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12,574 Posts
Discussion Starter #1 (Edited)
After ALLLLLLL the tire questions & what not, I'd figured lets make a thread that consist of as much "simplified" information as possible. :thumb: If i missed anything or some information is incorrect pelase PM me and updates will be made accordingly :wavey: Thanks again peoples!!


Tire Size Viewed On Sidewall
P215/45R17 87V M+S

-P = Type of tire
-215= width of the tire across the tread in millimeters
-45= Aspect ratio of the sidewall compared to the width
-R = Radial construction
-17= Diameter of the rim in inches
-87 = Tire's load rating
-V = Tire's speed rating
-M+S = Tire is suitable for all-season driving

Speed Ratings

M 81 mph (130 km/h)

N 87 mph (140km/h) Temporary Spare Tires

P 93 mph (150 km/h)

Q 99 mph (160 km/h) Studless & Studdable Winter Tires

R 106 mph (170 km/h) H.D. Light Truck Tires

S 112 mph (180 km/h) Family Sedans & Vans

T 118 mph (190 km/h) Family Sedans & Vans

U 124 mph (200 km/h)

H 130 mph (210 km/h) Sport Sedans & Coupes

V 149 mph (240 km/h) Sport Sedans, Coupes & Sports Cars

Alot of Tire Manufacters now adays DO NOT encourage downgrading the speed rating of your tires. This may result in poor handling and VERY unpredictable steering. If you want better cornering response, there is no problem installing a higher speed rated tire on your vehicle.

Understanding DOT's

How to read the serial number:

Example "DOT OB XO C60 2206"

DOT = US Dept. of Transportation
OB = Manuf. and Plant Code
XO - Tire Size and Code
C60 - Tire Manuf. Symbols and Keys
2206 = Production Date (ie: week/year, 22nd week of 2006)

(6,000 - 7,000 Miles or Every Other Oil Change)

Tires need to rotate in more than one direction, rotating a vehicle's tires is essential to prevent uneven tire wear even MORE encourage if your dropped from OEM height. If left unserviced, unrotated tires will cause increased road noise due to "cupping", lower fuel economy, and decreased wet-weather traction. Additionally, badly neglected tires will have to be replaced ALOT sooner then if properly maintained. :thumb:

Although typical rotation patterns consist of "Front > Back Rotation", It is now becoming generally accepted that on front-drive vehicles (like ours), you rotate the front tires to the rear in a straight line and cross the back tires to the front to inscrease traction and longevity of tires. In a rear-drive vehicle, you rotate the backs in a straight line to the front and cross the front tires to the back


All handling modifications and adjustments come down to improving the traction of the four tire patches on the road. Tires are actually their grippiest when there is about 5% slippage involved.
Driver smoothness is a major factor in the car's overall grip. All the fancy hardware in the world won't cure the loss of grip created by a jerky driver (and we don't mean personality).”



- Toe can be a very critical part in a wheel alignment because it has the greatest effect on tire wear. Toe refers to the parallelism between the wheels as viewed from the above view and is usually measured in inches or sometimes millimeters. When both front wheels are aimed straight ahead and the distance between the leading front edges of both front tires is exactly the same as the distance between the trailing edges, the wheels have "zero toe" and are "suppose to be" aligned. I "suppose to be" because toe alignment changes when the vehicle is being driven on a daily basis.

- Toe-in means the front edges of the tires are closer together than the rear edges

- Toe-out is when the front edges of the tires are farther apart than the rear edges. This may occur if the tie rod ends are worn, or if the control arm bushings have collapsed. Toe-out is a bad condition to have because it causes the tires to scrub as they roll along.


- Camber refers to the tilt of the wheels as viewed from the front or rear direct eye sight. Camber is the inward (negative) or outward (positive) tilt of the wheels. It is usually measured in degrees

- With zero camber (perfectly perpendicular to the road) will be the ideal alignment setting. But like toe, camber changes as the vehicle is being loaded and every time the vehicle goes over a bump or dip in the road. The up and down motions of the suspension change the specs of the control arms and struts, which causes camber to change on a regular basis.


- The third most important wheel alignment angle is caster, which is the forward (negative) or rearward (positive) tilt of the steering axis as viewed from the side. Caster is usually measured in degrees, and only applies to the front wheels because they are the only ones that steer (except for the few oddball Japanese cars that had four-wheel steering).

- Caster is a weird angle because it doesn't affect tire wear DIRECTLY first hand. It's greatest effect is on steering ability, steering effort and steering return when you recover from a turn. So it is often the most ignored measurement.


Where To Find Tire Info

- This picture is the actual placard in your vehicle, it can be find inside the driver door jam one the right hand side once the door is open. Such information listed is the OEM Tire size, and proper air pressure

- How much air is the right amount to use? It depends on the application, the vehicle, the size of the tires and how much weight is on the tires. The simple answer is to follow the recommended inflation pressures specified by the vehicle manufacturer. The tire inflation specifications are generally listed in the owner's manual or on a decal in the glove box or door jamb.

- For many passenger cars and light trucks, the recommended OE tire pressure may range from 28 up to 34 psi. Recommended pressures for front and rear may also vary, and higher pressures may be recommended for towing or hauling loads.

- Also Keep in mind that recommended inflation pressure are for COLD tires. This means tires that have not been driven on for several hours (ideally overnight). It also means tires that are at a normal outside temperature of about 70 degrees F.

- To accurately inflate a tire, you have to compensate for changes in temperature. For every 10 degrees F change in ambient temperature, tire pressure will change a little more than half a pound.

- A tire that contains 32 psi of air at 70 degrees F will have a little over 35 psi at 100 degrees F - even if the vehicle has not been driven. Take a quick drive down the freeway and heat up the tires even more, and the pressure may read 38 to 40 psi

*Air pressure DOES NOT CHANGE b/c of different tire sizes or different rims but although can be changed for different driving conditions*


- Wheel balancing is a must anytime tires are mounted on wheels. The wheel may also require rebalancing if the tire has been dismounted for repair such as when you have a nailed pulled

- Wheel balancing provides a smoother ride by minimizing tire hop while in motion. This helps improve traction, steering wheel control and extends the life of the tires themselves. But no matter how carefully wheels and tires are balanced, they will eventually lose their balance from the roads we drive on day to day. As the tread wears, the distribution of weight around the entire tire changes altering the balance of the tire and wheel assembly. Eventually the tire may have to be rebalanced because only 1/4 ounce of imbalance can produce a noticeable vibration.

- Basic rule of thumb and good habit, would to have your tires balanced each time you have them rotated

Check out our Sponsor Site for other VERY useful tips!! :thumb:

Tire Rack - Tire Tech


That is pretty much it......thats ALOT of info :pat: so please be friendly and let me know if i missed something and i will update this original post.....Critcism welcomed but roasting or bashing is NOT apprecaited! :xyxnervou

12,574 Posts
Discussion Starter #11
Kid Red said:
What about inflation? Do 225/17/45 take the same 32psi as 205/16/55 stock?
aaaaaaaaaaaaah nice nice......while Im at work today i'll snap some pictures on places to read how much your tires take in PSI and different sizes. Thanks!

13,281 Posts
CrackThatTec45 said:

- Caster is the orientation of the wheel on the axle. Imagine standing to the side of your vehicle and looking at the wheel and its position within the fender or wheel-well. If your wheel was pushed towards the front of the wheel-well it would have negative caster. If your wheel was pushed towards the back of the wheel-well it would have positive caster

In positvie caster the wheel is moved toward the front of the car realitive to the top of the suspension mount just like the picture shows. There is a little arrow next to the 0 caster picture indicating where the front of the car is. Positive caster adds negitive camber to the outside wheel in a turn and postive camber to the inside wheel in a turn. This increases the contact patch of both tires when turning. The only negitive to postive caster is an increase in steering effort. So, got to change that. change that. Good effort though, i will rep you as well.

Here is a little info on caster and other alignment stuff from one of our sponsors


180 Posts
CrackThatTec45 said:
aaaaaaaaaaaaah nice nice......while Im at work today i'll snap some pictures on places to read how much your tires take in PSI and different sizes. Thanks!
Thanks for clarifying that all tires and sizes use the same OEM PSI rating. I knew the sticker and the rated 32psi, but I have (replaced stock) bigger tires but at 32psi they look almost flat. I've just been unsure about it and nice to have it confirmed.
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