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Wheel & Tire Tech Info

Wheel Tech Info Guide

Tire Tech Info Guide

Bolt Patterns

A wheel’s bolt-circle-diameter is the diameter of an imaginary circle drawn through the center of the wheel’s mounting-bolt holes. Bolt patterns vary by vehicle make and model.

If the pattern has an even number of mounting holes (four, six or eight lugs) simply measure from the center of one stud hole directly across the center of the wheel to the center of an opposite stud hole.

With a five-lug pattern, measure from the center of one stud hole to the center of the farthest stud hole, skipping the adjacent hole. The resulting measurement is slightly smaller than the actual bolt-circle diameter.

For example, a vehicle with a bolt pattern of (5 x 120) means this vehicle’s hub has five bolts or lugs, which measure 120 millimeters apart from one another diagonally.

Centerbore and Hubcentric Rings

This refers to the opening in the back of the wheel that centers the wheel on the hub of the car. Since most wheels are mass produced, they have a large centerbore to accommodate different vehicles. If there is a vibration problem, it is recommended that you use hubcentric rings. Hub rings are hard plastic rings that link the wheel to the vehicle. This centers the wheel and makes your wheel hubcentric. Without hub rings it is possible to get vibrations even if the wheel and tire package is completely balanced.

Plus Sizing

Plus sizing your wheel and tire package can enhance vehicle performance and looks by allowing fitment of larger diameter rims and lower profile tires. If you make plus sizing changes, keep the overall tire diameter within 3% of the original equipment. Exceeding 3% can lead to a number of problems.


It’s important to torque the lugs on your wheels properly. The best way to torque your wheels is by hand, using a torque wrench. Wheels are frequently over-torqued onto a vehicle’s hub bore. Over-torquing can lead to brake problems or cause the lugs to break off the wheel. Your owner’s manual contains the optimal torque specifications for your vehicle. Always re-torque after your first 50 miles.

Wheel Care

Protect your investment by keeping your wheels clean at all times. Dust or dirt sitting on your wheels might destroy the finish. Always wait until your wheels are cool before cleaning them. Never use steam cleaners or automatic car washes; they can damage your wheels. The best wheel cleaning product is mild soap. Clean one wheel at a time and rinse immediately to avoid soap scum buildup. After the wheels are clean and dry apply a very light coat of wheel wax to protect your wheels from the elements.

Wheel Construction

Most alloy wheels are made in one-, two- or three-piece construction types. One-piece wheels are made in a mold as a single piece of metal. Two-piece wheels are made of separate center and barrel pieces that are welded or bolted together. Three-piece wheels are made of three separate pieces bolted together.

The most common methods of wheel manufacturing are: Forging, Low pressure Casting and Counter Pressure Casting.


This is the process of forcing a solid billet of aluminum between the forging dies under an extreme amount of pressure. This creates a finished product that is very dense, very strong and therefore very light.

Low Pressure Casting

This is the most common form of rim manufacturing. Liquid metal is poured into a mold and allowed to harden until the finished wheel is cool enough to be taken out of the casting.

Counter Pressure Casting

This method actually sucks the metal into a mold using a vacuum. This reduces impurities making the wheel much stronger than a low pressure cast rim.

Wheel Fitment

The optimal specification of wheels to fit your vehicle flush with the body.  PowerHouse Wheels not only has a team with a combined experienced of over 25 years.  Additionally we use the leading software to aids us even with the newest of vehicles to ensure your wheels & tires fit.

Please let us know if any of the brake or suspension system in your vehicle has been modified so we can make sure your wheels and tires fit.

Wheel Offset

The wheel offset is the distance from the hub mounting surface to the centerline of the wheel. There are three types of offsets.
Positive Offset
A positive offset means the mounting surface of the wheel is positioned in front of the true centerline of the wheel. Most factory rims will have this type of offset.
Zero Offset
When the hub mounting surface is centered within the rim, it is known as a zero offset.
Negative Offset
If the hub mounting surface is on the brake side of the center line of the rim, it is considered a negative offset or “deep dish”.

Load Index

The load index for any tire indicates the maximum weight that each tire is able to sustain.

Load IndexPoundsKilograms

Noise & Vibration Problems

Some of the most common causes of noise and vibration problems (There could be others):

  • Tire and wheel out of balance
  • No hub centric rings on aftermarket wheels
  • Incorrect hardware for aftermarket wheels
  • Irregular tire wear
  • Rim is damaged
  • Tire is damaged

Do not ignore pulling or vibration. If you have this problem have a professional inspect the issue.

Speed Ratings

Speed rating is a letter that indicates the maximum speed capability of a tire. In Europe, speed ratings were originally developed to help owners of high performance sports cars choose replacement tires designed to match the speed capabilities of their vehicles. The speed rating of any tire is a measurement of the top safe speed the tire can carry a load under specified conditions. It is also a suggestion of how the tire will handle at lesser speeds. A higher rated tire will give you better traction and improved steering response.

Below is a listing of common speed ratings:
  • Q = 99 MPH, 160km/h
  • S = 112 MPH, 180km/h
  • T = 118 MPH, 190km/h
  • U = 124 MPH, 200km/h
  • H = 130 MPH, 210km/h
  • V = 149 MPH, 240km/h
  • Z = 149 MPH, 240km/h and over
  • W = 168 MPH, 270km/h
  • Y = 186 MPH, 300km/h

Tire Pressure

The best possible tire performance requires proper tire inflation. Tire pressure can vary over time due to many factors such as climate, regular air loss, and your driving style. To maintain proper inflation, you should check your tires at least once a month. Under and over inflation of tires can lead to early or uneven wear, traction problems, and possible tire failure.

The best place to find proper tire pressure is in your owner’s manual. Never inflate your tires to the maximum PSI, it can cause serious damage. Remember to check your tire pressure monthly.

Tire Sizing

It is important to know how to read the side of a tire. For example P225/50R17 89W

  • P = Passenger Car Tire
  • 225 = Section Width in Millimeters
  • 50 = Aspect Ratio
  • R = Radial Construction
  • 17 = Rim Diameter in Inches
  • 89= Load index
  • W = speed rating

Treadwear, Traction & Temperature

The Uniform Tire Quality Grading System (UTQGS) is a tire information system that provides buyers with information on three categories:

  • Treadwear
  • Traction
  • Temperature

Each tire manufacturer performs its own tests in these areas, following government prescribed test procedures. Each manufacturer then assigns grades that are branded on the tire. This is known as the Uniform Tire Quality Grade Labeling (UTQGL).


Treadwear grades typically range from 60 to over 500, in twenty point increments. It’s important to remember that the actual life of any tire is determined by the road surface quality, driving habits, inflation, wheel alignment and the rotation it experiences. To receive a treadwear grade, a tire is tested under controlled conditions on a government prescribed test course, which does not necessarily simulate the actual application for which a given tire is designed to perform. As a result of these test parameters, there is no reliable way to assign miles of wear to treadwear grade points.

Treadwear ratings are determined on a 400 mile government test course covering specified sections of public roads near San Angelo, Texas. A group of not more than four test vehicles travels the course in a convoy so that all tires experience the same conditions. Tread groove depths of the tires being tested are measured after each 800 miles. The same procedure is followed for a set of control or “course monitoring tires”. Upon completion of the 7200 mile test, the rating results of both tests are compared, and the tires being tested are assigned a treadwear rating by the tire manufacturer.

The best way to use treadwear ratings when selling tires is to compare one rating to another. For instance, a tire with a treadwear grade of 400 might be expected to last twice as long as a tire that has a grade of 200.


Traction grades indicate the measurement of a tire’s ability to stop a car in straight-ahead motion on a wet test surface pavement. It does not measure straight-ahead acceleration. It’s important to remember that traction rating tests are performed only for straight-ahead sliding on concrete and asphalt surfaces that have a specified degree of wetting that simulates most road surfaces in a rainstorm. The ratings that result from these tests may not apply to cornering traction or peak values of straight-ahead braking those experienced in non-skid braking tests. Traction grades range from “A” to “C”, with “A” being the highest attainable grade.

Traction ratings are established on government maintained skid pads. Twenty measurements are taken with an industry standard control tire on an asphalt surface and averaged. The same numbers of measurements are made on a concrete surface. Corresponding measurements are then made on the tires being tested. Once the results of the tests are compared, traction ratings based on government prescribed coefficient levels are assigned to the tires that were tested.


Temperature grades also range from “A” to “C”, with A being the highest. Temperature grades represent a properly maintained tire’s ability to dissipate heat under controlled indoor test wheel conditions.

Temperature ratings are determined by running tires on an indoor roadwheel test under specified conditions. Successive 30 minute runs are made in 5 mph increments starting at 75 mph and continuing until the tire fails. A tire is graded from “A” to “C”, with “A” being the highest.