I'm glad you asked. The info below came from 3 separate tire businesses. They deal in...tires. All day, every day. One might even call them experts. Tire experts. People who have a lot of training and first hand knowledge about...tires. They also have strong motivation to give accurate information to the public- it's called liability. Are you going to dismiss them as hobbyists too and tell us again that you're a mechanical engineer? As if that gives you any actual credibility.

 

I have, had them on my Vette when I first got it for 4 years and they still had perfectly even wear and tread on them at 40,000miles + I was able to sell them as they were in such good condition.

 

ok I cant believe this is still going.....
Slicks as we all or may know know get screwed to the rim to help keep the tire to the attached to the wheel. Because we use low air pressures why we do this.
If we ran higher pressure for slicks, we would get a rounder tire which equals less contact patch decreasing traction. This would also stop the wheel from spinning within the tire.
Its not just the bottom side wall of the tire that supports the total vehicle weight.

An underinflated tire will cause more drag which causes heat which causes rubber separation and well you can figure out the rest because on another post you run your c3 up to 120mph. Where are you located because I don't want to be around you.
Second -you are using more energy or fore to do the same required work using a lower air pressure.
Third- unsafe and sloppy handling increasing braking and steering especially on wet and oil slicked roads.
Lastly it is not recommended by GM (the manufacturer) or BF Goodrich to run 20psi in their tires. You are also welcome to check with ASE, they would like to hear your results and findings.

Now in your defense maybe your pressure gauge is an antique and you really have more pressure than you think. Or possibly your Vette is on a 4 wheel drive chassis where they run low tire pressure for off road in that case please post in a 4 wheel drive forum this is for Corvettes.
Now the correct answer for the correct pressure is see your owners manual or vehicle placard. You can adjust your pressure from there. Do not go above the max pressure or below the minimum indicated on the sidewall.

 

The sidewall never shows a minimum pressure; just a maximum pressure for a maximum load which it'll never see on a C3.

 

yes you are correct I was mistaken!!!! see... its not that hard to say

 

I wouldn't care if you found 100,000 people who would claim I'm wrong but that wouldn't faze me a bit. Right is right and wrong is wrong and I'm right.

 

My 3000 lb Camaro wore the centers out at 8 Lbs of pressure.....

 

Yep. Exactly my point.

 

Wow, that speaks volumes. I'm amazed that you would even put something like that out for all the forum to see. Believe it or not, I actually feel sorry for you.

In any case, this discussion has brought out some very good info and that's a good thing. I learned a couple things and I'll bet a few other folks did too.

 

Okay, lets take two identical 26" bicycles with 200# riders. One has 1" wide tires and the other has balloon tires. The 1" tires require 100 psi whereas the balloon tires require 50 psi. Are you getting the picture NOW?

 

There are way too many variables to consider, but these would be my two statements on the above hypothetical:

1) I totally agree that if "balloon tire" were fitted to two Corvettes of like weight, the "balloon tire" would require less pressure. Find me a Corvette with 16" inch wide "balloon tires" mounted on it so we can test the theory. Not a problem.
---how I arrived at 16" wide: 255 section = 25.5 cm = ~8.8"...call it 8" for sport...now multiply by two to account for the "balloon tire" thought.

2) Take the thusly fitted "balloon tire" Corvette and drive it at 120 mph. I'd love to see how that ends. And please don't bring up dragsters. Those are TOTALLY different. The tube-type bead-lock tires that are run in dragsters have absolutely no relationship to a road-going tire other than they are round, black, and made of somewhat similar rubber material.

My daughter is turning 12 in a couple of months. A few years from a Learners Permit. My biggest fear in the UNIVERSE right now is my having to nurse her to health after some yahoo hits her car. And under the "some yahoo" definition EASILY fits a person who thinks running the tires in their high-performance automobile at 20 psi. While occasionally going 120 mph to 'blow out the cobwebs'. This combination is simply staggering to me. Unbelievable.

For the record, I don't live in a world of absolutes. The "Right is right and wrong is wrong and I'm right" mentality is fundamentally flawed. That implies that there is NOTHING to be learned from the other 100,000 people. Never has ANYONE said that there is not a great deal of merit in adjusting tire pressures based on personal experience. I run pressures in the fronts/rears of each of my cars based on tire wear. I go near the max in the front of my V8-engine Volvo because it is so darn heavy and keeps wearing the shoulders.

The only point made here is that 20 PSI is pretty darn low. And it is DARN SURE low for a car that is admitted to travel 120 MPH on occasion...a speed that is no joke. I have personally never had my Corvette over 100.

 

Keith
You can't get him to admit it, this debate is all he has to do...
Sure he is right on the air to maintain a certain weight, but that is not all that is happening here. The vehicle dynamics - turning, braking, accelerating, and the construction of the tires - are a major part of the correct pressure to operate the tires. He refuses to factor this into his theory. All you can hope to do is point out this flaw to those who don't know.... and I think you have.

 

Balloon tires - From the era that TBTR is stuck in, the balloon tires were used as the suspension on many of the 3-wheelers and 4-wheelers. They are soft and mushy at the typical operating pressure. It's a completely different application and completely different tire structure. So, I'm not sure how or why anyone would expect the air pressure used in this application could have any bearing on the air pressure used in a road-going tire.

 

Here are a few examples of tire deflection under cornering or side loading.


about 1:20-


Do you really want to rely on an under-inflated tire when you need to do an emergency maneuver?

 

Yes, and now its a verbal battle between a mechanical engineer who knows what kind of pressures tires need versus weekend hobbyists who THINK they know what kind of pressures tires need

Complete arrogance
I think its a shame that you need to post you are a ME just to get merit. So a mechanical engineer that works on say heating systems knows what's best for a nuclear power system??? no I think not.
I'm sure we have other E's here but don't feel they need to post such nonsense.

So lets forget about tire pressure for a moment.
Lets say a given tire has a mileage of say 40,000. Lets times that by 3 still with me??? That will be 120,000 correct?
Tire manufactures say 6 years from the date on the tire to replace. They say this because the tires rubber gets old dries out and becomes brittle.(same with most things that are old). They say this can lead to blow outs roll overs and possibly pushing up some flowers.No joke here guys, especially if you run hard.

So lets take my little turd. It has the same tires on it from when I bought it. They are now 5 years old not even close to wearing out. I don't give a rats a$$ about trying to maintain the best pressure for the most useful tread life. its going to be time to replace them due to age. How many else are in the same boat?.
Now lets talk speed ratings on tires shall we?? Most are rated as S up to 112 mph. Now to use that 112 speed you need to raise the inflation pressure on most tires. For a T speed rated tire that will give you up 118. Again you will need to increase the air pressure.
I m sure many "weekend hobbyist" my already now some of this LOL
okay take care TBTRT off to clean my headlights. Thanks for the tip

 

Those videos are awesome. VERY, VERY telling.

To wrap up the exceptional points made by Mr. Jkippin, the "102S" rating that the BFG Radial T/A tire in the 255/60-15 size means it is rated for a tire capable of being loaded 1,874 lbs (each) to a top rated speed of 112 MPH.

From the Tire Rack web site: "It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded."

From the Bridgestone web site: Think of your tire’s speed rating as an indicator of the product’s capability under controlled conditions (i.e. fully inflated, vehicle running properly, good weather conditions). Speed ratings do not apply to tires that have been damaged, altered, under-inflated, overloaded or repaired.


From the Toyo web site: Speed ratings are based on laboratory tests that relate to performance on the road, but are not applicable if tires are underinflated, overloaded, worn out, damaged or altered.

During the speed rating process, the tire is loaded to full load and full pressure and tested under a particular regimen (10 MPH for 10 mins and increased 10 MPH every 10 min continuously until the tire no longer does what it is supposed to do).

"Underinflation" is defined pretty comprehensively as running a tire pressure lower than that recommended on the vehicle sticker inside the door sill. I will once again refer to the information provided in the sill of the 1982 Corvette. That's our starting point.

I love you guys. This has been an entertaining discussion. It has lead to a handful of new "tid bits" for me to consider as I make decisions in car life.

NOW I'm out.

 

You've made some excellent posts- well done! Everybody gets it except toobroke. His own posts have embarrassed him to the point that there's really nothing else that needs to be said.

 

Thank you for posting those great track racing type videos so we could see how a tire performs when pushed to it's limit when going around corners. If I were to track race my C3's I would certainly run higher pressures but since I don't and never will I'll continue running my lower 24/20 psi pressures to ensure maximum tread life and comfortable ride.

Now regarding the speed ratings. The very few times I run my C3 up to 100 mph or more its there for no more than 3 seconds maximum which is 200 times less than the 10 MINUTES stated in the speed rating specifications. If I were going to push my C3 to it's limit I would certainly boost the tire's pressures to their maximum for safety.

Now lets talk about the stock classes of drag racing. When a vehicle has enough power to spin it's tires at will the tire pressures are reduced a LOT to give the most traction. And how fast do these stock classes go? A 120 mph quarter mile is very common now days and you don't see those tires exploding when going thru the traps.

About 99.99% of my driving is at speeds of 50 to 65 mph on dry country roads in very low traffic conditions so I don't have any need to run maximum pressures in my tires. If you guys feel the need to do so go ahead but you'll be doing it at the expense of drastically reduced tread life.

 

YES...back in 1974..that may have been true.. but I am SURE that you agree that tire technology has improved.... AND...OH MY GOSH...TESTS that show that......I know.......they may have been wrong.

I choose NOT to follow your way of thinking because I HAVE a mind of my own.

And for the HECK of it.....set your tire pressure to 20psi as you state that you do and on a level shop floor...try to push your car....then air them up and see what happens. I can tell you for a fact that the air pressure makes a difference. And I am NOT pumping 44 PSI COLD in a tire.

DUB

 

HELLO. One video was driving down the street and through a roundabout at 20mph. It showed about as much deflection as the racing tire video. Read it again in case you missed it. A ROUNDABOUT AT 20MPH. Clue in and quit making up excuses for how the evidence doesn't apply to your crap.