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Open Roads Forum  >  Truck Campers

 > New Cooper tires behavior

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Buzzcut1

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Posted: 03/01/21 08:47pm Link  |  Quote  |  Print  |  Notify Moderator

gitpicker2009 wrote:

Is 80 PSI really considered low??? What do you recommend?


19.5s are commercial tires. They have a different bead type than LT tires. They are designed for load and stability not flotation. you will lose the bead at low pressures

Depending on the MFG, minimum inflation is between 70-80 psi with max up around 120psi

look at the load inflation table for the roadmaster 245/70R19.5 on this table, It starts at 70psi
http://roadmastertires.com/CooperRoadmas........edia/Documents/LoadandInflationTable.pdf


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jimh425

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Posted: 03/02/21 04:48am Link  |  Quote  |  Print  |  Notify Moderator

I’ve run down to 60 in rear unloaded when I had 19.5s on a F350 SRW. In the front, even 70 will help to stop wandering.

Fwiw, my F450 comes stock with 19.5s. The recommeneded pressure for max Axle weight rating is 75 in rear, so you can at least go that low or a little lower.


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K Mac

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Posted: 03/02/21 06:02pm Link  |  Quote  |  Print  |  Notify Moderator

I run 80 psi loaded,and my tire guy said 10% less front and 15% in rear unloaded for better ride and handling.

markchengr

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Posted: 03/03/21 10:17am Link  |  Quote  |  Print  |  Notify Moderator

Weigh your axles loaded and unloaded then go to the tire manufacturers website checking the column for your tire width. Most of them have an inflation guide for different loads. These can vary quite a bit among different tire brands. There is no one-fits-all pressure among different 19.5's. I run my rears at 50psi empty and 110psi loaded.

Kayteg1

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Posted: 03/03/21 10:52am Link  |  Quote  |  Print  |  Notify Moderator

markchengr wrote:

Weigh your axles loaded and unloaded then go to the tire manufacturers website checking the column for your tire width. Most of them have an inflation guide for different loads. These can vary quite a bit among different tire brands. There is no one-fits-all pressure among different 19.5's. I run my rears at 50psi empty and 110psi loaded.

X2
when mechanic tells you to run specified pressure without checking the weight - it might be good time to change the mechanic.
Even my camper weight over 6000lb, my rear dually pressure comes lower than front.





jimh425

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Posted: 03/03/21 04:12pm Link  |  Quote  |  Print  |  Notify Moderator

Except 19.5s aren’t normal tires with normal beads. The tires will come off the bead way before you have the pressure low enough unloaded to be “correct” for a empty bed truck. So, using a chart for the minimum is fine as long as you aren’t worried about coming off the bead.

You don’t have to believe us though buy a set of 19.5s, go to a beach, and air down. [emoticon] The beach isn’t really required, but that’s when people usually find out that they can’t air their 19.5s down. [emoticon]

Kayteg1

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Posted: 03/04/21 08:53am Link  |  Quote  |  Print  |  Notify Moderator

jimh425 wrote:

Except 19.5s aren’t normal tires with normal beads. The tires will come off the bead way before you have the pressure low enough unloaded to be “correct” for a empty bed truck. So, using a chart for the minimum is fine as long as you aren’t worried about coming off the bead.

You don’t have to believe us though buy a set of 19.5s, go to a beach, and air down. [emoticon] The beach isn’t really required, but that’s when people usually find out that they can’t air their 19.5s down. [emoticon]

This is what tire manufacturers website will tell you.
Other tires have min inflation as well, although I watch "Matt's recovery" on youtube and he drops the pressure to 5 psi for blow sand on his Jeep. Than he pulled the tire out of the rim on couple of occasions.

jimh425

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Posted: 03/04/21 03:55pm Link  |  Quote  |  Print  |  Notify Moderator

Kayteg1 wrote:

This is what tire manufacturers website will tell you.
Other tires have min inflation as well, although I watch "Matt's recovery" on youtube and he drops the pressure to 5 psi for blow sand on his Jeep. Than he pulled the tire out of the rim on couple of occasions.


Feel free to point out a 19.5 tire inflation chart that has a minimum tire pressure. As Buzzcut1 stated his chart started at 70. Maybe you are calling that a minimum. The lowest I’ve ever seen on a chart is 65, so that tire guy was pretty close when he said 10% off of 80, or 72.

As I noted, other than seeing the lowest pressure listed on the chart, the chart for a 19.5 doesn’t help when you go to an empty bed truck. You’ll never be anywhere near the “correct” pressure for the load. So again, the chart doesn’t help get you to the recommended pressure for a empty bed truck.

As you noted, Matt had issues sometimes until he made his bead lockers. Maybe you have a line on 19.5 bead locker though since you want to use him as an example. Or, maybe you should just stop comparing conventional tires used offroad to 19.5s.

Bedlam

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Posted: 03/06/21 01:28pm Link  |  Quote  |  Print  |  Notify Moderator

70 psi worked fine on my steer axle running 19.5's. I have aired my drive axle ties down to 50 trying to get some squat, but it really does not help with these stiff commercial tires. If you need flotation, this is the wrong type tire. Deflating the rear 70 psi when unloaded does help ride quality, but still be stiffer than any LT tire.


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joeshmoe

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Posted: 03/07/21 05:54am Link  |  Quote  |  Print  |  Notify Moderator

Not 19.5's but I bought some Cooper Evolution 295/70/18 M/T's tires last summer. Load cap: 4080lbs. I bought them due to the higher weight and to put me at ease. LoL

Put about 1K miles on them from SoCal to Lake Powell. White knuckled ride the entire time, to and from. They felt as if they were walking around. Couldn't drive any faster than 60ish mph. 65+ and they became very mushy-feeling is how I would describe it. They wandered and pushed around a lot when correcting the wheel. If I over-corrected, they would get squirrelly and wander almost into the next lane. Never stable, nor comfortable unless driving well under 60mph. I didn't feel in control. Not sure if it was because they were new or because the aggressive tread lugs or the taller sidewall. My wife observed me the whole time saying when we got back home that she never saw me hold so tightly to the wheel as did with these new tires.

Did I not give them enough time to break-in? Replaced them with Cooper ATP's when we returned home. I really wanted to like them as they were great in sand, just not on the hwy, loaded. Unloaded, with the camper
off, they were fine.


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