Tire pressure question

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my68barracuda

my68barracuda

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car is a 68 Barracuda
tires front 215/60/16 on 7 inch wide wheels
tires rear 225/60/16 on 8 inch wide wheels
the car is somewhat light weight, fiberglass hood and front bumper, aluminum front bumper brackets, light weight last year built slant. Carpet and interior trim is present, but no back seat, no under carpet sound deadening material.

The side wall of the tires says that max load capacity is at 51 psi.

Does a cold tire pressure on 38 psi seem about right?
The car rides and drives fine.
Thought I would ask to see what other folks run for tire pressure with non stock sized tires.
 
Dicer said:
I have used this method numerous of times, a good "Rule of Thumb".
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Neat method for sure. Pay close attention to the word of caution at the end.... it alludes to the fact that underinflation can definitely cause overheating, especially at highway speed. I watch this carefully on the heavy trucks when loaded especially....don't want to do damage that cant be undone... A trip to the drag strip is a completely different story...
 
51 is too high for sure. 38 seems a little high too. I get them somewhere around 32-35 and call it good.
 
Tire pressures as far as what is on the sidewall have increased over the years for better fuel mileage.
It is up to you with what you feel comfortable with. That said, 51 at max load you can easily decrease that to 40-44 and have no problem. I run old school 15'' that say 36 max psi,between 30-32 psi. For our other cars that have a max of 44 psi I run 36-38 . Now my old truck the side wall says 80 psi max. If not hauling I run 50 front and 40 rear because of weight distribution and a empty bed.
 
tires were not designed for a old mopar / maybe a light truck or off road app.
 
I was in the tire and alignment business many years. On P metric tires, we found consistently time and again that the best tire wear happens at 35psi, but on light cars sometimes gave a little bit of a harsh ride so we'd back it off to 32. I couldn't imagine a low profile tire at 51 psi. Talk about riding like a wagon.
 
IMO;
28 all round should get you fairly even tire wear.
in my 68 Barracuda, on the Street, formerly a DD:
I run 29 in 235/60-14s on the front, @1800 pounds on them; and in the rear @1600pounds;
28 with 275/60-15s on 8.5s or
24 with 295/50-15s on 10s
I prefer to start off at a lil less than optimum cuz the tire-wear is easier to correct, than if the centers get rubbed off.
 
teringer said:
tires were not designed for a old mopar / maybe a light truck or off road app.
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toolmanmike said:
Common sense and years in the business tells us that.
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I am thinking that you guys are thinking of typical driver M&S radials. Maybe even a driver classic from years past like BF Goodrich White Letter tires or Cooper Cobra’s.
32 to 35 psi is a typical inflation pressure for those.
These Firestone Firehawk tires are a step and a half up from that:
Asymmetric tread, A traction, A temperature and V (149 mph) speed rating.
A lot more of a performance tire.
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Yea, I would contact the manufactuer--With his max psi being 51, 32-35 seems too low.
 
Lightly wet the tire thread and roll the car and look at the wet thread mark on the ground. If the mark is narrow then remove air. If the edges are heavy and the center is light the add air.
 
AJ/FormS said:
IMO;
28 all round should get you fairly even tire wear.
in my 68 Barracuda, on the Street, formerly a DD:
I run 29 in 235/60-14s on the front, @1800 pounds on them; and in the rear @1600pounds;
28 with 275/60-15s on 8.5s or
24 with 295/50-15s on 10s
I prefer to start off at a lil less than optimum cuz the tire-wear is easier to correct, than if the centers get rubbed off.
Click to expand...
Yeah, fairly evenly worn on the edges. That's too low.
 
I run about 60% of max pressure on my pickup truck tires around town, 80% for long trips or loads or towing. 100% on my trailer tires, and manufacturers rec for my 20s on my late model pony car. (44lbs, if I remember right.)
100%, or more, on front drag tires.
I would probably run 35lbs in your tires, 40lbs if it doesn't make the ride too harsh.
 
A lot of funny answers. Since the tire is supporting weight and a tire is just an air container with a specific volume of air capacity the pressure is always dependent on load.
Find out what the axle weight of the vehicle is first.
Using water and chalk and anything other than a good quality air gauge is just too funny. And I would never admit to "being in the business" and giving such unprofessional advice about pressures. I have to assume you were talking about a car with the correct, factory sized tire on it.
The pressure on the side of the tire is Not a recommendation. It is the maximum safe tire pressure for that particular tire.
Look up a load and inflation chart to find the load capacity of the tires you are thinking of using. Now look up the factory tire that came on that car and look up the load capacity of that tire. The tire you want to use should have at least the same capacity at the same pressure as what the car came with. Armed with the actual axle weight you can see what the safe limits are for the amount air pressure used.
Do a little reading to educate yourself a little more on tires. Not complete but has some good info for the average guy.
Tire Load And Inflation Chart at Tire Rack
 
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MoparLeo said:
A lot of funny answers. Since the tire is supporting weight and a tire is just an air container with a specific volume of air capacity the pressure is always dependent on load.
Find out what the axle weight of the vehicle is first.
Using water and chalk and anything other than a good quality air gauge is just too funny. And I would never admit to "being in the business" and giving such unprofessional advice about pressures. I have to assume you were talking about a car with the correct, factory sized tire on it.
The pressure on the side of the tire is Not a recommendation. It is the maximum safe tire pressure for that particular tire.
Look up a load and inflation chart to find the load capacity of the tires you are thinking of using. Now look up the factory tire that came on that car and look up the load capacity of that tire. The tire you want to use should have at least the same capacity at the same pressure as what the car came with. Armed with the actual axle weight you can see what the safe limits are for the amount air pressure used.
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I'm full aware of what the pressure on the tire represents. It's the maximum psi for the maximum load of that particular tire. In "the business" you learn to go with what the customer wants. If they want 28 PSI, you do it. If they want 40 PSI, you do it. I can tell you've not been in "the business" much if at all and also lack proper etiquette on how to politely speak to people with your stupid little veiled insults. Keep it up. My insults won't be veiled one single bit.
 
33IMP said:
I run about 60% of max pressure on my pickup truck tires around town, 80% for long trips or loads or towing. 100% on my trailer tires, and manufacturers rec for my 20s on my late model pony car. (44lbs, if I remember right.)
100%, or more, on front drag tires.
I would probably run 35lbs in your tires, 40lbs if it doesn't make the ride too harsh.
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Exactly. Nothing's written in stone, which was what I was going the long way around the barn to say. No one's an expert here, because it all depends on what the owner WANTS, not some self proclaimed experts on an internet forum, myself included. Run whatever amount of air makes your car behave the way YOU want and be done with it. It's just not that difficult. lol
 
RustyRatRod said:
Exactly. Nothing's written in stone, which was what I was going the long way around the barn to say. No one's an expert here, because it all depends on what the owner WANTS, not some self proclaimed experts on an internet forum, myself included. Run whatever amount of air makes your car behave the way YOU want and be done with it. It's just not that difficult. lol
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Actually I was looking for information on a method that would tell me if the tire was making full contact with the road across the width of the tread. Without having to roll up miles and watch for wear either in the center or on the edges.
I got what I was looking for with the second post.
Thanks.
 
my68barracuda said:
Actually I was looking for information on a method that would tell me if the tire was making full contact with the road across the width of the tread. Without having to roll up miles and watch for wear either in the center or on the edges.
I got what I was looking for with the second post.
Thanks.
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That method works well. Regardless of what some might think.
 
Actually, I just do a burnout on clean dry pavement. Even mark across, ding ding, winner. Heavy in the center, too hard, heavier on the edges, too soft.
Easy peasy.
 
33IMP said:
Actually, I just do a burnout on clean dry pavement. Even mark across, ding ding, winner. Heavy in the center, too hard, heavier on the edges, too soft.
Easy peasy.
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Perfect!
 
OP stated
my68barracuda said:
car is a 68 Barracuda
The car rides and drives fine......
Thought I would ask to see what other folks run for tire pressure with non stock sized tires.
Click to expand...
I responded;
AJ/FormS said:
IMO;
28 all round should get you fairly even tire wear.
Click to expand...
And then proceeded to answer his question; namely;
what other folks run for tire pressure with non stock sized tires
Click to expand...

You offered;
RustyRatRod said:
That's too low.
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Well, you are of course entitled to your opinion.
As for my tires, they are doing extremely well at those pressures and I included all the details so OP could have an informed and accurate base for comparison.
Please note that;
I did not tell him to run my pressures.
 
Actually RustyRatRod I speak from over 40 years retail experience working for tire manufacturers .
You never "wing it" on tire pressure. Number #1 cause of tire failure. I have been involved with 2 major tire recalls in 1978 and again in 2000 in which millions of tires were replaced primarily because the Vehicle manufacturer recommend their "own pressures" based on comfort, not load and most people never give the air in their tires a second thought until someone tells them their tire is low or they get a flat.
We found that the average tire pressure when people came in to replace their tires was 18 lbs.
The law is now to install the vehicle placard pressure. The customer may change that but it is never recommended or done "for the customer"
We are supposed to be the experts. Why would you endangerer the safety of a customer and open the company you work for open to liability if there ever was a problem. The first thing their lawyer will say is, But my client is not an expert...
What if you did oil changes and the customer told you how much oil he wanted. Would you put in a quart more or a quart less because "that is what the customer wanted?" or would you use your own common sense and educate him on why he shouldn't do that.
The customer isn't always right...
Go back to post # 15
 
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