- Tire Numbers Meaning
- Reading Tire Size
- Loading & Speed Rating
- Tire Pressure & Temperature
- Tires Rotation
- Run Flat Tires
- TPMS Sensors
- Mounting & Balancing
- Wheel Alignment
- Wheel Torque Chart
- Auto Parts Grading
Tire Numbers Meaning
There's a massive amount of information branded on the sidewall of every tire ... but it's written in code. The tire size is just one small piece of this code. The tire size "P225/45R17 91V" may not mean much to the average person, but to tire geeks like us it speaks volumes. Read on to learn how to crack the tire code with this handy guide dedicated to tire types, sizes, and construction.
Tire service type ratings
Most tire sizes begin with one or more letters -- for example, P or LT. The letter tells us what type of vehicle or service the tire was designed for.
P = P-Metric (Example: P215/65R17 98T)
P-Metric tires are the most common type of tire. The P stands for passenger vehicle, meaning that these tires are designed for use on passenger vehicles like cars, minivans, light-duty pickup trucks (¼ ton or ½ ton capacity), and SUVs.
Metric / Euro-Metric (Example: 185/65R15 88T)
Metric tires, also known as Euro-Metric tires because the sizing originated in Europe, don't have a letter designation. Euro-Metric sizes are equivalent to P-Metric sizes in dimensions, but Euro-Metric sizes have subtle differences in their load-carrying ratings and capabilities. Euro-Metric tires are usually found on European cars, but they're also used frequently used on SUVs and vans.
LT - Light Truck (prefix) (Example: LT235/75R15 104/101S/C)
Light Truck Metric tires sizes begin with the letters LT. These tires are designed for use on vehicles used to tow trailers or carry heavy loads. This includes SUVs, full-size vans, and medium-duty and heavy-duty pickup trucks with ¾ ton to 1-ton capacity.
LT - Light Truck (suffix) (Example: 9.5-16.5 LT121/117R)
These tires are made for light-duty, medium-duty, and heavy-duty pickup trucks (typically ½ ton, ¾ ton or 1-ton load capacity), sport utility vehicles, and vans.
When a tire's descriptor ends in LT, it falls into one of three light truck categories:
Earlier numeric sizes are designed to carry heavy cargo loads and/or tow trailers.
Wide base tires are also designed to carry heavy cargo loads and/or tow trailers on a wheel rim with a diameter of 16.5 inches.
Flotation tires are wider, oversized tires designed to carry heavy cargo loads and/or tow trailers on loose surfaces such as sand, gravel, or dirt.
T = Temporary Spare (Example: T145/70R17 106M)
If the tire size begins with a T, it means that the tire is a temporary spare. Also known as mini spares or space savers, temporary spares are designed for short-term use until the regular tire is repaired or replaced.
ST - Special Trailer (Example: ST175/80R13)
Tires beginning with ST are special trailer tires and should only be used on car, boat, or utility trailers.
C = Commercial (Example: 31x10.50R15/ C109R)
Euro-Metric tire sizes ending with a C are commercial tires, for use on delivery trucks and vans capable of carrying heavy loads. In addition to the C designation, these sizes are also branded with a load range and service description rating (load range B, C, or D).
Reading Tire Size
Section width of tire (Example: P 225/45R17 91V)
The three digits following the service type prefix (if present) tell us the cross-sectional width of the tire in millimeters.
In the example above, the tires width, measured from the widest point of the inner sidewall to the widest point of the outer sidewall when properly mounted, is 225 millimeters. The section width can be converted to inches by dividing the width in millimeters by 25.4 like so: (225 millimeters) / (25.4 mm/in) = 8.86 inches.
Aspect ratio of sidewall (Example: P225/ 45R17 91V)
The two-digit number that usually follows the tire's section width tells us the aspect ratio, or tire profile measurement.
In this example, the 45 indicates that the sidewall distance, from the wheel rim to the outside of the tread, is 45% of the section width. A lower aspect ratio means a lower-profile tire with a shorter sidewall, while a tire with a higher aspect ratio will have a taller sidewall and look more like a donut. Because we know that the tire size shown in this example has a section width of 8.86 inches and the aspect ratio is 45%, the sidewall height for this tire is 3.98 inches: (8.86 inches) x (.45) = 3.98 inches.
Tire and wheel diameter (Example: P225/45R 1791V)
Again using our example tire size from above, the 17 means that the tire should be matched to a 17-inch diameter wheel.
Tires usually come in the following widths (in inches): 8, 10, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 24, 26, and 28. Tires in these sizes are typically found on most passenger cars, light-duty light trucks, SUVs, minivans, and vans. Tires with a rim diameter measured in inches are called "inch rim" sizes.
Unique wheel diameters
In addition to the inch rim sizes, there are also some unique tire sizes out there. Although not as common, tires are made in half-inch diameters for some heavy-duty light trucks, box vans, and heavy-duty trailers. These sizes are usually 14.5, 15.5, 16.5, 17.5, and 19.5 inches, and an example would be 33x12.5R16.5 118R.
Tires and wheels with unique rim diameters should never be combined with traditional inch rim tires and wheels. Before mounting tires on wheels, the tire and wheel diameters should always be confirmed to match.
More info included in the tire size
Internal construction (example: P225/45 R17 91V)
When a letter (R, D, or B) follows the two-digit aspect ratio, it tells us the tire's construction. In this example, the R means that the tire has radial construction. Over 98% of all tires sold today are radial tires, where the internal body plies of the tire radiate outward from the center. If there's a D instead of an R, the tire has a bias ply construction, meaning that the internal body plies of the tire crisscross on a diagonal pattern. In belted tires (marked as B), the internal plies crisscross like in a D construction, but there's also an extra layer of reinforcing belts under the tread area. Belted tires are rarely seen these days.
Speed rating (Example: P225/45R17 91 V)
Today, the only speed rating still included in the tire size is the Z rating (sports cars). Since 1991, all other speed ratings are included in the service description, as shown below.
Service description rating (Example: P225/45R17 91V)
Since 1991, the service description rating is mandatory for all speed ratings (except Z-rated tires) and appears at the end of the tire's size brand. The service description is used to identify the tire's load index (91 in the example above) and speed rating (V in the example).
Loading & Speed Rating
Understanding tire service description, load rating, and speed rating
If you look at the sidewall of a tire, you’ll see a whole slew of characters and numbers. This is basically a code that includes information about size, construction, and guidelines for use of the tire -- and we’re here to help you decipher it. In this article, we’ll look at just one small part of the code: the service description.
As an example, we’ll be using a 2012 Audi A3 TDI. This car’s “tire code” is 225/45R17 94H. You can usually find this information on a sticker on the driver’s side door jamb.
Tire load index chart and understanding your tire's code
The service description is simply the speed rating and the load rating together. In our example, the service description is the last three characters: 225/45R17 94H
94 is the load rating and H is the speed rating. But what exactly does that mean…?
Tire load rating or load index
The load rating tells you how many pounds a tire can safely carry. In our example, the number 94 has been assigned to a load carrying capacity of 1477 pounds (per tire). So if your car was fully loaded up with, let’s say, bags and bags of dog food, you’d want to be sure the weight of the car plus the weight of the cargo didn’t exceed 5908 pounds (1477 x 4).
The GVWR (gross vehicle weight rating) for the Audi A3 is 4597 pounds. This includes the car, driver, passengers, dog, and dog food. Since the combined load rating (5908 pounds) for the four tires is greater than the 4597-pound GVWR, you’re good to go.
If you know the tire load rating for your vehicle, you can use our handy load index chart to check out the load carrying capacity of your tires.
|Load Index||Pounds (lbs)||Kilograms||Load Index||Pounds (lbs)||Kilograms|
When you shop for tires and give us your vehicle’s make/model/style information, we show you only the tires that have the proper load rating for that vehicle. If you choose a tire with a different load rating for some reason, that tire must meet or exceed the load rating for your vehicle.
Tire speed rating
Speed rating ensures that a vehicle’s tires match its top speed capability. Going back to our Audi, the “H” speed rating is equal to 130 miles per hour, meaning that under optimal conditions**, the tire can perform at speeds up to 130 mph. Now just a second, leadfoot … that doesn’t mean you should drive 130 mph. It means that the Audi A3 is capable of a top speed of 130 – but here in the U.S., it’s generally a good idea to observe the posted speed limits.
Just like with load rating, when you shop by vehicle we only show you tires with the correct speed rating for your car. If necessary, you can use a tire with a speed rating that is greater than the speed rating recommended for your car (for example, instead of using an H-rated tire on the Audi A3, you could use a V-rated tire (149 mph). If you must mix tires with different speed ratings, be sure to observe the lowest speed rating when driving.
|M||81 mph||130 km/h|
|N||87 mph||140 km/h||Temporary spare tires|
|P||93 mph||150 km/h|
|Q||99 mph||160 km/h||Studless and studded winter tires|
|R||106 mph||170 km/h||Heavy duty light truck tires|
|S||112 mph||180 km/h||Family sedans and vans|
|T||118 mph||190 km/h||Family sedans and vans|
|U||124 mph||200 km/h|
|H||130 mph||210 km/h||Sport sedans and coupes|
|V||149 mph||240 km/h||Sport sedans, coupes and sports cars|
|W||168 mph||270 km/h||Exotic sports cars|
|Y||186 mph||300 km/h||Exotic sports cars|
|Z||149+ mph||240+ km/h||Sports cars|
Tire Pressure & Temperature
As discussed in some of our other articles on inflation pressure, tires must be properly inflated to achieve maximum handling, traction, and durability as designed by the tire manufacturer. It is the air pressure that supports the weight of your vehicle, not the tire itself. Tire pressure should be monitored frequently for safe driving and optimal tire performance.
Tire pressure can change with fluctuations in temperature. So, how should you correctly monitor tire pressure as the outside temperature changes?
First, it's important to remember that gas expands when heated and contracts when the temperature declines. In North America, the daily temperatures rise and fall between day and night, as well as seasonally. As the days get shorter and colder during fall and winter, it's especially important to check your tire pressure.
Second, it's important to know that the recommended tire pressure for your vehicle (as specified in the owner's manual and the tire placard for the vehicle) are both based on cold inflation pressure. This means that the tire pressure should be checked in the morning before the tire has been run, before the ambient temperature rises during the day, and before the tire is exposed to direct sunlight.
A good estimate to use when comparing tire pressure to air temperature is for every 10 degrees F, tire pressure will adjust by 1 psi. For example, if the outside air temperature increases 10 degrees, the tire pressure will increase by 1 psi. Conversely, if the air temperature falls 10 degrees, the tire pressure will decrease by 1 psi.
In most parts of North America, the difference between average summer temperatures and average winter temperatures is about 50 degrees F. This means that your tires will fluctuate approximately 5 psi (assuming no other air loss) between the coldest and warmest times of the year. A drop of 5 psi during colder months will affect traction, handling, and durability. This is why it's important to remember to check your inflation pressure, especially during colder times of the year.
In most parts of North America, the average daily air temperature fluctuates by approximately 20 degrees F. Using our rule-of-thumb formula from above, this means that the inflation pressure can fluctuate by approximately 2 psi during the day. This fluctuation can be even more pronounced if the tire is subject to direct sunlight.
In addition to changes from sunlight, the tires temperature is also affected by driving. Tire pressures can increase by up to 5 psi in the first 20-30 minutes of driving, before finally stabilizing.
If you live in a cold climate and have a heated garage, the opposite problem can occur. As soon as you leave the confines of your heated garage and go out into the colder weather, your tires can lose inflation pressure. Again, for every 10 degrees F dropped, the tires will lose approximately 1 psi each.
In all three scenarios, the same problem arises, regardless if you check the air pressure when the tires are warm from driving, when there are ambient temperatures, or if the tires are in direct sunlight. If the inflation pressure is correct when a tire is warm, then it will likely be anywhere from 2-5 psi under-inflated when it is cold.
Bottom line -- you should always check your tire inflation pressure when your tires are cold, and inflate them to the recommended pressure at that time.
Knowing your tire pressure
Believe it or not, tire pressure is a pretty big deal—it can affect your gas mileage, ride comfort, tire life, and most importantly, your safety and the safety of everyone else in your vehicle. After the brakes, your tires are actually your vehicle’s most important safety equipment!
How often do I need to check tire pressure?
Since tire pressure is so important, we recommend that you check your tires at least once a month, or even more frequently if you can. The good news is it only takes a few minutes. But before you can check your tires, you’ll need to know your vehicle’s recommended tire pressure.
Where to find your vehicle’s recommended tire pressure
Every tire's sidewall identifies a maximum cold inflation pressure, but that’s not necessarily the correct pressure to use for your vehicle. Vehicle manufacturers predetermine the best tire inflation pressure for each vehicle, so you should follow the manufacturer's recommendation. To find this, first check your vehicle owner's manual. In many cases, you’ll find tire pressure recommendations here, and sometimes the manufacturer may also specify alternate pressures based on load and/or speed.
Another place to find tire inflation information is on the vehicle's tire information placard. Beginning in 2003, vehicle manufacturers were directed to standardize the format and placement of tire information placards.
On new vehicles, the placard must be located on the “B-pillar,” which is the driver's side doorjamb. For vehicles that do not have a B-pillar, the placard should be attached to the rear edge of the driver's door, unless it’s too narrow, in which case it should be placed on an inward-facing surface next to the driver's seat. On older vehicles, look for placards in these locations:
The driver-side door or doorjamb
Rear passenger doorjamb of Ford sedans
Fuel filler door
Glove box or center console door
The engine compartment
The tire information placard will tell you the vehicle’s weight capacity, the OE (Original Equipment) tire sizes (including the spare tire), and the recommended inflation pressures for the tires.
Check tires when they’re chilly
Now that you’ve found the recommended cold tire inflation pressure and vehicle load, it’s important to understand how temperature can affect the reading. Tire inflation pressure should be checked first thing in the morning when the tires are at their coldest—before the vehicle has been driven, before the tires have been in direct sunlight, and before the temperature rises.
More tire pressure tips
Always use a quality tire gauge to measure tire inflation pressure.
Don’t rely on a visual check—it simply isn’t possible to measure tire pressure this way.
Check all four tires. Just because the first two are good to go doesn’t mean they all are.
Going on a road trip? Check your tire pressure before you take off.
Check the pressure of your spare tire every once in a while, too. If you have a “space saver” spare, use the pressure rating on the sidewall of the tire.
That’s pretty much everything you need to know about tire inflation pressure. Just remember how important tire pressure is, and be sure to check your tires at least once a month!
Why do I have to rotate my tires?
Rotating your tires is like exercise. It's one of those things that everyone knows they should do -- but they still might not always do it. Here's why you should rotate your tires every 3,000 - 5,000 miles:
- Helps maintain your vehicle's handling and safety
- Helps the tires wear more evenly, so they last longer
- Many tire warranties require tire rotation to keep the warranty valid
How tires wear
As you drive your vehicle, your tires will inevitably wear. The placement and extent of the wear depends on a few factors, like the tire's position on the vehicle. Each axle has different external forces to deal with -- for example, in a front-wheel drive vehicle, the front tires are exposed to more intense forces than the back tires. So the front tires on a front-wheel drive car will show more wear than the front tires on a rear-wheel or all-wheel drive vehicle.
If your tires wear unevenly, you may eventually need to replace one or two while the others are still perfectly fine. Uneven tire wear can also affect the stability and handling of your vehicle. If your tires are unevenly worn, they may not respond as quickly and this can jeopardize your vehicle's safety.
How tire rotation can help
Rotating your tires regularly helps to evenly distribute tire wear. This will prevent one or two of your tires from becoming significantly more worn than the others -- so ultimately, it prolongs the lives of all your tires. Tire rotation can also help keep your tire warranty valid, because many manufacturers require you to rotate your tires.
For the best results, you should rotate your tires every 3,000 - 5,000 miles. To make it easy to remember, just have them rotated every time you get your oil changed.
If your tires are showing severe signs of wear, you should have your mechanic check them for mechanical issues. If no mechanical issues can be found, the wear may simply be a result of your driving style. In this case you may want to have your tires rotated more frequently than the standard 3,000 - 5,000 miles.
Run Flat Tires
How run flat tires work? While we’d all like to think we’re invincible on the road, deep down we know better. And nothing deflates the ego faster than a flat tire. If you’ve been there, and chances are you have, you know the feeling: that sudden dip in the pit of your stomach as you realize that you need to pull over in rush-hour traffic, and can’t quite remember where you left your jack.
Some choice words and a once-clean pair of pants later, you’re back on the road, but your mood is in the gutter, you’ve lost valuable time, and possibly risked your safety while becoming your own one-person pit crew. Wish there was a way to avoid the hassle of a flat tire?
There is: enter the run-flat tire. This is a broad term that encompasses a range of tire technologies designed to keep you on the road and out of harm’s way, even after suffering a complete loss of air pressure. Of course, while run-flat tires may seem like superheroes wrapped in silicone, they aren’t invincible. In order to fully understand run-flat technology, it’s important to weigh the pros and cons of driving with it.
Here are a few things you should know before equipping your car with run-flats and running over a box of nails:
What do run-flat tires do?
Simply put, run-flats keep you driving after a flat. Boasting safety first and foremost, run-flat technology allows you to continue driving for a certain distance at adequate speed after a continuous leak or puncture, and also prevents having to get underneath your vehicle on the side of the road as traffic whips by.
How do run-flat tires work?
The vast majority of run-flat tires available today are what's known as "self-supporting" run-flats. These tires use a thicker, and therefore stronger, sidewall that’s able to safely carry the weight of a vehicle (generally up to 50 miles at up to 50 MPH) so you can get where you need to be. A number of popular brands provide run-flat options for their most popular tires, which are easily identified by the seemingly random abbreviations attached to them -- Bridgestone and Firestone call their technology RFT (Run-Flat Tire); Dunlop calls it DSST (Dunlop Self-Supporting Technology); Goodyear goes with ROF (RunOnFlat) or EMT (Extended Mobility Technology) – these are all examples of self-supporting run-flat tires.
Now, since the main purpose of a run-flat is to eliminate the ugly, let’s take a look at the good and bad aspects of the technology.
Benefits of Run Flat Tires
Mobility after a flat
This is the obvious advantage. When pesky nails or other sharp objects puncture your tire, you can just keep open driving, so you don’t have to stop in an unknown area or dangerous stretch along the road. Which leads us to the next advantage...
Aside from convenience, run-flats provide immeasurable safety because they allow you to stay mobile, without the sudden and sometimes violent changes in maneuverability that can happen when you suddenly lose air pressure.
Less weight and more space
Since you don’t have to change a run-flat right away, you can do away with that heavy, space-consuming spare—though we recommend using caution before tossing that donut by the wayside.
Run-flats: The Bad
Compared to your everyday tire, run-flats on average cost one-third more—and you can’t pair them with traditional tires, either. You’ll also be replacing run-flats more often: in a recent study, J.D. Power and Associates discovered that drivers who rely on run-flats replace their tires an average of 6,000 miles faster than standard tires, and that vehicles riding on run-flats are twice as likely to need to replace their tires after a flat or blow out—because after they do their job, run-flats can’t be repaired.
Reduced fuel economy
All that technology is heavy, and weightier run-flats can reduce your fuel economy by 1-2%.
Run flats require specific configuration standards, and it can be hard to find exactly what you need. That said, we have a pretty strong selection of run-flats, so be sure to check out carwheelstires.com if you need a set.
Run-flats vs. traditional tires
While run-flats offer obvious benefits, there has been some backlash recently. Drivers have cited faster and uneven wear and a stiffer ride, as well as the aforementioned replacement bills and limited replacement choices when compared to regular tires. And then there’s this: though many upscale and sports vehicles come equipped with run-flat technology, drivers have cited a noticeable decrease in overall ride quality. Automakers counter this claim by stating that the free weight from eliminating a spare produces better handling and improved economy, and that OE applications equipped with run-flats are specifically tuned to counter the stiffer sidewalls. That said, while you may not have to deal with a roadside tire change, certain disadvantages can certainly flatten your mood.
Bottom line: Is run-flat technology worth it?
Despite the downsides, many manufacturers and drivers alike say the safety and convenience of having run-flats outweighs the cost and replacement woes. And the fact is, as technology increases, so does run-flat usability. Most major manufacturers attach run-flat technology to their leading tires, which is a reaffirming testament to their trust in them, as well as the public’s acceptance. Ultimately, of course, it’s up to you and your preferences.
What is TPMS?
TPMS stands for Tire Pressure Monitoring System. It’s a safety system built into your vehicle (or retrofitted) that monitors your tire pressure, and alerts you when the pressure in one or more tires falls to an unacceptable level.
Why are underinflated tires such a big deal?
Underinflated tires are susceptible to a variety of problems, from mild (premature wear and increased fuel consumption) to major (tire failure, including tread separation and blowouts). According to Schrader, a leading manufacturer of tire pressure monitoring systems, underinflated tires wreak a staggering amount of havoc on our nation’s roads and highways, contributing to 250,000 crashes, 33,000 injuries, and 660 deaths every year.¹ TPMS can have a huge impact on these sobering statistics. The U.S. government believes that once all vehicles are equipped with TPMS, as many as 120 fatalities and 8,500 crash-related injuries could be prevented each year.²
And there are even more benefits to TPMS. Schrader tells us that underinflated tires waste 3.5 million gallons of gas every single day.³ That’s fuel that could be saved (and money that could stay in drivers’ wallets) if tires were properly inflated. An uninflated tire will also wear more quickly, which can cost you money because the tire may need to be replaced earlier than expected.
History of TPMS
TPMS originated on European luxury cars in the 1980s; the first American car equipped with TPMS was the 1997 Chevrolet Corvette. TPMS got its big break in 2000, when the Clinton Administration enacted the TREAD (Transportation Recall Enhancement Accountability and Documentation) Act. Among other transportation safety improvements, the TREAD Act mandated that every new car sold in the United States after September 2007 be equipped with TPMS.
How do I know if I have TPMS?
Most passenger cars and light trucks model year 2008 or newer have tire pressure monitoring systems.
If your vehicle is TPMS-equipped, a warning light or other display will alert you when one or more of your tires falls below its recommended pressure, as stated on the vehicle’s door jamb placard. Here are a few examples of these displays:
There are also aftermarket TPMS systems, which usually have a display that mounts on the vehicle’s dashboard.
I have TPMS — do I still need to check my tire pressure?
Yes. Even with TPMS, it’s still important to check your tire pressure regularly because many systems won’t alert you until a tire is 25% or more below its recommended inflation pressure. The sooner you catch an underinflated tire and return it to the correct pressure, the better.
How do I get my TPMS serviced?
Rebuilding TPMS sensors
Servicing a vehicle’s TPMS requires special tools and training. In most cases, each wheel will have a TPMS sensor attached to the valve stem where the air is added. Between this stem and the wheel is a rubber grommet that seals the air inside the tire and protects the sensor from the elements.
Just like the rubber valve stem that was replaced at every tire change for years because the weather and other elements caused wear, the rubber grommet needs to be replaced, along with the nut that holds the stem and the nickel-plated valve core in the stem.
Moisture and corrosion eat away at the stem, which is why the caps have moisture seals to protect the internal components. To make sure you don’t create a leak when replacing the tires, all these components should be replaced (or in tire lingo, the TPMS sensor needs to be rebuilt). Your installer will generally charge a small additional fee for performing this service.
There may also be a small extra cost involved when rotating tires, because some vehicles require “relearning” of the position of each sensor after the tires have been moved. Each vehicle make and model has its own unique relearning procedure, so it takes special knowledge, equipment, and time for the technician to ensure that the system is working properly.
Replacing TPMS sensors
TPMS sensors will typically need to be replaced after 5 to 10 years of use, as the sealed batteries wear out. Timing varies due to use, weather conditions, and maintenance. New sensors have to be programmed into the vehicle’s onboard computer system with special equipment, and in most cases there is a charge for this service. Replacing sensors can be an expensive proposition (up to $200 per sensor in some cases), but we believe that the safety and savings benefits of TPMS far outweigh the cost.
Mounting & Balancing
Whenever you get a new set of tires or wheels, you’re going to want to have an expert mount and balance them – unless, of course, you’re an expert and you have your own mounting and balancing equipment.
What do “mounting” and “balancing” mean?
Mounting is pretty self-explanatory – it’s simply the act of putting the tires onto the wheels, then installing the wheels onto your vehicle’s axles.
Balancing is a bit more complicated. A wheel is said to be in balance when the center of gravity is identical to the axis of rotation – in other words, when the mass of the wheel and the tire is evenly distributed around the axle, so there’s no vibration when the tire spins. An easy way to understand the concept of a balanced tire is to think about your washing machine during the spin cycle. If the clothes are evenly distributed inside the washer, no problem. But when things get unbalanced, it’s a completely different experience – and you certainly wouldn’t want that to happen to your tires!
So how does balancing work?
Your installer uses special equipment to analyze the tires and wheels and find any heavy spots that could cause them to vibrate when spinning. One at a time, the tire and wheel assemblies are placed on the balancing machine and run through a series of diagnostic tests. The machine identifies where the tire and wheel assembly is out of balance, and then the technician corrects any imbalances by applying small weights to the rim at specific locations, in order to even out the distribution of weight.
Road Force Balancing
While spin balancing spins the tire assembly in the air to find imbalances, a Road Force balancer simulates the force of the road on a tire by pressing a large roller against the tire as it spins. Then the machine measures the deviation from perfect roundness so the technician can balance the tire. Road Force balancing may be able to detect tire issues not found by spin balancing.
Road Force balancer image courtesy of Hunter Engineering Company
How unbalanced wheels can take you on a bumpy ride
If your wheels and tires are out of balance, your vehicle’s ride can be affected. If you’re experiencing vibration that starts at around 40-45 mph, and worsens as your speed increases, chances are you have an out of balance tire.
Most of us are sensitive to vibrations while driving, and even a small vibration can be extremely annoying. And that’s not all – the repetitive vibrations can make your tires wear out faster, along with the wheel bearings, shocks, and other suspension components.
Vibrations can also occur if the wheel and/or tire are not completely round. If there’s a high spot on the wheel and also a high spot on the tire, and they happen to be lined up with each other, then the high spot will be even more pronounced. A trained technician can usually correct this problem by rotating the tire slightly on the wheel, so the high spots are no longer matched up.
Alignment is one of the key maintenance factors in getting the most wear and performance from your tires. In addition, wheel alignment provides safe, predictable vehicle control as well as a smooth and comfortable ride that's free of pulling or vibration. Today's modern suspensions require a precise four-wheel alignment that can only be achieved through a modern alignment system. This applies to both front and rear wheel drive vehicles. While we do not perform alignment work, the following information should help to explain the importance of proper alignment.
Aligning a car or truck involves the adjustment of the vehicle's suspension, not the tires and wheels. The direction and the angles that the tires point in after the alignment is complete, however, are critically important. There are four factors involved in setting the alignment to specification: caster, camber, toe and ride height. The following brief discussion of each aspect will help you understand the process and spot potential problems. Misalignment and Tire Wear By now you may have concluded that poor tire wear and misalignment are closely related. That is true, of course. But what can be done to minimize this condition? It turns out that many of these misalignment conditions can be easily "read" by your tire dealer; and they can recommend the appropriate solution, which will be "get an alignment." For your assistance, the following troubleshooting guide will help you see what your tire expert sees. Armed with this knowledge you can check your tires periodically. Remember that a knowledgeable glance at your tires on occasion can pay big dividends. This is not meant to be an exhaustive listing of all the possibilities. However, if you learn to spot these symptoms early, you can get a lot more wear from your tires. Remember that tires take the brunt of many problems. Simply replacing the old ones is not a solution. Shortly after replacing your old tires, your new tires will begin to reflect the same problems if you have not made the appropriate alignment changes. Worn Parts: Very often a worn suspension part is the cause of an alignment problem. On older vehicles, worn springs can lower a vehicle's ride height, altering its geometry and creating misalignment (all alignment settings refer to ride height). Weak springs can also contribute to uneven or "cupped" tire wear. Another common problem is worn ball joints. The symptoms here are erratic handling, slow steering response, and irregular tire wear. Finally, worn tie rods can allow the tire to wander left to right, effectively changing toe as the vehicle rolls down the road. Irregular feathering will develop on the tire tread when this is the problem. Again, this is not an exhaustive listing, but if you stay alert to these common problems, it may help you schedule an early visit to your mechanic and save on tire wear.
Wheel Torque Chart
Lug nuts are a crucial component of a vehicle, as they are what keep a wheel securely attached to the hub. Every driver should be aware of the proper amount of torque for their specific vehicle and ensure that the lug nuts are checked often to keep them at this measurement
Auto Parts Grading
The Parts Grading and Description Guidelines are intended to improve the part condition. Many customers cannot decipher the codes used to describe the conditions and options of a like new or used part. As a result to avoid the part returns because it did not meet the customer’s expectations, the standardized parts descriptions and terminology is necessary in the inventory process also this identifies common parts and terms used to describe conditions and other options. Please see the parts grade scale below:
Like New Grade: is the highest quality part and contains a minimum visible cosmetic defects because it is a take off or low o no mileage car part, looks mint, or like new condition.
A++ Grade: is a good condition part and contains light visible or minimum cosmetic defects, nicks or scratches because it is a fair mileage used part.
B Grade: is a second level quality part, contains a moderate nicks, scratches or visible cosmetic imperfections only and not mechanical.
C Grade: is the third level quality part. Although still useable, a C grade exceeds a moderate amount of cosmetic visible imperfections like nicks, scratches only but still usable part.