Tire Maintenance
Tire Size Information
What is UTQG?
Speed Rating
Load Index
Sidewall Styles
Glossary of Terms
How Do I Get My New Tires Mounted?
Rubber Manufacturers Association (RMA) urges motorists to follow several maintenance tips, including:
- Measure tire pressure monthly using a good quality tire gauge. A visual inspection is not sufficient to detect under- or over-inflated tire problems.
- Have tires aligned regularly and check owner's manual for specific recommendations. A pulling or vibration means that alignment should be checked sooner.
- Rotate tires regularly, usually every 5,000-8,000 miles.
- Monitor tread wear and replace tires when tire tread is worn down to 1/16 of an inch. Proper tire tread prevents skidding and hydroplaning.
- Tires should be balanced periodically or when drivers feel a vibration.
- Conduct a visual check for embedded stones, glass and other foreign objects that could work their way into the tire and cause a leak.
How to Check Tire Air Pressure*
- Refer to your vehicle's owners manual for the proper level of inflation; it may also be posted on the door post or in the glove box.
- When you check the inflation pressure, make sure the tires are cool - meaning they are not hot from driving even a mile. (Note: If you have to drive a distance to get air, check and record the tire pressure first and add the appropriate inflation pressure when you get to the pump. It is normal for tires to heat up and the inflation pressure inside to increase as you drive. Never "bleed" or reduce air pressure when tires are hot.)
- Check inflation pressure once a month and before long trips.
- If you overfill the tire, you can release air by pushing on the metal stem in the center of the valve with a fingernail or the tip of a pen. Then recheck the pressure with your tire gauge.
- Replace the valve cap.
- Remember to check the spare. (Note: Some spare tires require higher inflation pressure).
How to Check Tread*
- When the tread is worn down to 2/32 of an inch, tires must be replaced.
- All tires have "wear bars," which are small, raised bars of rubber in the groove that indicate when tires are worn out. If your tread is worn down to the wear bars, it's time for a new tire.
- A penny is a reliable tool to check tire tread. 1. Take a penny and put Lincoln's head into one of the grooves of the tire tread. If part of his head is covered by the tread, you're driving with the legal amount of tread. 2. If you can see all of Lincoln's head, it's time to replace the tire.
- Visually check your tires for signs of uneven wear. You may have irregular tread wear if there are high and low areas or unusually smooth areas. Also make sure no nails or other objects are embedded in the tire. Consult your tire dealer as soon as possible if you see problems.
235/35 R19 91Y – What Do These Numbers Mean?
We are all pretty familiar with tire sizes, but few understand what those numbers represent, and also what the all that other writing on the sidewalls of your tires means and why it’s important.
Tire Sizes Explained: 235/35 R19 91Y
235 is the tire’s section width (measured at its widest point in MM)
35 is the aspect ratio (the tire’s height is 35% of its section width)
R stands for radial tire. If the R is not present the tire is probably a bias ply tire.
19 is the wheel diameter in inches
91 is the tire’s load rating that it can safely carry – in this case 1356 pounds per tire.
Y is the tire’s speed rating. A “Y” speed rating is good for 186+mph or 300+kph.
Tire Calculations
Section Width in inches = Section Width / 25.4 (number of mm in one inch)
235/25.4= 9.25” Section Width tire
Tire Height = Section Width X Aspect Ratio
9.25” X .35 = 3.24” Tire Height
Overall Tire Height = (Tire Height X 2) + Wheel Diameter
3.24” X 2 = 6.48” + 19” = 25.48”
Uniform Tire Quality Grade (UTQG)
Example: 280AA/A
(280) Treadwear Rating – Higher rating (number) is better, lower numbers are poorer ratings 100 is considered the baseline.
(AA) Traction Grade – AA, A, B, & C Are letter designations from the highest traction grade to lowest. These grades represent the tire’s ability to stop on wet pavement as measured under controlled conditions on government-specified test surfaces of asphalt and concrete.
(A) Temperature/Speed – Temperature grades represent the tire’s resistance to heat generated by running at high speed. Sustained high temperatures can cause the tire’s materials to degenerate and reduce tire life. Excessive temperature can lead to complete tire failure. The letter designations for Temperature/Speed are “A”= Best, “B”= Intermediate and “C”= Acceptable
A common trade-off for higher speed-rating is reduced ride comfort. An S speed-rated tire will give a more comfortable ride compared to an H speed-rated tire - and an H speed-rated tire will give a more comfortable ride compared to a Z speed-rated tire. The ride comfort characteristics can be attributed to the tire's overall stiffness. A tire capable of running at high speeds requires a more stiff construction, in order to provide the necessary high speed stability and durability.
Z speed-rated tires originally reflected the highest tire speed rating - i.e., in excess of 149 mph. When new cars were developed that could exceed this speed, the automotive industry added the W and Y ratings. While a Z speed-rating still often appears, such as 215/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph; the W in the service description indicates the tire's 168 mph maximum speed. When the Y speed-rating in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph.
A number that corresponds to the maximum load, in pounds, that a tire can support when properly inflated. Example: If a tire has a load index of 97, it can support 1,609 pounds (see chart below). Multiply … 1,609 x 4 = 6,436 pounds – the vehicle’s maximum load-carrying capacity. Because the maximum tire load capacity is branded on the tire's sidewall, the load index is used as a quick reference.**
B01- Broken Serrated Band
B02- Broken Serrated Band- EMT
BLK- Blackwall
BSL- Black Serrated Letters
BSW- Black Sidewall
BW- Black Wall
DSB- Diagonal Serrated Band
OBL- Outlined Black Letters
ORWL- Outlined Raised White Letters
OWL- Outline White Letters
RBL- Raised Black Letters
RGL- Raised Gold Letters
ROWL- Raised Outline White Letters
RSB- Raised Serrated Band
RWL- Raised White Letters
SBL- Serrated Black Letters
VSB- Vertical Serrated Band
WB- 6mm White Band
WL- White Letter
WS- White Stripe
WSL- White Slim Line
WSW- White Sidewall
WW- White Wall
XNW- Extra Narrow White Stripe
Overall Diameter- Diameter of the tire from tread surface to tread surface while inflated but unladen.
Tread Width- The width of the trast surface, designed for contact with the road.
Static Load Radius- Distance from the center of the axie to the ground at the rated load and inflation pressure.
Rim Width- Distance between the inside of the riim flanges.
Section Height- Distance from bead seat to the outer tread surface of the inflated tire.
Section Width- Distance between the outer sidewalls of an inflated tire.
Backspace- The backspace measurement (BSM) is simply the dimension from the inner edge of the wheel’s rim to the back pad, or the flat mounting surface of the wheel that mounts to the hub of your vehicle. So basically, backspace is how far the wheel extends toward your vehicle from the hub. This measurement is usually measured in inches.
Offset- Offset is the measurement from the exact centerline of the wheel to the back pad, or the flat mounting surface that bolts to the hub of your vehicle. If the back pad is set to the outside (away from the vehicle) of the exact centerline of the wheel, you would have a positive offset. If the back pad is set to the inside (towards the vehicle) of the exact centerline of the wheel, you would have a negative offset. This measurement is usually measured in millimeters.
EMT- Run Flat Radial
LL - Light Load
RD- Reinforced
RE- Reinforced
ROF- Run-On-Flat
RFT- Run Flat Technology SL- Standard Load
SSR- Self Supporting Run Flat
STD- Standard Load
XL- Extra Load
ZP- Zero Pressure
How Do I Get My New Tires Mounted?
Purchasing tires online has become such a common thing that most tire shops will welcome the opportunity to mount and balance your tires. The truth is that tire shops actually make more money on the installation labor than selling the tires in most cases. Expect to pay about $20 per tire for mounting and balancing, and slightly more for difficult installations like run-flats and low profile tires on large diameter wheels. Also, you may be charged the required tire disposal fee if your state has one.
* Information from the Rubber Manufacturers Association Website
** Information from Kumho Tire
(877)898-0885
