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Old 06-02-2019, 11:06 AM   #1
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I was looking for some tire answers for my 1989 T150 Sunline and was told about this club looks great! Thanks for sharing all your knowledge!

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Old 06-02-2019, 06:16 PM   #2
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SUN #11296
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Hi, does anyone know the correct size tire for a 1989 Sunline T150?

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Old 06-03-2019, 11:22 PM   #3
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Originally Posted by BeeHappy View Post
Hi, does anyone know the correct size tire for a 1989 Sunline T150?
According to the 1989 Sunline brochure, A Sunline Star Ray T150 had a F78-14-B tire. See page 15 in this brochure located in our files section

Sunline Coach Owner's Club - Sunline Owner's Files - 1989 Sunline

The camper has a GVWR of 2,720# using a single axle.

Now to convert the old 78 alpha numeric tire size to modern day tires. I am not an expert at this conversion but following all 4 of these conversion charts,

Vintage Tire Size Conversion Chart - Vintage Car Connection

The F78-14-B tire would convert to a ST205-75R14 load range B tire of today.

Finding B load range tire is not super common. From the Kenda Karrier site,
they make a ST205-75R14 LR B tire, 35psi at 1,430# per tire. Two of those tires would cover a 2,720# GVWR as they have 1,430 X 2= 2,860# of rating and this is a single axle camper.

Finding load range C is more common, ST205-75R14 LR C tire, These would be 1,760# / tire loading at 50psi Or 3,520# of capacity at 50psi. That would be 750# more load capacity then the camper GVWR or approx 26% more tire capacity then the GVWR. I would not think that it to overly large a jump.

Carlisle HD trailer tires, Their C load range tire is 1,760# at 50 psi

Maxxis Trailer tires, is the same in the LR C tire. 1,760# at 5o psi

There are other brands as well I'm sure in the C load range and possibly the B load range. I did not look for all of them. Your local tire store may have brands they trust and can recommend. You are looking for an ST trailer tire.

If you upgrade to the C load range, make sure your rim is rated for the 50psi rating. They may/should have a stamped load rating in the inner part of the rim. It may only be a load rating and from the load rating we can back into a pressure rating.

As I stated, I'm not an expert on this tire conversion. Someone who has been through it many times before can hopefully chime in.

Hope this helps

Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

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Old 06-04-2019, 11:40 AM   #4
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JohnB asked me to check his numbers.

According to my reference books (1980 Tire & Rim Association), an F78-14 would be a "78 Series" bias (Diagonal) tire. 26.5 OD with 7.90" overall width when mounted on a 5.5" wide wheel. The tire would be rated to carry 1,500# when inflated to 32 psi. This was a popular size Passenger type tire.

In 1980 there were "7.75-14ST" tires but those would be impossible to find today.

A modern ST205/75R14 LR-C would be about 26.14" OD and 7.99" overall width and rated for 1,760# @ 60 psi. There is a good chance your wheels are not rated for 60 psi or for more than 1,600# load so I would not go that route.

If your trailer GVWR is 2,720 and we were to assume 10% hitch weight then the GAWR would probably be 2,448# so by current RVIA standards the MINIMUM load capacity (+10% margin) of the tires should be (2,448/2)x1.10 or 1,346#.
I would recommend you look for 1,468# as a 20% margin would be preferred for your minimum load capacity.

A P205/75R14 is rated 1,532 @ 35 psi and would be 26.14 OD and 7.99 wide.

Hope this helps.
Retired Design & Quality Tire Engineer. Check out my tire Blog for over 300 in-depth posts on tires, valves, and TPMS. I give seminars on RV tires various RV events for FMCA across America.
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