Load range D instead of C?

[Tom Nugler]

Hate to start up yet another tire thread but bear with me. The latest thread on this I could find was 3 years old.
Has anyone had any experience running load range D tires instead of Cs on a vintage tandem axle trailer?
I’ll be mounting Goodyear Marathons despite all the warnings of a looming catastrophe.
The local dealer warehouse only stocks Ds. I can get them same day. I can get Cs from Tire Rack sometime next week, but, with shipping and handling that adds another $80.
The tire dimensions spec out the same, but I’m wondering about the sidewall flex due to the lower inflation pressures. The Goodyear inflation chart lumps both Cs and Ds on the same line indicating comparable pressure for both tires up to the max load of the Cs. Ball-parking my weight I’d be running about 35psi. Seems low to me.

That’s all I’ve got. Thanks for any input in advance,
Tom.

[Silvertwinkie]

I have "D" rated. I would stick with those. I know vintage weighs less than late model, but I think the two extra plies (sp?) is not a bad thing. I don't believe the extra 2 plies will be too stiff for your coach IMHO.

You can read a bit about the difference here:

Tire code - Wikipedia, the free encyclopedia

[Road Ruler]

I'm running P235's with the XL (extra load rating). The 23 tows great with these tires and I like them because they run at 36 lbs. They are also rated for 2,165lbs each so lots of head room for the 4,500lb road ready trailer.

[RickDavis]

I have run both D and even E on my 5000 lbb tandem tradewind.. Due to the generally questionable quality of some trailer tires I won't even use C. Be aware of the inflation rating of your wheels also. I usually run 60 lbs or so even though the E will take more.
It does seem like the tires are starting to get a bit better than in past years

[Wabbiteer]

It boils down to whether you have the stock stamped steel wheels of have upgraded to aluminum wheels.

Stock steel wheels have a nasty habit of brittle fracture when stepping up load ranges - not a pretty sight, Andy has posted on it many times. Even if you have Aluminum wheels it might not be the best choice...

I went with 'C' range from Tire Rack; if you bump up the load range with the stiffer sidewalls on lighter 1970's trailers there might be a trade off of lower air pressure (tire runs hotter) to keep the slightly "low on air" (bulging) look that radial tire sidewalls NEED to maximize handling and performance.

Explanation of radial tire characteristic advantages

[2airishuman]

tom

the D rated tires don't appear 2 have any more PLYs than the Cs...

they DO have 4-5 lbs MORE RUBBER per tire and perhaps larger threads in the poly/steel belts...

and the reports of "stiffer sidewalls" don't hold water...

just a couple of weeks ago i personally FIDDLED with c, d and e ST tires...

the sidewalls ALL felt the same and flexed the same by touch.

the caps/tread sections ARE thicker and that can be felt,

but the sidewalls had no PERCEPTIBLE differences.
____________

the questions really are

1. do you WANT 5 lbs more rubber at each contact point...
2. what does that 5 lbs ROLLING do to the current suspension...
3. what does that 5 lbs ROLLING and FLEXING do to heat retention...
4. what does that 5 lbs ROLLING FORWARD do the the braking distance/time and magnet/shoe wear...

in addition the only 15 C rated gyms are 205 width (per the TR chart) while the D rated are 225s...

so IF that's correct info, nearly 1 inch wider tires IF u go to the Ds...

given how light the trailer and the load per tire, functional GRIP may actually go down with the LARGER contact patch...

5. will the 225s FIT in the wheel well space correctly...
6. what impact will the 225s have on the RIMS (wider tires)...

shipping cost aside TR generally has very FRESHly made tires and ships to MOST usa location in 2-3 days.

get the C rated tires and properly inflate them.

((the ONE upside to D rated, IF they will fit the rims and wells is....

the extra 800 lbs of rating would come in handy, IF you don't have a spare and need to roll on ONE))

cheers
2air'

[Tom Nugler]

VBulletin template.
Thanks all.
I did read 2Airs thread a while back. A lot of meat to chew on.
I did see the thread concerning wheel failures. I’m not too concerned about that aspect of the equation. I’m not intending to increase the weight of the rig. The wheels are getting cleaned and painted before I mount the tires so if anything looks odd I'll deal with it then.
In fact the dinette conversion currently underway will weigh 20 to 30 pounds less than the stock front couch, cabinetry and pullout table. The better half packs heavy so I think we’ll even out.
Dimensionally the 225/75 R15 Marathons are speced out nearly the same in diameter and only a ½ inch wider that the 13 year old LT 7.00 15s on there now. Plenty of clearance.
I’ll have the parts guys order up the Ds tomorrow. I am still concerned about the sidewall flex/heat aspect, but I’ll bring my IR thermometer and keep an eye on it the next trip.

See you on the road,
Tom.

[2airishuman]

good choice

post pics after mounting and installing.

the 35 psi is a bit unsettling with a max pressure of 65 as the norm?

there are folks here who report running that low,

but on a 75 series tire that might be an issue...

just how much lateral stiffness will a 75 series tire provide at 35 psi?

and what will the contact patch look like?

IF the trailer is parked long term, what cracking/sidewall changes might occur...

at such a LOW pressure?

lookin' forward to the f/u reports.

cheers
2air'

[TomW]

Originally Posted by Tom Nugler

... I’ll be mounting Goodyear Marathons ...The local dealer warehouse only stocks Ds. I can get them same day. I can get Cs from Tire Rack sometime next week...

I decided to go with load range C Marathons and found my Goodyear dealer only stocks Ds. But his computer indicated two other stores had two LR Cs each, and he could round those up in the space of a couple of days. So, on the 22nd of last month, I pulled my Overlander's wheels off, and started a new thread on something else I noticed.

My Overlander is still on stands.

At least one of the tires the other store had was more than a year old, and no one else had any newer LR Cs. It appears I am waiting for rubber to be molded. If that does not occur soon, I will probably have to go with LR D and take my chances.

I am surprised acquiring trailer tires is this much trouble.

Tom

[Wabbiteer]

Adding load is said NOT part of the steel wheel failures - it's just stepping up the load range and differences in the tire husk.

I bead blasted my rims and saw multiple crevices of corrosion inside the bead seat area extending 60° or 90° around the rim from years of weathering & wicking in morning dew and such I'm pretty sure its a valid engineering issue...

[RickDavis]

I run my tires at 60 psi even though load charts based on weight would suggest a lower pressure. I get excellent tire life and don't think I am beating the trailer to death based on the "gas lite lantern mantle test" One mantle is usually good for the season.
I also run my truck tires near maximum inflation, regardless of load and typically see 100 k plus per set of michelins.
The only time I purposely lowered my tire pressure was on the haul road in Alaska to keep from beating both the trailer and us to death. Of course our speeds were limited to about 30 miles an hour also on that dirt road.
I am using aftermarket rims rated at 65 PSI since I had to replace the old split rims.

[ZoominC6]

We went to Carlisle "D" rated last year and so far, so good. Time will tell.

[utee94]

My goodyear dealer wanted to put me on Es for my 63 Overlander that currently weighs 4,000 lbs. I told him it needed Cs. But he only stocks Ds and Es. He doesn't want to sell me Cs at all.

So, I'm looking for another dealer.

[2airishuman]

there is no E rated gym in 15s.

unless it's an unpublished size.

E rated gyms are limited to 16s.

on the PLUS side and 2 add to confusion gy does make C rated 15s...

in two different widths and with 2 different load ratings



(TR only shows the 205s on their site)

cheers
2air'

[RickDavis]

Originally Posted by utee94

My goodyear dealer wanted to put me on Es for my 63 Overlander that currently weighs 4,000 lbs. I told him it needed Cs. But he only stocks Ds and Es. He doesn't want to sell me Cs at all.

So, I'm looking for another dealer.

Have you actually weighed the trailer ready for the road? Many overlanders were single axle. ( maybe not in your year) C would be ok on the tandem but would be very borderline on a single.
Despite the supposed weight ratings of trailer tires a lot of people have a lot of trouble with them.
I would prefer the safety factor of D rated tires. My 61 tradewind weighs in at 5000 ready for the road which is why i question your weight. Even with D rated tires , careful maintenance etc I have caught some impending tire failures before they actually happened

[ts8501]

Originally Posted by ZoominC6

We went to Carlisle "D" rated last year and so far, so good. Time will tell.

And I am running Carlisle "E" since last year on my single axle '64, and so far no issues. I do run the psi at 60. I believe the tire is rated for 85 psi.

[joecolao]

Originally Posted by Tom Nugler

Hate to start up yet another tire thread but bear with me. The latest thread on this I could find was 3 years old.
Has anyone had any experience running load range D tires instead of Cs on a vintage tandem axle trailer?
I’ll be mounting Goodyear Marathons despite all the warnings of a looming catastrophe.
The local dealer warehouse only stocks Ds. I can get them same day. I can get Cs from Tire Rack sometime next week, but, with shipping and handling that adds another $80.
The tire dimensions spec out the same, but I’m wondering about the sidewall flex due to the lower inflation pressures. The Goodyear inflation chart lumps both Cs and Ds on the same line indicating comparable pressure for both tires up to the max load of the Cs. Ball-parking my weight I’d be running about 35psi. Seems low to me.

That’s all I’ve got. Thanks for any input in advance,
Tom.

Dear Tom,
To make your decision you need to know the weight being applied to your tires. The only real accurate way to do this is to weigh each wheel. If you can't weigh each wheel, second best is to go by the axle weight rating.
Having a higher load range has many disadvantages too.
The load range D tires are usually rated at about 2650 pounds at maximum pressure. If you have slightly less than the maximum load on that tire, you can go to the manufactures "tire inflation schedule" and see what tire pressure they recommend for the weight that you actually have exerted on your tires.
Very often - the weight that you will be carrying on that tire will be significantly lower than the manufacturers recommendations if you arbitrarily decide to go to a higher load range than recommended.
If the latter is the case then you will be in an "over-inflated condition". While most people would concur that this condition would lead to premature tire wear in the center - more importantly it will leave a significantly smaller "footprint" on the road. This factor is very important because less rubber on the road compromises your tracking and more importantly your braking.
For convenience I have found the lower the load range - the easier to find compressors and gauges too!
By the way on my 34' Airstream I have load range D only because I could not get load range C at the time. On a tri-axle trailer I have much less weight on each tire than a dual-axle!
I am not within the tire inflation schedule's parameters. I only have 1300 pounds on my tire but at - my load range D tires are 2650 pounds. This means that even though I have significantly reduced my tire pressures I am still in an over inflated condition which results in a harder ride for my trailer and a smaller road footprint.
Sorry for the wordy response but I felt it was important to you.

[utee94]

Originally Posted by RickDavis

Have you actually weighed the trailer ready for the road? Many overlanders were single axle. ( maybe not in your year) C would be ok on the tandem but would be very borderline on a single.
Despite the supposed weight ratings of trailer tires a lot of people have a lot of trouble with them.
I would prefer the safety factor of D rated tires. My 61 tradewind weighs in at 5000 ready for the road which is why i question your weight. Even with D rated tires , careful maintenance etc I have caught some impending tire failures before they actually happened

It weights 3800 lbs unloaded, around 4300-4500 loaded for the road. In 1963 Overlanders came stock w/ tandem axles, and mine is no exception. C rated tires are appropriate for my trailer, E rated tires are not appropriate, and D are somewhere in-between.

[Action]

Originally Posted by TomW

I am surprised acquiring trailer tires is this much trouble.

Tom

Has to do with supply and demand. Trailer tires don't sell as fast as car and truck tires. The manufacturer has to make a decision as to how many tires to make in a run. Obviously when you find a tire that has a manufacturing code from a year ago, you know that specific tire and size isn't moving very fast or it would have been sold 6 to 9 months ago.

Just the world we play in.

>>>>>>>>>>>>>>Action

[TomW]

Originally Posted by Action

Has to do with supply and demand. ... Just the world we play in.

Dave,

Since you do a lot with boat trailers and all, would you happen to know another tire maker (any tire maker) who is marketing (and delivering) LR C tires?

My quandary now is whether to purchase Marathon LR D tires, or more suitable LR tires from another tire maker.

Thanks,
Tom