Sorry for the confusion .I'm only discussing radial tires. Bias-ply (cross-ply) shall have much lower pressure, and can use the factory recommendations.

Diamond Back (radials) recommends 35 psi cold as a starting point, but also recommend higher for Hot Rods, 40-44 psi.

http://www.dbtires.com/airpressure.html

I think we are on the same track, radials need more pressure .

1955 Mercury

My DBs also say max 44 like my other radials so I feel safe at 40 lbs. You're on the right track.

-Gary Burnette-

Diamond Back recommends 40-44 psi on my DB II (Toyo) extra-wide-whites. Running less runs the risk of cracking the whitewall.
My tbird handles fine with these, no surprises and no squeals.

Diamond Back also has a brief article on air pressure which is informative.

You guys must have different sizes? I have 205 x 75 x15. my D/B 's the tyre is made in Mexico, on it its only rated to 35 psi. Max



"Came too close to dying to stop living now!"

When talking radials there are two types of construction which is extremely important to know from a safety aspect.Nylon belted radials are not as critical with tyre pressure as steel belted radials. Nowadays, most radials sold are steel belted.
It is absolutely critical to the life of the tyre not to run it under-inflated - tread separation will result with disastrous consequence - remember the Ford Explorer (Exploder). I have used steel radials for over 35 years with never a problem. I run the tyres at 32psi all round and the steering is light, responsive and as sure footed as any new car.
The older nylon belted radials could be run at cross ply pressures but they gave you "ARM-STRONG" steering when run at those pressures. I always ran those radials at 28psi all round.
I would think that pressures over 35 would make the ride a bit harsher.

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

Rick, Try 35 or 40 once, you'll be surprised at how little difference in harshness there is. But I'd bet you will notice a difference in steering feel and effort.

Frank/Rebop

Bristol, In ( by Elkhart) 

I run 40#'s F & R on my '01 Crown Vic with Goodyear Eagle GT's. It rides fine but stopping and traction suffer on wet pavement.

~DJ~ AKA "Bleach"
1956 Ford Fairlane Town Sedan 30K original miles

Might be too narrow a rim. That would show up as a darker or heavier center and lighter edges on the tread. I have 7" wheels, with 215's no problem although I don't intentionally drive the car in the rain.

Frank/Rebop

Bristol, In ( by Elkhart) 

Frank, I did what you suggested this weekend and put 35psi all round. I am running 205x70/15 tyres. I didn't notice any difference in ride, handling or steering. I did see something on the Hankook site that suggested maximum recommended pressure should not exceed 90% of maximum pressure - which would suggest that the maximum pressure for my tyres should be about 40psi (90% of 45psi). Surprizingly, my late model Nissan Xtrail is much more sensitive to tyre pressure than my old Ford.

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

Car mfg's have almost always recommended way less tire pressure then the tire Mfg's or their vehicles would not ride "Smooth Enough". Bias should always have been 32 P.S.I. (even in '56) as the tire Mfg noted on the tire side wall, and radial tires 35 to 60 P.S.I. depending on the tire style, size, and MFG. I run 35 P.S.I in the Tigerpaw radials on the Bird and have Great handling and a Smooth ride. My guess you would be in the 35 P.S.I. bracket also.

312T85Bird

What?