All About Wheels & Tires 101

[BradMph]

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Wheel Bolt Pattern Reference:
Lug pattern, or bolt circle is the diameter of an imaginary circle formed by the centers of the wheel lugs. Bolt patterns can be 4, 5, 6 or 8 lug holes. The bolt pattern is comprised of two numbers - the first indicates how many bolt holes are on the wheel, and the other describes how far apart they are. for example, a bolt circle of 5x108 would indicate a 5 lug bolt pattern in a circle with a diameter of 108mm.

Dual Bolt Pattern:
More and more manufacturers are building their wheels with two bolt patterns. This expands the number of fitments the wheel applies to. For example: a wheel with a 4-100/114.3 bolt pattern has 8 lug holes and will fit both 4-100mm and 4-114.3mm fitments.

The diagrams indicate the proper measuring methods

Four (4) Bolt

Measure center to center of two holes directly across from each other.

Five (5) Bolt

Measure from the CENTER on one hole to the BACK of the third hole. This is the easiest and most accurate way to "Estimate" a 5-lug bolt circle. You can also measure from the CENTER of one hole to the CENTER of the third hole using 1.05 multiplier to find your bolt circle.

Six (6) Bolt

Measure center to center of two holes directly across from each other.

Eight (8) Bolt

Measure center to center of two holes directly across from each other.

Wheel Lug Nut / Bolt Torque Sequence


Bolt Pattern Conversions


Offset:

The distance from the mounting surface of the wheel to the true centerline of the rim. A positive offset means the mounting surface of the wheel is positioned in front of the true centerline of the rim / tire assembly. This in effect brings the tire in to the fender well more. Conversely, a negative offset means the mounting surface of the wheel is behind the true centerline of the rim / tire assembly. This will cause the tire to stick out away from the vehicle.

H = High Positive or FWD (Front Wheel Drive) typically +45, 40, 35 offsets

M = Medium Offset or RWD (Rear Wheel Drive) Typically +20 offset

L = Low Offset or RWD (Rear Wheel Drive) Typically 0 offset

Wheel Plus Sizing

Plus sizing your wheel & tire combination was designed to enhance vehicle performance and looks by allowing fitment of larger diameter rims and lower profile tires. The theory is that while making these changes, you keep the overall tire diameter within 3% of the original equipment tires. This is important because larger variances can cause problems with transmission shift points which can decrease fuel mileage. It can also confuse braking system computers which can even lead to brake failure,as well as cause inaccuracies in your speedometer.
Changing to a wider tire requires reducing the aspect ratio (the second number in the sequence of numbers that describes the tire's size). Since the aspect ratio is a percentage which is used to calculate the height of the tire's sidewall, if follows that if a larger number is used for the width, a smaller number must be substituted if the final result is to remain the same - which is the objective of Plus Sizing.

Here's the rule of thumb for "plus sizing":


Plus 0:
Changing to a wider tire size while using the same diameter wheel.

Plus 1:
Increase section width by 10mm
Decrease aspect ratio by 10 points
Increase rim diameter by 1 inch

Plus 2:
Increase section width by 20mm
Decrease aspect ratio by 20 points
Increase rim diameter by 2 inches.

Advantages of Plus Sizing

Stability: Larger tires will generally improve stability, handling and cornering due to larger footprint (contact patch) and stiffer sidewalls.
Braking Distance: Wider tires can also decrease braking distances required on dry pavement.

Disadvantages of Plus Sizing

Cost: Larger wheels typically cost more. Wider tires tend to be more expensive.
Performance: Improvements beyond what is achieved in a Plus One sizing are negligible.
Ride: Low(er) profile tires generally have stiffer sidewalls, which can effect ride comfort.
Fuel Efficiency: Larger and wider wheels decrease fuel efficiency and increase consumption.
Handling: A larger tire footprint can increase the time taken for "return to center" (steering).
Winter Performance: Wider tires perform worse in winter driving conditions. Narrower tires exert more pressure on the contact patch, maintaining better road contact in winter driving conditions (snow).

Hub Center Bore:
Relates to the center hole in the wheel that centers the wheel on the hub of the car. Since most wheels are mass produced, they have a large center bore to accommodate several different vehicles. If this is the case, it is recommended that you use a hub ring. Hub rings are hard plastic or metal ring that fits between the wheel and the vehicle. This centers the wheel perfectly on the hub ensuring that there is no run out when the wheel is installed on to the vehicle. Without hub rings it is possible to get vibrations even if the wheel / tire assembly is perfectly balanced.

Torque:
All alloy wheels should be installed using a torque wrench. This ensures that the wheels are not too tight or too loose. Check your vehicle's manual for correct settings. When you install wheels for the first time, you should re-torque wheels after about 100km to 150km (60 to 90 miles). Always refer to Owner's Manual for proper factory specifications that take precedence over the listed recommendations.
12mm = 70~80
7/16" = 55~65
1/2" = 75~85
14mm = 85~95
9/16" = 95~115
5/8" =135~145


DOT- means the tire meets or exceeds Department of Transportation's safety standards.
MA- is the code number assigned by DOT to the manufacturing plant.
L9- is the tire size; in this case a P195/75R14.
ABCD- is a group of up to four symbols, optional with the manufacturer, to identify the brand or other significant characteristics of the tire.
036- means the tire was made during the 3rd week of 1996. The first two numbers designates the week, the last number the year.