What’s the best way to replace a single tire or pair of tires on a vehicle?
Never mix radial and bias ply tires on the same axle (because of their different handling characteristics discussed earlier in this article)
If you have radials on one axle and bias ply on another, run the radials on the rear
If you are replacing a pair of tires, put the new ones on the rear
If you have to replace just one tire, pair the new one with the best of the other three and run them on the rear
What is the maximum weight it should take to balance my tire?
The industry standard is approx. 2% of the tire weight. So, because a 42” TSL weighs about 100lbs, 2% is 2lbs or 32ozs of lead! That’s industry standard. Keep this in mind next time you’re wondering why your 42” Swampers don’t balance well - it’s not because of the quality of the tire – it’s because it weighs so much – it’s just the physics of dynamically balancing that much rolling mass – and it’s the price you must pay for large, aggressive tires.
What are tires made of?
The average steel-belted radial tire is made up of:
28% Carbon Black
27% Synthetic Rubber
14% Natural Rubber
10% Steel Wire
10% Extender Oil
4% Organic Fiber
4% Other Petroleum Products
3% (S, ZnO, Ti02, etc...)
How round is round?
Generally, a passenger-car tire is considered round if it has less than 0.030" radial or lateral runout. An LT tire is considered round if it has less than 0.060" radial and lateral runout.
Does it matter how I mount the tire on the rim?
There are two schools of thought on this.
The first has that you should mount the high-spot of the tire (often indicated by a red dot) aligned with the low-spot of the rim (often the valve hole, but may be separately indicated, depending on the wheel in question).
The other method is to mount the lightest spot of the tire (often indicated by a yellow dot) aligned with the heaviest spot on the rim (the valve).
What effect do different rim widths have on my tires?
The wider the rim, the greater the section width. Section width increases about 0.4” for each additional inch of rim width (and vice versa).
A wider rim increases the distance between the beads, which results in a straighter sidewall, which stiffens it. The straighter sidewall also exposes the rim, making the wheel more susceptible to damage.
A narrower rim pulls the beads closer together, curving the sidewalls. This increased curvature allows the sidewall to flex more readily. It can also help with bead retention at lower air pressures, although using narrow rims is no substitute for beadlocks.
Why do race teams use Nitrogen in their tires instead of air?
Race cars, aircraft, and other ultra-high performance machines use Nitrogen in their tires instead of air because, when heated or cooled, nitrogen has a much more consistent rate of expansion and contraction than air.
This is because air contains varying amounts of moisture due to changes in the relative humidity. This water vapour causes air to be inconsistent in its rate of expansion and contraction.
What is the difference between an LT and P tire of the same size?
LT tires that are load range C or greater tend to be rougher riding and noisier than their P-Metric counterparts and more expensive since the LTR size equivalent to the P-Metric has heavier body ply construction and the tread lugs are generally more aggressive.
P and LT tires are also often rated slightly differently. If P-rated tire is used in an LT application, you need to de-rate the sidewall load capacity by 9% - 10%.
How should I store unmounted tires?
Store them on their sides in a clean, cool, dry, dark, and well-ventilated area (but with a minimum of circulating air).
Keep them out of direct sunlight.
Keep them away from sources of ozone such as operating welders and electric motors. Store tires away from the furnace, sump pump, power tools, etc.
If you must stack them, do so only to a height where the bottom tire retains its shape, usually no more than four high.
What about tires on my rig in storage?
Store the vehicle on blocks to remove all weight from the tires.
If the vehicle cannot be blocked up, completely unload it so minimum weight will rest on the tires. The surface should be firm, reasonably level, well drained, and clean.
Keep tires inflated to recommended operating pressure.
Move the vehicle at least every three months to prevent ozone cracking in the bulge area, to help maintain oil dispersion within the rubber compounds, and to prevent a "flat spot" from developing.
What’s so special about “ST” tires for my trailer? Why can’t I replace them with P tires with an equivalent load rating?
“ST” or “Special Trailer” tires are designed specifically for trailer service, whether they are radial or bias ply. They feature materials and construction to meet the higher load requirements and unique demands of trailering. For example, ST tires are constructed for better high speed durability and bruise resistance under heavy loads and they have stiffer sidewalls that help to reduce trailer sway. Passenger car (P) or light truck (LT) tires do not have the structural components to provide stability and handle the stress and dynamics imposed by a trailered load.
ST tires typically have larger chords in the body plies and the steel wire in the beads has a larger diameter and greater tensile strength to meet the additional load requirements. ST tire rubber compounds also contain more chemicals to resist weather and ozone cracking.
Similarly, trailer tires are designed for use on trailer axle positions only, not for the loads applied to, or the traction required by, drive or steering axles.
Are there special considerations with trailer tires that are not present with other tires?
While the majority of the following factors also apply to other tires, they have special significance for trailer tires. There are two main reasons for this. First, absolutely nothing good happens when you experience a tire failure while towing a heavy load. A blowout in your car during the morning commute is bad enough – but when it happens as you’re towing 4 tons at 70mph in the dark on a curvy, rain-slick road the stakes are incredibly high! Secondly, trailer tires tend to get used, abused, and neglected or forgotten about. Because we don’t use them every day and because there’s nothing sexy about them we tend to take them for granted and not pay them the attention they deserve. We do so at our own peril!
Inflation
· Always inflate trailer tires to the maximum inflation indicated on the sidewall.
· Check inflation when the tires are cool and have not been exposed to the sun.
· If the tires are hot to the touch from operation, add 3 psi to the max inflation.
· Underinflation is the number 1 cause of trailer tire failure.
· Tires lose approximately 1 psi per month as well as 1 psi for every 10-degree drop in temperature.
Load Carrying Capacity
· All tires must be identical in size for the tires to properly manage the weight of the trailer.
· The combined capacity of the tires must equal or exceed the GVW of the axle.
· The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent. If the actual weight is not available, use the trailer GVW
· If a tire fails on a tandem axle trailer, you should replace both tires on that side. The remaining tire was likely subjected to excessive loading.
· If tires are replaced with tires of larger diameter, the tongue height may need to be adjusted to maintain proper weight distribution.
· One key to extending tire life on a tandem- or tri-axle trailer is to ensure that the trailer is riding level, thus distributing the load equally among all the tires. If the trailer tongue sits too high, the rear tires may bear the brunt of the load: with the trailer tongue too low, the front tires may be unduly stressed.
Speed
· All "ST" tires have a maximum speed rating of 65 mph.
· As heat builds up, the tire's structure starts to disintegrate and weaken.
· The load carrying capacity gradually decreases as the heat and stresses generated by higher speed increase.
Time
· Time and the elements weaken a trailer tire. The structural components and bonding agents slowly break down. This is due primarily to internal air pressure forcing oxidation of the tire materials. Ultraviolet rays also attack the rubber on a tire left exposed to the sun. As a result, a 15-year-old tire that was rarely used may look virtually new, but because of the ravages of time and elements, it does not have the same strength as when it was new.
· In about 3 years roughly one third of the tire's strength is gone.
· Three to five years is the projected life of a normal trailer tire.
· It is suggested that trailer tires be replaced after 3 to 4 years of service regardless of tread depth or tire appearance.
Mileage
· Trailer tires are not designed to wear out.
· The life of a trailer tire is limited by time and duty cycle.
· The mileage expectation of a trailer tire would be 5,000 to 12,000 miles.
Storage
· The ideal storage is in a cool, dark garage at maximum inflation.
· Use tire covers to protect the tires from direct sunlight.
· Use thin plywood sections between the tire and the pavement.
· For long term storage: Put the trailer on blocks to take the weight off the tires, lower the air pressure and cover tires to protect from direct sunlight.
Info courtesy of Billavista
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