daamac wrote: Is there a 15" LT tire that could replace a 15" Load Range D ST tire?
Not that I am aware of - except there are LT235/75R15 Load Range C's. Perhaps that might work, but you'll have to check to see if there is enough clearance (and the rim width).
Oh and one tidbit I left off - the 40% rule:
If the rim you want to put a tire on is wider (or narrower) than the rim width specified, then the tire's section width is wider (or narrower) by 0.20" for every 1/2" change in rim width.
Wayne Dohnal wrote: With a nonsense statement like this (from at least some of the tire manufacturers), how can you take any of the specs seriously? I thought the definition of maximum was pretty clear cut. Must be my outdated dictionary.
Wayne, I can understand the confusion - and under normal circumstances maximum's mean maximum's. But we are talking about altering things in order to get out of a situation that's leading to failures - and when it comes to tires, the inflation pressure thing is a little more flexible than what we normally think of as maximum's.
BTW, this 10 psi increase is in the standards manual. There are other things like that in the standards manual for other types of tires. For example: Did you know that Off-The-Road Slow Speed Service tires (Loader/Dozer type limited to 5mph) that a stationary tire can be used at 160% of the rated load?
Yup. Plenty confusing.
* This post was
edited 02/07/12 05:13pm by CapriRacer *
I agree with Wayne, maximum is maximum and tire manufacturers don't say you should exceed this under ANY circumstances This is just plain bad advice.
If I am wrong then I would like to see where a MANUFACTURER says it a good idea.
Scott, Grace and Wesly
2003 Dodge 3500 4x4, 6 speed Cummins (lightly bombed),
2004 Forest River 25RKS many, many mods.
H0NDA eu2000i
CapriRacer writes "ST tires can be inflated 10 psi over the maximum pressure listed in the sidewall of the tire - and I'd recommend that if you can't get to a 15% reserve capacity.
Recent bulletins from the tire industry indicate that tires degrade simply due to time. The age of a tire is important even if the tire is unused."
Umm.. did you READ the link you posted?
According to the RMA link that you gave you are incorrect on on inflating above the side wall rating. They CLEARLY state that it is not allowed.
They also clearly state that there is NO reason to replace the tire according to age.
So I am inclined to disagree with your theory's and assumptions.
My conclusion is if you "feel" that you NEED more capacity that you are much better off to bump up to the next tire load range in a ST tire provided your rims are rated for the extra pressure.
If no range above your current tire is available then you may need to consider REMOVING some of your load. This is due to the fact that you are overloading the rest of the trailer. The manufacturers use components rated slightly above the max GVW including the tires.
We are ALL guilty for dragging along more stuff than needed.
HTElectrical, they clearly state to not use any petroleum based products and even mention to not use silicone based products.
This basically eliminates every tire "dressing" known to man, in other words don't waste your money unless you like the shiny look and don't care about the tire life.
That link provided by CapriRacer is a very useful and valuable resource for tire info.
Proper Tire Inflation
The recommended inflation pressures for tires are
typically measured in pounds per square inch (psi)
and are indicated on the vehicle tire placard,
certification label or in the owner's manual. Never
set tire inflation pressures below the recommended
inflation pressure found on the vehicle tire placard,
certification label or owner's manual. Under
inflation causes excessive heat build-up and internal
structural damage that may lead to a tire failure,
even at a later date. Do not exceed the maximum
inflation pressure shown on tire sidewall. Over
inflated tires (over the maximum molded on the tire
sidewall) are more likely to be cut, punctured or
damaged by sudden impact from hitting an obstacle,
such as a pothole.
NOTE
The pressure indicated on the tire sidewall is the
maximum allowed in the tire, irrespective of the
vehicle. Follow the vehicle manufacturer’s
recommendations for inflation pressure found
on the vehicle tire placard, certification label or
in the owner’s manual.
Per PDF Page 22
Treating tires with incompatible dressings or harsh
cleaning agents will hasten oxidation and result in
premature cracking. Always avoid petroleum-based
tire dressings/cleaners. Check with the tire
manufacturer recommendations for cleaning tires.
See “Cleaning Tires” on p. 27.
Per PDF Page 24
Tire Service Life is Not Determined by
Chronological Age
Per PDF page 53
Tires specifically designed for travel trailer use in
highway service have an "ST" (Special Trailer)
molded on the tire sidewall (ST225/75R15 or
ST235/80R16). ST tires have different load capacity
characteristics. Therefore, ST tires should not be
replaced with any other type tire.
The maximum load for each tire is molded on the
tire sidewall (along with the maximum inflation
pressure for that load). Never exceed the stated
maximum limits on the tire, rim or wheel assembly.
The major components of an RV - the vehicle frame,
brakes, axles, rims/wheels, tires, etc. - are designed
to accommodate a particular weight. If these weight
ratings are exceeded, these parts may wear rapidly
or may fail prematurely in-service. The RV
manufacturer provides the weight ratings and load
specifications printed on the vehicle tire placard or
certification label as follows:"
HTElectrical wrote: Do you recommend using any tire treatment chemicals if so what and why, if not why? The obvious would be to keep the tires covered, and not park on dirt or wet ground. Anything else to prolong tire life?
Thanks in advance!
Nathan
I know that there are treatments I would not recommend. Those are the types that dissolve the waxes that migrate to the surface to form a barrier to oxydation. You can tell these types because after you apply them, you get a black mark on your finger when you rub the tire.
Personally, I would stay away from tire treatments, but I don't have the chemistry background to be definitive.
kedanie wrote: Let me see if I understand correctly.
You say that an ST tire needs a 15% reserve and should not be loaded beyond 85% of sidewall capacity. Also, you indicate that the LT tire can be used at 100% of it's sidewall capacity.
If this is true, then a lot of manufacturers of RV's are doing their customers a disservice by putting underrated tires on their vehicles. One that comes to mind is JAYCO that still installs 16" load range "D" ST tires with a 3000# load capacity on rigs with 6K axles. Don't believe me? Go to your nearest dealer and take a look.
Keith
Keith,
There's a lot of dirt to be thrown around when it comes to trailer manufacturers and the way they size tires - just like the dirt that was thrown around with the Ford/Firestone thing some 11 years ago. I suspect its because trailer manufacturers don't tire issues as part of their problem - an understandable reaction. Nevertheless, my opinion is that this whole area could use some cleaning up.
ExRocketScientist wrote: You mention monitoring the rise in air pressure. Based on my knowledge of the ideal gas law, what you are in effect measuring is the increase in temperature. For me, twisting the valve caps off an on that often is a real pain, plus, the guages available that will handle my 80 psi tires are not exactly high fidelity.
I know you have said you are not an RVer, so I will let you in on what some of us do. We carry these infrared non contact thermometers that are available from Home Depot, Lowes, Harbor Freight, or an auto parts store. Whenever we stop, we check the temperatures of our tires, our hubs, and our brakes. It is real quick and convenient. If we knew the air temperature outside the tires (i.e. have a wireless thermometer stashed somewhere where the sun doesn't shine underneath the trailer), shouldn't there be a maximum temperature above that for the tire?
First, you are exactly right about the ideal gas law thing.
What I have is lots of experience with passenger car tires and I know it works there. I've expanded the recommendation to accommodate tires with starting pressure higher than 35 psi.
As far as surface temperature goes. This is where I don't have experience. The passenger car thing goes back to the days before the IR devices - and I'm quite comfortable with that. What I am not comfortable with is making recommendations without that kind of research. Perhaps those of you who have these devices can get a correlation going between what we know works for inflation pressure buildup and surface temperature.
ScottG wrote: I agree with Wayne, maximum is maximum and tire manufacturers don't say you should exceed this under ANY circumstances This is just plain bad advice.
If I am wrong then I would like to see where a MANUFACTURER says it a good idea.
Here's a quote:
Light Truck Tires
The inflations shown in the load tables are minimum cold pressures for the various loads listed. Higher pressures should be used as follows:
A. When required by the speed/load table, table 1 on Page L-2.
B. When higher pressures are desirable to obtain improved operating performance.
The combined increases of A and B should not exceed 10 PSI above the inflation specified for the maximum load of the tire.
THE MAXIMUM RIM CAPACITY MUST NOT BE EXCEEDED.
Interestingly, this is straight out of the standards manual. However, there is a similar statement in the standards manual for ST tires that Goodyear doesn't put in this pdf file.
Look elsewhere in this document and you'll see what I mean about maximum pressure being a little more flexible than you might normally think. Like Page 2 Table 1.
* This post was
edited 02/07/12 05:44pm by CapriRacer *
daamac wrote: Is there a 15" LT tire that could replace a 15" Load Range D ST tire?
Not that I am aware of - except there are LT235/75R15 Load Range C's. Perhaps that might work, but you'll have to check to see if there is enough clearance (and the rim width).
Oh and one tidbit I left off - the 40% rule:
If the rim you want to put a tire on is wider (or narrower) than the rim width specified, then the tire's section width is wider (or narrower) by 0.20" for every 1/2" change in rim width.
Maxxis makes an LT235/75R15 load range D tire (UE168 Bravo). The load rating is 2335 pounds at 65 psi. It is 28.9 inches in diameter. This will not replace an ST225/75R15 load range D (2540 pounds at 65 psi) but will replace the load range C ST tire (2150 pounds at 50 psi) in the same size if it is compatible with your rims. Note that the diameter of the ST tire is nominally 28 inches so as stated you must make sure it will fit. The tread pattern of the UE168 is appropriate for trailer use.
I thought the GY Marathon 10lb pressure increase was to exceed the 65mph limit, but not to exceed the max pressure on sidewall. That is that it is applied to pressure/load chart. ??? Chris
My Rig
2001.5 2500 STD CAB AUTO SLT 4x4, CTD 4:10's, Bomb'd to Tow
2005 Cardinal 29WBLX.
Offline
