Tyre choice

Tyre choice

Postby Taziiy » Tue Jan 23, 2007 10:53 pm

How to Pick the Right
Tires for your Truck
Selecting or buying truck tires is one of the best ways to improve the performance of your truck, but making that decision can be difficult if you have never been faced with it before. One of the first considerations to make is where you will be driving your vehicle. Do you drive mostly on the street, a combination of street and off road, or exclusively off road? Most truck tires that are equipped on a new vehicle from the factory are what would be considered standard “street” driving tires. To go off road in difficult terrain like steep rocks or mud, the biggest factor you have to overcome is height so you will need to choose a bigger tire that is at least one or two sizes taller, regardless of the tread type. A good place to start is by looking at the decal inside your driver side door or glove compartment. In there you will see the standard tire allowed and the biggest possible choice you can have if your vehicle has it as an option.

Here are some important steps in purchasing truck tires and wheels for your truck:

Be able to read the truck tire sidewall to determine the over-all performance of your chosen tires. Every truck manufacturer has separate ratings for the tires, but what is important to you is the warranty coverage. Who will give you the most in savings for your truck tires and wheels?
Truck tire size rating is usually shown in metric, which can be traced on the side of your original truck tire. However, when better performance is required for your truck, you can select an upgrade to what your current rating is as long as you keep this in mind: Never go to the extreme, always stay in the middle ground of what the list suggest to make sure that the tires you get are not out rated for your vehicle. If they are then reduced tread life and other issues can occur.
Truck tire speed rating is the speed range at which a truck tire can be used in different speed and load conditions. For example, the most common designation uses the “V” category for 240 km/h or 149mph speed range and the “Z” speed rating for top speed. This ensures that you can safely drive the tire on the speed you choose.
Truck tire load rating index is the assigned numbers delegated to a tire that will tell you the safe load that can be used for a tire. Again use moderation when selecting this but know first what kind of load you will be using on the tires. The higher the number the higher the load they will handle.

When selecting truck tires that you are not familiar about, always go to the vehicles identification sticker (located in the vehicles door or glove box) or owners manual as your guide. In there you will see the speed, rim size and allowable payload intended for your truck tire and wheel.

Choosing the tire that’s right for your truck involves numerous considerations. But to make the process less scary, keep these two simple guidelines in mind when considering tires. First, know your expected needs and driving uses. This consideration is important to overall driving enjoyment and a well-run tire shop will help you determine your tire needs before you lay down any green. Second, find a source or store that you trust enough to recommend the type of tire that fits your needs. Remember, the sales people don’t know your needs, you have to tell them. If they’re good, they’ll ask you the right questions to come up with the right tire.

You might be wondering what some of the questions could be. Here’s a quick list of what you should think about before entering a tire store:

Tread life considerations: What’s your idea of how long a set of tires should last? Keep in mind that in some instances, a tire’s wear rating is done through manufacturer testing and may not be the most accurate representation of a tire’s true life expectancy. One way to get a handle on a tire’s projected life expectancy (besides what they’re warranted for, say, 40,000 miles for example) is to look at part of the UTQG (Uniform Tire Quality Grading) rating. The U.S. Department of Transportation requires each manufacturer to grade its tires under the UTQG labeling system and establish ratings for tread wear, traction and temperature resistance.

Wet weather requirements: Most of us live in a climate where inclement weather is a factor at least part of the time. Clearly if you live in, say, Washington or Oregon, you’ll want to look more closely at a capable wet-weather tire for your truck than if you’re living in Arizona or Nevada. For those of you in Snow Belt states, some kind of four-season type of tire will be the minimum you should consider if not an all-out snow tire for the winter that you swap for standard tires in the milder months.

Speed rating: Even in the plains and Western states like South Dakota, Nebraska, Idaho, Montana, New Mexico, Colorado, Wyoming, Utah, and Nevada where the rural interstate speed limit is 75 mph, how often do you think you’re going to need a tire that’s speed rated for anything over 150 mph? Be honest and knock down your required speed rating to, say, an H-speed rated tire that’s still good for 130 mph.

Ride Quality: A low-profile tire such as a 50 or a 40-series looks great, but can be harsh over bumps or potholes when compared to a 55 or 60. In general, a lower profile tire also exposes the wheel to damage more easily. Lower profile tires also have stiffer sidewalls, which improves handling but increases rides harshness. It’s all about compromise and there’s no such thing as a free lunch. If you do any off roading at all then make sure you stay away from low profile tires. When going over rough terrain you want more sidewall in between the ground and your trucks rims. Otherwise, a dented wheel will be the result.

Most online stores have the proper size index from where you can input your vehicle information. After feeding this info, a corresponding truck tire’s specs will be given to you based on the different brands available. You can then make your comparison.

While some truck tires are lower quality than others, there are so many good ones out there that you will usually have several possibilities from which to choose. We’ve discovered here that it’s best to be straightforward with what you really need and factor it in with that ever-present budget consideration. Then you will have the ability to keep your truck well grounded.
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Postby Taziiy » Tue Jan 23, 2007 10:59 pm


Offset: The distance from the centerline of the wheel to the face of the mounting surface of the wheel that contacts the hub.

Negative offset: Indicates the mounting pad is behind (or inboard) the centerline of the rim. This is often found on standard rear-wheel-drive vehicles and on so-called reversed rims.

Positive offset: Refers to wheel s that have the mounting pad in front (or outboard) of the centerline of the rim. Most often found on front-drive applications.

Centerline: The exact center of the rim width. The width is measured between where the tires rest.

Bolt circle size: The bolt circle represents the diameter of an imaginary circle that goes through the center of the bolt holes (A). On a four-lug wheel, this is determined by measuring the distance between opposite holes (B). For a five-lug application, measure the center-to-center distance between two adjacent wheel studs (C) and reference the table below,

2.645 in. = 4 ½ in. circle

2.792 in. = 4 3/4 in. circle

2.939 in. = 5 in. circle

3.233 in. = 5 ½ circle

Moving up to a larger tire and wheel requires planning, considering the effects on gearing. The most important factor is the actual rolling height and width of the tire. Actual height often differs from nominal heights, so measuring the actual rolling radius of the tire would be the ideal way to know the exact effect on gearing, speedometer, etc. But measuring rolling tires, which may "grow" a little at speed, is impractical, so tires are measured as they sit.

There is no more practical method for sizing new tires than to simply tape measure the old against the (proposed) new rubber. For most calculations, this measurement is accurate enough. However understanding tire-size nomenclature is important, and will help immensely in getting the most tire with the least hassle.

Many types of high-performance specialty-tread truck tires are sized according to height, width, and wheel diameter. A tire listed as a 33/12.50R-15 is a 33-inch-tall radial (R), 12.50 inches wide and built for a 15-inch wheel. If there is no R in the designation, you can assume it is a bias-ply tire. Keep in mind, this 33-inch diameter is a nominal number which could vary by as much as seven percent (in this case, more than two full inches) according to industry standards.

Today, more and more tires built for light trucks and SUVs carry metric designations, which can be very helpful when figuring your tire and wheel upgrade. First, a few terms:

Diameter: The actual height of the tire measured through the center, in inches. Not always marked on the tire.

Section height: The vertical distance between the edge of the wheel rim and the top of the tire tread. Expressed in millimeters, this number is not usually marked on the tire.

Section width: The horizontal distance between the tire’s sidewalls. Expressed in millimeters, this number is usually the first number in a metric designation.

Aspect ratio: The relationship between section height and section width. The higher the aspect ratio number, the skinnier the tire, relative to its height. An aspect ratio of 75 means that section height is 75 percent of section width. A tire with a lower aspect ratio of 60 will have a "lower profile" than a 75, and a fatter look. This is normally the second number listed on a metric-sized tire.

LT : Metric tire designation a light truck tire.

ST : Designation for a trailer tire.

P : Designation for a passenger-car tire.

Looking at a tire marked LT305/85R16, the buyer knows that it is a 16-inch radial tire built for light trucks with an 85-percent aspect ratio and 305 millimeters of section width. To determine the height of the tire, you must calculate its section height in inches, dividing by 25.4, the number of millimeters in an inch (see equivalency chart). Next, convert the aspect ratio to a decimal by dividing by 100. Multiply the quotients of these two numbers to find the section height in inches. Double that figure and add the wheel diameter, and you will have the tire’s height. Using a 305/85R tire as an example, the equation works out as:

2 x section width x aspect ratio x aspect ratio + wheel size
25.4 100

2 x 305 x 85 + 16 = 36.4 inches
25.4 100

Some of the most popular tire sizes, and their approximate metric equivalents, can be found in the chart below.

Flotation Diameter (in.) Metric size
27x8.50R14 26.5 225/75R14
27.5 215/75R15
29x9.50R15 28.5 235/75R15
30x9.50R15 29.5 245/75R15
31x10.50R15 30.5 265/75R15
32x11.50R15 31.5 295/75R15
33x12.50R15 32.5 315/70R15
33x12.50R16 32.8 285/75-16
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