Tire Pressures

[John H]

Here is a note from an allied representative of Sumitomo Tires regarding tire pressures and loads for a Toyota Sunrader, 21ft. with reported scale weights of front = 1780lbs and rear = 4040lbs.

Mr. Huntington, Thanks for your recent inquiry about the correct air pressure for your 185sr14LT tires. According to the weights you gave, I suggest you use: 32 psi (cold) in all your tires. The weights given will be supported by using 26 psi, but with highway speeds, an extra 6 psi (cold) should be added. In all cases, air pressures should only be checked and changed before moving the vehicle any distance. Or to wait one hour after coming in from a trip. This practice will give the most accurate reading, and allow tires to operate at their best.

Hope this helps those of you who over inflate your tires. I've found that the ride is a bit harsh when inflating to the stated sidewall pressure of 65 lbs (load D tires)

John SW Ohio

[Pat]

While I do not believe 65 psi is necessary, I do believe that 32 is a bit low. Think best to remember what happened to Ford and Firestone a number of years ago.

[bufbooth]

I was thinking the same thing about the Ford / Firestone problem, 26 and 32 do sound extremely

low, I would of expected closer to the 65psi, like in the 50psi to 55psi rating.

I would get a second opinion from another tire dealer, I think the first one might of read

the specs for a Toyota SUV.

Dennis...

[Pat]

John,

I suggest you contact them again with the question. Hankook Tire advised me much higher psi, both steer and drive. This is for my 21 foot 87 Sunrader.

Pat

[John H]

I think Pat and Bufbooth are on target. I also think 32lbs is too low. I have a tire pressure/load table and yes, 32 lbs will cover the weights I sent to the tire representative but I'll increase the pressures until the ride gets too harsh. Drove the Sunrader with four people several hundred miles in July with temperatures near 100 degrees and 45lbs in the tires and upon stopping felt the tires and they were not hot.

John SW Ohio

'86 21ft Sunrader; 22RE, auto

[Pat]

Hankook said 55 psi for 6 ply and 65 psi for 8 ply. That is full load.

[WME]

Why don' you ask your tires what they need.

OLD trick posted here before. Take some kids sidewalk chalk and make a inch wide mark across the tread. Driv in a streight line for a mile or so and look at the mark. Adjust the airpressure so that all the chalk wears off at the same time.

[John H]

To WME; That's a neat procedure. I think I'll follow Dutch's advice and keep closer to 65lbs than 40lbs but will adjust some for ride. My tires are load range "D" tires and have max=65lbs on the sidewall.

Thanks, all for your replies. John SW Ohio

[Gottasmilealot]

I run 45 psi in the rear duals and 35 psi in the front tires, and it drives like a dream. When I had it in for state inspection, the mechanic did me a "favor" and reduced the rear tire pressures to the stated 32 psi, and the vehicle was all over the road in the wind and when buffeted by passing trucks. 45 psi is well below the maximum recommended by the manufacturer, and plenty to handle the load.

[Pat]

the mechanic did me a "favor" and reduced the rear tire pressures to the stated 32 psi, and the vehicle was all over the road in the wind and when buffeted by passing trucks.

This goes to prove what I've always said, "some mechanics know nothing about tires or motor oils". And regretfully today, many are nothing but replacement artists.