20 PSI - Really?
Thread Starter
Race Director
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From: Feverish All Over
20 PSI - Really?
Just got a new C3 - 1975 Vert - and the door jam says tire pressure is 20 PSI. Tire are Goodyears 255/60/15 (not that the brand of tire impacts what pressure to run).
What does the crew here recommend - stick with GM's 39 year-old guideline??
Thanks
What does the crew here recommend - stick with GM's 39 year-old guideline??
Thanks
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Thread Starter
Race Director
Joined: May 2007
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From: Feverish All Over
Tire sidewall is just the manufactures' MAXIMUM pressue - that's not what you should run your tires at.
I have a C6 and GM say 30 PSI and that's teh correct pressure to run at. 38 PSI wouold strike me as very high and might be giving a punishing ride.
Just was surprised to see that pressures in the 70's were 20 PSI, and today it's at 30 PSI.
Anyways....FYI
I have a C6 and GM say 30 PSI and that's teh correct pressure to run at. 38 PSI wouold strike me as very high and might be giving a punishing ride.
Just was surprised to see that pressures in the 70's were 20 PSI, and today it's at 30 PSI.
Anyways....FYI
Burning Brakes
Joined: Aug 2013
Posts: 1,231
Likes: 115
From: Yelm Wa
Tire sidewall is just the manufactures' MAXIMUM pressue - that's not what you should run your tires at.
I have a C6 and GM say 30 PSI and that's teh correct pressure to run at. 38 PSI wouold strike me as very high and might be giving a punishing ride.
Just was surprised to see that pressures in the 70's were 20 PSI, and today it's at 30 PSI.
Anyways....FYI
I have a C6 and GM say 30 PSI and that's teh correct pressure to run at. 38 PSI wouold strike me as very high and might be giving a punishing ride.
Just was surprised to see that pressures in the 70's were 20 PSI, and today it's at 30 PSI.
Anyways....FYI
Last edited by tokim; Apr 27, 2014 at 11:19 AM.
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I run 32 psi in mine.
Team Owner
Joined: Jan 2006
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From: Crossville TN
During the first couple of years radials were installed on Detroit cars, car companies thought they should be at much lower pressures because of the MUCH larger 'footprint' of the radial tires. Well, very shortly there were LOTS of radial tire failures because they would flex too much, build heat, and have blowouts at highway speed.
By the late 70's those tire pressure charts had all been changed to show 25 psi MINIMUMS. Set your tires at 30 psi. And, if the ride seems 'spongy' in the turns, bump it up a couple of pounds.
By the late 70's those tire pressure charts had all been changed to show 25 psi MINIMUMS. Set your tires at 30 psi. And, if the ride seems 'spongy' in the turns, bump it up a couple of pounds.
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Burning Brakes
Joined: Aug 2013
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From: Yelm Wa
My BFG radial T/A's actually state (35 max psi)..didn't notice a "do not exceed" number..hmm.
Race Director
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How does a 'maximum' number NOT equate to 'do not exceed'?
Burning Brakes
Joined: Aug 2013
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From: Yelm Wa
Le Mans Master
Joined: Feb 2011
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From: Southern NH
I run 32 in mine.
I would never run under 30 psi in a tire. remember the Ford Explorer tire fiasco a few years ago? Explorers recommended tire pressure from the factory was something like 26psi.
I would never run under 30 psi in a tire. remember the Ford Explorer tire fiasco a few years ago? Explorers recommended tire pressure from the factory was something like 26psi.
Pro
Joined: Feb 2000
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From: Hebron IN
Can you post a photo of your tire's sidewall? I know there will be a maximum pressure but I'd also like to see the recommended tire pressure.
Burning Brakes
Joined: Oct 2013
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From: Killeen Texas
The # in your door jam I'm guessing is for the Original Tire, I would consult with the store that you purchased the tire from then adjust from that point.
Have a great day.
Tim
Thread Starter
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From: Feverish All Over
The recommended pressure is specified by the vehicle manufacturer and is usually on the door jam or in the manual.
I am going to heed tokim's advice and start at 30 PSI
Tx Crew
Pro
Joined: Feb 2000
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From: Hebron IN
varixpert - tires aren't usually stamped with a recommended pressure because the recommended operating pressure is specific to the vehicle. All you will see is a max or not-to-exceed pressure on the tire.
The recommended pressure is specified by the vehicle manufacturer and is usually on the door jam or in the manual.
I am going to heed tokim's advice and start at 30 PSI
Tx Crew
The recommended pressure is specified by the vehicle manufacturer and is usually on the door jam or in the manual.
I am going to heed tokim's advice and start at 30 PSI
Tx Crew
One of my first cars was a Corvair which required 15 psi front and 26 rear. It HAD to be at that! I remember having new tires put on and they did 32 psi all around. When I left and got up to 30 mph, I thought something in the steering let go.
Of course they didn't know because they couldn't find the decal in the door jamb. Back then it was on the glove compartment door.
Burning Brakes
Joined: Feb 2011
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From: Woodland California
My tire shop wants to run 34 to 36 pounds in my Komos.
Smoothest ride is at 30 pounds.
I'm sure there is an ideal pressure for maximum mileage and one for best traction. One for just you and One for a heavily loaded car.
I've been going to paint a stripe across my tire to see what the road contact was. That way I could adjust pressure accordingly.
Maybe someday I will.
R~
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Go look at a brand new car- any car. Please find us even ONE where the door card pressure matches what's written on the OEM tire.
Melting Slicks
Joined: Jan 2006
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From: Madison WI
Two completely different things. But if you are running the factory tires, the door card is relevant technically. I say technically because I've always preferred using their number as a starting point but finding for myself what pressure level works best for me and how I use it.
For instance on my Wrangler, the recommended pressure is 43psi. It rode pretty rough there. I worked my way down to 36 psi while still passing the "chalk test" and the was much ride improved.
But that was with the factory tires. I've since upgraded to larger tires by a different manufacturer and I'm running them at 33 psi. It really freaks out the oil techs when I take it in for my free oil changes at the dealer.
They want to go off of what the door says. 
Last edited by overBlown; Apr 27, 2014 at 08:22 PM.