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

[Chargerman]

I’m referring to the Monaco placard this has been shown and finding it hard to understand how they would have come up with a higher recommended pressure for the rears. My feeling is that it’s an error and am curious if anyone with a single rear axle coach has ever had to run higher pressures in the rear. We can come up with possible scenarios where a higher pressure would be needed such as hauling a lunar rock collection around the country 😂 but I’m wondering if anyone has had to run higher rear pressures based on scale weights. Feeling pretty sure that the answer is no. 

[Paul J A]

5 hours ago, Tom Cherry said:

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…. Tags are typically 20K drive (4 tires) and 10K tag (2 tires) so whatever load you have…and it should be weighed and your tag “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 

"Tags are typically 20K drive (4 tires) and 10K tag (2 tires)"  That is a little confusing.  

"Tags are typically 10K, {2 tires}, 20K drive {4 tires}" may be what you intended to type.   

[Tom Cherry]

59 minutes ago, Paul J A said:

"Tags are typically 20K drive (4 tires) and 10K tag (2 tires)"  That is a little confusing.  

"Tags are typically 10K, {2 tires}, 20K drive {4 tires}" may be what you intended to type.   

Most 3 axle or “TAG” MH have the drive (4 wheels) and the rear Tag (2 wheels) rated at 10K.

Sorry if my shorthand was confusing….

Hope this  clears it up. I edited the text on the post…

Thanks

[Tom Cherry]

5 hours ago, Chargerman said:

I’m referring to the Monaco placard this has been shown and finding it hard to understand how they would have come up with a higher recommended pressure for the rears. My feeling is that it’s an error and am curious if anyone with a single rear axle coach has ever had to run higher pressures in the rear. We can come up with possible scenarios where a higher pressure would be needed such as hauling a lunar rock collection around the country 😂 but I’m wondering if anyone has had to run higher rear pressures based on scale weights. Feeling pretty sure that the answer is no. 

@Chargerman & @Kuhlbreeze…. Please read this carefully….I hope it answers the plaguing questions and also verifies the pressures for the new Hankooks.

I alway thought that Monaco made their Tire Pressure plate according to a simple calculation.  But, as you say, this one does, when i step back…looks a little crazy…. NOW the caveat….what tires did they use and what was the Load Range…. So here goes…please check me out on this…

Per the ORIGINAL plate that was posted….and we DO NOT know the Load range  BUT…I looked up Bridgestone as their “specs” almost mirror the Goodyears that  Monaco was using…  I also looked at the Hankook.  The chart that was a screen shot matches the Goodyear…it gets a bit dicey…but here goes…

https://commercial.bridgestone.com/content/dam/commercial/bridgestone/pdfs/l-and-i-tables/Bridgestone-TBR-Load-And-Inflation-Tables.pdf

255/70R22.5.  The Load Range G tires max out at 4675.  The front needs 10K dvided by 2 or 5K. The rears need 19 K divided by 4 or 4,750.  The Load range G will NOT work

Thus…we go to a Load Range H.  So. Bridgestone…. Front 5K or 105 PSI..(please check me out and verify).  Rear 4,750 remember to use the DUAL and that is PER tire. 115 PSI will get you 4,916 but 110 PSI will only get 4,675…which is the MAX for a Load Range G…but the H keeps on going up.  SO…today…10 PSI more in the rear with the present day, same oem tire, load range H…read on.

NOW….where did Monaco come up with the PSI.  24 years ago….who knows.  BUT if you walked into a knowledgeable Bridgestone shop and they pulled out the tables (attached) younwould,buy Load Range H and run a HIGHER pressure in the rear.  Thus…the plate is correct, sort of, maybe back when…but today there is 10 PSI MORE in the rears than the front.

NOW…we do NOT have that situation today.  He has a LARGER tire size and it is a whopping Load Range J.  So, the OP can, unless I misread, run a much lower pressure…I just rechecked…. Hankook 275/70R22.5 18 Ply or Load Range.  Front…90…never go below 90…. Rear 90 PSI = 18,940.  OPPS..need 19,000. 95 PSI will give 19,780.  So, add, interpolating, one PSI…run 91…. BUT…the rears are STILL higher…if you follow the “use the next 5 PSI as a “safety factor”.

So, to answer your question….yes, depending on the tire and axle and load range, yes, Monaco DID produce a MH that required MORE rear air than the front….a MINORITY….yes…but NOT a “math error”.  Hope that finally clears it up.  This topic is beginning to look like a dead equine…

Thanks for being diligent and forcing me to do the research…again…

[FLynes]

7 hours ago, Chargerman said:

What makes perfect sense?  

That our coach’s tire label would match Michelin’s chart.

Edited August 12, 2023 by FLynes

[6Wheels]

The original tires were 255/70R22.5 and are fine per the specs from Hankook on their AH34 with 100 on the front and 120 on the rears.

By jumping to the next size up you shift the load range up and the inflation down, but you get a stiffer ride with no benefit.

Based on their inflation chart if you ignore the axle number you should be running 90 psi on the front and 80 psi on the rear (see below). 

Then take into account the axle on the front @ 10,000 lbs. and you can use the single axle number of 90 psi, but on the rear since your axle is rated 19,000 lbs. you will have to run @ 95 psi.

Hankook technical manual - page 26

Edited August 12, 2023 by 6Wheels
error correction

[saflyer]

On 8/8/2023 at 2:27 PM, Kuhlbreeze said:

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 

If possible best advice is to weigh each wheel position rather than axle then use heaviest side time 2 for the tables. But that’s not always possible to get position weights.

[Tom Cherry]

1 hour ago, 6Wheels said:

The original tires were 255/70R22.5 and are fine per the specs from Hankook on their AH34 with 100 on the front and 120 on the rears.

By jumping to the next size up you shift the load range up and the inflation down, but you get a stiffer ride with no benefit.

Based on their inflation chart if you ignore the axle number you should be running 80 psi on the front and 95 psi on the rear. 

Then take into account the axle on the front @ 10,000 lbs. and you can use the single axle number of 90 psi, but on the rear since your axle is rated 19,000 lbs. you will have to run @ 95 psi.

Hankook technical manual - page 26

HOWEVER…the conventional wisdom of our founders and many here that attended the various Monaco rallies and talked to tire engineers from the factories.  Running a 22.5 MH tire below 90 is not recommended.  Yes, the charts say that, but the increased pressure from 80 to 90 will have negligible impact on ride quality and prevent some major issues…. So that is the advice that we offer…

 

[VinceB]

On 8/9/2023 at 11:20 AM, Dick Roberts said:

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.

As for the 275's: I had the same thought when I first got the coach and called Monaco. Tech support said to stay with the 255's stating that ride height, transmission shifting, handling, and engine tune would all be negatively affected.

[Ivan K]

The above depends on tire diameter change. If you find a wider tire with lower profile so that the diameter difference is negligible and can carry the same weight at less tire pressure and still fits the rim width and the wheel well, you would do good. In truckers world, wearing the tires down changes diameter more than we would ever see and therefore rotations per mile changes much more for them than our irregular driving could ever do. There is actually a setting in my ECM that can vary the rotations per mile value based on expected wear over distance driven. I doubt anyone worries about it much, I don't. 

[Oldgoat]

On 8/8/2023 at 2:27 PM, Kuhlbreeze said:

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 

I run 295 75R22.5 Toyos on my 97 Dynasty. Tire dealer said to run 110 psi. I do depending on the load.

[jimc99999]

My 97 Windsor weighed at 9200 front, 18500 rear, on Falken 255/70R22.5. The Falken inflation chart indicated 90 psi was good. I usually ran 92-95 psi. After 20K miles, the front tires were worn evenly except for a 1/8" strip around the outside edges of each front tire. When I had them replaced (aged out) I asked the tire guy about that and he suggested running higher pressure. I run the new tires (Cooper, I think?) at 100-105 psi, no real difference in ride quality.

One thing I've noticed is that on a hot day (95+ ambient, 140+ road surface), the hot pressures still go up to 115-120 psi. However that was a 20-25 psi increase from 95 psi, but only a 10-15 psi increase from 105.

So overall, I'd suggest running higher pressures than lower pressures. If your tires usually run 115-120psi hot, then it takes more heat to hit that pressure from 95 than 105. 

Edited August 13, 2023 by jimc99999

[Tom Cherry]

23 hours ago, VinceB said:

As for the 275's: I had the same thought when I first got the coach and called Monaco. Tech support said to stay with the 255's stating that ride height, transmission shifting, handling, and engine tune would all be negatively affected.

Well…as they say, that depends.  If you had a Cummins shop or a qualified repair shop with the Insight software, they MIGHT have been able to make a simple change.  When folks loose their ECM’s and they have to be “modified” by the tech installing a replacement…the Cummins or OEM equivalrnt has all the hard parameters.  But things like tire size, rev’s per mile, rear end ratio, turns per whatever from the Allison….PLUS a hold host of others pertaining to the type of .exhaust brake and cruise control parameters were Monaco SUPPLIED and programmed by a third party into the ECM.

So, change tires…a tech just updates the tire size and revs per mile…assuming that ECM had that field or parameter.  NOW if it did not…maybe.  But the info that is in most of the mid to later 2005 or so…probably earlier…could be changed. 

Unless you did the calculations on the centerline to “road surface”, you might be surprised to see very little change.  Some folks have gone to dealers and measured the center point on the hubs for a larger tire and it is NOT that different.  Conversely, there was a world of difference in the original (2010 or so) tire tread patch of the OEM GY compared to the SAME Michelin equivalent.  That is why a lot of folks, especially in Dynasty and up, went one tire size greater as they did NOT want less “rubber on the ground”.  Had friends that sw tht and did on their Camelot’s.  Never changed the ride height that you could measure…

Just what folks have reported here since 2010….and we had a world of uogrades after that…no issues…and the owners were very picky about ride and handling…one was a professional sports car driver…so he probably knew his stuff…

Just passing on…to clarify…. We have also had way too many “reputable” tire shops tell owners what pressures to run without a clue as to their axle ratings and load pounds…

3 hours ago, jimc99999 said:

My 97 Windsor weighed at 9200 front, 18500 rear, on Falken 255/70R22.5. The Falken inflation chart indicated 90 psi was good. I usually ran 92-95 psi. After 20K miles, the front tires were worn evenly except for a 1/8" strip around the outside edges of each front tire. When I had them replaced (aged out) I asked the tire guy about that and he suggested running higher pressure. I run the new tires (Cooper, I think?) at 100-105 psi, no real difference in ride quality.

One thing I've noticed is that on a hot day (95+ ambient, 140+ road surface), the hot pressures still go up to 115-120 psi. However that was a 20-25 psi increase from 95 psi, but only a 10-15 psi increase from 105.

So overall, I'd suggest running higher pressures than lower pressures. If your tires usually run 115-120psi hot, then it takes more heat to hit that pressure from 95 than 105. 

Good info….to clarify, i spent some time tslking to,the Bridgestone tire (commercial) engineering manager…also a MH owner.  He said to follow the ratings and pressures for the individual tires, but not to go “too low”.  Thus, if it says 80/85…go up 5 - 10 pounds.  

BUT…that is NOT a hard and fast rule.  GY Engineers told Monaco owners at rallies and company sponsored events that the “rivering” was NORMAL.  RIGHT.  Then they said to bump up the pressures…would cure it and NO Problems.  RIGHT. He, the Bridgestone engineering manager, said if you were above 100 - say 110.  KNOW YOUR WEIGHTS and follow the guidelines.  I needed 114 (weights) for my front axle.  Ran the GY at 123.  Helluva ride.  He told me to check the rim.  It maxed out at 129.  He said that the failure rate for increasing say a 1 PSI “needed - proper) inflation just increased the probability of early tire failure. I have a TPMS.  I am a retired engineer.  I started watching the “Thermal Equilibrium” pressures on say a 90 deg day, black surface from 123/4 or so.  It was almost to 145 PSI.  Did some research.  The internal temps of my tires were getting close to the worry point of a TRUE 165/170.  Dropped back to 114.  Then it was lower…like in the mid to low 130’s…may be off in the magnitude, but the delta T for a highly inflated tire was maybe 25% where using s lower pressure only went up 20% of so.  Never did that again…got rid of the GY (BadYears as they were called here)…. Bridgestones ran less…as does my Toyo’s…

[Dennis N - 2005 Windsor]

18 hours ago, Tom Cherry said:

 Dropped back to 114.  Then it was lower…li

Interesting, that's counterintuitive. Lower pressure will typically cause the tire to flex more and produce more heat. I assume all other conditions were similar like running the higher pressure? Similar road conditions?

[Tom Cherry]

16 minutes ago, Dennis N - 2005 Windsor said:

Interesting, that's counterintuitive. Lower pressure will typically cause the tire to flex more and produce more heat. I assume all other conditions were similar like running the higher pressure? Similar road conditions?

His comment was that higher pressures, even within the recommended guidelines cause more stress on the belts and the side wall and that you are a greater or more risk if you hit a pothole.  Therefore, he or Bridgestone, since he authored their “TIRE DOCTOR” site, recommended only inflating to the required TP for the “load” or measured weights and not arbitrarily adding a 5 - 10 PSI increase….based on “more is better” which is what, per many older members, the GY engineers recommended.

He explained that higher pressures and higher speeds, based on their tests as well as warranty claims lead to increased risk of failure.  Yes, I totally agree about low pressure and heat and such.  But, having run the 123/4 PSI for at least 15K, I felt, and he agreed, that there was more than a possibility that I had some minute or microscopic damage to the belts.  That was one compelling reason, I got rid of them.

 

[JimC295]

Moderator EDIT

This new topic and same tire size was covered in a recent and and very informative topic.  Therefore the new tooic has been merged into the current one.

End EDIT

@JimC295….please note…

I am gonna replace the steer tires right away on this coach. The window sticker says 255 70r 22.5 for OEM tires any recommendations from this group. Also I think I'll keep 1 of the old tires for a spare. The Date codes on the tires are 2015

[DavidL]

Having just gone through that, you likely need to replace all tires with that old of a date code.  When the tires were deflated on mine, the cracks became very apparent.

I got mine via the FMCA Michelin tire program.  Picked them up and had them mounted near locally.  Used balancing beads and replaced all stems.

 

And did air bags, shocks, grease etc. too.

Edited September 6, 2023 by DavidL

[Steve P]

Plenty of recent threads... seemingly leaning toward Toyo or Yokohama.  Michelin is said to have a hard ride.  Everyone is thumbs down on Goodyear, but before I knew better, I bought 6 of those on day 1 of ownership with a very old date code and have had reliable service from them for the past 3 years.  I am budgeting for new tires every 5 years unless they show issues sooner.  Other options like beads, bands, are discretionary purchases, and owner preferences abound. 

[JimC295]

1 hour ago, DavidL said:

Having just gone through that, you likely need to replace all tires with that old of a date code.  When the tires were deflated on mine, the cracks became very apparent.

I got mine via the FMCA Michelin tire program.  Picked them up and had them mounted near locally.  Used balancing beads and replaced all stems.

 

And did air bags, shocks, grease etc. too.

Any thoughts on 295 vs 255

[DavidL]

Increasing the tire size:

The rim width needs to be correct for the tire

The bigger tire might hit shocks, body.

Bigger tires cost more

Bigger tires generally have more weight capacity

Bigger tires might ride a bit smoother (more tire to "give" over bumps)

 

[Tom Cherry]

@JimC295

Merged your new topic with a recent ongoing one where your questions and such was just covered with a lot of detail and also explanations of how tires “work” and how to select the proper size as well as what you need to know and do for safety and the best ride.  Please start at the beginning of it and read…as well as take a little time to totally understand.

David made a good point.  Before you arbitrarily increase….to any tire size…do NOT depend on a tire dealer to be the KNOW IT ALL.  Anytime you increase a tire size…you MUST know if your rim is “OK” or “also approved…but NOT” in the normal size. If you don’t have the rim spec from the data plate (inside the MH”, then get the rim model or PN from the rim and the manufacturer.  Call them.  You probably have Alcoa or Accuride.  Find out what the width is.  

I could NOT find the 2003 manual or brochure for your MH…Monaco was sort of a “dead” year in 2003 for some models.

ODDS ARE….from the 2002…you have the following…

Tire 255/70R22.5.  Rear axle 16,000. Front axle 10,000.

BUT in 2004, Monaco did a little redesign….then it was

Tire 275/70R22.5. Rear axle 20K. Front axle 12K.

MEMORY tells me the wheels were the same…so, MAYBE the 275/70 is “the tire”.  But, I would really want to know everything about the wheel and what the manufacturer says and such before I jumped head long in to the “295 water”.  Even when an “alternative rim width” is listed for a certain tire, that gives me concerns….

MAYBE there is a 2004 Knight owner that can give you the brand and model or PN of the rims off their rig.  If it is the same…then you are good to go on the upgrade that Monaco did…and save some time….but if not…do the research…

BUT…if you take the time to read this entire topic from the beginning….I know, since I contributed to it, that it is a great “Primer” on MH & MH tires….and since this is your “home”, you want the best for safety and the best for “good value” as well as ride.

BTW…if you start to use the search box in the upper right….I used TIRE and then clicked on EVERYWHERE.  There is a drop down and I chose Topics.  Then you sort of eyeball and sample.  Usually the most recent…but also with a fair number of posts is what I click on and scroll….that sill be invaluable as you continue to learn…

Good luck and welcome aboard….

[Simplysmn]

I get my toyo tires from  Bbwheels.com.  or also try Simpletire.com.  they both offer free shipping and  Great prices. 

[cbr046]

19 minutes ago, Tom Cherry said:

@JimC295

ODDS ARE….from the 2002…you have the following - Tire 255/70R22.5.  Rear axle 16,000. Front axle 10,000.

BUT in 2004, Monaco did a little redesign….then it was - Tire 275/70R22.5. Rear axle 20K. Front axle 12K.

The 2002 Knight was on a Roadmaster RM4C (Safari Magnum) chassis, the 2004 Knight used the RR4R chassis.  2003 is still a mystery.  Now, where was that discussion on Roadmaster chassis?  Here's one, but not the one I was thinking of -  https://www.irv2.com/forums/f24/roadmaster-m-series-chassis-why-432176.html 

Here's a link to some brochures - https://recreationalvehicles.info/tags/Monaco/page/2/

I also searched Holiday Rambler (Neptune 15,500 / 8,500) and found a 2003 brochure but the only chassis description was "Raised Rail", which I guess is the RR chassis.  I couldn't find an Ambassador brochure with weights in it.  HR's are sisters to the Monaco line. 

Was Monaco on the weight bubble and decided the 2002 coach was too close to chassis GVWR and didn't allow for customer loading (all the junk we pile in) to dictate an upgraded chassis?  Or did they just run out of Safari Magnum chassis? 

It's all a mystery . . . .

- bob

 

[cbr046]

34 minutes ago, Simplysmn said:

I get my toyo tires from  Bbwheels.com.  or also try Simpletire.com.  they both offer free shipping and  Great prices. 

Also consider speed rating.  Speed rating is based on sustained speed over a period of time (5 minutes?) not just peak speed.  Most are L speed rated (75mph) which sounds like plenty of margin but I've had my coach over that a few times (not intentionally) and appreciate more margin than that.  I have my eye on a set of Sumitomo ST719's with an M speed rating (81mph). 

I seem to recall running across 2 tires of the same brand / model in the same size . . . . difference, besides speed rating, turned out to be in the ply rating, which also translated to load capacity. 

- bob

[Tom Cherry]

30 minutes ago, cbr046 said:

Also consider speed rating.  Speed rating is based on sustained speed over a period of time (5 minutes?) not just peak speed.  Most are L speed rated (75mph) which sounds like plenty of margin but I've had my coach over that a few times (not intentionally) and appreciate more margin than that.  I have my eye on a set of Sumitomo ST719's with an M speed rating (81mph). 

I seem to recall running across 2 tires of the same brand / model in the same size . . . . difference, besides speed rating, turned out to be in the ply rating, which also translated to load capacity. 

- bob

Technically, for a truck or bus tire, the Alpha Code is “LOAD RANGE”.  Yes, you can look up the max speed for that tire based on what the manufacturer says is max.  Somewhere in the back of my mind, one company says X and the others might say Y MPH.

Speed ratings on passenger tire are Alpha-Numeric…

The general rule of thumb.  Many of the major manufacturers have a blanket 70…maybe 75…for sustained speeds.  Most adhere to the 70 as a safe, but, OK, passing or for a sustained hour or so….maybe 75.

Purely judgement unless you know the max speed for your size and model(series) from the manufacturer’s specs.

The other rule…whatever speed you shift into top gear 4 - 5 on the lower Allison’s or 5 - 6 on the MH3000 or higher….one or two MPH above is your sweet spot…for FUEL EFFICIENCY.  For every (lots of papers written on this), you loose 0.1 MPG.  Many of us have records from day one and tested….pretty good rule.

Fuel economy discourages a lot of folks…but I used to caravan with folks where we had a Prevost & 3 or so new Navigators….those puppies like 73 MPH as tge cruise set point….spooky…but you get used to it…and if I need to make camp before dark…70 or a smidge is what I do…

Just a little clarification….