What tire pressures to run - new Cooper Discoverer A/T3, 305/70/16

[Joe Mc]

Just got new Cooper’s (truck in signature) and they’re a bit different than the first set I bought back in 01. I’ve had several different brand tires over the years and not sure of what pressures would be best for the new shoes.

I’m hoping that someone has already figured out the best pressures to run front and rear = unloaded and hauling a loaded car trailer.

I’m hauling my daughter’s 02 Sable from Levittown, PA to Marysville, WA this weekend...

 

[jeepit]

I have this tire in a 265.
I run max pressure (80)in all tires when towing.
Empty 65 front 45 rear.

 

[JR]

No real input, just an observation if I may

6,000 miles (round trip) to deliver a 15 year old vehicle
The things we do for our kids!
Safe travels Joe.

 

[AEdelheit]

There are a lot of factors that will effect the numbers but that is a pretty light trailer, I would try about 10 psi more then normal. Dont see any need to run 80 psi as I doubt you will be anywhere near the max load of the tires and your front axle usually gets lighter with a bumper pull so no need to increase front tire psi.

 

[seafish]

I have a different tire size then you, so I cannot help you directly. Here is a link to a Toyo tire load/pressure chart and you can get in the ballpark by using the same tire size and load rating by Toyo to approximate your Cooper, as all NHTSA tire size load ratings are now roughly equivalent.



https://toyo-arhxo0vh6d1oh9i0c.stac...ication_of_load_inflation_tables_20170203.pdf



That being said, the best way to fine tune your tire PSI for your truck is to get some thick chalk, mark a line across each tire with the chalk and then drive about 50 feet or so on dry, flat pavement or concrete. Then check the tire(s) for the chalk mark and adjust PSI based on what part of the chalk is still visible on the tire.
If the center of the chalk is gone.,but chalk is still visible near the tire edges, then you are overinflated...vice versa means underinflated. Then adjust PSI, repeat the chalk mark, drive 50 feet again and adjust PSI until mark is evenly worn/gone across the tire. Shouldn't take more then 20 minutes as long as you have access to a compressor and a dry day.

 

[Joe Mc]

JR - I hear ya! I would have sold the car givers her the money to get another one but, this Merc has 65k miles and she’s driven it since it had 48 when we bought it 3 - 4 years ago. It’s a solid car. If I sold it, I might get $2500, doubtful since it isn’t a real looker. Then she’d end up buying a $2500 ****box out west that wouldn’t last....

Selfish - thanks for the charts. I initially had 60# and then did the chaulk thing ended up with 40F - 30R. But the tires look way under inflated. I think I’ll go to 55 F & R and adjust from there.

BTW - thanks to AEdelheit and jeepit for their replies. I previously had Michelin 285/75/16’s load range E that had a max inflation of 80#. They were perfect at 70F and 54R, the previous tires were Nittos 305/70/16’s load range E (forget max) that ran great at 65F and 50R.

The Coppers are load range E with a max inflation of 65#

So many variables to figure out to get the correct PSI.

I hope someone else replies with a tested true front and rear for the Cooper A/T3’s I have.

Thanks again to all.

 

[Killer223]

love my cooper tires,
i run 50F 45R, and when towing 50F/65R, when towing heavy i run 70 R.

LR D is 65 psi, are you sure you have LR E?

 

[seafish]

LR D is 65 psi, are you sure you have LR E?

OP, I was going to ask the same thing...something is wrong there...LRE should be 80psi max and LRD 65 psi max, no matter what tire brand...part of the NHTSA standards afaik. These trucks almost always want an LRE due to the stiffer sidewalls.

 

[NIsaacs]

OP, I was going to ask the same thing...something is wrong there...LRE should be 80psi max and LRD 65 psi max, no matter what tire brand...part of the NHTSA standards afaik. These trucks almost always want an LRE due to the stiffer sidewalls.

Per this info link, the OP has it right: https://r.search.yahoo.com/_ylt=AwrTHRQjkgVaG3AARh5XNyoA;_ylu=X3oDMTExYzhzYWZtBGNvbG8DZ3ExBHBvcwM4BHZ0aWQDVUlDMV8xBHNlYwNzcg--/RV=2/RE=1510343331/RO=10/RU=https%3a%2f%2ftiresize.com%2ftires%2fCooper%2fDiscoverer-AT3-305-70R16.htm/RK=1/RS=PHphul2loooncCU4iP.rkAlWsPk-

Nick

 

[seafish]

Per this info link, the OP has it right: https://r.search.yahoo.com/_ylt=AwrTHRQjkgVaG3AARh5XNyoA;_ylu=X3oDMTExYzhzYWZtBGNvbG8DZ3ExBHBvcwM4BHZ0aWQDVUlDMV8xBHNlYwNzcg--/RV=2/RE=1510343331/RO=10/RU=https%3a%2f%2ftiresize.com%2ftires%2fCooper%2fDiscoverer-AT3-305-70R16.htm/RK=1/RS=PHphul2loooncCU4iP.rkAlWsPk-

Nick

Thanks for that...I am humbled AND confused ...who woulda guessed??!!!

 

[AnonEd]

I use seafish's method, then graduate to paint and a slightly longer drive, always starting cold since that's where I measure. Run the same tire size, different brand, on a different generation truck with a Detroit in back which likes 1-2 psi more in the driver's side rear.

 

[Joe Mc]

Nick, thanks for posting tire info from tire size.com. Sorry I couldn't get all the great info from everyone above before I left. So what I found worked best on my trip out loaded was front 54 rear 62. Empty on way back I ran 50 front and 46 rear. I made a Bro-P-Touch label with psi's loaded and unloaded and placed on door jamb under manuf. orig label. So I don't forget, along with lug torque 135#.

 

[Joe Mc]

Oh, awesome trip! Truck (8800gvw) did great! 02 Merc, loaded with things that wouldn't fit under the hard tonneau about 4,000# + U-Haul Auto Transport 2,200# and around another 1,000# in the long bed/under hard tonneau = smooth ride. Only time I really had to disengage OD was pulling the east to west Snowqualmie Pass (North Bend, WA) I forget the % of grade (think it was at least 6 or 7 degrees) but out of OD I was maintaining 55 mph @ 30# boost and 1200 degrees, minimal exhaust haze (no real smoke). All in all it was a great trip, real good Father - Daughter time. Spent about a week helping get the house set up and then headed back east. Beautiful country we live in folks, anyone who hasn't made a cross country "drive" has got to do it at least once in their life. This one is my 4th = 2 to Yellowstone, 1 to Grand Canyon and this one. AWESOME!