Which tire pressure guide to follow

[jadatis]

Then I do my calculation for the 1750 lbs.
The ST has to be derated by 6 loadindex-steps to give maximum reserve, and make 1750 lbs 90% of the loadcapacity for that new maxload.

1750+ 10% = 1925 lbs.
Then the maxload of the 225/75 R 15 is 2830 lbs for 65mph is LI 117 - 6= 111 / maxload 2400lbs.
Lineair calculated, wich is not even that bad gives
1925/ 2400 × 80 = 64.16 psi is 65 psi.

So my system with maximum reserve without bumping ,gives milder advice then Capri-racer's .

I think the 85% use of maxload is meanth at " maximum" pressure, so 80 psi here, to already give the tire the reserves for things like inbalance.
So the dont lower the pressure for that 85% load% ( as I babtised it in former post.).

[Mollysdad]

Originally Posted by Adventure.AS

Not sure what chart you are looking at, but the chart that was posted earlier in this thread shows inflation of 35 PSI for 7000 lbs trailer (four tires, each carrying 1750, if trailer is perfectly balanced.) I have re-posted it for your convenience.

45 PSI if you add 10% safety margin to each tire. This is with rounding UP to the next closest carrying weight for the GYE ST225/75R15.

Attachment 387234

I'm using the same chart. You're trying too hard to justify what's not there.
First, not all of the 7,000 pounds are on the tires, so I subtracted the tongue weight.
Next, you want to round UP? Why? I interpolated it.
Finally, you want to add 10% fudge factor? Didn't Goodyear build that in already?
With all due respect, and I love a good discussion, but I'm not swayed (no pun intended).
NEXT!

[Mollysdad]

Originally Posted by jadatis

Then I do my calculation for the 1750 lbs.
The ST has to be derated by 6 loadindex-steps to give maximum reserve, and make 1750 lbs 90% of the loadcapacity for that new maxload.

1750+ 10% = 1925 lbs.
Then the maxload of the 225/75 R 15 is 2830 lbs for 65mph is LI 117 - 6= 111 / maxload 2400lbs.
Lineair calculated, wich is not even that bad gives
1925/ 2400 × 80 = 64.16 psi is 65 psi.

So my system with maximum reserve without bumping ,gives milder advice then Capri-racer's .

I think the 85% use of maxload is meanth at " maximum" pressure, so 80 psi here, to already give the tire the reserves for things like inbalance.
So the dont lower the pressure for that 85% load% ( as I babtised it in former post.).

You start with an invalid premise, that the 7,000 pound weight is applied to the tires. It's not, 1,000 pounds is on the tongue, so only 6,000 pounds are on the tires.
You're trying too hard to arrive at a number you preselected.
Toss in all the formulas you want, my point is still, "Can't the engineers at Goodyear do the math and publish an accurate chart?"
Is it too much to ask for a tire chart (which is often quoted here) Have X and Y data and where they intersect is my tire pressure? Because it sure looks that way!
Or, add a line to the chart saying, "Add 10% factor, then consult the engineering guide, and attend the industry convention before using our chart."

. The ST has to be derated by 6 loadindex-steps to give maximum reserve, and make 1750 lbs 90% of the loadcapacity for that new maxload.

1750+ 10% = 1925 lbs.
Then the maxload of the 225/75 R 15 is 2830 lbs for 65mph is LI 117 - 6= 111 / maxload 2400lbs.
Lineair calculated, wich is not even that bad gives
1925/ 2400 × 80 = 64.16 psi is 65 psi.

Seriously?

[ROBERT CROSS]

Originally Posted by jadatis

Then I do my calculation for the 1750 lbs.
The ST has to be derated by 6 loadindex-steps to give maximum reserve, and make 1750 lbs 90% of the loadcapacity for that new maxload.
).

There is only ONE maximum Load rating.
It's @ max pressure.
All others are just a guess, unless you are constantly weighing the AS.
I use ONE pressure based on the highest load I have had in the AS.

'Ye all fret too muchly.

Bob
🇺🇸

[jadatis]

That given maxload is speedrelated is a fact.
See for that this picture I made in the Netherlands, but a Goodyear trucktire. Above the yellow line the additional sevice description.
The head service description 156/150 L
The additional service description 154/150M
This is the same tire, so material and construction does not suddenly chanche when used for 81mph( M) instead of 75mph ( L).

I dont know if in America this is also given on trucktyres, but the add serv descr is an officially used term, german is zuzatz-betriebskennung.

And also maxspeed acording to speedcode ( that M and L here) is not always the speed for wich maxload is given.

P-tires above speedcode Q up to V are all given maxload for 160kmph/ 99mph.

V, W and Y speedrated have to be derated in maxload from 30kmph/ 18mph below maximum, V 9% is about 3 to 4 LI steps
W and Y 15% is about 6 LI steps.

And then the ST , speed for wich maxload is given is 65 mph / 104kmph.
Prove that the Endurance with speedcode N ( 87mph max) also 65mph, is that the list is yust an extension of the old Marathon tires, wich had 65mph.
Will also add a paint-image I made of the system for highening up referencepressure of 36 psi for standard load , and the maxload-derating.

So in short, higher speed needs higher pressure, or gives lower maxload

[ROBERT CROSS]

^
??

In my experience, If the tire is not under or over inflated the speed rating is what it is.
Higher load requires a higher pressure.
The faster you go the lower the tires load carrying capacity.
Won't affect us much when towing 'Cloudsplitter" 'cuz we usually stay under 140mph.

Bob
🇺🇸

[gjsittler]

Last time I bought trailer tires, I bought Load Range E. Partly because that's all they had in stock at the tire store for my size rims. In some places, the lower load range is cheaper, but my experience with trailers has been that running on the edge gets me in trouble. 5 tires was right at $500. The reason I replaced them was that they were almost 10 years old, and had spent their winters in subzero weather in Minnesota, on the ground, weight on the axles.

Some people are upgrading their trailer rims to truck rims and putting on the truck tires for better reliability. Seems like unnecessary expense to some, but after you blow a tire, and have the tread peel off and rip out the plastic wheel well and the bottom of the wardrobe closet, destroying your heater ducts in the process -- well, it doesn't happen often, but it might be avoidable.

Things like that can be avoided simply by paying attention to your tires whenever you stop. Walk around the trailer once, right away, and lay your hand on the sidewall of each tire. If one of them seems hotter than the rest, check and compare pressures (they'll be higher than the cold pressure you started at, but should all be about the same). If one seems to be leaking down, change it for the spare and get it inspected ASAP. I didn't do that, and had to fix my trailer after the steel belt blew open and got whipped around the axle, tearing out the wheel well. Should have known better, but I thought I was in a hurry to get somewhere.

The most sage advice here in this forum seems to be "Take your time, don't drive too fast, know your trailer, buy tires with adequate load range for your trailer, and don't overload that little trailer. It's not designed for hauling furniture! It's a roadside abode, not a moving and storage facility.