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Articles

Comprehensive Vehicle Alignment Services

Retread Tires: Dispelling the Myths

Wheel Reconditioning and Retread Tires

Maintaining Your Tires

Reasons to Retread Your Commercial Tires

Retreads: Good for the Environment and Your Pocketbook

Air Pressure

The Benefits of Correct Air Pressure

Keeping the correct air pressure in your tires is as important as giving your engine a tune up. The economic benefits are perhaps even greater. With the right amount of air pressure, your tires wear longer, save fuel, enhance handling and prevent accidents. If you consider the liabilities of not maintaining the correct air pressure — poor gas mileage, loss of tire life, bad handling (perhaps even loss of control), and potential vehicle overloading — then the need to routinely add air to your tires will become clearer.

Check Air Pressure Routinely

Perhaps because our tires do so much without seeming to need any attention, we tend to overlook this important task. But tires do lose pressure, slowly but surely everyday, through the process of permeation. Generally, a tire will lose one or two pounds of air per month in cool weather and even more in warmer weather. Also, tires are subjected to flexing and impacts that can diminish air pressure. So, think in terms of refilling your tire just like you do your gas tank; actually that’s a good reminder, refill your tires every other time you fill up at the gas station. That’s the recommended interval. Another time to check air pressure is when the tires are rotated. many vehicles have different tire pressures on the front and rear axle, so remember to have this adjustment made. Also remember to have the pressure in your spare checked. The space-saver type spare requires a much higher air pressure level than other tires and is virtually useless (due to overloading) at lower air pressure levels.

Where to Find Air Pressure Information

The correct air pressure may be found in the vehicle owner’s manual or on the tire placard (attached to the vehicle door edge, doorpost, glove box door or fuel door). The placard tells you the maximum vehicle load, the cold tire pressures and the tire size recommended by the vehicle manufacturer. If you have trouble, see a local tire dealer for assistance. Check our locations to find the nearest Service Tire Truck Center.

Another valuable resource is the Tire Load/Inflation Tables. Your nearby tire dealer should have a copy. Not only will this document tell you the correct tire pressure for stock sizes,but it will provide the information on optional plus sizes as will. A good example would be the findings on a Honda Civic with the stock size 185/65R-14; the recommended air pressure is 28 psi., front and back. Plus two size is 205/45R-16 with a recommended air pressure of 36 psi. note how the air pressure increases with plus sizing to meet the load carrying capacity for the car.

Other Factors Change Air Pressure

Besides the routine air pressure checks, other circumstances necessitate a visit to the air pump. Seasonal changes or altitude changes create a rise or drop in air pressure (for every 10 degrees change in temperature, tire pressure changes 1 psi). But perhaps the most overlooked factor is vehicle loading for trucks and RVs. Since these vehicles can be configured and loaded in many ways, the proper inflation pressure should be determined by actual tire loads. This is best determined by weighing the vehicle; vehicle loading can change from trip to trip.

Environmental Impact

How can routine air pressure maintenance impact our environment? Consider that fewer tires per year would end up in the landfills and scrap heaps that trouble our ecology. How many tires are we talking about? We estimate that most drivers lose from 10% to as much as 50% of tire tread life due to underinflation. That’s a significant statistic. Now consider the extra fuel we burn to push cars along on soft, underinflated tires. Tires do require extra energy to roll if they are underinflated. While the statistics vary widely and inconclusively, the implications are staggering. So maintaining tire pressure is a small line item in our busy daily routines, but it adds up to big environmental consequences. We must all care and take action to do the right thing.

There is a lot of talk about putting nitrogen in truck tires.
Is this good or bad?

Nitrogen is an inert gas with large molecules and in theory it should have less osmosis through the tire casing as compared to air. Our tests show no significant advantage of using nitrogen over air in our commercial radial truck tires. That’s because our casing construction features chlorobutyl innerliners which does a great job of trapping air. In a lesser-brand tire with less advanced innerliners, nitrogen may help tires retain their inflation levels.

Heavy truck tires. Wheelbarrow tires. Golf cart tires. Off road tires. Light truck tires. All of these and more can be found at STTC’s industry-leading service centers. With 24/7 roadside service and 40 stores in 8 states – from truck tires in Eagle, PA to trailer readiness in Manassas, VA – STTC’s well-trained and certified technicians offer maximum flexibility and convenience.

Gas Pumps

Pinched at the Pumps

We’re all getting that feeling of being “pinched at the pump.” When you pass by a filling station, do you find yourself checking to see if the price went up even more? It can be a defenseless feeling; gas prices are something we can’t control…

While we can’t control prices, we can control how efficiently our vehicle is using the fuel. You are riding on one of the best ways to do that – keeping your tires properly inflated.

The Benefits of Correct Air Pressure

It has been stated that keeping the correct air pressure in your tires is as important as giving your engine a tune up. The economic benefits may even be greater. keeping your tires properly inflated may result in up to 10% better fuel efficiency. Your tires will also wear longer and have improved handling.

Check Air Pressure Routinely

Perhaps because our tires do so much without seeming to need any attention, we tend to overlook this important task. But the tires on your vehicle do lose pressure a little bit everyday. Generally, a tire will lose one or two pounds of air per month in cool weather. In warm weather it could be even more. So think in terms of refilling your tires just like you do your gas tank, which can help to be a reminder. Check your tires every other time you fill up at the gas station. That is a very good interval.

Terminology

Alignment

The mechanical condition of adjustable components within the vehicle’s suspension. When a vehicle is in alignment, the caster, camber, toe-in and thrust settings are set to specification. Severe impacts (hitting potholes or curbs) and worn suspension parts are the leading causes of misalignment.

All Season Tires

Tires designed to provide good traction in a wide variety of road conditions, including wet, dry and mud and snow. This design also limits the tire’s performance in extreme conditions, or when compared to tires built for a particular category.

Aspect Ratio

A term that describes a tire’s height-to-width proportion. If a tire’s sidewall height were 75% of its section width, its aspect ratio would be 75. In the tire size expressed as 295/75R225, the number 75 is the aspect ratio.

Balance

The state in which a tire and wheel assembly spins with all its weight distributed equally. A wheel balancer is used to place weights compensating for static and dynamic imbalances that exist in all assemblies. Not balancing an assembly may result in extreme vibration.

Bead

A round hoop of steel wires, wrapped or reinforced by steel cords, placed at the very inside of the tire’s diameter.

Bias Ply Tire

A pneumatic tire manufactured such that the plies are laid at alternate angles less than 90 degrees to the centerline of the tread. These criss-cross plies give the tire its strength, but generate heat during operation and limit the tire’s wear and performance.

Contact Patch

The portion of the tread that contacts the road during operation.

Cord

The strands of material forming the plies or layers of tire. Cords may be made from fiberglass, rayon, nylon, polyester or steel.

DOT Markings

Each tire has a required Department Of Transportation number imprinted on at least one of its sidewalls. That number begins with the letters “DOT” and may contain up to 12 additional numbers and letters.

The first and last digits are the most important for the tire owner. The first two letters/numbers identify the manufacturer of the tires.

For example, if the last four digits are 1601, then the tire was produced in the 16th week of 2001.

Hydroplaning

A skimming effect caused by tires losing contact with a surface covered by water

Maximum Inflation Pressure

The maximum air pressure to which a cold tire may be inflated; found molded on the tire’s sidewall.

Overall Diameter

The diameter of an inflated tire without any load

Overall Width

The distance between a tire’s outside sidewalls.

P Metric

Uniform designation of tire sizes in metric measurements originally introduced by American tire manufacturers in 1977. Commonly called “P-metric series.” A typical P-metric tire size is P215/70R-15.

Ply Rating

A method of expressing load carrying capacity in terms of plies. A 14-ply rating is now expressed as Load Range G; however, the tire is not built with 12 individual plies. Instead, it contains one or two plies of equivalent strength. The result is a cooler running, longer lasting tire.

Radial Ply

Tire construction where the cords in the body run at 90 degrees to the centerline of the tread.

Rim Width

Distance between the two opposite inside edges of the rim flanges.

Rolling Resistance

The force required to keep a tire moving at a constant speed. The lower the rolling resistance, the less energy needed to keep a tire moving.

Section Height

The height of a tire measured from the rim to the outer tread.

Section Width

The distance between outside side-walls, not including any lettering or design.

Series

A numerical representation of a tire’s aspect ratio. For example, 70 series indicates the tire’s section height is 70% of its section width (See Aspect Ratio).

Shoulder

The part of a tire where the sidewall and tread meet. Certain tire design features shoulder blocks for better traction.

Sidewall

The part of the tire between the tread and the bead.

Size

An expression that defines a particular tire in terms of its width, height, rim diameter, aspect ratio and construction type. 295/75R22.5 expresses tire size using the metric system.

Tread

The part of the tire that comes into contact with the road. The tread type is distinguished by the design of its ribs and grooves.

Treadwear Indicator

Narrow bands, sometimes called “wear bars,” that appear across the tread when 2/32″ of tread remains.

Tread Width

The width of a tire’s tread.

Valve

A device mounted in the wheel that lets air in or out of the tire. Valves include caps to keep out dirt and moisture and a check-valve to prevent air from escaping.

Ply Rating

How is the load capacity of a tire determined?

Let’s begin by reminding ourselves that it is not the tire that carries the load, but the air inside it. The tire is just the container for the air. So, if you need to carry more load, you need more air.
You might accomplish that with a larger air chamber or by forcing more air molecules into the same size air chamber you’d normally use for a tire with a lower load capacity.
In other words, you might use a bigger tire or a tire running at a higher inflation pressure. Either way, the tire needs to be strong enough to handle the higher capacity. The traditional ways of defining this are “Ply Rating,” “Load Range” and “Load Index.”

What is meant by “Ply Rating?”

In the early days of bias tires, casing strength was built up by adding layer upon layer of cotton fabric. The layers were placed with the thread in each layer at an angle to each other. That added strength, because the tensions would be distributed throughout the layers of fabric. The Ply Rating used to refer to the number of layers of cotton.

Ply Rating Load Range
2 A
4 B
6 C
8 D
10 E
12 F
14 G
16 H
18 J
20 L

Why aren’t there any odd numbers?

Since you have to have at least two plies to have a “bias” arrangement, bias ply tires always had an even number
of plies.

Is cotton still used?

Cotton went away a long time ago. One of the major improvements was making plies out of nylon. Nylon is so much stronger that if you’re old enough, you may remember seeing your tires stamped with the words, “2 Ply/4 Ply Rating.”
That meant there were only two nylon plies, but they were so strong the tire was equivalent to one made of four cotton plies.
And that’s about when things started to get complicated.

How so?

Ply materials continued to improve, especially with the introduction of steel ply materials and radial construction, making the old Ply Number less and less meaningful. And that resulted in the newer designation we use today, called “Load Range.”
On the chart, you can see how today’s Load Ranges correspond to the older Ply Rating system.

And why isn’t there an “I” or a “K” Load Range?

Just to avoid confusion. An “I” might, depending on the typeface, look like the numeral “1″ and “K” is a very common abbreviation for “kilo” meaning “thousand.”

What does the Load Range really mean?

Load Range indicates the maximum load recommended for the tire. This varies by tire size and inflation pressure: A bigger tire can hold more air and can be rated for a higher load. Also, a given tire size at a higher air pressure results in a higher rated load.

Load Capacities for Some “G” Load Range Single Tires

Size Maximum Single Load (lbs) Inflation Pressure (psi)
295/75R22.5 6175 110
285/75R24.5 6175 110
11R22.5 6175 105
11R24.5 6610 105
12R22.5 6610 105
12R24.5 7160 105

And here are the same tire sizes, but in a higher load rating:

Load Capacities for Some “H” Load Range Single Tires

Size Maximum Single Load (lbs) Inflation Pressure (psi)
295/75R22.5 6610 120
285/75R24.5 6780 120
11R22.5 6610 120
11R24.5 7160 120
12R22.5 7390 120
12R24.5 7830 120

So what’s the difference between tires of the same size but different load ranges?

It’s no longer the number of plies. Most radial truck tires, for example, have a total of five plies. There’s one steel body ply and four belts under the tread.
What is different nowadays is the strength of the steel cables in those plies or the number of cables per inch. We’re now at the point where we no longer add more and more plies, but instead, adjust the strength of the entire casing to achieve the desired load capacity.

Will a tire with a higher Load Range last longer?

It might, but it also might not. What usually determines tire life is the rate at which the tread wears and whether or not the tread wears evenly. Or how many retreads you can get from its casing.
As long as the tire has enough load capacity for the maximum load you will be putting on it, buying extra load capacity may not increase your tire life.

FAQ’s


Is it legal to repair a steer tire?

A steer axle tire with a puncture repair in the crown area that is 3/8 inch or less in diameter can be repaired using a rubber stem and a repair unit. If the injury is larger than that or in the shoulder or sidewall, the tire can be repaired with a section repair but it cannot be returned to the steer axle.

Is there an age limit to casings?

The simple answer is no. You cannot determine the retreadability of a casing based solely on age. Air pressure maintenance, the number of repairs, and the number of retreads also pay important roles, so the age is just another component of the inspection criteria. In fact, most truck tire manufacturers have at least a five year warranty on their casings, yet it’s not uncommon to see the life span of a well-maintained casing in the correct application(s) perform beyond that time period.

Why should I pay extra to properly repair a flat tire when plugging is so much cheaper?

Unless you have x-ray vision, any damage on the inside of the tire cannot be detected when plugging the tire on the rim. By removing the tire from the rim, inspecting the interior, and repairing the damage with a rubber stem and a repair unit, the integrity of the tire can be restored or potential problems can be identified. Proper tire repair also protects the casing, so the tire can either be retreaded or returned for credit.

Why should I check the lug nuts 50 to 100 miles after the wheels have been installed?

When wheels are installed, the bolted joint that encompasses the stud, hub/drum, wheels, and fastener is going to flex as soon as the axle is loaded. The initial flexing results in joint settling that can cause the wheels to become loose. By checking the lug nuts after the first 50 to 100 miles of service, any joint settling that has occurred can be corrected by tightening or replacing the fasteners.

What are the Red/Yellow Dots on a sidewall for?

A red dot applied to the sidewall of a new radial medium commercial truck tire indicates the high point of radial run out, and must be considered for optimal match mounting of the assembly. For steel wheels, align the red dot with the dimple. For the aluminum wheels align the red dot with the valve stem. Some new tires have only yellow dots and they should be mounted with the yellow dot aligned to the valve stem, on both steel and aluminum wheels. Always ignore the yellow dots on new tires that have both red and yellow dots. Red dots always over-ride yellow dots.

Must I replace my present tires with the same size tires?

Never choose a smaller size than those that came with the car. Tires should always be replaced with the same size destination (or approved options) as recommended by the vehicle manufacturer.

When buying just two new tires, should they be put on the front
or rear?

When radial tires are used with bias or bias belted tires on the same car, the radials must always be placed on the rear axle. Never mix radial and bias-ply tires on the same axle. When you select a pair of replacement tires in the same size and construction as those on the car, we recommend you put them on the rear axle. A single new tire should be paired on the rear axle with the tire having the most tread depth of the other three.

Tire Videos

The images and videos below provide examples of the superior tire service you can expect from an STTC service center. To view all videos, please visit the Michelin Website. Be sure to check out the newest video titled “Wheel End Safety.” This is a must see video for fleet truck and tire safety.


Tire FAQ

Introduction to
Michelin

Pre-Trip Inspection
 

Tubeless Radial
Truck Tire Safety

Run-Out & Match
Mounting

Axle Parallelism,
Axle Thrust, Toe,
Ackermann, Plus
 

Laurens Proving
Grounds

Saving Through
Scrap Tire Analysis

AntiSplash
Technology
 

Steer Run Flat

What Every RV
Owner Should Know

How A Tire Is Built
 

Fundamentals of
Tire Wear

Troubleshooting
Vibrations

Rapid Air Loss,
Truck – The Critical Factor