RE: Weight rating/tire pressure

MtnCamper · Sep 30, 2003, 02:01 PM

slowpezSusan, I have the same tires as you, and I ve used 50 lbs. Forever.

mike4947 · Sep 30, 2003, 04:32 PM

slowpezMaximum pressure for the tire is posted on the tire. The pressure posted on the rim is the maximum pressure for the rim. As long as the rim s pressure rating is higher than the tire s you re OK. Use the 50psi listed on the tires.

tlhdoc · Sep 30, 2003, 09:04 PM

slowpezUse the 50 psi that the tire says.[

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Ab Diver · Sep 30, 2003, 10:59 PM

slowpez

QuoteAb Diver asked me to check the weight rating on the tires to make sure they aren t underinflated.

No, I asked you to check the weight rating of the tires to make sure you weren t using tires that were less than you needed. [

] I don t have my 02 Coleman brochure handy, but the WFKAC (Website Formerly Known As Coleman) shows the Gross Axle Weight Rating (GAWR) for the current Cheyenne at 2650 lbs. The Duro web site shows 13" Special Trailer tires ranging from 1100 to 1660 lbs weight rating.

I *know* the C78-13ST (185/80D-13) needs 65 psi to support it s rated 1660 lbs. I did not know if the " 4" ply, 1100 lbs rated B78-13ST (175/80D-13) or " 6" ply, 1360 lbs rated B78-13ST (175/80D-13) needed 50 psi to support their rated loads.

You can see where this is heading, right? If your tires were only rated for 1100 lbs @ 50 psi, they are not rated to support your GAWR of 2650 lbs. This is NOT GOOD. If your tires are rated to support 1360 lbs @ 50 psi , they will support your GAWR, but be very close to their limit. Tires of the same size can be rated for different loads.

The " lighter" rated tires are also slightly smaller in diameter (24.0" vs. 25.12" ) and width (7.00" vs. 7.68" ) than the 1660 lbs rated tires. If you have the room, I would upgrade to the higher 1660 lbs rated tires when you are due for anew set, and give yourself some breathing room. In the long run, it may prevent a blown tire in the middle of Resume Speed, U.S.A. (Imagine trying to find a replacemant Duro tire at that little gas station in the middle of the Arizona desert, or some other godforsaken place... it ain t gunna happen) The trailer may ride a little stiffer with the stronger tires, but Mike4947 ( a man who s input I trust a lot) has more experience with that aspect, and says a bump up in the higher-psi 12" tires made a big (bad) difference in his trailer s ride. (Mike, I did quote you correctly, right?) However, in this case I don t think it would be that drastic to go from a 50 psi rated 13" tire to a 65 psi- 1660 lbs rated 13" tire, cuz those little 12" tires are hard as rocks when filled to 90 psi. Your call.

The rims are stamped with the max psi *they* are rated for. You can mount any appropriately sized tire on them, and fill the tire to it s rated pressure, " provided" the tire s psi rating is *less than or equal to* 65 psi. A 90 psi rated, 13" tire (if you could find such a beast) would require more air prssure than that particular 13" rim is rated for.

Ok. Did all that make sense? I hope I haven t muddied the waters further for you. But the whole idea is to make sure ALL your components are up to the rated specs needed by your trailer.

mike4947 · Oct 01, 2003, 12:21 AM

slowpezAb you got it as close as I ve really ever put the details out. Going from a load range C 1330 to a load range D 1660 will have a very slight effect on the trailer handling and if you right at the weight limit of the C the ride and handling will improve.
What I did was go from a 720 pound rated 12 inch tire to a 1330 pound rated 13 inch tires with an axle flop for clearance and a little grinding on the wheel wells. I also tried a IIRC the top 12 incher of around 1100 pounds. The 13 inchers had the PU off the ground at every expansion strip and bounding around corners. The 12 inchers behaved when loaded down with more than the 720 rated tires could hold, but at the 720 rating they also hopped and skidded around corners. Just not as bad as the 13 inchers.
A little bit of slack in your weight carrying capacity is good, a whole lot isn t.

5 ers, class A, and large TT s have inflation schedules they follow depending on the weight their towing/carrying. Since we re at or very near the max anyway such tables wouldn t do us much good even if the manufaturers had them.

otter · Oct 01, 2003, 12:27 AM

slowpezWe

QuoteOk. Did all that make sense? I hope I haven t muddied the waters further for you. But the whole idea is to make sure ALL your components are up to the rated specs needed by your trailer.

l

I m not sure you confused me, but I will have to read it all again when I have the camper with me. Lon is insistant on getting some new tires before we take it out again and I intended to replace the ones we have. Know I will have to check out the upgrading possibilities. We have about 7000 miles on ours and they have always been underinflated. The weight thing mistifyies me too. I d like to find some place to weigh the beast when it is loaded for camping. Now I need to check axel weight and rim psi. [

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What else do we retired folks have to do?

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Ab Diver · Oct 01, 2003, 12:43 AM

slowpezDianne, tell you what-- you and Lon come visit us, and I ll personally weigh your rig at the local truck stop for you. You want total weights, axle weights, combined weights, paper weights... you got em!

Or--- call your county Dept. of Weights and Measures. They ll know where scales suitable for weighing your rig are located in your area.

QuoteWhat else do we retired folks have to do?

Ummmm.... you could knit me a blanket. [

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otter · Oct 02, 2003, 01:11 AM

Ab Diver

QuoteUmmmm.... you could knit me a blanket.

I don t knit much anymore, but Iam a professional blanket maker/polartec and flannel usually. something other than " brown" I presume.
Hugs to the family. Can t wait to camp with you and your wonderful women again.
Lon leaves for Spain this week, so rallies too far from home are out of my rach, but I am considering Casini ranch. Looking for someone to come along with me.
I will call Weights and Measures and see what they say.

hugs

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