What PSI should I be running?

[johnnybgood]

I've finally learned (after a year[emoji3]) that Sunline recommends 35 psi in my T-1700 tires. The owner of my local tire shop told me to keep them at max pressure (50 psi). What do you guys do?

[Sunline Fan]

Max pressure. Allows for the most weight carrying capacity per tire. Cutting down the pressure severely cuts down on weight capacity for those tires, and generates more heat, which can lead to failure.

You shouldn't really notice a difference in towing quality of 35 vs. 50.

[mainah]

50 in my T1700 tires.

[johnnybgood]

Thanks for the replies, much appreciated. Fifty it is.

[BCS Guy]

Max rate on the TT, and I usually bump up the tires on the truck too.

[JohnB]

Originally Posted by Sunline Fan

Max pressure. Allows for the most weight carrying capacity per tire. Cutting down the pressure severely cuts down on weight capacity for those tires, and generates more heat, which can lead to failure.

You shouldn't really notice a difference in towing quality of 35 vs. 50.

X4

Yes, fully agree. Another thing to realize is the camper wheel loading is not equal. On a tandem axle setup, odds are high there is one tire that is loaded the heaviest. The camper is not made exactly equal weight side to side nor are cargo holes or gear added to them equal. Having the extra pressure allows you more room for error.

I'm curious, where did you see the 35psi? What size and load range tire are these?

Thanks

John

[johnnybgood]

Tires are ST 205/75 R14 which is printed on the badly peeling placard on the side of the camper. That's also where it calls for 35 psi.

[JohnB]

Originally Posted by johnnybgood

Tires are ST 205/75 R14 which is printed on the badly peeling placard on the side of the camper. That's also where it calls for 35 psi.

Well, here is a thought on what Sunline may have been thinking. I have no idea if this why they did that but here goes.

Assuming the ST 205/75 R14 are load range C, make sure I have the load range right.

This means at 35psi, each tire can hold 1,430# of weight. This comes from the only easy to find trailer tire pressure chart I know to find. Granted this is for Maxxis tires but lets consider it close for trailer tires. Trailer Tire Load/Inflation Chart | Maxxis Tires USA


The 1999 T-1750 brochure states a 4,000# GVWR. Please confirm this is right. Sunline made it a special effort to put running gear on the camper, including tires that can support the entire GVWR. They are not counting on the truck to hold the tongue weight, which it does but this gives more safety factor on the tires and axles.

If we use 35psi, at 1,430# each tire x 4 tires = 5,720# of tire support.

That is already 1,720# above the GVWR. Which is a lot and a good thing. Sunline may have just stayed with 14" tires as a standard thing back then and lowered the pressure to still use the larger tire for the load but lowered the pressure.

If they air them up to 50psi, that is 1,760# per tire x 4 = 7,040# total or 3,040# above the GVWR of the camper which would be a boat load more.

I think this is a case of a very light rated camper with an over size tire on it.

Again I do not know this as fact, but by the numbers it does have some merit to the path they may have taken.

They use to use that same tire I believe on the newer 5,000# GVWR campers. Then in the newer years, they up'ed to 5,500# GVWR and went to the ST205/75/R15's Load range C as my 2004 T1950 has them. And so did my 2004 T2499 which had a GVWR of 7,000#. Sunline was not known for skimping on tires and axle sizes like many of the other brands still today do. Which is good for us. We have good sized running gear.

Hope this helps

John

[johnnybgood]

Yes John, the tires are C rated, the GVWR is 4,000 pounds, and the tire sidewall says 1760 pound weight limit at 50 psi.

Interestingly enough, I was browsing the brochure section (big shoutout to Jon for doing all that) and saw that the older T-1700's had a GVWR of 5,000 lbs.

So I'm guessing the older models called for 50 psi or Sunline switched to a lighter axle on my 1996?

Your 1950 calls for 50 psi and has 15" wheels?

Thanks for the info.

[JohnB]

Hi John,

H'mm learning some new stuff today from your post. Sunline Fan may know something about this as he is the Guru on the older campers. And for sure, Sunline Fan doing up all these brochure was a major effort and a very appreciated one. He even did them twice to help the layout of the PDF's. These get looked at a lot and are invaluable now.

Taking your lead out of curiosity, I went through brochures back to 1988 (I just stopped there) and up to year 2000.

• It seems from 1988 to 1992 the T-1700 had a GVWR of 4,000#.
• In 1993 and 1994 it went up to 5,000#.
• In 1995 all the way until year 1999 it went back to 4,000.

• In 1997 they did away with the T-1700 model number and changed that same floor plan to a T-17A from 97 up to 1999 and that was the last of them. They all had 4,000# GVWR's.

Seems come year 2000 when all those smaller campers had been discontinued. The T1950 was then the smallest camper they offered.

I do not know if the 93 and 94 T-1700 with a GVWR of 5,000# was a miss print in the brochure or they actually up'ed the GVWR. I cannot imagine they changed the camper build enough to need the extra 1,000# of capacity so they must of just gave it as extra cargo capacity but they did change the build somehow as the dry weights also changed.

• The 88 T1700 weighed dry 2,300# giving a 1,700# cargo capacity
• The 92 T1700 weighed dry 2,300# giving a 1,700# cargo capacity

• The 93 T1700 weighed dry 2,410# with the new GVWR of 5,000 giving a 2,590# cargo capacity. Odd the 94 T1700 brochure does not list a dry weight only the 5,000# GVWR.

• The 95 weighed dry 2,385# giving a 1,615# cargo capacity
• The 99 T-17A weighed dry 2,855# giving a 1,145# cargo capacity

Don't know what all changed to shifts the weights, maybe heavier cabinets or larger tanks etc (I did not drill down into tank size), or why they seemed to only offer the 5,000# GVWR for 2 model years?? They may have found a problem with allowing that much cargo and went back to the 4,000#

That floor plan must of been a good seller as it has a good long run and the T-17A was the only little camper left in 99. In 97 & 98 they had the T17-A and B models as the smallest. In 96 the T-1550 was the smallest.

At this point it is a mystery on the 93 & 94 GVWR increases. Maybe some day we will lean why.

On my 2004 T1950 it has a GVWR of 5,500, that was a 2004 upgrade and the ST205/75/R15's load range C are called out on the VIN tag as 50psi. the brochure dry weight is 3,815# with the 5,500 GVWR leaving 1,685# cargo capacity.

Here is the VIN tag


Hope this helps

John

[johnnybgood]

John, thanks for researching that. I'm wondering, like you, if that isn't a typo for the two year 5,000 GVWR.

It's pretty impressive that your 1950 has 15" wheels. Don't normally see that on smaller campers. Appears Sunline overbuilt your 1950 as well as my 1700. That's some great cargo carrying capacity compared to a bunch of other trailers I've looked at.

[Sunline Fan]

Thanks guys! Yes, it seems they decided to go toward standardization/cost savings by buying 15" wheel/tire combos in more of a bulk and eliminating the 14". Not sure if that was the motive, but it seems likely.

Also, I just pulled a hard copy of the '94 brochure to verify it did say the GVWR was 5000, and it was. Just wanted to make sure it wasn't a typo on my part in the PDF...

[mainah]

A larger wheel will be easier on bearings it will also wear a bit longer and the camper will sit a bit higher so maybe that was a thought or maybe a deal was to be had.

[johnnybgood]

Interestingly enough, my new to me 2000 T2370 calls for 35 psi.

That seems strange for a camper with a GVWR of 5500 pounds and a dry weight of 4319.

Wheels/Tires are the same size as my T1700 (205/75R14). Load range C.

My tiny T1700 can haul more “stuff” than my T2370!

Guess it’s all part of the “lite” series.

[Sunline Fan]

Hmm, that is interesting. I'd still run them at 50 (the max) anyway, but at least it sounds like they aren't as overloaded as most. I believe the biggest reason why we run trailer tires at max is for weight carrying capacity, but if the max trailer weight is nowhere near the capacity, it should be ok to be down a little.

[johnnybgood]

Thanks, I’m going to run them at 50 psi.

Just seems strange that Sunline even states to run 35 on my T2370 and T1700.

[JohnB]

Originally Posted by johnnybgood

Thanks, I’m going to run them at 50 psi.

Just seems strange that Sunline even states to run 35 on my T2370 and T1700.

Hi John,

Yes that does seem strange. I for sure would run them at 50 psi too. With the learnings of "interply shear" and other issues that comes from tandem and triple axle turns, we need more reserve capacity in the tire to help ward off interply shear.

Tireman9's reply here talks to what can help with the interply shear. Bottom line more, reserve capacity. http://www.sunlineclub.com/forums/f7...tml#post143566

The only thing that may add up on the old listings Sunline used was, they may have not known about the turning issues as much then as we do today. Even today, there are still brand new campers being sold with tires sized right at the load chart max with no reserve. And on top of it, they down size the tire and running gear to have the truck hold part of the GVWR. Sunline was good to us, they would size the running gear to the entire GVWR which naturally gave us a form of reserve. The only issue still is, it may not have been enough in some applications. The heavier campers, like mine, are most likely in that league I feel.

Thanks