Imperial Home Page -> Repair -> Wheels & Tires -> Pressure
Stamped on the outside of many of your tires is a recommended tire pressure range. (At least an upper limit.) For longest tire life it is my recommendation that you strive to keep them at the higher limit of those recommendations Further, this pressure should be determined while the tires are cold - meaning, have not been used for a couple of hours.
Time and outside temperature effect the pressure within your tires. It is NORMAL for a tire to lose about 1 pound per square inch (psi) per month. Outside temperatures affect your tire pressure far more profoundly, however. A tire's pressure can change by 1 psi for every 10 degrees Fahrenheit of temperature change. As temperature goes, so goes pressure.
For example, if a tire is found to have 38 psi on an 80-degree mid-summer day, it could lose enough air to have an inflation pressure of 26 psi on a 20-degree day six months later. This represents a loss of 6 psi over six months and an additional loss of 6 psi due to the 60 degree temperature reduction.
At 26 psi, your tire is severely under inflated and dangerous!
You MUST check your tire pressure on a regular basis (about once a week is reasonable) and to be particularly aware of it on cold days.
Tip from John:
If you put new tires on a 35-40 year old car, the FSM or the label on the vehicle is telling you what was correct for tire technology of the time & bears little relation to what is correct for today's tires. If you read a tech article on the proper care of tires it will tell you that the maximum tire pressure stated on the tire is the maximum COLD pressure & when you check the tires hot, you will find the pressure exceeds this if they were at maximum cold pressure & this would be normal.
Tip from Joe:
Tire pressure effects fuel mileage. I had 29 lbs in my 80 New Yorker. It was getting 19 miles per gallon. I aired them to 35 and it jumped to 23 miles per gallon. This was on a trip in 1983. Yes, it rides stiffer. The tires will wear on the outside edge if too low and wear the inside, or center of tread if too high a pressure. I put what it says on the tire. Also, if you live where the air temperature is extreme in the yearly changes, that effects air pressure also. I have had it vary to 6 lbs even when not using the tires, then check them again in the next year and they were back to the preset pressure. But I live where it goes from the high 30's in winter to 128 in the summer.
Because checking your tire pressure is so important, there now is a free service provided by Tire Safety.com : they will send you a monthly, automated notice letting you know that it is time to check the tire pressure on your Imperial.
INFLATION PRESSURE:
Proper inflation pressure is essential for achieving maximum performance and mileage. Improper tire inflation pressure can cause severe internal tire damage, which can lead to sudden tire failure and resulting in serious personal injury or death.
Improper inflation pressure may result in rapid or irregular wear. Pressures should always be checked when the tires are cold and at least monthly. Under normal tire operation, approximately 1psi of tire pressure will escape every month. Also, for every 10 degrees F change in ambient temperature, tire pressure will change by approximately 1psi.
Vehicle manufacturers list recommended tire pressures for original vehicle tires in the owner's manual or on a placard on the end of the driver's side door or in the glove box.
For continuous high speed driving, tire pressures should be increased by 3 to 5psi above the normal cold inflation recommended. However, for passenger tires, never exceed the maximum inflation pressure molded on the sidewall. The inflation pressure for light truck tires may exceed that molded on the tire by 10psi. Any recommended front to rear pressure differential should be maintained.
Question from Rob (1964):
I have been running Goodyear radials on my 64 Crown Coupe for several years now. I just had the front-end rebuilt. (Contact me for info on front-end rebuilt shop advice in the Wash DC area if needed.) With a solid and quiet front-end, I am finding that the radials seem to be giving a harsh ride when inflated to the tire shops recommended inflation level. I contacted Goodyear and they will not give me advice on how low the tire pressure could be set without causing tread separation. I know the FSM calls for 24 lbs of pressure for bias-ply tires, and 24 lbs in a radial does not look right on my car. Does anyone know whether the majority of IMLers are running on radials or bias-ply tires? Does anyone have any thoughts on tire pressure for radials on a 64?
Replies:
From Kerry:
I run the Goodyears on my 64 at 30-32. Love em.
From John:
I have radials on my Imperials & inflate to 29-30 PSI. I did have a 64 some years ago & did the same on that. My current 60 has had the same tires for nearly 11 years & still fine, the 69 for 6 years & fine also.
Tip from Chris (1967):
I run 31 front/29 rear in the 721s on both my '67Crown and '78 NYB. Seems like a good match of ride, handling and sidewall appearance (minimal bulge).
Tip from Bill (1968):
On 68's I use 35 lbs all around.
Tip from Steve (1968):
I run 32lbs in the front and 30 in the rear. Being that the front is heavier than the back, more pressure is used. I find that with less pressure, poor handling, worse mileage and uneven tire wear are the result. It seems to be a good compromise between a hard ride and a bad handling car. I would have to assume that you have P235-75-R-15's.
Tip from John (1960 and 1969):
I put 30 in my 60 & 69 Imperials & I find that this works well.
This page last updated October 3, 2003. Send us your feedback, and come join the Imperial Mailing List - Online Car Club
