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Open Roads Forum  >  Folding Trailers

 > 12" tire size equivalency/durability question

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bondebond

Searcy, AR

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Posted: 02/17/12 10:01am Link  |  Print  |  Notify Moderator

I have a pop-up camper with 5.30-12 load C tires on it. I cannot seem to get a decent quality tire in this size anymore as they tend to leak air significantly or blow too frequently for my taste. I understand the two previous ideas can be directly related: driving with under-inflated tires, so I check before each trip to make sure I am at the stated 80 psi.

Even so, I lose almost a tire a year. I am sure driving too fast has nothing to do with (end sarcasm).

I have added fix-a-flat or slime to the tires and that has helped slow the air loss, but still not satisfactorily. Nothing will stop it, I know.

As the price of 5.30-12 tires approaches $60 and $70 even unmounted, I am wondering about other choices.

Quick info on my set-up: I have a Dexter torsion axle that doesn't allow for flipping the axle, which has 4 on 4" hubs. I've previously looked at the mounting brackets and it sure didn't look as easy as spring axles seem to be in that regard but it's been a while and my memory can be foggy to say the least.
So going up in tire size isn't an easy route for me, especially with limited resources.

And now to my question. I noticed on etrailer.com that their "expert" has recommended folks looking for a 5.30-12 tire consider the 145/80R12 instead (which is rated for load D, not that I care about the extra load rating). It looks and reads as a more durable tire than the 5.30-12.
A similar weight rating at only 65psi instead of 80psi for the 5.30-12.
The actual tread width sure appears wider and it is a steel belted radial versus only bias on the 5.30-12.
If you're curious about the exact tires I'm referring to, the 5.30-12 here and the 145/80R12 here.

The difference in diameter is the 145/80R12 is about 1/2" smaller overall. That seems quite acceptable to me. Going up in size puts me at risk of clearance in the wheel well, IMO.

So, am I correct or not in assuming that the 145/80R12 has some inherent strength/durability in it over the 5.30-12, all other factors being the same?

The price isn't so much more that I wouldn't mind paying it, especially if it increases the longevity.

Thoughts?


This space left intentionally.

2006 Fleetwood Sequoia and mods...one of the tallest highwall pop-ups on the planet after flipping the axle.


BenK

SF BayArea

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Posted: 02/17/12 10:12am Link  |  Print  |  Notify Moderator

You are experiencing what many don't understand, nor believe...limits and ratings

Whenever something is used at or over it's rated limits...their MTBF is reduced
(mean time between failure)

Makes no matter a bolt, tire, wheel, whole vehicle, your body...

Then the architecture or design of the tire. A radial is much better both in
thermal and rolling resistance vs a bias ply. This is where accelerated consumption
of it's life span by over or high temp vs it's design temp range

Loading a key component of all that

Going to a radial 'might' help/fix, but (not knowing your loading vs tire
rating), suggest going even farther up the tire class scale and go to a 15"
or even a 16" tire...if your popup has the room.

The best is a whole axle swap, but if you wish to stick to the existing axle,
then the wheel bolt pattern will become an issue

A 'good' tire dealer and/or mechanic is critical in this

Good luck


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

hugemoth

Bend

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Posted: 02/17/12 10:52am Link  |  Print  |  Notify Moderator

I had the same issue a few years ago with a teardrop trailer. The 12" bias ply trailer tires would wear out after a few thousand miles and I had a couple of them come apart on the highway. I put on some 155/80R12 car tires and never had another problem. Towed it over 10,000 miles and they still looked brand new.

Nowadays 12" car tires are hard to find and many tire shops won't mount them on a trailer. You can usually get around that by taking the wheels off and carrying them to the shop.

I'm not saying you should do it, but it worked great for me.

bondebond

Searcy, AR

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Posted: 02/17/12 11:42am Link  |  Print  |  Notify Moderator

hugemoth,
Yes, it seems particularly difficult on long trips due to the constant driving, with the tires never really getting a chance to cool down due to marathon driving. Obviously not the conditions the tires were designed for. That I understand.
The 155/80R12 passenger tire is an interesting option but not one I'm too excited about because it's not designed for a trailer and would be too wide for axle and trailer frame clearance. Thanks for sharing and knowing where I'm coming from.

As for going up in size, it would take quite a bit of modification and cost to get me there. Going to a 15" or 16" wheel would certainly set me up in the looks of the "offroad" pop ups. That's appealing but I think a bit too out of my grasp at the moment. All of my stabilizers would need blocks just to touch the ground as well as a new door step with a second or third step on it. Just keeps adding up.

I do understand design limits, limitations and the costs of pushing them. That's why I am looking at alternatives. I am wondering (and I know not many will have direct experience) if the 145/80r12 has better longevity than the scrawny things I have now.

BarneyS

S.E. Lower Michigan

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Posted: 02/17/12 12:06pm Link  |  Print  |  Notify Moderator

I am going to move your thread to the Tech Issues forum. I think you may get some more responses there. Good luck.
Barney


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96Bounder30E

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Posted: 02/17/12 01:43pm Link  |  Print  |  Notify Moderator

At the request of Moderator: mike4947 I am going to move this thread over to the Folding trailers forum.

mike4947

N. Syracuse, NY

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Posted: 02/17/12 01:55pm Link  |  Print  |  Notify Moderator

SInce I've been around PopUps for the last 38 years I've had a few problems like your's.
A few suggestions:
The bias ply tires were designed in the late 50's early 60's. The radials are a newer design from the late 80's to the early 90's. I'd go with the radials.

It's never a bad idea to increase the weight rating of the tires. Some cushion helps.

JMHO but since you've had problems with air leaking over the years if it were me I'd be looking at new wheels. Can't count the number of rims that have had rust or other problems with the bead areas and cause slow leaks.

Anther thing to do is to always replace valve stems with new one when changing tires. All stems have some sort of rubber seal that dry rots as fast or faster than the tires. Make sure they are high pressure stems. Passenger car stems are only rated for 50 PSI.

As for "flipping the axle" it can be done on Torison axles by using a block between the axle and frame. But also as well as a step, and stabilzers (they do make longer ones) you'll need a new drawbar as well.


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bondebond

Searcy, AR

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Posted: 02/17/12 04:02pm Link  |  Print  |  Notify Moderator

Mike,
Thanks for the thought-provoking responses. Some things to chew on. I will certainly be buying radials instead. And I certainly am not shying away from the weight capacity increase; it just wasn't a primary goal. But, that can't hurt at all, as it makes me think of overall increased strength.

Tireman9

Akron, OH

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Posted: 02/18/12 09:03am Link  |  Print  |  Notify Moderator

bondebond wrote:

I have a pop-up camper with 5.30-12 load C tires on it. I cannot seem to get a decent quality tire in this size anymore as they tend to leak air significantly


Snip

Thoughts?


You didn't mention if the valve stems are rubber "snap-in" or bolt in metal. I'll bet that if rubber they are standard low cost passenger type valves which are rated at 60 psi Max.
Rubber valve info HERE.

Rubber vs metal info HERE.

Some soap and water should help find where the air is leaking out.


40 years experience as tire Design & Quality engineer with focus on failed tire forensics.

Google "Tireman9" if you want to learn more on RV Tire Safety

Lowsuv

Oregon

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Posted: 02/19/12 10:13am Link  |  Print  |  Notify Moderator

Are those axles on a " SPLINE " setup for the torsion bar hookup ?
Some boat trailers have the ability to Raise ( or lower ) the trailer height by adjusting the location of the spring bars on the "SPLINED" end of the torsion bar.
Jack up your trailer. Lower your axle by a couple of notches. Repeat for the other side. Find higher (larger ) tires and wheels that fit your bolt pattern.

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