Suspension Series 101: Tire Basics by Dezoris

[Dezoris]

Welcome to the revised suspension series.



This article should be a readers starting point for learning the basics before moving on to further lessons.

Many may understand the information presented, however understanding how important rubber is for the car is something that should be on every tuner's priority list.

Lets get started.


Suspension Series 101: Tire Basics by Dezoris @ Hondalife.com

An automotive suspension, is probably the most key element to a vehicles performance. A suspension system keeps the car level, absorbs vibration and shock from the road, and most importantly keeps the tires gripping the pavement.

Behind all the technical information, debate, and tuning discussion, there is a univeral key to every setup one that, despite the make and model, or type of suspension all of them share one common thread:


Section 1
Tires

Tires are the only thing keeping the vehicle sticking to the ground.
Be it, rain, heat, snow, or typhoon they must be up to keeping contact.

Tires are not just about grip. In fact, more issues include driver saftey, gas mileage, and shock absorbtion.

With all this said, it is understood that cars need tires as much as they need a motor to move.

The mis-conception is that, as long as a car has tires, upgrading the suspension comes next. This is the biggest mistake, would be tuners make.

Lets look at common reasons why people modify suspensions.


1.)To just reduce fender gap, or have that lowered look
2.)To get better performance, as far as handling, and maintain good ride
3.)To go all performance with racing in mind
4.)For a slammed look, for either show, or for style


We will be able to help the first three most common reasons in this series.

This is more of a primer to get your vehicle well tuned.
The tires discussed in this article may not be for everyone, secondary to sizing, or price.

Most new tuners tend to come to us saying or asking the following:

"My car rolls all over the place during cornering"
"I hate the fender gap/wheel gap, what can I do that is safe"
"My tires scream all the time"
"Is lowering my car safe"
"How low can I go on stock shocks"

Instead of jumping ahead of ourselves and commenting on these issues, lets just say that if a tuner does not have a performance oriented tire, finding one that fits the car is the first step in tuning as suspension.

Now it is just a question of what kind of tires to buy.

Most of the more seasoned drivers on the site, don't go by what others say about tires, nor do they go by brand or price.

This may seem strange to some, because in our tire culture we grow up hearing people saying brands like "Michelin, Goodyear. Pirelli, Firestone" are the best and to accept no substitute.

In this day and age of technology, do not be fooled by this, indeed these companies are major players and have some amazing products, but they also have tires that are not what we would like to call "a good buy."

Some of these companies make money on their names alone, because people are will to pay for the name.

The point of this is to mention that the most expensive is not the best in the case of tires anymore.

The people who work in the AF suspension forums as well as the automotivetech forums, pick their tires from experience, testing and from seeing what works on the track, and on the street.

Lets get to know tires and their indentifying factors.
The below is more detailed information on understanding tires.

Continued

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On everyside wall of tires you will find this type of information.

Calculating Tire Demensions, by Tire Rack


Width x Aspect Ratio = Section Height x 2 = Combined Section Height + Wheel Diameter = Tire Diameter

Example...185/60R14 85H or 185/60HR14

185mm x .60=111mm x 2=222mm + 355.6mm(14")= 577.6mm or 22.74"

The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In the example above, the width is 185mm or 7.28".

The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".

The last number is the diameter of the wheel in inches.

To figure the outside diameter of a tire, take the sidewall height and multiply by 2,(remember that the diameter is made up of 2 sidewalls, the one above the wheel, and the one below the wheel) and add the diameter of the wheel to get your answer.

Now that you understand sizing you will need to know what the UTQG is.

UTQG
Something comonly used to determine the longevity of a tire. Which is difficult to do, so this is a generic guidline.

The Department of Transportation requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction, and temperature resistance. These tests are conducted independently by each manufacturer following government guidelines to assign values that represent a comparison between the tested tire and a control tire. While traction and temperature resistance ratings are specific performance levels, the treadwear ratings are assigned by the manufacturers following field testing and are most accurate when comparing tires of the same brand.

Other tire ratings included on the sidewall are as follows below.

Treadwear

Treadwear receives a comparative rating based on wear rate of the the tire in field testing following a government specified course. For example, a tire grade of 150 wears 1.5 times as long as a tire graded 100. Actual performance of the tire can vary significantly depending on conditions, driving habits, care, road characteristics, and climate.

Traction

Straight-a-head wet braking traction has been represented by a grade of A, B, or C with A being the highest. In 1997 a new top rating of "AA" has been introduced to indicate even greater wet braking traction. However, due to its newness, this grade will probably be applied initially to new tire lines as they are introduced and later to existing lines which excel in wet braking, but had been limited to the previous top grade of "A". Traction grades do not indicate wet cornering ability.

Temperature

Temperature resistance is graded A, B or C. It represents the tire's resistance to the heat generated by running at high speed. Grade C is the minimum level of performance for all passenger car tires as set under Federal Motor Vehicle Safety Standards. This grade is established for a tire that is properly inflated and not overloaded.

Note: UTQG ratings are not required on winter and light truck sized tires.


It should be easy to now to look at the side of any tire and point these items out. But don't get to happy yet.

Picking out tires is the hard part.

As an enthusiest I have a hard time understanding why people tend to gravitate toward the cheapest tires they can find. But I also understand that most of the time people just want to save some money, and don't care so much about performance.

Many people come to me, and say "I just don't care about tires and suspension as much as you do!"

With that said I have change my approach to help many people find good tires that perform well for low costs.

Written by [email protected]
Your tires are what determine how fast you can go, how fast you slow down, and which direction you go, which is what makes them the most important thing on the car. They are what make you go, so to go faster, you need to understand what they do. The part of the tire that touches the ground is the contact patch.

That’s where all your inputs, steering, braking, and accelerating are channeled. There is friction between the tires and the road, which allows the driver to control the car. For accelerating and decelerating, it’s pretty straight forward – if you go faster than the tire can handle, you spin the wheels, and if you apply too much brake torque you overload the tires and slide. Turns are a little more complicated.

Cornering force measures the tire's ability to resist sliding. Cornering force causes the tire to distort at the contact patch, and the distortion results in a difference between the direction the car travels and the way the wheels are pointed. The angle between the direction of travel and the direction the wheel is pointed is called the slip angle. The tire distorts 'cause it's elastic, and it tries to pull the rubber back into shape because it's elastic. Side force is the force that 'pushes' out in a turn. Side force and cornering force are equal and opposite. The tricky part here is that cornering force causes slip angle, and slip angle causes cornering force. Sort of a can't have one without the other thing.
So, cornering force causes slip angle, which causes cornering force, which is equal and opposite to side force.

As the slip angle increases, following the chain shows that side force increases. Eventually, you come to a point where side force overpowers the grip of the tire, and the tire slides. The point at which that happens is the limit of adhesion. After the limit of adhesion, the tire has lost almost all grip. Grip is the amount of side force divided by vertical force (the weight pushing down, usu. the vehicle weight for that corner, plus or minus whatever weight transferred in the turn). This is where speed is gained by suspension tuning. The higher the limit of adhesion, the faster you can go to reach it. You can create smaller slip angles for the same force, and reduce how much the tire will distort. The catch is that in the equation for grip, you'll see the higher the vertical load (weight on the tire), the more grip it has. Even though that's the case, it's not a linear relationship. Doubling vertical force doesn't double grip.

What happens when you try two inputs at the same time? Like braking and turning for example. Well, the tires have to do both, but the only have X amount of grip, so they’ll do both jobs, but less well than doing them separately. So if you braked in a straight line, you have 100% of grip slowing you down. Brake and turn, and you have maybe 75% grip slowing you down and 25% grip turning.

Tires are the single best modification you can do to your car. Tires make your car go, tires stop the car (note: brakes do not stop the car, they transfer rotational energy to heat), and make your car turn.

Below is the recommended tire list per Brand. Below some will be a description as to why we see these as being top choices.

This list comprises of summer performance tires of all ranges.
That have been used sucessfully in autox, and some that are just great street tires for the price. These are by far the most used, performance steet tires.

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Bridgestone
Potenza S03 Pole Position in 16-20" sizes

FAVORITE
This tire is one of the best all around street tires many of us have tested, their average life is about 20,000 miles. They perform well all the way through their life, and are equally as good in wet conditions as they are in dry. For autocross or race situations they tend to heat up quickly and stay hot, and that is their only weakness, compared to some of the more racey compounds. But even with that said, this tire does not quit until there is no usable tread left.

Potenza S-02

Great tire very equal to the S03, tends to exceed the performance of them in dry conditions, however wet performance is less, as well a tire wear, and usable tire life. But still a great choice

Potenza RE750

Updated more agressive version of the old RE730, great dry traction thus far with good water evacuation.

Potenza RE-950

Probably the best all season tire I have tested, mainly due to the tread compound wet grip and performance through the life of the tire. This is not a performance tire, but by far the best rounded, tire for all seasons made.
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Kumho

Kumho MX
Great tire as far as quality and dry traction thus far, treadware seems to be it's weak point. But rivals the best max performers for the cost.


ECSTA Supra 712
Probably one of the best buys ($$$) of performance tires, good dry traction, and water evacuation for the price. Treadware, as well as traction through the life is the weak point. One of the best budget tires out there now.


ECSTA 711
Another forum favorite for high performance, and street duty.
This tire is priced well with good traction and water evacuation


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Yokohama

AVS Sport
Yokos max performance tire, great grip, good water evac, and positive treadlife, just a bit on the pricey side.


AVS ES100
So far a great tire, the definitive replacement for the AVS Intermediate.
Side walls are softer than the A520s, and dry traction disappears near the end of their life. However the price makes this a great tire for the money.


A520
Classic old Yoko design, noisey tread, stiff sidewall, very sticky, but treadlife is low.


Avid H4/V4
Great choice for those with the 14" rims looking for an all season performer for less money. Average in all areas even can handle snow. Treadware is good, as well as water evacuation. Most people on stock 14" tires switching to these will enjoy the improvement.

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Sumitomo

HTR Z II


HTR+
Great choice for all season performance mainly do to cost, and dry grip.


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Falken

Azenis RS Sport
Straight performance tire, that is close to a race compound. Treadlife is between 10-15,000 miles, but is the king of heat for racing, an average street tire, due to average water evacuation. But dollar for dollar this is the stickiest street tire on earth for the price.


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BFG BFGoodrich

g-Force T/A KD
Another king of dry performance, rivaling the Azenis RS and S03, only more resistant to heat. Expensive tire, but the king of street tires for autox, and road race, if you can afford it.


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Goodyear

Eagle F1 GS-D3

A lot of hype and marketing consistant with the big name, but in this case the tire performs. Dry grip is great, water evacuation is good, and tread life is good. This is one of the first max performance Goodyears that is affordable and performs at the same time. The sidewall is spongy when compared to the S03 PP, and their is noticable more road noise as well when compared. However the tire is more resistant to overheating than the S03 is in race conditions


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Dunlop

FM901
These tires are a great bargain for the price as far as performance tires go, they tend to be louder than the other tires in their class, however dry grip is good and water evacuation is not an issue. Treadware is the weakness, as well as usable treadlife.



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This is the end of our most recommended list.

So if the reader wants to build a suspension from the ground up, a set great tires will tranform the vehicle, more than any other suspension change other than alignment.


Keep in mind the list above is more of a performance oriented list, and not for someone looking to replace stock tires with something exactly the same.

All of the tires above are unacceptable in snow, ice and sleet, unless mentioned.

The all season tires in there were mentioned because there were worth mentioning as replacements for those looking for it.

In addition there are some brands not listed, or tires. This may be because some of these tires do not perform as well as they should for the price, not worthy of mentioning or that we just chose to leave them out.

Our own testing with reviews will be coming soon.

To view a major list of available tires check out http://www.tirerack.com or
http://www.discounttire.com/dtc/home.jsp (They have shops for installation, that will guarentee no damage to rims)

Tire Rack is by far the best internet wheel/tire company on the net.
You can find two types of reviews on tires on their site.

Customer reviews
http://www.tirerack.com/survey/Surve...ommentStatus=P

Or Objective tests on a closed course (recommended)
http://www.tirerack.com/tires/tests/...ke=Bridgestone

Customer reviews are a good way to see what people are buying however, they are rarely an accurate representation of tire performance overall.