Load range D instead of C?

[Action]

Boat trailer tires swim in a different world again ....

I have a 27' express cruiser on a dual axle trailer the combo weighes over 7000#'s. (I believe close to 7500) To keep the center of gravity down low the trailer manufacture installed 14" rims on this 1997 built trailer. (At least that is what I made up about why I have 14" rims on this set up.) The trailer is rated to a weight capacity of 9500 #'s. Tires not so much.

The largest non-passenger 14" tire I am able to get is a 215x75x14 in a "C rating. (1880 #'s each at max pressure for a total of 7520 #s) This tire size is at the load limit I am towing so I push the envelope because of availablity. The manufacturers that build that kind of tire in "C" range are Goodyear & Greenball that come to mind.

"D" ratings ....... well that is a dream that I have had for a 14" rim size tire. I have not been able to make that one come true. Of course if I wasn't so cheap, I'd pony up to 15" rims and tires to match. Then I could get the load capacity in tires which is my weakest link in my towing set up for this rig.

Sorry not much help for you in the water world of towing because of rim size I work with.

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

[Tom Nugler]

As many of you have discovered there seems to be drought of load range Cs out there. Which, of course, is one of the reasons for this thread.
I’ve been checking out tires for the last 3 months. The skins on there now had been sitting at least 7 years with minimal use, leak constantly and are basically junk. My dilemma was that the first trip of the season is 2 weeks from today. Warning!! Blatant plug: http://www.airforums.com/forums/f288...ois-61599.html
Six other trailers have confirmed so we’ve got to show.
I needed tires yesterday.
To sum things up. 4 load range D Marathons showed up at 2 PM. Made in the USA during the last week of ‘09. After work I mounted 1 on a prepped rim. It balanced out at 1.5oz. total. No need to even match mount the tire to the rim.
I knew this thread would open the proverbial can of worms but it’s enjoyable and informative to read everyone’s comments and experiences.

Thanks, See you on the road,
Tom.

[TomW]

The load range C Marathons I asked my Goodyear dealer to order finally came in this past Friday, and all four tires were made during the 2nd & 3rd weeks of this year.



These tires replaced bias ply tires purchased when my Overlander was new to me. While I knew the Marathons would have a lower profile than my old LT 7.00X15s, surprisingly, my Airstream now sits 7/8” lower than it did 3-1/2 years ago when the new axles were installed. I hope the bulk of this difference is due to the new tires and NOT to sagging axles.

Now I have to get comfortable with the tire inflation pressures. The old bias ply tires were run at their max pressure of 45 psig. According to Goodyear’s inflation guide for radials, at my Airstream’s fully loaded weight the new radials only need 30 psig to get us safely to a campground.

The tire shop inflated the new tires to their max rating of 50 psig. I deflated them to 35 psig. 30 psig, while it may be optimum, seems too low, and makes me uncomfortable.

On the lighter side, I might pump the tires back up to 50 psig if more ground clearance is needed – The Overlander lost 1/16” of height going from 50 to 35 psig.

Tom

[2airishuman]

Originally Posted by TomW

... According to Goodyear’s inflation guide for radials, at my Airstream’s fully loaded weight the new radials only need 30 psig to get us safely to a campground...

yeah that's ONE interpretation of the table but in what language?

this is sorta the opposite of "if 1 is good 2 is better"

the table is only a reference for LOAD LIMITS at a given pressure.

it is NOT a GUIDE TO INFLATION pressures.

and it's not a "we recommend u run them at this lower pressure" endorsement.

30-35 is a bad idea.

more lateral INstablity leading to sway and WOBBLE,

more vulnerable to pot holes, curbs and so on...

more sidewall ROLLING when backing or in turns/corners...

more HEAT when moving,

LESS round when parked/stored.

and should ANY ONE TIRE go down for some reason the OTHER TIRE is now over stressed.

this is WHY folks who have one flat or low slow leak end up with a 2nd tire on the same side falling apart.

((then they cry about crappy quality tires))

the issue is VOLUME of air in the tire (for support) and protecting the rim.

at 35 psi the VOLUME of air is ~1/3 to 1/2 LESS than at 50 psi.

that volume is important for a lotta reasons.
___________

if the axles are good run them at 50 psi.

50 psi is NOT a firm tire by any means (inflate a bicycle tire to 50 psi and THUMB IT)

crappy old hard/flat/dead axles hurt old streams.

not tires properly inflated.

besides these are radials so even at 50 psi they will be MUCH softer than bias ply tires.

ignore the side wall LOOK, just inflate the damn things.


IF one is dragging around an old trailer on axles that NEED replacement,

towing HOME on softer tires might be ok.

but with fresh axles and fresh tires, TRAVEL is safer at proper inflations.

i know there are nerds here who THINK dialing in the pressure (at much lower levels) provides some sort of magic...

it doesn't.
_________

it's unlikely that anyone will go to the trouble of checking pressures and temps while traveling...

but that would be very useful feedback

cheers
2air'

[TomW]

Originally Posted by 2airishuman

the table is only a reference for LOAD LIMITS at a given pressure... it is NOT a GUIDE TO INFLATION pressures... and it's not a "we recommend u run them at this lower pressure" endorsement.

30-35 is a bad idea.

I like your words, Joe, and will probably go back and pump the tires back up since my axles are fairly new.

Would anyone care to "second" 2air's words?

Tom

[barts]

I'm inclined to inflate tires more than the values shown in that chart. Airstreams don't have equalizing gear, so the trailer's attitude will significantly affect per-axle loadings. The downside of over-inflation can be more wear in the center of the tire, but this is not as critical with the narrower tires used on trailers as compared to low profile tires on cars, and is less of an issue with radials than w/ bias ply tires.

Under inflation leads to rapid tire wear, hidden sidewall damage and the possibility of catastrophic failure. Over-inflation for the load leads to possibly lower tire mileage, and a harder ride.

Rule of thumb - split the difference. If the chart says 35 psi and the sidewall max is 50, inflate to 43 psi. Check tire temps w/ your hand after towing for a while at speed; if one axle's tires are hotter, give that axle a bit more air.

- Bart

[RickDavis]

I am inclined to inflate tires to near max inflation even when lightly loaded. I run my D range tires at 60 psi cold even though it is a tandem axle. weighing 5000lbs. My older pair now has about 30,000 miles, is wearing evenly and shows a tread depth of 7/32, New they had 11/32. I have never seen center wear from overinflation. I have seen outside wear, heat and sidewall problems from underinflation. It should be noted the axles on the 61 are original.
One thing to keep in mind also is on your tow vehicle you will usually feel a tire problem developing. On the trailer you will not.
I deliver trailers and have experienced both lost wheels and blowout and never felt anything back there

[Ahzmyrah]

I run ST 225/75R15 Load range "E" inflated to 65 lbs. on my 31' Excella. Just finished 12,000 miles around the western U.S.. Everything from sea level to 11,000 feet above and 20 degrees F. to the Death Valley below sea level and 116 degrees F., snow, wet, dry, hot, whatever. The tires now have over 25,000 miles on them and they are in great shape after three years with no failures what so ever. The E's are max rated at 80 psi but I don't run that much pressure because our trailer does not weigh that as much as the tires are rated for. We do not have a problem with rivet popping or stuff shaken out of the cabinets. We did have some problems in the past caused by a collapsed suspension and load range "D" tires would not have made it any better. We have had no problems since replacing the axles with new Henschens. Going to load range "D" tires from "C" should not cause any problems if your axles are in good shape. You could run lower tire pressures but I would try it checking tire temps and ride characteristics at both lower and higher pressures and run a higher pressure if the trailer performs ok. There is also the considration of whether or not you ever have a problem with a tire out on the road. If you are having problems finding a "C" rated tire at home imagine what it would be like on a Sunday in Podunk, USA.

[TomW]

I have just experienced another reason to run higher pressure in my new tires after doing stuff inside my Airstream. The camper is really squirrelly without stabilizers deployed. Since I had gotten used to stiff, bias ply tires, the "give" these new radials have at 35 psig is unsettling.

Part of the reason I worried about running the tires at max inflation pressure was it would make the ride too harsh. It does not appear that will be an issue.

Tom

[ts8501]

Originally Posted by Ahzmyrah

I run ST 225/75R15 Load range "E" inflated to 65 lbs. on my 31' Excella. Just finished 12,000 miles around the western U.S.. Everything from sea level to 11,000 feet above and 20 degrees F. to the Death Valley below sea level and 116 degrees F., snow, wet, dry, hot, whatever. The tires now have over 25,000 miles on them and they are in great shape after three years with no failures what so ever. The E's are max rated at 80 psi but I don't run that much pressure because our trailer does not weigh that as much as the tires are rated for. We do not have a problem with rivet popping or stuff shaken out of the cabinets. We did have some problems in the past caused by a collapsed suspension and load range "D" tires would not have made it any better. We have had no problems since replacing the axles with new Henschens.

This is exactly what I am running; Carlisle ST 225/R15 Load range "E" inflated to 65 lbs. I do not have the miles that you have, but so far, I do not see any issues. I also have a new Henschen on my single axle.

[2airishuman]

Originally Posted by TomW

...The camper is really squirrelly without stabilizers deployed. ...

and if it is squirrelly parked in the yard,

imagine the handling while goin' 65...
__________

i expected some1 2 offer this true statement as a counter to my lunacy...

"50 psi is NOT the recommended inflation pressure either, it's the MAX cold inflation limit" for C rated gyms...

and YES that's also a true/valid observation.

i've yet to find ANY tire manufacture that provides an inflation recommendation for any vehicle.

typically THAT is the domain of the vehicle maker.

gy does advise that those going 65-75mph ADD 10 psi (not to exceed the max)

which automatically mean 45 psi+, were I drivin'...

the owners manual says what ? 45 psi?

of course that PREdates radial tires OR dexter axles...

were u to buy C rated tires in j/c my guess is they'd send the trailer OUT with 50 psi...

another option is 2 inflate all 4 tires differently, for example 50, 40, 35, 30...

then run'em for a couple of years and report what happens...

the challenge being which tire goes where...

cheers
2air'

[knunut]

Replaced orig.tires Approx @15K miles.07 /Safari. The sidewall were bulging/seams were deep grooves.(made in Canada).Nxt day 5/8 lv for Moab-Lake Powell.Inspect tires @Every Stop.They ran Cool.At powell 2K miles new tires show same.seams and slight bulge.
To our luck we rtnd. to camp to find approx.30 units.had arrived, the American Southwest Caravan.Great Bunch of People !!! Got lots of feedback.
Also had tires inspected in Lake Powell & Kanab,Ut. The first Question they ask is "Weight" of trailer.They both also suggested 10 Ply.(Not GoodYear)Well i did not know Actual Wght. So somewhere down the Road i stopped @ Flying J. Very Helpful and i did not need a CB to talk to them they had a phone @ scale. Well i was a little suprised. The Gross truck/trailer was 11085 # the Trailer 4660#. It was 1/2 tnk. fresh,mt gry/blk. 1/2 the food,full clothing. To me this is Very Close (Too Close) to Limit.
Well we made it Home and Learned:
1. Get a Pressure Monitor System. A Must!!
2. Next tires 10 ply. Mich.? (Never Goodyears Again.)
3. Get torque wrench for wheel chk.
4. Weigh trailer /On trips that its Close to Full.

[paddler3d]

Originally Posted by ZoominC6

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

Good luck if you have a warranty issue...currently having one and it isn't fun.