The Stovebolt Site Forums The Shop Area General Truck Talk Tire Pressure Recommendation

I have a new set of tires for the truck. They are 205/75 R 15 97T passenger car radials.

The "97" in the tire spec is the load index. There is a load inflation table that says the max load is 1609 lbs at 36 psi. The load table provides max loads at different pressures starting at 22 psi. At 22 psi the max load is 1069 lbs. I won't list all the entries in the table. If you are interested, see page 28 in this document: https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Since these are passengers tires used on a truck, the load should be reduced (according to highway regulation) by 10%. This means the max load is about 1450 lbs at 36 psi.

According to the specs for a 1954 3100 pickup, the curb weight is 1855 lbs on the front and 1430 lbs on the rear. So load on each front tire is about 930 lbs

It looks like I could inflate the tires to a minimum of 23 psi; table says load is 1124 lbs. 90% of 1124 = 1012 which is greater than 930.

23 (or even 24) psi seems low. Is there a common sense solution that is better than these calculations? I'm thinking 30 psi (easy to remember) and call it done.

97T...............T= Trailer? Trailer tires have a stronger side wall. On an RV or trailer it is recommended by some that they be inflated nearer max.

A quick cursory check shows a 1994 S10 Blazer uses 205/75 R 15, has about the same curb weight and vehicle label says 32psi. You can use the "similar weight/tire size" method like that or use 32psi and sleep well.

the "T" is the speed rating (118 mph)

Run them as firm as your comfortable with for better mileage but watch that they wear well, adjust pressure if necessary for even wear.

I've got 205/75R15s on my '53. I run them at 35psi. I like the ride and handling at that pressure.

The “norm” for many many years was 32psi. We would put a few more lbs in when hauling a heavy load or towing a trailer and air back down to 32psi when done. Unless your going to be using your truck as a truck, my recommendation is adjust to a level that is comfortable to you and at least the amount listed by the tire manufacturer.🛠

When I had my Willys wagon, I had 33" swampers on it. I ran them at 25 psi on the road, anything more and it was a real stiff wide. I dropped them to 8 when wheeling, if I forgot to drop them, it sure was noticeable. I would run them home from wheeling sometimes at 8 since I didn't have an onboard compressor. If my friend was with me that had a compressor on his jeep, and we had time, I'd air them back up.

Yes, "T" is speed rating. I will be sure to keep it under 118 mph!

Sounds like 32 to 35 psi is good.

Thanks for the replies.

The old rule of thumb I've used is 1 psi per 100 lbs vehicle weight which in your case would put you right in the 32 to 33 psi range. Then as Martin said if you are adding a lot of extra weight run it up a bit more.

I should clarify my post. I don't keep the pressure at 35 all the time. I don't check my tire pressure as often as I should. When it drops below 30 I air up to 35 so technically anything between 30 and 35 works for me.

LT 215/85R16 Radial - black-walled tires (and inner tubes) on my 1954 original 3100 rims/wheels (for over 14 years - about 12K miles on them).

31-32 lbs pressure is this combination's "sweet spot"

Annually, I vary/adjust the psi to obtain the the best "balance" between ease-of-steering versus smooth straight tracking on a level road (up to 65 mph).

Also, I keep the front-end parts and steering greased and properly adjusted as described in the Shop Manual (all original style parts).

14 years is a long time for tires - the tires show no checking or slits (the truck has been parked in a garage).

I keep 45 lbs. in my front tires. It makes it easier to steer.
George