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Old 02-27-2015, 06:30 PM   #883
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"De-Rating" and "Reserve Load", which some call a safety factor are not the same thing.

P type tires have the loads reduced by dividing the numbers found in the load inflation tables by 1.1 when the tire is to be applied to multi-purpose vehicles (SUV, trucks or trailers)

LT type and ST type do not have the load Infl table number s reduced.

Now Reserve load is the difference between the load number in the table at the tire's actual cold inflation and the measured load on that tire (not estimated based on axle divided by 2)

Some suggest a good reserve load is 15%. You will find that a majority of cars have reserve load in the 12 to 20% range.

RV sellers, always looking for cheapest option will many times go with a 0% Reserve Load.

If you always inflate the trailer tire to the pressure shown on the sidewall, which should be done to lower the "Inter-Ply Shear" forces found on multi-axle trailers you can see what your Reserve load is by comparing the tire capacity with its actual measure load.

To have a productive discussion it is important that we all use and understand the proper terminology.
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Old 02-28-2015, 05:50 PM   #884
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We just acquired 16" Sendel wheels and a set of XPS Ribs for our 2009 28' International to help deal with our tendency to have a front left wheel blowout. We have been through a set of Goodyear Marathons and a set of Towmarks (e-rated, 80 psi cold max). I have not had access to individual scales, but I have reason to believe that the left front is carrying more weight because we have 130 lbs of extra battery forward in the coach on the left side. We will be addressing that by replacing all 260 lbs of battery with 84 lbs of lithiums. This will result in an overall tongue weight reduction of close to 100+, but most importantly, it will take at least 50 pounds off the left front, too.

The question is proper inflation. Our Airstream weighs 5960 on the axles when the WD hitch is engaged. Our tire dealer divided by four, which of course, is not accurate, as we can guess that there is much more weight on that particular wheel. But I'm getting input to inflate to less than 80psi when checking on a cool or cold early morning based on the reasoning that the 80psi recommendation is for cold pressure at around 68F. The theory is that as the ambient pressure rises, that same air will increase in pressure, with the coach just sitting there. Therefore, if one inflated to the max 80psi at 68F, that would be way over a "cold" tire pressure taken later in the day when the temp hits 100F. This is what they say all there 18 wheeler customers do when running on a day that they know will be considerably hotter later--and I've had the same advice from three different tire dealers.

Would our resident tire expert care to "weigh in" on this subject? It would be most appreciated.
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Old 03-01-2015, 09:03 AM   #885
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Originally Posted by gecko View Post
We just acquired 16" Sendel wheels and a set of XPS Ribs for our 2009 28' International to help deal with our tendency to have a front left wheel blowout. We have been through a set of Goodyear Marathons and a set of Towmarks (e-rated, 80 psi cold max). I have not had access to individual scales, but I have reason to believe that the left front is carrying more weight because we have 130 lbs of extra battery forward in the coach on the left side. We will be addressing that by replacing all 260 lbs of battery with 84 lbs of lithiums. This will result in an overall tongue weight reduction of close to 100+, but most importantly, it will take at least 50 pounds off the left front, too.

The question is proper inflation. Our Airstream weighs 5960 on the axles when the WD hitch is engaged. Our tire dealer divided by four, which of course, is not accurate, as we can guess that there is much more weight on that particular wheel. But I'm getting input to inflate to less than 80psi when checking on a cool or cold early morning based on the reasoning that the 80psi recommendation is for cold pressure at around 68F. The theory is that as the ambient pressure rises, that same air will increase in pressure, with the coach just sitting there. Therefore, if one inflated to the max 80psi at 68F, that would be way over a "cold" tire pressure taken later in the day when the temp hits 100F. This is what they say all there 18 wheeler customers do when running on a day that they know will be considerably hotter later--and I've had the same advice from three different tire dealers.

Would our resident tire expert care to "weigh in" on this subject? It would be most appreciated.
You are correct that simply dividing by 4 does not give you the actual load on each tire.

The worksheet on THIS page will show you how to do the math.

I have a blog post from Aug 22 2014 with an example how to get your weights for free. Some folks have had success in contacting their State Police and asking if they could go to a location where they are checking trucks.

But setting aside the need to confirm your load balance.
I suggest that to lower the internal structural forces that are trying to tear the belts apart you should set your "cold" inflation to the max on the tire sidewall. The "why" of this was covered Nov 20 2013 on my blog. My position was developed based on the work done by Turner & Ford as seen in the book "Mechanics of Pneumatic tires" pub by U.S. Department of Transportation, National Highway Traffic Safety Administration, 1981 .

Now to your specific question on how to set the "cold" pressure.

I covered pressure vs temperature Mar 13 2014 and when you review that post you will see that the pressure in a tire will change by about 2% for each 10F change so in tour example of 68 vs 100F I would expect about 6% change. The intention of the "Set the pressure in the morning" is to not use a warm (higher than ambient) tire pressure when it has been in the Sun.
I think the reality is that if you check your tires in early AM before you start your travels and before the tire is in full Sunlight, you will be fine for the rest of that day, no matter what the temperature is over the rest of the day. Tires generate heat internally (not on their surface as many think). This heat is transferred to the moving air around the tire and wheel until a steady state is reached where the heat being generated equals the heat flowing away from the tire.

Sorry for only giving you the dates of my blog but I am not allowed to post hot links to my blog on this site.

Hope this helps
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Old 04-06-2015, 08:43 PM   #886
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Tireman 9

I seem to remember a discussion on this thread several years back by a tire engineer and the discussion was along the lines of tires getting overheated and I am thinking 140F was the point you did not want to pass.

Am I remembering this right?

Thanks
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Old 04-06-2015, 10:28 PM   #887
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This thread is really about 16" wheels and LT tires, so tire temperature is a bit off topic. And at nearly 900 posts - anyone interested in other topics besides the orignal one will take much effort to get this data. So realy these posts are for the subscribers and the hardy few that read past 800 posts.

With that said, if the limit on using tires in service was set to 140 degrees, a sigificant area of this country would need to shut down to prevent tire failures.

Bridgestone Commercial Truck Tires

Attached a 2006 Minnesota study showing pavement possible extremes to surface temps to 63C or 145f (In MN no less)

And while heat does have a negative impact on tires, the design of tires would not be such that certain markets (Phoenix, Tucson, Las Vegas to name 3 in the US) could not routinely use a modern vehicle on paved roads at posted speed limits with rubber tires in the summer time because the heat induced into tires from the pavement can easily exceed 140 degrees f.

My guess is road tires are designed to handle much higher temps such as 200 f. Because road tires are going to start at 115 to 120 around here and pick up heat from the road surface AND generate heat internally due to flexing. However that is a guess on my part.

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Attached Files
File Type: pdf pr480.pdf (665.3 KB, 31 views)
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Old 04-07-2015, 06:28 AM   #888
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Thanks for the attachment and I agree the temps may well get up there.

That is one benefit of having CRS, you are not responsible for remembering anything and just when I thought it would not get worse I wound up with a Grade 3 concussion from getting rearended and that made it worse haha.

For instance I just remembered I have a log in the truck and I started adding up towed miles on the trailer. Now I gotta see if I can remember where the log is in the truck ! ! ! !

Hang in there Sir, I think the post office boys will deliver your CRS within a few years haha.
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Old 04-07-2015, 07:05 AM   #889
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Action, I agree, here in Fl the air temp might be a hundred so the road temps would be very high. Tires suffer as can be seen by the number if vehicles with flats on the interstates. Jim
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Old 04-07-2015, 12:35 PM   #890
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Hi,
Late to this discussion, and have been working my way through it, but just wanted to get confirmation from any Bambi owners that came with 15" OEM wheels, on this tire and wheel combo: Sendel T03 16x6 wheel with 0 offset, and Michelin 225-75/16 XPS RIB tires. Need to know ASAP.
Thanks much,
Tom
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Old 04-08-2015, 06:34 PM   #891
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Quote:
Originally Posted by jambie View Post
Hi,
Late to this discussion, and have been working my way through it, but just wanted to get confirmation from any Bambi owners that came with 15" OEM wheels, on this tire and wheel combo: Sendel T03 16x6 wheel with 0 offset, and Michelin 225-75/16 XPS RIB tires. Need to know ASAP.
Thanks much,
Tom
Contact Phoenix through the forums. He has this exact setup for his Bambi (and loves it) and is quite knowledgeable on this subject
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Old 08-21-2015, 08:27 PM   #892
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I need tires now.
What do y'all think?
Options:
1. Buy 15" Michelin MS/2 in the town where we are camping
2. Try to find 16" zero offset wheels and Michelin LT tires in this town
3. Put on the spare, go home, and order tires/wheels off the internet


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Old 08-22-2015, 06:22 AM   #893
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MHoney, FWIW I got mine from Tredit tire and wheel corporation.

Tredit Tire Home All they make is wheels and wheel/tire combos for the trailer industry. They have a distribution center in Arlington, Texas which I am guessing is closest to you? I got mine in Athens, Ga. I got the steel modular wheels which are rated heavier than AS wheels.

I called them four years ago and got four modular rims (gray) and four E or F rated tires for 600.00 out the door. Tires were made in China, still look new. I store rig under shed when not on the road and cover the tires with black vinyl covered fiberglass covers to keep them totally blacked out. I called closest distribution center and I drove to Athens,Ga the next morning and they were sitting at dock door waiting for me, put them in back of Honda wagon and back home. I run them at 80 PSI and check temps with IR thermometer every time I stop.

I was not concerned with looks, I wanted security and reliability and I have seen alloy wheels crack between lug holes on a number of them.

I got them with 225X70x16 LT tires ( heaviest rating they had E or F, can't remember for sure) but I have nothing but praise for them and would buy the same set up again if needed.

Also FWIW I just had to purchase a equipment trailer to haul my tractor on. Guy I got it from used to manufacture the utility trailers for HD, Lowes etc and he carried eight trailers at a time on the one he built (6X21 bed) 5200 lb axles and he installed E rated tires and steel wheels on his. The bed is 1/4" steel plate 6x19 feet one piece of steel and frame is L Angle 4X6X3/8". I figure it weighs 2500 lbs. Tried to upload pic but for some reason I can't get it to work today.
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Old 08-22-2015, 07:44 AM   #894
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What's available locally:
15" load range E Hercules 10-ply- manufactured by Cooper-
Opinions?
I might try a local trailer place for some zero offset 16" wheels-


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Old 08-22-2015, 07:54 AM   #895
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Quote:
Originally Posted by m.hony View Post
I need tires now.
What do y'all think?
Options:
1. Buy 15" Michelin MS/2 in the town where we are camping
2. Try to find 16" zero offset wheels and Michelin LT tires in this town
3. Put on the spare, go home, and order tires/wheels off the internet


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I got 15" LT tires, but I have 25' safari with 6300 gvw, so it's a different animal than yours. My tires 15" tires are rated for about 8400 lbs.
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Old 08-22-2015, 07:59 AM   #896
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The local tire store man acts like there is no such thing as a 15" LT, but he has some load range E 10 ply ST tires-


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