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  #16  
Old 05-06-2006, 10:21 PM
AutoTchr AutoTchr is offline
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Quote:
Originally Posted by Suby Fan
the main issue im seeing here is every one is running to high of pressure causing reduced traction when a tire is over inflated it dosent make full contact with the ground
Why would this be true with manufactures emphasizing safety more and more and at the same time increasing the recomended tire pressure?

A tire is safer if it is run at its max inflation or a couple of pounds less. Not overinflated, not 9psi less as you suggest.
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  #17  
Old 05-07-2006, 12:26 AM
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Tire pressure

Quote:
Originally Posted by AutoTchr
Why would this be true with manufactures emphasizing safety more and more and at the same time increasing the recomended tire pressure?

A tire is safer if it is run at its max inflation or a couple of pounds less. Not overinflated, not 9psi less as you suggest.
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.

Recommended Inflation Pressure
Many people ask "what air pressures do you (meaning tire companies) recommend for cars under normal conditions?" The answer is "we recommend what the vehicle manufacturer recommends."

What criteria do the car manufacturers use to determine inflation recommendations
* Ride
* Load capacity
* Traction, wear
* Fuel economy/Rolling resistance

.....are all correct. But, consider another question: "Why did Ford recommend 30 in the front and 34 in the rear on a 1997 Crown Victoria?"

The additional air stiffens the sidewall and makes it more stable. In order to achieve the handling, tracking, and other driving characteristics, one of the things the manufacturer can do is balance front to rear handling by adjusting the tire pressures. In adding the same air pressure in the front as the rear you will change the handling characteristics from what the manufacturer intended. Quite a few station wagons and light trucks have different pressures for the front and rear. But, it's not just station wagons and light trucks; it's also Porsches, Nissans, Corvettes, Hondas, and BMW's to name just a few. Quote from Firestone"



Now what tires came on the SVX.1992 225/50/16. but what rating- V-- Z --Wr-- I got Fuzion by firestone --225/50/16 with a ZRi with a wr16 which is a high speed touring tire Max is 51LBS , My sticker shows 28 rear 33 front with stock tires, Tire pressure is hard on the steering senser and the rear end with the LSD also gas mileage
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  #18  
Old 05-07-2006, 12:07 PM
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Just a reminder that the max recommended on the tyre is a COLD inflation pressure, or at least ambient.

Also the manufacturer will always want the car to ride as smoothly as possible, so they are always using a compromise between comfort (low pressure) and performance/tyre wear etc (higher pressures) - hence what we are finding here that many people run their tyres at higher pressures due to the increase in performance benefits.
Other things to consider, especially if your roads aren't the best is that a higher pressure increases your road noise as well.


Personally I run 32r/37F cold - always maintaining that 5psi difference. Anything more and she roars at me.. I find you've gotta check your pressures all the time. Certainly makes a difference too, the 4wd system really works (or should I say feels) a lot better if you have the pressures nicely balanced.

Matt
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  #19  
Old 05-07-2006, 12:10 PM
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Quote:
Originally Posted by Suby Fan
the main issue im seeing here is every one is running to high of pressure causing reduced traction when a tire is over inflated it dosent make full contact with the ground
You require a massive overpressure to do this with todays wider tyres, certainly >60psi would do it, but below that I would say you're having more issues with wear and "feel" of the tyres you're on.
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  #20  
Old 05-08-2006, 06:23 AM
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I started "over"-inflating my tires years ago on the suggestion of a garage owner after I wondered aloud what it was about my driving style that scrubbed tread off the tire shoulder right down to the cord while leaving plenty of healthy tread in the middle. Those few extra pounds of air not only stiffen the sidewall, as others have mentioned, but cause the tire to ride-up more on the center of the tread footprint. Just look at the profile a modern radial under weight and it's easy to understand why they tend to wear more at the shoulder. As an incidental plus, tires with less flex return better fuel economy.

Of course, I agree that one shouldn't exceed the maximum PSI recommended by the tire manufacturer. But generally speaking, UNDER-inflation is the bugabooo that causes heat buildup that can lead to tire (usually sidewall) failure. I had that happen once: Slow leak on an Interstate highway run, started feeling a shudder at reduced speed, took a look and found the tire not flat but very low, but with a big knot in the sidewall, literally smoldering. It's a wonder that thing didn't blow.

dcb
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  #21  
Old 05-08-2006, 08:59 AM
AutoTchr AutoTchr is offline
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AJ4U2,

I was not really asking the question that you quoted. It was part of a reply to subyfan. But thanks for answering anyway!!
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  #22  
Old 05-08-2006, 02:21 PM
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I just have an anecdote from this morning's commute.

I pulled up behind a Pathfinder that seemed to be tilted. I look closer and her rear right tire appeared to be under inflated by about 20lbs...

Some people are completely oblivious.

Not only drivers, but some teenaged female jaywalked across a 3 lane road without even looking. Luckily she heard the Blizzaks screaming at 40mph as I was about 20ft away cuz I had no intention of stopping for the dumb *****.
She had a stupid surprised look on her face like I came out of nowhere.

Noisy tires though. Saved her life they did.

Stupid ass people.
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  #23  
Old 05-08-2006, 03:23 PM
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I see it everyday. High schoolers walk across the traffic all the time. They ASSUME that people will see them and they ASSUME that people drive on good brakes. I know otherwise. One dummy with bad brakes runs over another dummy that doesnt look both ways.

I have seen rotors that are completely separated from the hub. I have seen brake pads gone missing and the caliper piston scraping the rotor.
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  #24  
Old 05-08-2006, 06:05 PM
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40F/36R (cold) on my car. Have checked them when hot and read 44psi front.
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  #25  
Old 05-08-2006, 07:02 PM
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47/44 on my 225/45/17

ran right around 40/36 on stockers on the wife's svx with good results.

The stock pressure suggestion is ridiculously low. The shoulders run to cords way too fast and the car rides too soft.
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  #26  
Old 05-08-2006, 10:10 PM
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Quote:
Originally Posted by AutoTchr
I see it everyday. High schoolers walk across the traffic all the time. They ASSUME that people will see them and they ASSUME that people drive on good brakes. I know otherwise. One dummy with bad brakes runs over another dummy that doesnt look both ways.

I have seen rotors that are completely separated from the hub. I have seen brake pads gone missing and the caliper piston scraping the rotor.
HA! yesterday i saturn came in and i was looking at the brakes....
i glanced at the rear rotor and thought humm that thing has a lot of surface rust... WAIT A MINUTE where the f is the caliper?!?! under further examination it seemed that it snaped off right from the slide bolts and the brake hose was being cut off by a bolt nut and two wahers (custom mod there)
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  #27  
Old 05-08-2006, 11:21 PM
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Quote:
Originally Posted by Suby Fan
HA! yesterday i saturn came in and i was looking at the brakes....
i glanced at the rear rotor and thought humm that thing has a lot of surface rust... WAIT A MINUTE where the f is the caliper?!?! under further examination it seemed that it snaped off right from the slide bolts and the brake hose was being cut off by a bolt nut and two wahers (custom mod there)
In this small country we have a "Warrant of Fitnss". Any car not displaying a warrant on the windscreen, is given a ticket. Parking wardens as well as police can issue these. Older cars must be inspected every six months and a new warrant issued. Newer cars every twelve months. Brakes must check out on a test machine and a carefull visual inspection covers hoses etc. All items relative to safety are covered.
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  #28  
Old 05-09-2006, 06:13 AM
dcarrb dcarrb is offline
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Quote:
Originally Posted by Trevor
In this small country we have a "Warrant of Fitnss". Any car not displaying a warrant on the windscreen, is given a ticket. Parking wardens as well as police can issue these. Older cars must be inspected every six months and a new warrant issued. Newer cars every twelve months. Brakes must check out on a test machine and a carefull visual inspection covers hoses etc. All items relative to safety are covered.
Once upon a time every auto in Georgia was subject to an annual safety inspection, but that made too much sense, so it was discontinued. Now there's no uniform standard whatsoever for passenger vehicle fitness. In my area we don't even have emissions inspections.

dcb
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  #29  
Old 05-09-2006, 06:06 PM
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Quote:
Originally Posted by dcarrb
Once upon a time every auto in Georgia was subject to an annual safety inspection, but that made too much sense, so it was discontinued. Now there's no uniform standard whatsoever for passenger vehicle fitness. In my area we don't even have emissions inspections.

dcb
AMAZING !!! One of the things I am very happy about down here, is that trailer hitches and trailers are well covered. A trailer on the loose is VERY bad news !!
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  #30  
Old 05-09-2006, 06:30 PM
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In new york they were really tight on the inspections - yearly for every car registered and they actually performed a good inspection as long as you didn't just go to a shady shop and slip the guy some cash. The cops up there will pull you over in a heartbeat and ticket you for an out of date inspection sitcker also.

In south carolina there are no required vehicle inspections and there are alot of cars on the road with bald tires, taillights that don't work, etc. I hate inspections because it is a pain in the neck to go through every year but I think it does make the roads safer to require inspections.
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