36 replies to this topic

[Wallowa]

I retired my Toyo II 6 plys for Cooper AT3 10 plies [E] and went to a narrower LT235x85 - 16.

 

These Cooper's have a max load rating [3,042 lbs] and max pressure at 80 psi....

 

My question is this:  What pressure do any of you run in a similar tire size and load?  Reasons?

 

Do you go for max pressure or adjust for the weight [scale weight wet is 3,020 lbs front and 3,780 lbs rear on my Tundra/Hawk].  Please no comments about GVW specters. 

 

My Tundra is an '05 Access Cab SR5 and carrying a fully kitted out '16 Hawk w/Firestone airbags/Hellwig anti-sway bar rear and wheel well height fore and aft of 35" ...primary use is off road and only pavement to get there...

 

FYI here is the approx load rating by pressure for these Coopers:

 

75 psi = 2,905 lbs

70 psi = 2,765 lbs

65 psi = 2,623 lbs

60 psi = 2,485 lbs

 

I understand there is a balance between ride quality/handling/puncture resistance vs traction on various surfaces but what has been your real world experience?

 

Thanks for any information,

 

Phil

Edited by Wallowa, 01 February 2019 - 05:57 PM.

[Ace!]

I adjust my pressure and don't go max pressure.  I've only run max pressure a couple of times, and not with the Hawk (only when I was pretty maxed out hauling landscaping material).  I have a different truck, but the weight ratings of the tires probably isn't that different.  I might also try putting a chalk line across your tires and run a block or so down the road.  See how much of the chalk is worn off.  You might adjust pressure dependent on how much of the tread you're using, or something similar.

[Wallowa]

ACE,

 

Thanks great idea using the chalk to see how much of the tread is in contact with the road...understanding that lower pressure elongates the contact patch rather than widens it, but I still would like to see what part of the tire width is subject to wear..

 

Thanks again...Phil

[klahanie]

Been a long time since I ran that size and weight ...

 

Myself, I would "adjust for the weight".

 

Meaning, scale like you have and look up the load and inflation tables like you have (?)

 

Even so I tend to over inflate*, in my world that has meant harsher ride off highway, more steering input need  on highway (wandering) and accelerated centre tread wear.

 

I would be looking here at:

 

35 psi = 1700

40 psi = 1870

45 psi = 2030

 

and prob calculate down a pressure for the front axle tires

 

EDIT * by over inflate, I mean put a bit more air pressure than stated in the tables. Makes me feel a bit "safer" on the hwy, and maybe reduces fuel economy. Force of habit really. Besides those table numbers are max load for a given psi. Nothing saying you can't go higher psi for the same load. But there may be noticeable

consequences.

 

HTH

Edited by klahanie, 01 February 2019 - 05:54 PM.

[Wallowa]

Been a long time since I ran that size and weight ...

 

Myself, I would "adjust for the weight".

 

Meaning, scale like you have and look up the load and inflation tables (like you have (?))

 

Even so I tend to over inflate, in my world that has meant harsher ride off highway, more steering input need on highway and accelerated centre tread wear.

 

Curious about the load ranges you listed, I would be looking here at:

 

35 psi = 1700

40 psi = 1870

45 psi = 2030

 

and prob calculate down a pressure for the front axle tires

 

Check page 21 on the site you referenced above...you listed the "C" rated tires.

 

"LT235/85R16 Single 1700 1870 2030 2205 © 108 2335 2485 2623 (D) 114 2765 2905 3042 (E) 120"

 

Again my tires are "E" or 10 ply tires....I gained about 400 lbs per tire with Cooper "E" tires over previous Toyo "D"s....plus more puncture resistance and going narrower better loose [mud/sand] off road traction.

 

Adjusting for weight yes, but what weight vs tire rating at what pressure for off road?  I do agree on selecting a higher pressure rather than shaving the weight vs pressure load too close.

 

Phil

Edited by Wallowa, 01 February 2019 - 05:54 PM.

[Ronin]

I have a '14 Tundra/'05 Hawk and run 70 lbs on my E Michelin Defenders. Rando had provided the attached link from Toyo that I found very useful :

 

https://www.toyotire...es_20170203.pdf

[klahanie]

 

 

Check page 21 on the site you referenced above...you listed the "C" rated tires.

 

"LT235/85R16 Single 1700 1870 2030 2205 © 108 2335 2485 2623 (D) 114 2765 2905 3042 (E) 120"

 

Again my tires are "E" or 10 ply tires....

 

 

 

Okay, and according to that site the 60 and 65 PSI ratings you posted (OP) are for the "D" rated tires

 

10 plies [E] and went to a narrower LT235x85 - 16.

 

...primary use is off road and only pavement to get there...

 

FYI here is the approx load rating by pressure for these Coopers:

 

75 psi = 2,905 lbs

70 psi = 2,765 lbs

65 psi = 2,623 lbs

60 psi = 2,485 lbs

 

Thanks for any information,

 

 

Yours are "E" right ?, so if the reasoning is to only use the "E" only ratings then in that case I'd say that would put you at 70 psi for regular road use.

 

Adjusting for weight yes, but what weight vs tire rating at what pressure for off road?

 

Off road is a whole different matter and depends greatly on a number of variables. I can only speak for my own experience "off highway" (FSRs) and I'm out of my depth here already for this vehicle weight class !

 

But, because I'm here, I would start with the load and inflation table for the tire size and the applicable tire load [EDIT scaled weight if possible] as a starting pressure. Then for off highway reduce pressure in stages, to suit desired comfort and traction. For me that has meant up to 10 psi lower than the tables, measured tires "hot" not "cold".

 

I consider the max loads stated at a given psi in the table for the higher tire load ratings ( E, F etc) to be an extension/continuation of the loads given for the lower ones (D,C) for the same tire size. That is, I believe the higher load ratings are inclusive of the lower load ratings. Therefore, I think the tables can still be a useful reference for loads quite a bit lighter than the tires max rated load.

Edited by klahanie, 01 February 2019 - 07:48 PM.

[Wallowa]

Toyo AT2s I retired [only 11K miles] were "C"; max pressure 50 psi [6ply] not "D" [8] ply. See first post.

Yes my vehicle weights were measured on a commercial scale with full gear including all tanks full & 100 lb Warn winch in front ...wet weight.

Your last comment gave me food for thought...that the pressure/load ratings listed for a 6 or 8 ply tire were applicable by extension for my 10 ply tire...makes sense. I am with you on only dropping pressure perhaps 10 psi from normal pressure if needed off road for sand or mud...I have a good compressor but hesitate to drop pressure and chance a flat...all this of course is a crap shoot and I prefer to stay pressured up and pick my routes with care...

Measuring hot and not cold? I always have set the pressure cold initially but see the wisdom to only drop the pressure if necessary based on the hot pressure while driving off road...that way it retains a % of needed pressure.

Currently I have 60 psi and will do a chalk test suggested by ACE and then inflate to 70 psi and repeat the chalk test...not certain how I will use that information but at 60 or 70 psi my E rated Coopers will handle the weight.

Thanks again..

Phil

Edited by Wallowa, 01 February 2019 - 09:08 PM.

[rando]

The load table doesn't vary depending on the load rating, only the maximum load changes because the max pressure for different load range (C/D/E) tires is different.   

 

For your application, the rear tires are loaded at about 1900 lbs per tire.   Go to the load table for 235/85R16 (page 21 of the Toyo document, poorly copied below) and you would see that you would need to be at least 40-45 psi in your rear tires:

 

                        Dual     35      40     45      50                    55       60         65                 70       75       80 

LT235/85R16 Single   1700  1870  2030  2205 © 108   2335   2485     2623 (D) 114 2765   2905   3042 (E) 120

 

I run the same size tires and typically run 50-55psi in the back and 45 psi in the front.  If I am doing a lot of rougher dirt roads I may air down to 35 back 30 front. 

 

You can go higher than this number, but shouldn't go lower on the highway. 

 

 

[Wallowa]

Thanks Rando...I know I was equating psi to max load for a given tire size and rating...

 

Your Fleet and Tacoma are probably lighter than my Tundra/Hawk...

 

I also try to balance the height of the Tundra fore and aft..if I may ask, why not run the rear pressure in the front tires?  All tires at same pressure, the higher one.

 

As stated I do use my airbags to level out the Tundra but tire pressure is in the mix.

 

Thanks again...Phil