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Old 04-05-2012, 10:41 AM   #1
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tire pressure

Hi All: Just want to make sure I'm right about the tire pressure. I have a 32 H Sunrise itasca with goodyear tires. I weighed the coach and came up with these approximate weights when fully loaded. Front right 3600 Front left 3510 Rear left duals 6910 Rear left duals 6830. I read the goodyear chart and it suggest 70 psi for the front tires and 80psi for the rear duals. If someone with a little more experience could validate this I would be most appreciative
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Old 04-05-2012, 10:46 AM   #2
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Post the exact tire size. Can't go to the charts without it.
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Old 04-05-2012, 11:09 AM   #3
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I also have a 32ft Itasca Spirit model H. I have used 70lbs in the front and 80lbs in the rear. Worked ok for almost 5 years.
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Old 04-05-2012, 08:29 PM   #4
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GVWR,tire size both needed to use inflation tables.19.5 tire or 22.5 tire
18000 lbs,22000lbs 24000lbs different gvwr for each,mine is 6000 front max and 12000 rear max on 19.5 tires
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Old 04-06-2012, 11:01 AM   #5
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tire pressure

Sorry about the missing info 19.5" tires gawr front 7,500 rear 13,500 gvwr is 20,500
gcwr is 26,000 thanks for the help.
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Old 04-06-2012, 01:18 PM   #6
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We also need the full tire size, not just the diameter: e.g. xxx/xxR19.5 Load Range x, where the 'x's need to be filled in. The actual model (G670 RV, G614 RST, etc.) would be helpful as well, although the inflation tables are generally the different models in the same size and load range tire from the same manufacturer.
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Old 04-06-2012, 02:18 PM   #7
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Olly,

I think you are a little confused so maybe I can help a little. First GAWR(Gross axle Weight Rating) and GVWR(Gross Vehicle Weight Rating) are exactly what the name implies....RATINGS(Not actual wts)

The GVWR is the max weight that the vehicle can weigh on all tires. The sum of the GAWR's may not equal the GVWR. Depends on the mfgr. It may be less or equal.

At any rate you should not exceed these "ratings."

If I read you correctly you have in the front wts of 3600 + 3510 7100 for the front. You list 7500 GAWR for your front so you are ok.

You listed actual wts of 6910 + 6830 for the rear which equals 13740 total wt. You list the rear GAWR as 13500 so you are overweight 240 on the rear.

You must also add 7100 plus 13740 to make sure that you are below the GVWR that is listed on the frame somewhere.

------
Of course I might be mistaken for your figures. Sorry if I am.

Now you want to take the actual weight of each wheel and the tire size (for example 225/70R19.5) and look into the table for your measured wts and then read the pressure. Use Single rows for the front and Dual rows for the rear. Tables I refer to are from Tire and Rim Assoc and there may be some difference for Michelin or GoodYear tables.

I hope this helps
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Old 04-07-2012, 08:35 AM   #8
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(per your posting on another forum you have 245/70R19.5 tires)

Looking at the Goodyear RV Tire Inflation chart we see that there are actually two sets of values for 245/70R19.5 tires. Tires produced in since 2-28-2006 require slightly higher pressures. Using the larger of your two front tire weights (3600#) the chart calls for 70 psi (to support 3640#) for pre-2006 tires and 80 psi (to support 3640#) for post-2006 tires. Similarly, using the larger rear weight of 6910# (3455# per tire) the chart calls for 75 psi (to support 3515#) for pre-2006 tires and 85 psi (to support 3515#) for post-2006 tires.

Personally, I would add 5 psi to those numbers so that you have a margin of error--your tire pressure can then fluctuate a few pounds and you'll still be safely above the required minimums.

As has been noted by others, while your total front weight (7110#) is within your front GAWR of 7500# your rear axle weight (13,740#) is actually over your rear GAWR of 13,500# by 240#. While that's not a lot (about 2%) you should watch your weight on the rear and see if you can shift a bit forward.
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Old 04-26-2012, 12:09 PM   #9
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I still am trying to find a place to get all 4 corners weighed but let's assume I'm at max weights and equally distributed.

GVWR = 24,000
GAWR - Front = 9,000
GAWR - Rear = 15,500

First, I assume that means I need to shed 500 lbs if I max out both front and rear. Correct?

Next...

Assuming left and right sides are balanced and ignoring the 500 lbs issue for now that would mean wheel weights are:

4,500 front
7,750 rear

When I go to the Michelin pressure charts for 235/80R 22.5 I get:

Single 100 psi for 4455 lbs & 105 psi for 4610 lbs
Dual 90 psi for 7530 lbs & 95 psi for 7940 lbs

I was a little surprised by the difference in psi front and back. Then again, everything surprises me at this state. LOL

Am I applying the charts correctly?

Being the anal type, I would then think with these numbers the "appropriate" psi for the front would be about 102 psi & the back be about 93 psi.

Finally, once I get a chance to get all 4 corners weighed, I believe that the highest weight on an axle determines the psi for the other side of the same axle. Correct?

Do I have the flick?

TANX.
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Old 04-26-2012, 02:21 PM   #10
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That sounds about right to me.
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Old 04-26-2012, 02:58 PM   #11
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Athuddriver, yes, you are applying the chart correctly, given your assumptions.

I prefer to set my pressure about 5 lbs over the value from the table because that way my tire pressure can fluctuate a bit (due to outside temp, etc.) without danger of going below the pressure called for in the table.

In dual configurations the weight rating for the tire (at a given pressure) is reduced somewhat to allow for the fact that at times one of the duals will briefly end up off the edge of the road or on a rock, etc. that causes one tire of the pair to be supporting much more weight than normally.
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