Upgrade tires not wheels?

[Bob662]

Originally Posted by J. Morgan

Remember, all of the trailer weight does not sit on your trailer tires.

Great point.
So in Mel's case a trailer with GVW of 8,800 lbs., less tongue weight (carried by TV) of, say, 1,000 lbs -- so his tires must carry 7,800 lbs -- a 600 lb. safety margin.

[robert claus]

Originally Posted by jcole

I am also thinking of replacing my 15" GYM on my single axle 2016 Sport 22FB to the Loadstar ST225/75R-15 Radial Load range E just to get the Xtra 2 Ply from 8 to 10. No need to change wheels because overall diameter is just .1" larger than the 15" Marathons. Also a few hundred pounds of Xtra weight carrying does not hurt.

Except that, in order to gain any benefit from the additional capacity of load range E tires, you will have to run them at the higher inflation rate of 85 lbs. Run them at 60-65 lbs, and you will only have the weight capacity of a D rated tire. The minimal suspension travel that Airstream trailers have requires that the tires absorb impacts to protect the trailer. Running E rated tires at 85 Lbs will not provide the cushioning needed by your relatively light trailer.

[swan]

There are so many threads about this stuff... I'm still scratching my head, though. I don't understand why everyone wants to max out their tire inflations.

I have a 28' 2013 International, which is dual axle, with the stock Goodyear ST225/75R15s. I had my trailer weighed at a truck stop when we were loaded up on a 6-month trip. It came in just under 7,000 lbs.

If you divide 7000/4, you come up with each tire being loaded with 1750lbs. If you look at Goodyear's inflation guide for those tires, it recommends 35lbs of pressure for 1760lbs of weight, cold—even thought the tire can take 65lbs of pressure, for a max rating of 2540lbs. Airstream says the trailer's loaded weight is 7500lbs. Divide that by 4, and you get 1875, which would be 40lbs cold. So, I should be running between 35 and 40 lbs cold, if I want to error on the cautious side. Why are people jacking them up to 65lbs?

Is there something I'm missing?

[SeaLevel]

Originally Posted by swan

Why are people jacking them up to 65lbs?

Is there something I'm missing?

Good questions, and I am curious to find out. Here is a link to the information you referenced.

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

[CapriRacer]

Originally Posted by Bob662

Great point.
So in Mel's case a trailer with GVW of 8,800 lbs., less tongue weight (carried by TV) of, say, 1,000 lbs -- so his tires must carry 7,800 lbs -- a 600 lb. safety margin.

Don't forget that the weight on the tires is NOT evenly distributed. I'm using a 15% variation until I find better data.

[CapriRacer]

Originally Posted by Bob662

Great point.
So in Mel's case a trailer with GVW of 8,800 lbs., less tongue weight (carried by TV) of, say, 1,000 lbs -- so his tires must carry 7,800 lbs -- a 600 lb. safety margin.

Don't forget that the weight on the tires is NOT evenly distributed. I'm using a 15% variation until I find better data.

Also, don't forget to provide a margin of unused capacity - commonly called "Reserve Capacity". I use 15% there as well!

[jcole]

Originally Posted by robert claus

Except that, in order to gain any benefit from the additional capacity of load range E tires, you will have to run them at the higher inflation rate of 85 lbs. Run them at 60-65 lbs, and you will only have the weight capacity of a D rated tire. The minimal suspension travel that Airstream trailers have requires that the tires absorb impacts to protect the trailer. Running E rated tires at 85 Lbs will not provide the cushioning needed by your relatively light trailer.

Ok, I can understand the minimal suspension impact why the 60-65Lbs instead of the 85 Lbs. In our case since we do not travel with any liquids in any tanks & put most if not all of our travel needs in our tow vehicle which is a Nissan 3500 HD cargo van I am not concerned with the xtra weight. I just want to get away from the Goodyear brand hoping the added 2 ply will give a little added protection from a blowout & still stay with a tire designated for travel trailer use. I am also thinking since the added weight we would add to the dry(empty) trailer weight will not exceed a few hundred pounds maybe its better to go with a Michelin 15" that just meets the load capacity in which we travel with ...... any thoughts ???

[switz]

We installed the 15" Michelin LTX (P) 235/75R15 XL tires on the stock wheels of the 2013 25FB with no problems. Going from 14" tires and wheels to the same 15" tires on the 23D required new 15" SenDel T03-56545T wheels as well with the five hole pattern for the 10" brake drums.

Going to the 16" tires and wheels on our 2014 Classic required new wheels as well and we acquired the same tires and wheels Airstream is now installing on 2015 and later Classics and the Eddie Bauer models.

[rbs]

we replaced the Goodyear Marathons on our previous 25' Classic with the 15" Michelins, and could not have been happier. Literally made the trailer pull and ride so much better, the 80 psi Goodyears were beating the trailer to death. I checked tire temp's constantly until I was convinced they were doing a very good job and nothing to worry about. I am still trying to determine a psi to run in my 16" Michelins on our new Classic.

[switz]

We looked at the weight table from Michelin for the 16" LT225/75R16/E LTX M/S2 tire and have selected 75 psi which has a load rating of 2,540 pounds. 70 psi has a 2,440 pound rating. Many are running 72/73 pounds for the 2,500 pound spot.

A TPMS system that displays both pressure and internal temperature (like the Dill 1506-453) is very useful for selecting the best tire pressure for your specific loading of your trailer.

[Bob662]

Originally Posted by SeaLevel

Good questions, and I am curious to find out. Here is a link to the information you referenced.

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

I hadn't seen this Goodyear loading chart before. If I'm reading it correctly, you can run the GYM at 40 PSI, or the LT235/75-15 at 50 PSI, and they have almost identical load ratings (1880 v. 1820, respectively). So one take-away is you don't have to run GYM's at 65 PSI and another is that I can install and run the LT's at 45 PSI and still have a margin for my FC25FB (7,300 GVW minus TW of about 1000 lbs. = 6300 lbs.; tire rating of 1660 X 4 = 6640 lbs.).

Did I miss a turn anywhere? The Goodyear chart doesn't talk about derating LT tires; is that already considered in the table?

[crispyboy]

Bob,
LT tires do not get derated, only passenger tires get derated.

[Phoenix]

Recent posts on several tire threads indicate that some are considering running GYMs at 40-46 psi. For those who decide to run lower tire pressures this summer, please mark your calendars with a reminder this fall to add your results to the tire failure poll (assuming you have not already participated). -- Thanks!

Link: Airstream Tire Failure Poll

[franklyfrank]

Originally Posted by swan

There are so many threads about this stuff... I'm still scratching my head, though. I don't understand why everyone wants to max out their tire inflations.

I have a 28' 2013 International, which is dual axle, with the stock Goodyear ST225/75R15s. I had my trailer weighed at a truck stop when we were loaded up on a 6-month trip. It came in just under 7,000 lbs.

If you divide 7000/4, you come up with each tire being loaded with 1750lbs. If you look at Goodyear's inflation guide for those tires, it recommends 35lbs of pressure for 1760lbs of weight, cold—even thought the tire can take 65lbs of pressure, for a max rating of 2540lbs. Airstream says the trailer's loaded weight is 7500lbs. Divide that by 4, and you get 1875, which would be 40lbs cold. So, I should be running between 35 and 40 lbs cold, if I want to error on the cautious side. Why are people jacking them up to 65lbs?

Is there something I'm missing?

A wise man once said " Over analysis induces Paralysis". My 30, International weighs in at a bit over 7,000 lbs on the trailer axles. And that is with a full tank of water. With no water I am at 6,700 lbs for our normal cruising, the truck rear axle at the recommended GVW. The reason to inflate the GYM pos tires is to keep the sidewalls from flexing. To prevent premature thread separation. What a joke! It will do that regardless.

[franklyfrank]

Originally Posted by CapriRacer

Don't forget that the weight on the tires is NOT evenly distributed. I'm using a 15% variation until I find better data.

Also, don't forget to provide a margin of unused capacity - commonly called "Reserve Capacity". I use 15% there as well!

Reserve capacity is built into the tires. You can run them at the rated loading stamped on the tires 24/7 and they will hold up just fine.

[switz]

If considering different wheels, make sure they are rated for the the loads to be imposed and check the maximum air pressure. In looking at the SenDel listing below: one sees even two 14" wheels rated 1,900 pounds each at 60 psi exceeds the 3,000 axle rating of a 23D. The recommended sidewall max tire pressure on the 14" tires and the 15" Michelins we installed on the five lug nut wheel (designed for the 10" brake drums) is 50 psi. The six lug 15" wheel is rated 2,830 pounds at 80 psi which covers all the airstreams not withstanding the tire choice issues. The six lug 16" wheel is rated 3,580 pounds at 80 psi.

http://www.sendelwheel.com/wheels/t03bm

[m.hony]

At the very least, keeping the same wheels, you could go from Load Range D to Load Range E.
That would be an improvement.

[perryg114]

E rated tires at 85 psi on a 8000lb trailer or less is insane and will shake your trailer to death and reduce the contact patch. You only need two out of the 4 tires touching the ground with those. The 235/75-XL15 tires are more than enough for all but the heaviest trailers. I run 50 psi in the above size tire and they run cooler than the E rated tow vehicle tires. The trailer rides comfortably and is not jarred to death by running dump truck tires on the equivalent of a Porsche. Tire pressure is best determined by measuring the temperature of the tire in the center and the sides. When you get all 3 close to each other you are golden.

Bigger rims give you the option of putting disk brakes on older trailers which is not a bad way to go. My old alloy Excella rims don't have room for disk brakes.

Perry

[NoResults]

I started this thread as I did not know what wheels came on my trailer. I just picked it up yesterday. It is a lightly used 2016 Intl serenity.

I hate to waste perfectly good rims. I can live with the cost of the new tires but was hoping there was a better tire and keep the existing rims.

Hope this clarifies what my point was. I purchased for a very good price so the cost of new wheels will not break the bank.

Thanks for all the comments.

Dave

[m.hony]

There may really be no real way to upgrade unless you get 16" wheels and LT tires.
Sell the current wheels on Airstream Classifieds.


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