Tire pressure? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*ZmOz* · 06-04-2005, 04:04 AM

I'm sure this has been talked about before, but the search is....

What tire pressure should I be running in my '79 C20? The manual is MIA and the sticker on the door is unreadable. Tires are stock size, with 16.5" wheels. Right now they're at about 25 PSI, that can't be helping the mileage.

ureckme · 06-04-2005, 05:35 AM

It should say on the tires

Ogier · 06-04-2005, 06:35 AM

Tire pressure, the right way.

Step one: Weigh your vehicle. You need to know how much weight is actually on the front axle and the back axle seperately.

For the sake of example, lets say it is 2500# on the front and 1500# on the rear.

Step two: look at the pressure rating of your tires. They will say something like "Max load 2500# at 35psi"

With this in mind, two of the tires are capable of carrying 5000# max at 35psi in the tires.

Step three: Take your Max load and divide it by your actual loads.

I.E. Front tires are 2500# / 5000# which comes to .5 or 50% of the total load.
Rear tires are 1500# / 5000# which comes to .3 or 30% of the total load.

Finally, multiply the max tire pressure by the percentage that you figured out.

In this example, Front psi = .5 * 35psi = 17.5psi
Rear psi = .3 * 35psi = 10.5psi

This is probably not right for your truck as I don't have your truck's weights. However, the method is correct. I usually won't run a 35# tire under 25# though. I have done my tires this way for years and don't burn the centers out of them or have premature failure unless some kind of foriegn body is involved. I.E. nail.

The nice thing about setting your tire pressures correctly is that no matter what you drive, you will get a nice ride out of it.

Please note: If you talk to your "Tire Professional" at your local tire shop, they will tell you that this is wrong. This is because they truely don't know any better.

Just my .02$ whatever it may be worth.

eagle23 · 06-04-2005, 10:21 AM

The correct answer imo is 'it depends'

If you don't carry much in the truck, I'd probably use 32 in front, and maybe 28 in the back. If you do carry a lot, use pressures closer to the max. The sidewall markings are really only good for max loads. The 'tire professionals' will always inflate them to the max: they aren't liable for anything going wrong if the tires are inflated to kidney-jarring pressures.

I just checked my owners manual on my '77 C10 just for grins...not a straight answer to be found, just a lot of pages of it depends/don't overinflate/don't underinflate/etc.

One indicator is the treadwear pattern. Is anything showing up? And what kinds of loads do you carry how often?

06-04-2005, 04:04 AM	#1
ZmOz Account Suspended Join Date: Apr 2005 Location: OR Posts: 235	Tire pressure? I'm sure this has been talked about before, but the search is.... What tire pressure should I be running in my '79 C20? The manual is MIA and the sticker on the door is unreadable. Tires are stock size, with 16.5" wheels. Right now they're at about 25 PSI, that can't be helping the mileage.

06-04-2005, 05:35 AM	#2
ureckme ureckmefixit2@cox.net Join Date: Dec 2004 Location: Mesa AZ. (Phoenix) Posts: 1,284	It should say on the tires __________________ That's U RECK ME FIX it 2 74 Chevy Short Bed 355ci Sportsman II 64cc Angle Plug Crower Custom Grind .462in .486ex Dyno Test 422hp @ 5600 And it's got a Holley 3.73 Gears 12 Bolt 3.73 w/Posi 700R4 Going In I'm a Body Man So There! That's why it's not painted

06-04-2005, 06:35 AM	#3
Ogier Chopper/Painter Join Date: Jul 2004 Location: Medford, Or. Posts: 284	Tire pressure, the right way. Step one: Weigh your vehicle. You need to know how much weight is actually on the front axle and the back axle seperately. For the sake of example, lets say it is 2500# on the front and 1500# on the rear. Step two: look at the pressure rating of your tires. They will say something like "Max load 2500# at 35psi" With this in mind, two of the tires are capable of carrying 5000# max at 35psi in the tires. Step three: Take your Max load and divide it by your actual loads. I.E. Front tires are 2500# / 5000# which comes to .5 or 50% of the total load. Rear tires are 1500# / 5000# which comes to .3 or 30% of the total load. Finally, multiply the max tire pressure by the percentage that you figured out. In this example, Front psi = .5 * 35psi = 17.5psi Rear psi = .3 * 35psi = 10.5psi This is probably not right for your truck as I don't have your truck's weights. However, the method is correct. I usually won't run a 35# tire under 25# though. I have done my tires this way for years and don't burn the centers out of them or have premature failure unless some kind of foriegn body is involved. I.E. nail. The nice thing about setting your tire pressures correctly is that no matter what you drive, you will get a nice ride out of it. Please note: If you talk to your "Tire Professional" at your local tire shop, they will tell you that this is wrong. This is because they truely don't know any better. Just my .02$ whatever it may be worth. __________________ With regards, Ogier 1969 Chevrolet C20 - Resto-Custom started!!!

06-04-2005, 10:21 AM	#4
eagle23 Active Member Join Date: Feb 2004 Location: Atlanta GA Posts: 174	The correct answer imo is 'it depends' If you don't carry much in the truck, I'd probably use 32 in front, and maybe 28 in the back. If you do carry a lot, use pressures closer to the max. The sidewall markings are really only good for max loads. The 'tire professionals' will always inflate them to the max: they aren't liable for anything going wrong if the tires are inflated to kidney-jarring pressures. I just checked my owners manual on my '77 C10 just for grins...not a straight answer to be found, just a lot of pages of it depends/don't overinflate/don't underinflate/etc. One indicator is the treadwear pattern. Is anything showing up? And what kinds of loads do you carry how often?



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