TIRE PRESSURE CHART TO DOWNLOAD ---and a question

**ForBruce** · 12-18-2022, 03:05 PM

there are 2 charts in this post .

one is a small one just for the solitude 17.5" cooper tires ; and the larger second one in pdf is a full cooper tire chart for different size tires.

Now my question : according to the Cat scale my trailer 2 axles weigh collectively 13,460 lbs. Divided by 4 tires =each tire is getting 3,365 lb each.
( actually that 3,365 will vary due to the stove , refrigerator and pantry being on one side of the trailer )

Now the approximate 3,365 weight will vary also due to up and down movement of road bumps . so lets add an additional 500lb margin weight.

So now each tire supports 3,865 lb and according to the tire pressure chart (cooper work service 275/75r17.5) the cold psi should be 95lbs. which supports 3,925lbs

I run my tires at 112lb cold..... am i setting pressures too high. And does that make for bumpy travel.

running at 65 mph raises tire pressure to about 125 - 132 lbs with virtually no heat build up in tires (warm to the touch)

**trailrydr** · 12-18-2022, 04:11 PM

We run our Goofyears (pun intended) at the rated max cold air pressure for the weight specified on the tire. That way we dont have to worry about over inflation and heat expansion related blowouts from "normal" road use. Now, bent wheels, axles, pot holes, curbs, etc heat related issues.... well what can a poorboy do but hope to get it fixed before stuff happens.

And yes, its true that higher pressures will cause a stiffer ride, but, "can" also reduce resistance for better mpg. I would still go by tire specified cold weight/pressure inflation.

Have had rental cars, when rented and used while touring with our RV camped, have tires over inflated for just that reason (mpg). Always check them and reduce back to vehicle spec cause eventhough I might get better mpg, I dont wont to find myself waiting on a tow truck because of a blowout and have no spare to replace.

**ajg617** · 12-18-2022, 04:36 PM

I ran 123-125 cold pressure this year and adjusted based upon ambient temps locally. I contacted Cooper truck and was also told to inflate them to the placard PSI. Air temps during travel ranged from low 40s to 105ish. Max pressure at high temps and rough road conditions was 148psi (under the +/- 20% Cooper also recommended) but the tire temps did not go over 110F unless I had used brakes coming off the highway and parked, i.e. fuel stop. I confirmed tire temps were warm to touch but my infrared gauge crept up a bit waiting to fuel up. Temps went down as soon as I started driving again.

My build sheet says I'm 600lbs heavier on off-door side empty though probably a bit less after washer/dryer installed on door side. With pantry, fridge, kitchen stocked I'm sure it is more. Oddly, the highest PSI and temp readings were on the door side during travel. Loaded, highest CAT scale for trailer was 12,240 this year so not as heavy as you.

**Calbar** · 12-18-2022, 07:40 PM

Originally Posted by ForBruce

there are 2 charts in this post .

one is a small one just for the solitude 17.5" cooper tires ; and the larger second one in pdf is a full cooper tire chart for different size tires.

Now my question : according to the Cat scale my trailer 2 axles weigh collectively 13,460 lbs. Divided by 4 tires =each tire is getting 3,365 lb each.
( actually that 3,365 will vary due to the stove , refrigerator and pantry being on one side of the trailer )

Now the approximate 3,365 weight will vary also due to up and down movement of road bumps . so lets add an additional 500lb margin weight.

So now each tire supports 3,865 lb and according to the tire pressure chart (cooper work service 275/75r17.5) the cold psi should be 95lbs. which supports 3,925lbs

I run my tires at 112lb cold..... am i setting pressures too high. And does that make for bumpy travel.

running at 65 mph raises tire pressure to about 125 - 132 lbs with virtually no heat build up in tires (warm to the touch)

I am running mine at 110PSI. I did much the same calculation you did. I prefer a bit of margin with tire pressure.

Rob

**ForBruce** · 12-18-2022, 07:46 PM

Originally Posted by ajg617

I ran 123-125 cold pressure this year and adjusted based upon ambient temps locally. I contacted Cooper truck and was also told to inflate them to the placard PSI. Air temps during travel ranged from low 40s to 105ish. Max pressure at high temps and rough road conditions was 148psi (under the +/- 20% Cooper also recommended) but the tire temps did not go over 110F unless I had used brakes coming off the highway and parked, i.e. fuel stop. I confirmed tire temps were warm to touch but my infrared gauge crept up a bit waiting to fuel up. Temps went down as soon as I started driving again.

My build sheet says I'm 600lbs heavier on off-door side empty though probably a bit less after washer/dryer installed on door side. With pantry, fridge, kitchen stocked I'm sure it is more. Oddly, the highest PSI and temp readings were on the door side during travel. Loaded, highest CAT scale for trailer was 12,240 this year so not as heavy as you.

saw from you signature that you have dual pane--would you get that again..and have you seen any benefit from it

**ForBruce** · 12-18-2022, 07:48 PM

Originally Posted by Calbar

I am running mine at 110PSI. I did much the same calculation you did. I prefer a bit of margin with tire pressure.

Rob

that's very interesting because we both have the exact same trailer 378mbs pulled with a single rear wheel truck.

**MoonShadow_1911** · 12-18-2022, 07:49 PM

Originally Posted by ForBruce

saw from you signature that you have dual pane--would you get that again..and have you seen any benefit from it

I know you weren't asking me, but we ordered ours with DP windows, and in short, yes, we'd do it again in a heart beat.

The help to block outside noise, help the coach stay warmer in winter and don't fog up, cooler in the summer, without blocking the window with Reflectix.

**Calbar** · 12-19-2022, 03:41 AM

Originally Posted by ForBruce

that's very interesting because we both have the exact same trailer 378mbs pulled with a single rear wheel truck.

Yes that is very interesting. I also have the 3rd A/C but no solar but I have the dual pane windows which we really like. I also have the RV fridge and not the residential one.

Rob

**ajg617** · 12-19-2022, 06:07 AM

Originally Posted by ForBruce

saw from you signature that you have dual pane--would you get that again..and have you seen any benefit from it

Yes - very pleased. We had temps that dipped into the upper 20's this year and as high as 106. Zero condensation, noise level was low, and I put my heat gun up against the windows with the furnace on and the temp in the 20s outside but holding 68 inside and a couple degree difference from the surrounding walls. Also, just have 2 ACs and could usually run on one once we cooled down after arrival quickly and kept cool even in 100plus temps. Would buy them again. Outside noise blocking was great since we seemed to find a lot of campgrounds near train tracks.

**jadatis** · 12-19-2022, 08:34 AM

I once determined that using 90% of the loadcapacity for the pressure for 99mph gives a deflection that still gives acceptable comfort and gripp.
And then maximum reserve for uneqall weight between the tires on your tandem.

Searched for your tires but could not find it.
So If you can give me the specifications, I can make a pressure/
total load on 4 tires list, for you, in wich 90% given if liadcapacity for 2 speedcode steps higher then your tires, to still give no bumping.

Need next, mostly can be read from sidewall
1. Maximum load or loadindex( you only use single)
2.loadrange to determine the referenxe-pressure, or better psi behind AT, if given
3. Speedcode, I think your tires L, M or N, for max 75, 81 or 87mph.

Road bumps you dont need to add weight for, its all about heatproduction, and that takes more cicles of tire than riding over bumps.
Reserve is mostly needed for weightdifference between the axles, and tires on a axle.