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Old 04-02-2013, 01:07 PM   #43
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Originally Posted by Hooligan View Post
I had the same result when I went to the Load Range H Goodyears, dealer said the 80psi is the minimum recommended pressure even if the weight falls below that. In my earlier post, that is how I got 80psi, but I also added 5psi as a cushion..

I have not seen a more recent load table for Goodyear.

Thanks, I'm going to go with 82psi (per mfgr. sticker in coach). First, long distance trip coming up, we'll see how it goes.
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Old 04-02-2013, 01:10 PM   #44
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Originally Posted by Tony Lee View Post
Fairly common - but perhaps illegal - for people to put tyres on that have a different load rating than the alternatives normally shown on the placard or other manufacturer's documentation and if the load rating on the new tyre is substantially higher than the original, inflating to placard pressures might result in an unduly harsh ride.
so which OEM? The coach builder is certainly not going to do anymore than bolt the house to the chassis. The chassis OEM is not going to come back and recertify the weights/tire pressures.

And whats ironic... your "harsh ride" could be "just right" for me.
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Old 04-02-2013, 01:13 PM   #45
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Might be illegal if you went to a lower rated tire. Les Schwab refuses to do that BTW, they claim it's illegal under Federal Law.
I always laugh at that. They know its illegal but cannot cite which code it is. Like the shop that told me they couldnt flip my uneven worn tires due to federal regulations. I told them I dont do business with liars. They got offended... boohoo. Shop right next door had no problems flipping the tires.
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Old 04-02-2013, 01:43 PM   #46
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I'm not sure why anyone would use some tag placed on their rig. Unless its new and you have no idea what it weighs. If a tire manufacturer developed a tire that could provide a stable safe ride with only 60 psi would you still use a tag placed on your rig?
Just weigh the rig and use the tire manufacturers recommendations. As long as you have at least the minimum proper psi for the weight anything over that up to the max will just effect the ride.
If the ride is okay at Max psi leave it there. imo
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Old 04-02-2013, 01:47 PM   #47
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Originally Posted by Clifftall View Post
I see your pressures as 90 and 85 according to this chart.


Attachment 36021

And I would add at least 5 lbs to each for good measure.
Dont use these lists , I checked it to be made with the power of 0.7 in the universal formula.
Stange that Michelin, an European tyre-manufacturer dont use the power of 0,8 in the formula that is used for all kind of tyres in Europe.
What they do good , is that they make a seperate list for G and H load tires.
That is another thing that is done wrong in American lists.

Best is to use my spreadsheet in the next map on my skydrive
https://skydrive.live.com/?cid=a526e...E092E6DC%21793
It uses my own formula wich is even saver then the European one for larger tires.
Download a spreadsheet first by right clicking on it and choosing Download, and not open in Excell or Web app. After download and eventual viruscheck you can open it in Excell or Open Office Calc.
Then it will look like this Example
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Old 04-03-2013, 11:22 AM   #48
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Originally Posted by Mr_D View Post
Might be illegal if you went to a lower rated tire. Les Schwab refuses to do that BTW, they claim it's illegal under Federal Law.
Weathertodd: Federal Regs do address truck tire load ratings:

DOT Federal Motor Carrier Safety Administration Regulations
"(h) Tire inflation pressure. (1) No motor vehicle shall be operated on a tire which has a cold inflation pressure less than that specified for the load being carried."
Complete Part 393.75 Tires is here. Did not know regroovable tire restrictions on front axle use... Tires. - Federal Motor Carrier Safety Administration
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Old 04-03-2013, 08:02 PM   #49
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Background info on tire inflation
#1

and
#2
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Old 04-03-2013, 08:10 PM   #50
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Quote:
Originally Posted by Hooligan View Post
Weathertodd: Federal Regs do address truck tire load ratings:

DOT Federal Motor Carrier Safety Administration Regulations
"(h) Tire inflation pressure. (1) No motor vehicle shall be operated on a tire which has a cold inflation pressure less than that specified for the load being carried."
Complete Part 393.75 Tires is here. Did not know regroovable tire restrictions on front axle use... Tires. - Federal Motor Carrier Safety Administration
But, we also know that DOT Federal Motor Carrier rules don't apply to privately owned and driven cars.
Besides I was referring to say replacing a "G" rated tire with a "D" rated one that won't have the same carrying capacity as the original tires.
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Old 04-03-2013, 08:11 PM   #51
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Dont use these lists , I checked it to be made with the power of 0.7 in the universal formula.
Stange that Michelin, an European tyre-manufacturer dont use the power of 0,8 in the formula that is used for all kind of tyres in Europe.
What they do good , is that they make a seperate list for G and H load tires.
That is another thing that is done wrong in American lists.

Best is to use my spreadsheet in the next map o


snip
Suggestion to all reading this thread. You might wan to think hard about if you want to follow the engineering guidelines developed and followed by the tire manufacturers and government safety experts around the world or an engineer that as best I can learn, has never designed or been responsible for a tire going into production.
Mr Jadatis has developed his own personal theories but I do not think he has bothered to back up his claims with the financial resources necessary to provide coverage if you have a tire fail while following his personal theories. I understand he does not live in the US so you would have a tough time bringing him to court. maybe he is willing to pay for any tire failure you have but I have not seen such an offer being made.
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Old 04-03-2013, 08:25 PM   #52
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We did a four corner weigh on a 2002 Suncruiser and the front axle was almost identical side to side. The rear was 910 pounds heavier on the passenger side as the basement air was on that side, the bedroom slide, and kitchen. There was nothing to move around to equalize the load. An alternative would have been to have a frame shop add spacers to the suspension to try to get it equalized. Rather than do that, I ran the tire pressures on both rear tire based on the heaviest side.
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Old 04-04-2013, 12:16 PM   #53
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We did a four corner weigh on a 2002 Suncruiser and the front axle was almost identical side to side. The rear was 910 pounds heavier on the passenger side as the basement air was on that side, the bedroom slide, and kitchen. There was nothing to move around to equalize the load. An alternative would have been to have a frame shop add spacers to the suspension to try to get it equalized. Rather than do that, I ran the tire pressures on both rear tire based on the heaviest side.
You did the right thing. 1,000# side to side unbalance is not unusual. Also on trailers axle to axle variation of 10% or more is not unheard of in addition to significant side to side variation.
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Old 04-04-2013, 09:26 PM   #54
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Just installed Michelin XZA2 275.70R22.5 tires all the way around on our '04 CC. Each corner has been weighed individually and the two fronts are exactly 6K each. Michelin tire book says to air to 110psi to support the 12k. Readout on the TST TPMS after a 50 mile drive shows both fronts now at 126psi. Pulled over at rest area and tested actual air pressure with both an analog and digital guage and the TST is on the money @126psi. Aluminum wheel manufacturer Accuride says no to exceed 120psi. Ambient air temp in Phoenix today about 91 degrees. A couple of people sugggest I set the cool tires at 100psi to allow for heat psi build up.

Is this right or am I misssing something very important here?

Thanks for the guidance.
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Old 04-04-2013, 09:37 PM   #55
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Originally Posted by chuydog View Post
Just installed Michelin XZA2 275.70R22.5 tires all the way around on our '04 CC. Each corner has been weighed individually and the two fronts are exactly 6K each. Michelin tire book says to air to 110psi to support the 12k. Readout on the TST TPMS after a 50 mile drive shows both fronts now at 126psi. Pulled over at rest area and tested actual air pressure with both an analog and digital guage and the TST is on the money @126psi. Aluminum wheel manufacturer Accuride says no to exceed 120psi. Ambient air temp in Phoenix today about 91 degrees. A couple of people sugggest I set the cool tires at 100psi to allow for heat psi build up.

Is this right or am I misssing something very important here?

Thanks for the guidance.
NOPE...don't do that.

Cold PSI is the standard. You will be fine following the normal PSI charts.

IMHO...the only reason you might fudge that is if you had a very cold night, early start and it was going to be a HOT day. (Sounds like PHX sometimes. LOL) But...even then I might be VERY cautious and not go over board. A lot of folks add 5 PSI to the chart for comfort, perhaps forgoing the extra 5 PSI might be reasonable.

Over time, you should get a good feeling for tire pressure changes from cold start to hot running. The TPMS can be a huge help in getting that knowledge.
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Old 04-05-2013, 12:13 AM   #56
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I was referring to say replacing a "G" rated tire with a "D" rated one that won't have the same carrying capacity as the original tires.
Same rules under Federal Motor Vehicle Safety Standard as the Federal Motor Carrier Standard.

FMVSS 120- 571.120 tire selection and rims, and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with GVWR of more than 10,000 pounds.

12.1 TIRE AND RIM SELECTION REQUIREMENTS (S5.1)
The sum of the maximum load ratings of tires fitted to an axle shall be not less than the gross axle weight rating (GAWR) of the axle system as specified on the vehicle's certification label.
(Rim and passenger tire info omitted)
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