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way2roll

Wilmington NC

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Posted: 02/14/19 01:37pm Link  |  Quote  |  Print  |  Notify Moderator

RLS7201 wrote:

The motor home manufacture puts a decal close to the drivers seat with recommended tire pressures on it. That should be all you need.

Richard


There are a few issues with this method. First, many owners change the brand and type of tires. This will change the specs based on tire manufacturers since they are different than what left the factory. Also I have found in the few MH's that I have owned, that when I weighed my rig it was pretty far off from what the actual weights were (even unloaded).

While I agree that some folks overthink this and tires being what they are engineered to do, will perform in a pretty wide range of temps and pressures.

But the most effective way to do it right - and you only have to do it once, is to weigh your rig as it's prepped for travel, and adjust PSI based on the tire manufacturers chart. That's it. Check it cold before driving, and get a TPMS. Not only is this the safest method it's probably also the best method for proper ride and control.

And have fun watching the TPMS as your tires go through all sorts of temp and psi changes as you drive. I was amazed at how one side heats more than the other based on road crown, wind or the sun. Hard not to freak out until you start to learn what tires are capable of.

rk911

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Posted: 02/14/19 02:58pm Link  |  Quote  |  Print  |  Notify Moderator

RLS7201 wrote:

The motor home manufacture puts a decal close to the drivers seat with recommended tire pressures on it. That should be all you need.

Richard

not really. you can't be sure what they base that pressure on...GVWR, something else?

best way to ensure that your tires are properly inflated is to load up the RV as you would for travel including full fresh water, LP and fuel tanks, food, supplies, pets, clothing, other stuff and people and then get it weighed. 4-corners is best but individual axle weights will do. this will be your worst case scenario. consult your tire mfg's inflation chart for correct inflation for the weight you're carrying. I usually add 5-psi just cuz.

as for your weight changing...of course it will. as you use fuel, fresh water and lp your weight will go down and as you add gray and black water your weight goes up but, at least the folks we hang with, the basic weight...the stuff, food, etc. changes very little.


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Posted: 02/15/19 09:20am Link  |  Quote  |  Print  |  Notify Moderator

Lurker52 wrote:

Hello Everyone,

I have a 2001 Monaco Night 36’ DP. My question is about tire pressure. The tires are Goodyear G 661 HAS load range H 255/70 R 22.5 The tires say max. pressure 120#

I am not sure what the correct pressure should be. I have not weighed the RV but I have a Cat Scale ticket from the previous owner. He weighted it ready to travel. Full fuel gear and water.
The ticket shows a total of 27,140# but 3120# of that is his toad. The front weight was 8640#. The rear was 15,380#. If I understand this right that means each front tire has 4320# on each. The rears (duallys) have 3845# on each of the four tires.

The sticker in the coach says to inflate front and rears to 80#. I have looked for an inflation chart on the internet for these tires and have not found an exact match. I have found very similar Goodyears that say the rears should be at 80# and the front at 85#.

When I checked the tires, they are at 90#. I would like to lower the pressure a little to help with handling. The RV has the steering box that is not adjustable and has some play in the wheel and wonders a bit at high way speed 60-65 mph.

Any insight on correct pressure or where I can find a chart is appreciated.

Thanks as always,
Lurker

Have put weigts of former user in my made extra safe calculator.
Gave Front 103 psi so make it 105, and rear 99psi so make it 100.

Ofcource new weighing, as suggested, is better, wich you then can use for years, the little variation will be covered by the reserves I put in.

Calculator spreadsheet first adds 10% to weighed axleloads, and then calculates with a safer formula then those are used for the official lists, so higher pressure outcome.

wa8yxm

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Posted: 02/15/19 02:45pm Link  |  Quote  |  Print  |  Notify Moderator

Cat Scales tend to be Bridge scales they give you axle weight but not wheel weight.. Some folks say you should set both sides to the same pressure. I AM NOT ONE OF THEM

You really need wheel weights. First the Easy Way
RVSAFETY.COM (may need a WWW.) and follow the links on that page. reasonable price. they use portable scales and will tell you the proper pressure.

Hard way (But less expensive I think (not sure)

Find a FLAT scale. Segmented. Pull on and get weighed. Now pull around so only one side of the RV is on the scale.. That's the wheel weights for that side. Axle - wheel = Wheel weight for the other side.

Then the Tire Company Support page will have a pressure/load chart.


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4x4van

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Posted: 03/20/19 02:18pm Link  |  Quote  |  Print  |  Notify Moderator

The axle weights (per the previous owner) suggest 85psi front, 80psi rear, using Goodyear's table, IF the weight is evenly distributed left/right (unlikely). So bumping those numbers up to 90 front, 85 rear is what I would likely go with till I got a new weigh done with MY load.

However, I see a dilemma here. The coach manufacturer's sticker says 80psi, front and rear, and since those numbers are (normally) based on the maximum GAWRs, it suggests that your coach's front axle may very well be overloaded (assuming that your current tires match the size listed on that sticker). You need to get on a scale, sooner, not later, to verify what you have to work with.

* This post was edited 03/20/19 02:30pm by 4x4van *


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rk911

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Posted: 03/20/19 02:30pm Link  |  Quote  |  Print  |  Notify Moderator

what are the GAWRs on your MH? compare that to the Goodyear inflation table. the info on the door may refer to something other than GAWR. or the original tires may have been a different brand or load rating. what’s the max cold psi marked on the tires?

wa8yxm

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Posted: 03/20/19 04:43pm Link  |  Quote  |  Print  |  Notify Moderator

First the correct tire pressure may be different from wheel to wheel. So you need 4 corner weights and the tire maker's inflation chart.. That's it folks

HOw to do that method one

Www.rvsafety.com and follow the links to get it weighed. They do most all the grunt work for you but it costs a bit.. (Generally more than a truck scale)

option 2: FInd a FLAT and I mean FLAT segmented truck scale. MOST CAT scales are bridge type and those will not work (you drive up on a bridge)

Park so each axle is on a segment by itself (Be loaded for travel) get a weight ticket

Now pull around so only one side of the RV is on the scale again one wheel per segment.. Axle weight - one side weight = other side weight.

now use the tire company's charts.

wolfe10

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Posted: 03/20/19 07:28pm Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

First the correct tire pressure may be different from wheel to wheel.


100% of the tire manufacturer recommendations I have read say ALL tires on an axle must have the same pressure based on the heavier wheel position.

If you have found contradictory info, please let us know.

Thanks.


Brett Wolfe
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hohenwald48

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Posted: 03/21/19 06:18am Link  |  Quote  |  Print  |  Notify Moderator

I'm not 100% sure (maybe like 99.99%), but I don't think it matters who's pressure chart you use. I think as long as you are looking at a chart with the correct tire size and load range then all charts will be the same for any given weight. So it's not necessary to find the specific tire manufacturers chart. However, in these days of Google and the internet that shouldn't be too hard to find.


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4x4van

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Posted: 03/21/19 07:46am Link  |  Quote  |  Print  |  Notify Moderator

hohenwald48 wrote:

I'm not 100% sure (maybe like 99.99%), but I don't think it matters who's pressure chart you use. I think as long as you are looking at a chart with the correct tire size and load range then all charts will be the same for any given weight. So it's not necessary to find the specific tire manufacturers chart. However, in these days of Google and the internet that shouldn't be too hard to find.
While there may be a few oddball tires out there, for the most part, that is correct. I also believe that all RV manufacturers base their tire pressure tag on GAWRs. So if the OP has the same size/load range tires as listed on the tag, it would appear that he is is overloaded on the front axle, since 80psi (listed on the tag) in a 225/70-22.5 tire supports a maximum of 4190 lbs, not the 4320 that the OP may be carrying.

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