.  From the TOP...it is really suggested that you read the section on weighing your rig.  There is also a PLATE or placard or label on the Driver's console or in a cabinet that tells the OEM pressures for the Tires.  You need to either FIND that or maybe the GVWR is in your manual...can NOT find your 1999 and don't know if the 2000 was different.  I guessed and thought you had a higher front axle.

https://hankooktire.com/us/files/technical-manual/4300_TBR_2022_Catalog.pdf

See Page 7.  MOST likely you have the AH37 Load Range J, which as Ben says, is an 18 ply tire.  That is a beast.  NOW, the next step would be to weigh the vehicle...do the FOUR corner routine in the manual or just look up or google how to do that.  Should be FULLY loaded with gear, full fuel and water...and your co-pilot.  YES, you may not ever travel that way...but that is the DEFACTO STANDARD...

BUT, for simplicity...if you can't find the GVWR plackard....the we will use 13 10K front and 20  19K rear. Scroll to Page 27 of the Catalog....blow up the chart....here is what you need.  You need a BALANCED load...so 13K divided by 2 equals 6.5K on each front. 

BINGO...the chart says.. 90 PSI up front.  Now, if you go HIGHER...the Axle will be overloaded.  BUT, LOWER...until you KNOW your exact weights....use the Axle rating....so 120 PSI it is.  That may be a bit "jaw jaring"... but with a Load Range J, it is what it is.  Some other tire manufacturers use different technology...but you gotta go with what you have.  ALL THE MORE INCENTIVE to WEIGH.

Rear...You use the DUAL ROW...  You need 9,500 when in a dual setup.  

BINGO... if you round up...then USE 90 PSI on rears.  There is an OLD RULE OF THUMB that many of us learned from our founders.  Never RUN BELOW 90 PSI in any tire....  SO, I opt for the 90...or maybe even a smidge more...  

That's it.  WEIGH and hope your Front is NOT too obese...LOL...then you can back off per the table.  I would RUN 90 or 92 in the rear...for safety....doesn't hurt and you will be fine...as I follow our founders and other's comments....90 Minimum...OK...some said 85...but they got flamed...  THAT IS THE GOSPEL....I have heard it many times.

Good Luck...let us know how it rides...

 

Edited August 10, 2023 by Tom Cherry
new information and data plate

[TomV48]

8 hours ago, Ivan K said:

I would imagine load range J to be a bit stiffer no matter what since it is 18 ply.

They are a bit stiff but boy the first set gave good service for 10 years.  We bought it at about 8+ yrs and went right to our Hankook dealer. He pulled them off and inspected them.   They were spotless.   Nonetheless I shortly replaced the fronts.  At ten years I replaced the rears.  At around 30k miles they were still solid inside and out and so we now have  a full new set.  Our gvrw is 20000 rear and 13000 front. 95 psi rear and 115 front.   After carefully weighing. I am safe at 110 front and 90-91 rear.    And yup.  They are still a bit stiff, but only 55% of the Michelin's my buddy mounted the same week.  $600 per wheel versus $1,100 

Oh yeah and the Michelins are only " 16 ply rated ".

[Tom Cherry]

10 hours ago, TomV48 said:

They are a bit stiff but boy the first set gave good service for 10 years.  We bought it at about 8+ yrs and went right to our Hankook dealer. He pulled them off and inspected them.   They were spotless.   Nonetheless I shortly replaced the fronts.  At ten years I replaced the rears.  At around 30k miles they were still solid inside and out and so we now have  a full new set.  Our gvrw is 20000 rear and 13000 front. 95 psi rear and 115 front.   After carefully weighing. I am safe at 110 front and 90-91 rear.    And yup.  They are still a bit stiff, but only 55% of the Michelin's my buddy mounted the same week.  $600 per wheel versus $1,100 

Oh yeah and the Michelins are only " 16 ply rated ".

Great…you seemed to know the drill.  Some don’t…you should be fine.

NOW…a generic comment.  Toyo’s have been the most recommended (my scanning of all posts and memory) lately.  Michelin used to be number 1…dry checking.  Bridgestone was a close second.  My set, on in 2012…way early around 20K to get rid of the OEM BadYears was great…up to around 55K.  Slight outer rib wear on front…i kept up with it,,,.not an issue.  OPPS, head to California from NC. Hit the Salt Flats.  OMG.  Outer rib is almost gone and you would see change in rubber layers. I consulted all our experts here and picturrs.  Finally called Josams and Brry walked me through an inspextion.  Was NOT Toe Ends.  otherwise the left would have been impacted.  He gave me specs and I measured the Toe Ends.  NOPE.

Finally, he said…been getting one of the same Bridgestone model had been having the same failure…maybe one every other month.  I found a Toyo dealer in Sacramento with two and put on the fronts and also transferred my Tyron Safety bands.  Barry at Josams said it was not a front end issue…they had never seen a front end or kingpin issue on Monaco’s under 150K or so.  Built like a tank.
 

ride is great or about the same as the Bridestones..  Later, I swopped the rears….no perceptible wear after 45K.  Bridgestone did discontinue that tire and replaced with a newer, improved design.  We had at least 50 or more members that were running them.  No issues and great mileage and NO BLOWOUTS.  Mine was the only reported failure. 

[Dick Roberts]

22 hours ago, Kuhlbreeze said:

I have new Hankook tires 275/70R22.5 load range J  in our 99 diplomat wondering  what tire pressures you guys like I was running 100psi in all seems like a slight harsher ride 

I have a 99 36B Diplomat, bought it in Jan. I put new Samson 255's on it and run them all at 110 psi. Rides good but I've also got new air bags so that may help. I didn't think 275's would fit, but if you don't have any issues I may have made a mistake going with the 255's.

On a side note, you don't have an owners manual for your 99 by any chance? The PO of mine misplaced his copy and I've been searching for a copy.

Good luck and have fun on your travels.

[FLynes]

It’s interesting that our coach’s tire tag has the front tires inflated higher than the rears…maybe because our engine sits up front.

[cbr046]

I'm sure it will be clear when you weigh the coach.  Also, those pressures are based on full GVWR.  If you weigh less you can inflate less.

Not too many places weigh 4 corners like we should but there are scales a-plenty at truck stops. 

- bob

 

[Chargerman]

5 minutes ago, FLynes said:

It’s interesting that our coach’s tire tag has the front tires inflated higher than the rears…maybe because our engine sits up front.

It’s because your fronts are single and your rears are dual therefore the fronts are each carrying more weight than each rear tire

[96 EVO]

43 minutes ago, FLynes said:

It’s interesting that our coach’s tire tag has the front tires inflated higher than the rears…maybe because our engine sits up front.

So does mine, and my engine is in the back 😃!

[FLynes]

11 hours ago, Chargerman said:

It’s because your fronts are single and your rears are dual therefore the fronts are each carrying more weight than each rear tire

Everyone’s rig is like that, look at Brian’s tag again, his is pretty much opposite of ours, 90 up front and 100 in rear; ours is 100 up front and 95 in rear. Why would Brian need more air in his duals than his singles?

Edited August 11, 2023 by FLynes

[Chargerman]

Yes, doesn’t make much sense

[Tom Cherry]

21 hours ago, FLynes said:

It’s interesting that our coach’s tire tag has the front tires inflated higher than the rears…maybe because our engine sits up front.

YES…it DOES…you gotta understand how that is calculated and it is simple  math….but based on what tires were on it when it left the factory.  NOW supposedly, the tires are supposed to be the (same).  But on some plates there is also the LOAD RANGE.  OK..how it works..

Use your Front Axle weight rating (Max).  The front axle above is a bit LOWER than most we see…don’t matter.  You have Single fronts.  Find the inflation table from the TIRE Manufacturer that you are CURRENTLY running or intend to buy.  Divide 9K by 2 = 4,500.  Look at the table for THAT specific tire or series or model on or to be put on.  Run across the table.  Find the column that has 4,500…or use the one that will support it…so if it is midway in between , use the higher pressure.  NOW if you know your specific corner or LF & RF, use the HIGHEST….and you can NOT be higher than 4,500 nor safely go below 90 PSI.

Rears are tricky.  Some tire charts list a rating for each tire…in a dual set up.  OK, divide the above 15.5K by FOUR (4). 3,875 pounds.  Look at the DUAL row or line and find the pressure that will support it or go to the next one higher if in between.

BUT, if the vendor has a “Axle” or some other designation…than that CAN  be the COMBINED rating for TWO tires…that is how Hankook did it…and we usually don’t see a combined…or 7,750….so you look for 7,750 and choose the one or next highest that will support it.

Again, in the 19.5 or 22.5 sizes, don’t go under 90…or so….the Rule of Thumb here.

That’s it.  MOST of our rigs will be front heavy….mine is almost 90% loaded…after I weighed it as the fresh water and Fuel are right behind the axle…so 115 on most major brands will work and I can’t drop it hardly a pound or two.  I also have a “hybrid” rear axle…one of the 23K and NO tag…so, I have to go higher, but in my 295/80, 100 PSI WORKS…. EDIT.  Most 3 axle or “Tags” will have the Middle Drive axle rated at typically 20K drive (4 tires) and the most rearward one or “Tag Axle” rated at 10K (2 tires) so whatever load you have…and it should be weighed and your “Tag Axle Downforce” regulator properly adjusted to achieve that….that dictates the individual pressure for each of the tag snd drive and they may NOT be the same 

[cbr046]

1 hour ago, Chargerman said:

Yes, doesn’t make much sense

Don't forget there's twice as much "tire" in the back to handle twice as much load but in the end it's all about weight distribution.  Well, maybe not 2x or the pressures would be the same (fully loaded to GVWR coach).

- bob

[Tom Cherry]

5 minutes ago, cbr046 said:

Don't forget there's twice as much "tire" in the back to handle twice as much load but in the end it's all about weight distribution.  Well, maybe not 2x or the pressures would be the same (fully loaded to GVWR coach).

- bob

Dont also forget that you have to use FRONT (single) or REAR (dual) and that can be expressed for an INDIVIDUAL tire….and assumes 4 tires…Or like Hankook, a combined weigh for TWO tires,,,,side by side,  so the number will be approximately 2X the front.  You gotta look at the chart, understand the nomenclature and know your front and rear axle(s) weight rating, but preferably your individual corner weights….then use the heaviest corner.

NOW…the ADVANCED method…and SOME don’t like it and others swear by it.  Your Inner rears will heat up more and typically be 3 PSI higher if you watch yiur TPMS screen.  Some set the outers to the COLD or say 100.  THEN set the inners to 97 or so.  Bingo…when the puppy is loaded and all tires in a state of thermal equilibrium….ALL  rears will read 100.

Class dismissed….have a nice recess…

[cbr046]

4 minutes ago, Tom Cherry said:

Dont also forget that you have to use FRONT (single) or REAR (dual) and that can be expressed for an INDIVIDUAL tire….

@Tom Cherry makes a great point . . . . This chart is typical but get the load inflation chart from the specific tire manufacturer. 

The more psi the more lbs . . . but don't forget duals get less loading.

 

- bob

[Chargerman]

To your point “with duals  you have less loading so less pressure would be needed. I’m not understanding how a coach could be so heavily loaded on the rear duals that more pressure would be need in them than the front. Has anyone here had to use higher pressure in your duals based on scale readings?

[FLynes]

Here's the chart for ours, and it makes perfect sense, per Monaco's label:

[Chargerman]

What makes perfect sense?  

[96 EVO]

19 minutes ago, Chargerman said:

To your point “with duals  you have less loading so less pressure would be needed. I’m not understanding how a coach could be so heavily loaded on the rear duals that more pressure would be need in them than the front. Has anyone here had to use higher pressure in your duals based on scale readings?

Maybe some of the single rear axle DP owners that hang a heavy motorcycle or golf cart off the back 🤔.

They are usually running over their GAWR though.

[Tom Cherry]

10 minutes ago, Chargerman said:

To your point “with duals  you have less loading so less pressure would be needed. I’m not understanding how a coach could be so heavily loaded on the rear duals that more pressure would be need in them than the front. Has anyone here had to use higher pressure in your duals based on scale readings?

You have got to do the math and know the axle ratings…that is all Monaco did….  I have 295/80/22R.  14.6K front axle or 115 PSI.  Rear 23K or 100 PSI. I have gone through two different tire manufacturers and that stays the same.  NOW, it depends.  IF your front axle is rated low and you aren’t careful with having a full fuel tank and fresh….my fronts would be much lower…but NOT when I weigh properly. I RARELY drive with a full fresh tank…25% max. So, for normal driving, I COULD lower my Fronts and jack them up when i have a full fresh for a week at a ballgame or such.  I leave alone.

BUT, if someone had a really LIGHT front axle and it weighed in some 20% LESS…due to how they load the rig or travel…and the rear bays were loaded with canned goods or monsterous tool boxes…they may be loaded to the hilt.  

We do NOT know the OP’s weights, but if he is loaded to max on rear and is way under the “norm” on the front….he would be at 85 or even 80 Front and s full 90 rear.