Upgrade Tires (14" -> 15") - Fiberglass RV
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Old 04-19-2021, 05:50 PM   #1
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Name: Jon
Trailer: 16' casita
California
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Upgrade Tires (14" -> 15")

Hi everyone,

Not sure if this being asked, but let me start a thread on this. My casita is a 2008, 16' and has all stocked. I like to upgrade the existing 14" tires to the 15". Was looking at alot of comments regarding from 205/75R15, 215/75 upto 225/75R15 and I kindna want to target 225/75r15 for more width and load capacity. Since mine is stocked and saw some an LT 225/75R15 (https://www.walmart.com/ip/Carlisle-...tire/176835419), was wondering if this will work? Are there better recommendations?

Note: I don't have a high lift (or plan to install one), but from the existing 14", it has a lot of clearance, my worry if it goes over a big bump, would the 15" tires rubs the inner walls?
-Yes to get new rims
-My current spare is the original Marathon tires that had a lot of issues, kind of pointed me toward upgrading.
-All that said, would it be ok to upgrade to 15" w/ out the lift? Anyone had one it?

-Worst case, I can still stick to 205/215 R14, but my selection is limited while with less load capacity, etc.
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Old 04-20-2021, 07:50 AM   #2
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LT = light truck tire, designed for that use. Get a trailer tire “ST” as the design is different. Google for the millions of tire debates as well as the difference.

I’ve had good service out of Carlisle trailer tires, all bought on Walmart.com. I got ~ 75,000 miles out of the OEM Carlisles on my Escape and replaced them early prior to a 11,000 mile trip. Tire shop (that mounted my Walmart tires) kept them to resell.
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Old 04-20-2021, 09:15 AM   #3
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Goodyear Endurance ST has a solid reputation. No relation to the older, failure-probe Marathons.

They offer two 14” sizes in load range D. The smaller is rated 2039# per tire, which combine for almost 4100# per axle. That should give you plenty of margin. After deducting hitch weight, gross axle weight on a Casita 16D should be around 2600#, give or take. Have you weighed yours?

I see no compelling reason to upgrade to 15”, except they’re often easier to find in stock. I don’t know if there are any clearance issues with the standard (not high-lift) axle. A call to Casita might give you an answer if no one here has direct experience.
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Old 04-20-2021, 02:01 PM   #4
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ST special trailer radials

Quote:
Originally Posted by thrifty bill View Post
LT = light truck tire, designed for that use. Get a trailer tire ST as the design is different. Google for the millions of tire debates as well as the difference.

Ive had good service out of Carlisle trailer tires, all bought on Walmart.com. I got ~ 75,000 miles out of the OEM Carlisles on my Escape and replaced them early prior to a 11,000 mile trip. Tire shop kept them to resell.
Well said Bill great advice. We went with ST205r tires They make both 14" and 15" tires with same circumference smaller side wall would add stiffness but would ride same and fit wheel well ok. As too load ST tires come in B, C and D ratings. Each has greater load capacity; stepped up two C rated the combined ratings is more then axle rating and they are radial tires as you know.
Hope the helps them
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Old 04-20-2021, 02:18 PM   #5
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Name: Charles
Trailer: 89 Scamp 13
Pennsylvania
Posts: 16
Spare tire

The trailer I just sold had been changed to 15s when I bought it.
The spare would not fit on the mounting bolts on the original set up.
I had to create a new mount for the 15 inch spare.
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Old 04-20-2021, 04:26 PM   #6
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a Casita 16 has a GWR of 3500 lbs, and if max loaded, probably 350-500 lbs hitch weight depending on where that load is. ours was consistently light on the tongue, and thats even when I put things like 24 packs of beer and flats of water in the bathroom and closet to put it as far forward as practical. so really, should plan on a 3100-3200 lb max axle weight to be safe. that said, ANY ST tires are more than adequate. on an 08, I'd want to do the high lift mod before going to 15" wheels, and I would use only the most basic 15" ST tire size, there's zero point in going oversize, you'll just increase rolling resistance with no significant gains, and increase the probability of the wheels scraping the wheel wells when hitting bumps.
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Old 04-21-2021, 10:23 PM   #7
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Someone has seriously messed up the Walmart tire listing. If you look at the Carslile web site, they do not make any motor vehicle tires, and that I know of, no one makes a 15 inch Light Truck tire any more. That is clearly a trailer tire.

Carslile does make a good tire but if you are depending on just two tires, you want the best. I bought Goodyear Endurance ST225/75R15 load range E tires. They do not make any other load range in this size.. That size in any brand requires a 6 inch wide rim however. Drop to the 205 and you can use a 5.5 inch wide rim.

John is correct, do a lift on the trailer first. Otherwise the tires will be scrubbing.

Charles
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Old 04-22-2021, 09:36 AM   #8
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Name: Steve
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15 tires

Several yeas ago I bought a rough 1999 16 Casita with 13 wheels. I dont think it was lifted at all. It looked to me like a low rider. We eventually installed new 15 rims and Carlisle tires. We never had any indication of tires rubbing the wheel wells. Larry Gamble who has worked on thousands of Casitas has seen tires rub when the axle was not positioned correctly on the frame in some older Casitas.
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Old 04-22-2021, 11:59 AM   #9
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Originally Posted by CharlesinGA View Post
Someone has seriously messed up the Walmart tire listing. If you look at the Carslile web site, they do not make any motor vehicle tires, and that I know of, no one makes a 15 inch Light Truck tire any more. That is clearly a trailer tire. And do not affect wheel well space. No trailer modifications required.

Carslile does make a good tire but if you are depending on just two tires, you want the best. I bought Goodyear Endurance ST225/75R15 load range E tires. They do not make any other load range in this size.. That size in any brand requires a 6 inch wide rim however. Drop to the 205 and you can use a 5.5 inch wide rim.

John is correct, do a lift on the trailer first. Otherwise the tires will be scrubbing.

Charles
Why not just go to tire size with smaller diameter that matches originally used diameter or higher load range in same size instead? Our trailer had equivalent of B rated bias belted tires so we went with original rim and diameter of tire in modern ST205/75r14 C rated steel belted tires. They exceed our axle ratings.
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Old 04-22-2021, 12:08 PM   #10
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There is a saying "keep it simple" so ST205/75r 14" Load range C gives us 3600 lbs limit on tires and axle limit is 3200 lbs so trailer max is still 3200 lbs. Yet we travel light as car limit is 2400 and trailer is just under 2000 empty �� has worked well for about 11 years. They say you have to change your tires every 5 years but they look and work fine
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Old 04-22-2021, 12:42 PM   #11
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Trailer: 1999 Casita 16' "Snufkin"
California
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Just swapped 13" to 15"

I just swapped original 13" wheels and tires to 15" radial ST 205/75R15 over a month ago. Mine is a 1999 16' Standard Casita with a regular (non-raised) axle and it's perfectly fine. I was considering 14" but after researching (there is my thread somewhere up there in February) and "trying on" my neighbor's 15" I went with a larger wheel/tire. Based on what I read, 225 may be too wide.
I took it to 2 trips already totaling probably just shy of a 1,000 miles. It's a huge improvement over 13" and I gained about 2" of clearance which is great for my driveway.
I bought mine on Ebay and in retrospect regret not going with an eTrailer or some other reputable source as mine came in range load C although I specified and seller advertised range load D. He gave me some $ back as a result but I ended up with a lesser load tire than I was willing to pay for.
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Old 04-22-2021, 03:35 PM   #12
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Quote:
Originally Posted by Alex in LA View Post
I just swapped original 13" wheels and tires to 15" radial ST 205/75R15 over a month ago. Mine is a 1999 16' Standard Casita with a regular (non-raised) axle and it's perfectly fine. I was considering 14" but after researching (there is my thread somewhere up there in February) and "trying on" my neighbor's 15" I went with a larger wheel/tire. Based on what I read, 225 may be too wide.
I took it to 2 trips already totaling probably just shy of a 1,000 miles. It's a huge improvement over 13" and I gained about 2" of clearance which is great for my driveway.
I bought mine on Ebay and in retrospect regret not going with an eTrailer or some other reputable source as mine came in range load C although I specified and seller advertised range load D. He gave me some $ back as a result but I ended up with a lesser load tire than I was willing to pay for.
We have ST205r/75 14 C rated tire combined load limit is 3600 lbs your tires should exceed your needs though.
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Old 04-28-2021, 01:17 PM   #13
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Name: Peter
Trailer: Casita
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14-inch to 15-inch with no problems

Jon my experience is similar to SB-Steve's. I read about all sorts of concerns with the increase in diameter for the stock Casita but it sure looked like there would be no issues. I went ahead and there were not; just no more problems.

My last tire blow out that I can recall was in my 1955 Chevy on Interstate 80 in about 1972. On my 14-inch tired Casita I had three of them. I bought the best 14-inch ST's I could find and still had blowouts; especially on nice paved roads in the summer.

It appears the load range of a few 14-inchers have come up over the 2,000 lbs. range but I would still be wary. Load carrying ability of trailer tires can diminish rather quickly for a number of reasons. Undoubtedly you will find happy contented users, but you are correct that you will have greater availability and selection in a 15-inch tire. (I also kind of wondered in the back of my mind what the dynamic load on a single tire was on my when I was driving through a sweeping curve on a freeway going 60 mph with a 2,600 pound trailer. Not the safety factor I'm pleased with).

I've had three Casitas for approximately 20 years and haven't had a single incident when I made the change to 15-inch tires. I agree with John that since you are not powering that trailer axle there is little benefit to be gained from trying to max-out the tires' width.

Good luck with your project.
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Old 04-28-2021, 01:39 PM   #14
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Load ratings are static loads. Surely engineering takes into account greater dynamic loads in actual towing conditions.

I wonder if one difference between then and now is a wider availability of D-rated tires in smaller sizes. Scamp now uses D-rated 13" tires on some models.

In this case, assuming you and others are correct that 15" tires will fit without any clearance issues, and as it sounds like the OP was planning to buy new wheels anyway, it seems like a no-brainer.

Definitely D load range either way.
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Old 04-28-2021, 02:40 PM   #15
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Trailer: Casita
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Yes on the greater availability of load range D in smaller diameters and yes on the brains.

If you take your trailer to a good tire shop, instead of just buying new wheels and tires and fitting them yourself, it's likely they will have a better idea what will fit and will not make you 'eat' a set of tires if they are not going to work.

If you are in the West I can recommend Les Schwab for this kind of work. There may be better stores people know of but with over 450 locations in nine states they are always nearby and ready to service what they sell. Often they don't even ask for a receipt; they look at your equipment, know its theirs, and just fix it.
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Old 04-29-2021, 09:35 AM   #16
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Tires Tires Tires

Quote:
Originally Posted by Jon in AZ View Post
Load ratings are static loads. Surely engineering takes into account greater dynamic loads in actual towing conditions.

I wonder if one difference between then and now is a wider availability of D-rated tires in smaller sizes. Scamp now uses D-rated 13" tires on some models.

In this case, assuming you and others are correct that 15" tires will fit without any clearance issues, and as it sounds like the OP was planning to buy new wheels anyway, it seems like a no-brainer.

Definitely D load range either way.
Agree: our utility trailer has 13" D rated Tires sets limit to 1950 lbs combined.
The larger Tires do ride smoother. Boler came with 14" We went to the Goodyear dealer for help with our boler they did not recommend light truck. The rep said trailer suspension was different when we got our Tires. The rep said B would be fine but upgrading to C was a good idea as B was less than axle max and C was greater.
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Old 05-01-2021, 01:06 AM   #17
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higher load range tires in the same size are designed for higher pressures. like the load range 'E' tires on my F250 are rated for 75 PSI or something, but on that truck I run like 60 PSI or something. stick with the tire pressure that the TRAILER maker specified, and you're golden.
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Old 05-01-2021, 07:09 AM   #18
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stick with the tire pressure that the TRAILER maker specified, and you're golden.

Is that right?

My trailer has a sticker that says 25 PSI and the tires say 70 PSI.
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Old 05-01-2021, 07:51 AM   #19
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Is that right?

My trailer has a sticker that says 25 PSI and the tires say 70 PSI.
What is the load rating on those tires? What is the axle weight of the trailer ?((GWR-tongue)/tirecount)
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Old 05-01-2021, 08:13 AM   #20
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25 psi screams vintage trailer, originally equipped with bias ply tires, possibly underrated for the real world weight of the trailer (as were many axles back then). Meaningless today.

(Late thought… It could also be a tandem axle Bigfoot, which supplies LT tires and bucks conventional tire wisdom with a fairly low tire pressure recommendation based on actual tire loads. That’s a different conversation.)

Every ST tire manufacturer I know recommends running at full sidewall pressure, and most trailer manufacturers follow that recommendation. If you upgrade to a higher load rating than original equipment, you may be able to reduce your pressure below the sidewall maximum, but you have to do your own engineering analysis using (1) an actual scaled axle weight at maximum load (divide by 2 and add 10% to estimate tire load, allowing for unequal left/right loading), (2) load-inflation charts from your tire manufacturer (giving safe minimums, not ideal or recommended pressures), and (3) some testing of the tire contact patch at various pressures.

For greatest safety- which trumps ride quality on a single axle trailer- you want to run the highest pressure (up to the sidewall maximum) that maintains even tread contact across the width of the tire,.
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