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Old 04-30-2013, 08:33 PM   #1
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19.5" Toyo Tire pressure

Actual MH, Trailer & Sand Rail with new tires and full fluids.
Front Axle: 5600 / 2 = 2800 / Tire
Rear Axle: 13120 / 4 = 3280 / Tire
Trailer weighs ~5000 and I have those tire ratings covered.
Side to side weight next trip, but I think I'm pretty well balanced by
the way I store things. Genny on left/propane on right. Tools on right
and camping stuff and unmounted spare on left.

Toyo Tire Rating for my 245/70R19.5 Toyo's
Inflation P. S. I.
- 80 - 85 - 90 -- 95 - - -100 - 105 - 110 - - 115 - 120
3640 3740 3890 4080(F) 4190 4335 4540(G) 4620 4805(H) Single
3415 3515 3655 3860(F) 3940 4075 4300(G) 4345 4540(H) Dual

If I'm reading that right, I can go down to 80 or lower psi. Currently 85.
Have no plan to go below 80.
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Old 05-01-2013, 02:43 AM   #2
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What I am missing is the loadrating of your tires.
In the list its given for H to F. On the sidewal there must be something like this,
"maximum load xxxx lbs AT yyy psi ( cold)", then what I need is that yyy, and that is called the reference-pressure or maxloadpressure, and is lower then the maximum pressure of the tire.
If you give that, I can make a new list for you, using my own formula, to look back in.
This list gives lower loadcapacity for the pressure then the American lists and even lower then the European lists, and to my opinion, takes care that the deflection of the tire stays the same over the whole range of pressure/loadcapacity. Also in my list for every loadrating ( H to C) seperate list. because a higher loadrating means stiffer tire and has lower loadcapacity for the same pressure.

But first add some reserve to the loads you determined before looking back in the list. Even adding up to 18% probably wont give discomfort and bad gripp.
So I advice 10% , so it leaves some space for misloading R/L.

Here the link to a map on my skydrive , with lists given per tire/axle single and Axle Dual,yust pick the one you want, and the name of the PDF's begin with the referencepressure.
https://skydrive.live.com/?cid=a526e...E092E6DC%21941

But I can also throw the data in my camperRVtirepressurecalculator for you and it might prove that you can savely go lower.
Dangerous part in all this , is if you , though you carefully estimated, still yudge the loads on the seperate tires to low.
added the 95F/110G and 120H per tire PDF's , but mind to use the right one and not use this G-load for F or H , that is a wrong thing that is done in the American lists, in Europe for every Loadrating a seperate list is made.
Attached Files
File Type: pdf 95psi100li143tire.pdf (75.1 KB, 62 views)
File Type: pdf 110psi100li143tire.pdf (75.4 KB, 23 views)
File Type: pdf 120psi110li153tire.pdf (75.2 KB, 30 views)
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Old 05-01-2013, 12:21 PM   #3
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Just checked the tire, only to find I already had those specs on my computer.

Toyo M143 Radial Tubeless Regrovable
DSOC II Technology
Tread 5 ply Steel
Sideway 1 ply Steel
E4 with a circle around it
E4 with a box around it.
136/134M
Made in Japan 143-3

Load Range H
4805 lbs max load @ 120 psi Single
4540 lbs max load @ 120 psi Dual
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Old 05-02-2013, 02:04 PM   #4
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Put your data in my calculator and printed it to pdf and made gif of it to include in this answer. Saw I forgot to fill in the dual load data behind, but this is calculated from the front so is 92.5% of max load single, so a little lower then given. this is because of the rounding down the loadindex.
Assumed the axle-loads you gave, where weighed, but can be wrong, and they are GAWR's. Also look at the La/Lv front of below 30% , once saw advice to keep that above 30%.
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Old 05-02-2013, 03:42 PM   #5
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Yes, those are the actual scale weights. Thx. Studying your chart now. Are you saying I need 75 front and 96 rear? You know what all that means, but I don't. Confusing to me.
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Old 05-03-2013, 04:15 PM   #6
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That is exactly what I mean, and this is with reserve load added for things like, unequall loading R/L , pressure-loss in time, misreadings of pressure- and load-scales, and incidental extra load or loadshifting, and what I might have forgoten.
On the sides are given extra information and the explanation is given in the yellow field. L% gives what percentage the (assumed) real load uses of the loadcapacity that belongs to the advice pressure. I keep this on 91% if you dont chanche it yourselfes, and this is the same as adding 10% to the filled in load .
Also gives the weightdifference R/L above wich damage and bumbing begins.
These are indications ,especially the bumping border is one I determined by reactions so is discussable.

But did you see the almost 30% La/Lv I already mentioned, getting some more load to the front so this persentage gets above 30% can give better handling of the car.
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Old 05-03-2013, 05:10 PM   #7
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The Toyo chart says that at 85 psi I can carry 3515/tire. I'm carrying 3280/tire. My front, rear and trailer tires are all about the same temperature and there are no abnormal pressures.

I've already moved all the heavy items to the front.
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Old 05-05-2013, 06:16 AM   #8
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What I am trying to make clear, is that those lists lead to to much deflection at lower load/pressure combinations. In my made list you only have 3295 lbs loadcapacity at 85 psi , so if the weight is devided equally , wich never is the case, you only yust have enaug . Thanks to the reserve there still is above the maximum load of tires that they give on the sidewall, and the relatively low speed of RV's, it still gives nog damage to the tires. You also go from the weighed axle loads , so that is already saver then assumed axlel loads.
But my advice is the highest pressure wich wont give discomfort and bad gripp, and so gives reserve for the things I mentioned already. And higher pressure is also good for full saving.
But If you filled to 96 psi and after a while you measure 90 psi you dont have to be alarmed, because most likely still no damage to the tires.

If you already moved much to the front, you cant do any more, and 29.9% is almost exact the minimum of 30% .
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Old 05-05-2013, 01:13 PM   #9
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I appreciate you building the chat, but it appears that you are taking every possible scenario into consideration. Many others are running their Toyos in the 80-85 range with no problems. Perhaps if a bird flew under a tire, your calculation would fit in. I'm not subjecting my MH to a harsh ride, tearing up equipment, just because this or that could happen on a rare occasion.
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Old 05-05-2013, 02:14 PM   #10
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Ok then yust remember that 75 psi front is even with reserve so you dont have to go higher .
Behind 96 psi is the highest to fill , without loosing to much comfort.
But in my calculator you also can give your own percentage reserve .

I filled in my calculator with the 4540 lbs /Loadindex 133 and it gave 94 psi .
then it still has the 10% reserve I advice.
When I chanche it to 5% it comes to 90 psi behind.
chanching to 0% it comes to 85 psi, so then the reserve is because the tire can carry savely to laws of nature , more then the maximum load calculated by the tire-maker(s), and the low speed wich allowes more deflection.

So try it out at 90 psi, if it's still comfortable , you have more reserve.

Also search the sidewall for an aditional loadindex with a lower speedindex.
For instance the 135 single at speedcode N=140km/85m?/h , then 137J would mean that if you dont go above 100km/65m/h you may use the maximum load that belongs to 137 loadindex. I am not shure if you may use that system for dual load, wiich you have behind, mayby it is only allowed for single load.

Mind that this is my advice, you must do what you want, but trying out the 90 behind is easy to do.
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Old 05-05-2013, 02:48 PM   #11
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I think Toyo takes your equations into consideration when they build their published chart. Besides, on the road, the tires do get up to 90 psi with the increased heat.
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Old 05-05-2013, 03:13 PM   #12
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Wow! All your calculations are way over my head. I just bought a 35 ft. 2001 Sea View by National. My previous motorhome was a 30' class C and I bought tires at Discount Tire. On my first big trip with this coach the inside dual tire on the driver's side lost the middle strip of tread. I limped into a Walmart parking lot and called AAA. They found someone from a neighboring city to come put my spare tire on but now that leaves me without a spare. The repairman said that tire was 6 years old and it was about time to start looking for new tires anyway. I have found that none of my previous tire sources (Discount, Sams Club, etc.) will touch my 19.5 tires. I thought it would probably be best to start with two new front tires but not sure where to go. My tires are 245/70 19.5. Thanks!
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Old 05-05-2013, 03:21 PM   #13
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The advice pressure is the cold pressure ( 18dgrC/65dgrF) and the temperature rising is included in the calculations.
this is because cold pressure is the only shure thing, if you measure warm, the temperature in the tire can rise even up to boiling point of water ( 100dgr C /??F) by the heat of the brakes transported trough the rimms.
The stemms and tires can stand this, stemms even are tested for this.

I can not check wich calculation TOYO used because I cant determine wich Loadrating they filled into the equation. But probably they used the universal formula of the tire-makers with the in America used power 0,7 in it. Europe uses 0,8 power, wich leads to lower loadcapacity for the pressure, and I even use my own formula, a combination of the conventional and one described by an American J.C.Daws, wich leads to even lower loadcapacity for the same pressure, and to my opinion takes care that the deflection stays the same over the whole range of pressure/loadcapacity, by wich you can theroratically go to zero pressure , and dont have to stop at 80 psi or 75% of the maxloadpressure as is usual in America.
Mr Daws his conclusion was that if you want to use the conventional universal formula, you should use power of 0,9 t0 0,95 for larger tires with high maxloadpressure, wich you have. Power 1 means pressure/maxloadpressure=loadcapacity/maximum load, so would give a straight line in a graphics made, and what people think logical calculation.
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Old 05-06-2013, 02:13 PM   #14
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I'm sure Toyo's chart for those tire's start at 80psi for a reason.
I would'nt go below that even if some calculator says I could get away with 75.
My Michelin XZE 'H' do start at 75psi.
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