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Following the thread on radials tire pressure, what pressure are people running on reproduction bias ply's? Some of us idiots haven't converted over yet.
Following the thread on radials tire pressure, what pressure are people running on reproduction bias ply's? Some of us idiots haven't converted over yet.
I have radials on my car, but my '61 owner's manual says 24 lbs cold, 27 warm (city), and 29 warm (highway).
You guys running higher pressures... they must get pretty high when warmed up?
This is pretty much what I remember back in the day - 24 cold minimum all around. I don't remember any recommendations for over 30 psi in that period. Maybe modern bias belted are different. What does the sidewall say.
24 and 27 from the manual for my '51 Ford as well. I was surprised and kinda confused by this when I first read it. Then I bought a set of radial WSW so I don't have to worry about it. I think you guys running much higher pressures will be looking a strips of cord down the middle of the tread if you run the tires for a long time.
I have been running 26 all around since I got the car three months ago. With the warm weather here in NC I think this is as high as I plan to go. Thanks for all of the responses.
Modern repro tires have a DOT- required placard molded into the sidewall that specifies maximum load at maximum COLD pressure, so that's the first thing to look for, and it's probably 35 psi.
Highway operation in hot weather will increase pressure by up to about 6 psi, and that's okay. The maximum pressure placarded on the sidewall is for a COLD tire, and pressure rise from operation is NORMAL.
Hot lapping a big race track will increase TP by 10-12 psi starting from 36 cold, and typical tire burst pressure is on the order of in excess of 100 psi. Tire cord is very strong.
The higher the cold pressure, the less rolling resistance, the lower the rate of temperature/pressure rise, the lower the wear rate, and the crisper the steering response, but you may notice increased high frequency ride harshness.
The OE tire pressure recommendation for my SWC of 24 psi was a joke. It was like driving on slim, so I increased cold TP to 35. There was no max load @ max cold pressure placarded on the sidewalls back then, but that's what my dad, an engineer (BSME U. of Wisconsin, 1927) who was in the Pontiac sales an service organization pre-War and owned a dealership post-War, ran in his cars.
So it's an individual choice between the original 24 psi recommendation and the maximum cold pressure placarded on the sidewall. Experiment and choose what works best for you.
I would agree with those that suggest 32 psi as a good starting point. (Or at least start with the placard found in the door jam of most new cars.) However, because every car, including similar make and model cars, are different it isn't particularly precise. The following method is a more precise way to determine (or verify) the correct psi to run in your tires and one I've used for years.
First pick a psi to start with and monitor it so that it will remain constant over a period of time. Then, using a tire tread depth gauge, check the tread depth across the face of the tire. At the very least 3 places across the tread, outboard edge, center and inboard edge and write these numbers down. This is the starting point and of course works best on new tires, but can be done really at any time.
Then, at about every 4-5k miles take a new set of readings. If the tread depth remains constant at the outside, center and inboard side of the tire the pressure you are using is good.
If the center starts to wear more than the outboard edges, then you have a bit too much air in the tires. Lower the pressure a couple of pounds and check tread depth again in 4-5k miles.
If the outboard edges are wearing faster then the center your pressure is too low, so add a few pounds and check again in 4-5k miles.
This method is a much more precise way to determine the correct PSI you need to run and takes into account factors such as non stock tire sizes, mods to the car that have changed it's weight from stock and even different tire compounds.
What ever psi you settle on, be sure to write it down and keep it in a handy location so you can refer back to it, such as the glove box with the owners manual.
Following the thread on radials tire pressure, what pressure are people running on reproduction bias ply's? Some of us idiots haven't converted over yet.
Take a look at your tires. My Kelsey Goodyear Power Cushion redlines (manufactured 52nd week of 2015) say “32 PSI MAX. PRESS.” I talked to John Kelsey when I bought the tires and he said they were designed to be inflated to the OEM recommendation (24 psi).
I have tried different pressures and like 24-26 psi. Higher pressures give a harsher ride. I don’t road race my car and I can’t tell any difference in cornering traction at normal speeds.
One thing taht hasn't been brought up is tire gauges.
I have oh, maybe 20 gauges, three on-hose type gauges, one digital gauge and 15 or more pencil type gauges.
They all read different, by up to 12 PSIG max spread at 30 PSIG. (readings from 28-40 on the the same tire)
Even the on-hose, service station type, supposed to be good quality plunger gauges are off by 5 PSIG between the two.
How am I supposed to know which ones are correct? Without buying a NSI certified dial pressure gauge for $100 or more and adapting it to a tire valve?
I have been thinking about using the in wheel pressure sensors from my '16 Z06, which has in dash readout of tire pressure, and using that as my standard and tossing any gauge that doesn't match that reading.
The OEM tire pressure recommendations for my ‘67 - still on the original sticker on the inside of my glove compartment door - are 24 psi cold and 30 psi hot on all 4 corners.
Your preference may vary..........
Last edited by tuxnharley; 05-17-2018 at 03:47 PM.
05-15-2018, 08:13 PM
Tire pressure on reproduction bias ply's?
Lower the pressure a couple of pounds and check tread depth again in 4-5k miles. 
