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Getting What you Need to Know in the Shoreline Tech Center
Seemingly simple, wheels, tires and other
vehicle modifications can be full of subtle details that
make the difference between a smile every time you get
behind the wheel and a perpetual bad mood. Whether you’re
just looking for a new set of tires for your daily driver
or are an experienced enthusiast deciding how to make your
latest creation everything it can be, Shoreline Motoring’s
Tech Center can help.
Tires
are your vehicle’s connection
to the ground. They are its shoes. Just like your shoes, tires
can vary
widely in fit and function. Some are specialized, some
are general purpose. Some cost more than others. Quality
provides
intangible but real benefits that may not be obvious. Even
within one category and price grouping, one tire may be
a better fit for you and your personal requirements than
another.
Select a topic below to learn more.
| Reading Sidewall
Info | Plus
Sizes |
Wheels
are most people’s first step in vehicle personalization
and, after the vehicle itself, are usually the largest single
investment. They are fundamental to a vehicle’s performance
and style. Its wheels define a vehicle’s character,
whether it is a pure performance car, luxury blended with
performance, pure bling (make it chrome, with shape) or a
down-and-dirty mud truck. They say what it is about. Their
size and weight and the way they interact with tires and
suspension are key to a vehicle’s driving characteristics.
Select a topic below to learn more.
|
Wheel Finishes |
Shoreline Motoring’s philosophy is that suspension
is even more important than horsepower; suspension is working
any time a vehicle is in motion, while maximum horsepower
is used only a few percent of the time. Suspension is the
system of springs, dampers, and structural members that connects
a vehicle to its wheels. Its design is a mix of art and science
that determines what it feels like to drive or ride in the
vehicle. Suspension determines the balance of comfort, handling
and responsiveness. Suspension modification is how ride height
is changed; it works together with wheels and tires to create
a vehicle’s stance, whether “slammed” in
the weeds or “rally.” Select a topic below
to learn more.
|
Suspension Safety |
Brakes are a vehicle’s most important safety system
and are typically several times as powerful as its engine.
Factory brake systems are designed to be more than most drivers
will ever need. However, when driving more enthusiastically,
increasing vehicle weight with extra equipment or heavy loads
and towing, or increasing power, enhanced braking capacity
is a necessity. Some drivers may choose a larger brake system
purely for style, but even then, it’s important
that the system be properly engineered to the highest
quality
standards. Select a topic below to learn more.
| What Stops My Vehicle | Brake Performance |
Sidewall 101
In recent years, the trend of performance and styling enthusiasts
has been toward making sidewalls smaller, which just makes
them more important than ever. The sidewall of a tire is an
owner's manual. It contains information needed to ensure your
safety and optimum performance of your vehicle. The designations
and classifications that appear on it identify everything from
common dimensions to standard test identification numbers.
Being able to read and understand sidewall moldings will help
you better understand the performance of each tire and make
the right choice for your vehicle and needs.
This page could have been made shorter, but we at Shoreline
wanted to provide the information for our customers. It’s
all important, but some of it may not be important to you,
so feel free to scan this page quickly for the answer to a
specific question, or skip over sections that don’t apply.
A tire's aspect ratio is the relationship of the tire's section
height to section width expressed as a percentage. The lower
the aspect ratio, the shorter the sidewall, and in most cases,
the quicker the steering response. When the aspect ratio appears
in the sizing of a tire, it precedes the tire construction
designation, except in the Alpha-Numeric system.
Three sizing systems exist for passenger tires today: P-Metric,
European Metric and Millimetric. Each of these systems evolved
from the numeric system, which was first tire sizing system
and is now obsolete. It was developed when all tires had the
same aspect ratio, and provided only the nominal cross section
width of the tire and the rim diameter in inches. The following
examples show three sizing systems that are commonly seen today.
Today, most tire manufacturers build tires that conform to
the P-Metric system. Based on the metric system, it evolved
in the late 1970s in an attempt to standardize tire sizing
worldwide. Several variations of each system may be used.
P215/65SR15 P215/65R15 P215/65R15 95S
P = Passenger car tire
215 = section width in millimeters
65 = aspect ratio
R = radial construction
15 = wheel diameter in inches
95S = service description (load index and speed rating)
European Metric is a conversion of the numeric system from
inches to millimeters. Aspect ratio appears in the size designation
in most cases where it is other than 82.
155SR13 155R13 155R13 78S
155 = section width in millimeters
S = speed rating
R = radial construction
13 = wheel diameter in inches
78S = service description (load index and speed rating)
185/70SR14 185/70R14 185/70R14 88S
185 = section width in millimeters
70 = aspect ratio
S = speed rating
R = radial construction
14 = wheel diameter in inches
88S = service description (load index and speed rating)
The Millimetric system is best remembered for its use with
Michelin TRX tires, which were fitted to certain European performance
sedans in the 1980s. In its time, the tire offered excellent
performance, but it has been obsolete for more than a decade.
Replacement tires are available from vintage-tire replica sources,
but it is generally more satisfactory to convert to standard
wheels and modern P-Metric or European Metric tires.
240/55R390
240 = section width in millimeters
55 = aspect ratio
R = radial construction
390 = wheel diameter in millimeters
Sizing for light truck tires accounts for the performance requirements
of the vehicle and its tires, which have evolved with the expanded
uses of trucks and vans for work, recreation and passenger
transport. There are three light truck tire sizing systems:
Light Truck Metric, Light Truck High Flotation and Light Truck
Numeric.
The Light Truck Metric system mirrors the P-Metric system,
and P-Metric tires are in fact sometimes used in light truck
applications when load capacity and other safety considerations
are satisfied.
LT235/75R15/C
LT = light truck designation
235 = section width in millimeters
75 = aspect ratio
R = radial construction
15 = wheel diameter in inches
C = load range
Light truck high flotation tires evolved in the mid-1970s as
lower aspect ratio tires became more popular on light trucks
and vans. The combination of lower aspect ratios and high flotation
yielded better traction on sand and soft soil found in off-road
situations.
31X10.5R15LT/C
31 = overall diameter in inches
10.50 = section width in inches
R = radial construction
15 = wheel diameter in inches
LT = light truck designation
C = load range
The Light Truck Numeric system is still widely used on commercial
vehicles.
9.50R16.5LT/D
9.50 = section width in inches
R = radial construction
16.5 = wheel diameter in inches
LT = light truck designation
D = load range
Speed Rating
A tire’s speed rating indicates the range of speeds
at which the tire can carry a load under specified service
conditions.
The speed rating system used today was developed in Europe
to ensure the safe performance of tires at standard speeds.
A letter indicates a tire's certified speed rating, ranging
from 5 km/h (3 mph) to above 300 km/h (186 mph). The speed
rating system describes the top speed for which a tire is
certified. It does not indicate the total performance capability
of a
tire.
When the speed rating system was originally developed, the
Unlimited V category of over 210 km/h (130 mph) was the top
speed rating a tire could achieve. As manufacturers made more
tires that fit into this category, it was necessary to better
regulate performance at high speeds to ensure safety in unlimited
speed zones. The Limited V category of 240 km/h (149 mph) was
then created, and the Z speed rating was added as the top speed
rating that a tire could achieve. Wand Y limited speed symbols
have been added as higher speed categories.
Always consult the manufacturer for the maximum speed of Unlimited
Z tires. Speed rating is identified as a part of the tire's
sizing or service description. In the latest attempt to standardize
tire designations, all ratings except unlimited ZR incorporate
the speed symbol and load index as the tire's service description.
For example:
205/60R15 91V
205 = section width in millimeters
60 = aspect ratio
R = radial construction
15 = wheel diameter in inches
91 = load index service
V = speed symbol description
"
ZR" Rated Tires
When "ZR" appears in the size designation with
the service description, the maximum speed is as indicated
by the
service description.
P275/40ZR17 93W 270 km/h (168 mph)
P275/40ZR17 93Y 300 km/h (186 mph)
For tires having a maximum speed capability above 240 km/h
(149 mph), a "ZR" may appear in the size designation.
For tires having a maximum speed capability above 300 km/h
(186 mph), a "ZR" must appear in the size designation.
Consult the tire manufacturer for maximum speed when there
is no service description.
The load index ranges from 0 to 279 and indicates the load capacity of a tire.
Most passenger car tire load indices range from 75 to 105. Using a previous example
of tire size 205/60R15 91V, the load index of 91 corresponds to a load carrying
capacity of 615kg (1356 lb) at maximum inflation pressure. The speed symbol of
the tire is the second part of the service description.
The service description system is used with all tires except Unlimited Z. For
Unlimited Z rated tires, consult the vehicle manufacturer for maximum speed.
For proper load carrying capacity, consult the "High-Speed Driving for Passenger
Tires" section of this guide.
Please note the load values in the table are derived from European Tyre and
Rim Technical Organization (ETRTO, European) standards and correspond to European
metric tires. For P-metric tires, the maximum load is derived from Tire and
Rim
Association (T&RA, American) load formulas and can be found in the data pages
or on the tire. Some T&RA load values are rounded to the nearest load index
value. This should clarify why sometimes the same load index for European and
P-metric sizes show different maximum load values.
One pound is equal to .4536 kg.
One kg is equal to 2.2 lb.
The Uniform Tire Quality Grading System (UTQGS) provides information in three
categories: treadwear, traction and temperature. Each tire manufacturer performs
its own tests in each area, following government-prescribed test procedures.
Each manufacturer then assigns grades that are branded on the tire. This is known
as Uniform Tire Quality Grade Labeling (UTQGL).
Example:
300 AA A
300 =treadwear
AA =traction
A =temperature
Treadwear grades typically range from 60 to more than 600, in twenty-point increments.
The actual life of any tire is determined by the road surface quality, driving
habits, inflation, wheel alignment and rotation practices.
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 7,200-mile test the rating results of both tests are compared,
and the tires being tested are assigned a treadwear rating by the manufacturer.
This test does not necessarily simulate the actual conditions under which a given
tire is designed to perform, so there is no reliable way to equate miles of wear
to treadwear grade points.
The best way to use treadwear ratings when choosing tires is to compare one rating
to another for a tire of similar design. 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. However, a tire with a higher treadwear rating may be quickly destroyed
if used outside its intended performance envelope, whereas a tire intended for
such use may have a much lower treadwear rating but last much longer under the
conditions.
Traction grades indicate a tire's ability to stop a car in straight-ahead motion
on wet test surface pavement with the wheels locked. UTQG traction tests are
performed in straight-ahead sliding on government-maintained concrete and asphalt
skid surfaces that have a specified degree of wetting to simulate most road surfaces
in a rainstorm.
Twenty measurements are taken with an industry standard control tire on an asphalt
surface and averaged. The same number of measurements is 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. Traction grades include AA, A,
B, C, with AA being the highest attainable grade.
UTQG traction ratings may not apply to straight-line acceleration, cornering
traction or peak values of straight-ahead braking force like those experienced
in non-skid braking tests.
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 conditions. Temperature ratings are determined by running
tires on an indoor road wheel 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 "C" if it meets the minimum performance
required by the U.S. Department of Transportation. Grades of "B" and "A" represent
higher levels of performance than the minimum required by DOT.
Maximum load and inflation indicate the maximum load that can be carried at
the tire’s maximum allowable inflation pressure.
Example:
MAX.LOAD 990 kg (2183 LBS.) AT 280 kPa (41 psi) MAX. PRESS.
Light truck tire sizes show specific load range symbols on the sidewall that
indicate how much load the tire is designed to carry at a specified pressure.
Many light truck size tires are Load Range C, meaning that they are restricted
to the load that can be carried with a maximum inflation pressure of 50 psi.
For greater load carrying capacity, load range D or E tires can be used, provided
the wheels can carry the increased load and pressure. Otherwise, new wheels are
required.
Note: For most load range C, D, and E tires and/or light truck applications,
the load-carrying capacity designation appears directly after the tire size as
below:
LT235/75R15/C
The load capacity of P-Metric tires is rated Light Load, Standard Load or Extra
Load. Light and Standard Load tires are limited to the load that can be carried
with a maximum inflation pressure of 35 psi. Light Load tires offer a slight
load reduction from Standard Load tires for certain applications. Light load
applies only to tires with aspect ratio of 45 or less. Extra Load tires are
limited to the load that can be carried with a maximum inflation pressure of
41 psi.
An Extra Load or Light Load tire (for example, P235/75R15XL) will be branded
with "Extra Load". A Standard Load tire does not bear any special
designations.
European metric tires are either Standard or Reinforced Load. Standard Load
tires are limited to the load that can be carried with a maximum inflation
pressure
that can range from 32 to 36 psi. Reinforced Load tires are limited by the
load that can be carried with a maximum inflation pressure of 42 psi. A Reinforced
tire (for example, 175/65R14RF) will be branded with "Reinforced".
Standard Load tires do not bear any special designations.
A standard load tire with a normal inflation pressure of 35 psi may be branded
with a maximum inflation of 44 or 51 psi. An extra load tire with a normal
inflation pressure of 41 psi may be branded with a maximum inflation of 50
psi. In both
cases, the marking indicates the tire’s ability to meet special vehicle
performance requirements. It does not increase the tire’s load capacity.
General Motors requires that the tires fitted on certain vehicles meet GM’s
own Tire Performance Criteria (TPC). These criteria are tested using performance
formulas. When a tire meets the requirements, the TPC specification number
is branded on its sidewall.
When any of the following markings appear on a tire, the tire meets the Rubber
Manufacturers Association (RMA) definition of a mud and snow tire: M+S, M/S
or M&S. In most cases, this marking identifies all-season performance.
When this mark appears on a tire in addition to the M&S marking, the tire
meets the Rubber Manufacturers Association definition of a tire designed for
use in severe snow conditions.
U.S. Department of Transportation
Example: DOT M5H3 459X 065
The DOT marking signifies that the tire complies with United States Department
of Transportation tire safety standards and is approved for highway use. The
first two characters following DOT designate the tire's manufacturer and plant
code. The third and fourth characters denote the tire size. The fifth, sixth,
seventh and eighth (optional) characters identify the brand and other significant
characteristics of the tire. The ninth and tenth characters denote the week the
tire was produced. The final number signifies the year in which the tire was
manufactured.
For Michelin brand tires only, DOT markings for the week and year of production
will have a triangle (<) following the last three numbers to indicate the
decade of the 1990s.
Example: 065<
This would designate the 6th week of 1995.
Beginning in year 2000, an additional digit was added to the serial number to
allow the year of production to have two digits.
Example: DOT BEHY TTLX 0800
The ninth and tenth digits still indicate the week of manufacture while 00 indicates
year 2000.
The Economic Commission of Europe (ECE) develops motor vehicle equipment requirements.
ECE-approved tires must meet ECE standards for physical dimensions, branding
requirements and high-speed endurance. When a tire bears the ECE symbol on its
sidewall, it is certified to the load index and speed symbol that appear in its
service description for use in Europe.
The letter and number combination circled at the beginning of the designation
represent the country originally granting approval, such as E2 for France or
E4 for the Netherlands. The first two digits of the number sequence indicate
the Regulation Amendment Series under which the tire was approved, such as “02" for
ECE Reg. 30. The last four or five digits represent the tire size and type.
Not all tires receive the ECE's approval. In order to be ECE branded, a tire
must receive laboratory approval, meet confirmation testing requirements and
have the facility where it was manufactured pass an inspection.
Plus Sizing
Plus sizing is the practice of increasing a vehicle’s
wheel diameter while maintaining the original outside diameter
of the tires by selecting a lower “profile,” or
sidewall height. Properly chosen plus size wheels and tires
can provide significant improvements in ride, handling and
safety.
“
Plus one” means increasing wheel diameter by 1 in., “plus
two” by 2 in., etc. “Plus zero” means keeping
the original wheel diameter, but increasing tire width, such
as by going from a 185/60-14 to a 195/55-14.
The example above shows two wheels for a 1993 BMW 325is. The
original size is a 205/50-16 on a factory 15x7-in. wheel. At
right is a 235/40-17 on a 17x8-in. SSR Type C wheel. Both have
the same overall diameter, but the performance wheel is two
inches larger in diameter.
Some very particular enthusiasts worry about small differences
in overall diameter, forgetting that this normally changes
as a tire wears. If a tire starts at 10/32-in. tread depth,
it has decreased by 1/2-in. in overall diameter when it reaches
1/16-in. tread depth and must be replaced. For most passenger
cars, this affects speedometer readings by about 2 to 2-1/2
percent. Keeping starting diameter within 0.2-0.5 in. of original
is usually close enough to avoid problems, except in very rare
cases.
The terminology of plus sizing originated when plus-one was
a good idea and plus-two was probably about as far as one would
want to go. Today, plus-three is almost considered a baseline
by many street tuning enthusiasts, though plus-one or plus-two
may actually provide the best performance when paired with
optimum tire selection.
In certain cases, such as newer Porsches, the best performance
may actually be obtained with the largest factory wheel sizes.
But while a plus-one, 19-in. fitment may not provide ultimate
performance, but it is aesthetically very pleasing to many
owners. On certain large vehicles, such as trucks and SUVs,
plus-ten is a possibility if one is willing to increase the
overall diameter of the tire.
An increase in tire width usually accompanies increased wheel
diameter when plus sizing. It is important to separate performance
improvements due to increased tire width from those due to
increased wheel diameter. More rubber on the road tends to
improve performance, but it may not take plus sizing to achieve.
The most common reason for plus sizing is to enhance a vehicles’ appearance.
Wheels are a car’s jewelry. To most people, tall, round
sidewalls evoke economy cars with skinny tires or trucks used
for work and off-road driving.
Factory-supplied wheels aren’t often designed with much
style; they give a vehicle a plain look. Some original wheels
are nice, but maybe you want your Mercedes to look different
than the hundreds of others you see. Larger, more stylish wheels
suggest a nicer car; if chosen well, they will indeed make
a car nicer.
Functional advantages to plus sizing are many. Perhaps the
greatest is the accommodation of premium tires and their benefits,
including ride, handling, braking and, for powerful cars, acceleration.
Because they are usually more expensive than original tires,
they can include more technology to eliminate compromises.
Given the same tire make and model, plus sizing has several
benefits. A shorter sidewall is typically stiffer, and will
improve handling. Steering may be enhanced, both in quickness
of response and feedback, or feel.
Slip angle, the difference between the direction a tire is
pointing and the direction of its travel, is typically smaller
and often more linear across the range of cornering load, making
the car easier to drive. Reduced tire flex reduces heat generation,
so lower-profile tires last longer when driven hard.
Two factors may improve ride quality with plus sizing. Premium
tires designed for plus sizing are usually engineered with
great attention to ride characteristics. If suspension modifications
are present on a vehicle, typically with stiffer springs and
dampers, the compliance of the tire becomes a greater factor.
Stiffening it often provides a better match for performance-oriented
suspension components, helping them do their job better.
There are some downsides to plus sizing, especially if not
done carefully. The most common is the tire rubbing fenders
or other parts due to excess width, increases in overall diameter
or wrong offset wheels. In some climates, it may be necessary
to leave clearance for tire chains.
Reduced sidewall height reduces the tire’s ability to
absorb impacts from bumps, potholes or debris on the road,
leading to wheel or suspension damage in extreme cases. If
plus sizing is taken too far, the car may feel harsh over smaller
bumps and freeway expansion joints. Preserving suspension travel
is an important factor in guarding against both these problems.
Low-profile tires have reduced load capacity, so they must
be made stronger. It is especially important when plus-sizing
SUVs and larger sedans to follow appropriate guidelines for
load ratings.
Larger-diameter wheels tend to be heavier, increasing unsprung
weight and rotational inertia. Unsprung weight reduces road
holding and braking traction, as well as ride quality. Rotational
inertia mostly affects braking and acceleration. For rotational
inertia, location of the weight is actually more important
than how much weight there is. Tests have shown measurable
differences in acceleration of the same car fitted with 1-in.
different wheel diameters, even when the overall weight of
the wheel and tire combination stayed the same. Paying attention
to wheel weight and purchasing higher-quality wheels with better
manufacturing processes for greater strength allows these disadvantages
to be overcome, and even significant improvements to be made
over stock components.
If plus sizing is pursued to an extent that the overall tire
diameter is increased, gearing is affected. On older vehicles,
this may adversely affect only acceleration and braking abilities.
On modern, computer-controlled vehicles, the performance of
both anti-lock braking systems and electronic stability control
systems can be diminished by tires of the wrong diameter, especially
if the relationship between the front and rear tires is changed.
Automatic transmission calibration, usually tied to vehicle
speed, can also be affected.
Despite its possible pitfalls, plus sizing usually leads to
overall improvement of a vehicle. Higher quality, more stylish
wheels are the first, best, simplest and most important change
that can be made to a vehicle. They lay the foundation for
any other changes, whether the objective is enhanced performance
or appearance.
The Basic Question: What stops your vehicle?
There are two links in the chain of forces that must stop
your vehicle. The first is traction, the grip of the tires
on the road. Traction depends on the rubber compound and tread
design, as well as on the road surface, weather conditions
such as dust, water, snow and temperature, and how well the
vehicle suspension is able to keep the rubber in contact with
the road as it rolls over bumps.
The second link is brake torque, which is created by the
friction of the brake pad clamping the brake rotor. Through
this friction,
the vehicle’s energy of motion is converted into heat,
which is then passed into the surrounding air. This friction
depends on the coefficient of friction of the brake pad material
against the rotor and the clamping force applied. Clamping
force is the pressure in the brakes’ hydraulic system
times the acting caliper piston area. Friction force is converted
to torque by acting at a distance from the axle center.
Traction
and brake torque are the two things that slow a vehicle.
Everything else is a detail aimed at creating these
two factors
and making them work properly together.
Suspension Safety
-- What you need to know:
Suspension is an active safety system, meaning it accomplishes
safety through driver input, whereas a passive safety system,
when activated, functions regardless of the driver’s
actions. Suspension safety means preserving the driver’s
ability to control the vehicle and arrive at a destination.
In order to achieve this, there can be no component failures.
The vehicle must have safe handling in regular and emergency
situations, and maximum load capacity (vehicle GVWR) must
be preserved. The vehicle must be able to make safe progress
in any weather conditions that could reasonably be expected,
whether rain, snow, ice, high heat or cold.
Modified suspension components must be engineered and installed
to prevent damage to themselves and the rest of the vehicle.
Corrosion, leading to weakening and possibly breakage of components,
must be guarded against. Dampers must not bottom out or top
out against internal components not intended for the purpose,
springs must be unable to reach coil bind (the point where
they are completely compressed and function as a solid block
of metal) and any required venting or dust control devices
must be in place.
Suspension changes cannot adversely affect other vehicle components.
Clearance between the tires and fenders, fender liners, suspension
and brake components must be preserved; rubbing is not acceptable
even with the suspension compressed and the steering turned. “Cut” tire
shoulders are unacceptable. Drive axles must clear all other
components and operate within their designed range of angles.
The integrity of the unibody or frame structure must never
be compromised, whether through excessive peak forces or binding
of mounting joints. All suspension components must move freely,
without binding, through their entire range of motion. Attention
should be given to approach, departure and breakover clearances
to prevent damage to bodywork, exhaust and other components.
In braking, suspension affects stability and steering. It also
affects how well the tire’s contact patch is held against
the pavement, partly determining how much traction the tire
is able to achieve.
Suspension must create safe handling characteristics. The balance
between oversteer and understeer must be stable under acceleration,
with neutral throttle and when the throttle is lifted. The
car must turn into a corner quickly and without oscillations
that can sap driver confidence. The performance limits should
be appropriate to the vehicle and its driver. Responses must
be progressive and smooth as the vehicle approaches and exceeds
its limits and then recovers. Finally, the suspension must
be able to maintain traction through a corner with reasonable
bumps; if it works only on perfectly smooth pavement, it doesn’t
really work.
It’s tempting, as an enthusiast, to focus only on appearance,
or else allow oneself to chase maximum cornering performance
if, for example, you enjoy track days. The most trouble-free,
reliable and overall enjoyable vehicle will balance those objectives
against all the requirements above, and others such as ride
comfort. It will always be a “real” vehicle, able
to serve you through the unexpected thick and thin that life
will inevitably throw at you.
Wheel Finishes:
Paint is the most common factory and aftermarket wheel finish.
It provides good corrosion protection, preserving a wheel’s
appearance, at low cost and with little weight. Paint colors
are easily chosen and changed. Painted wheels are easy to clean
and maintain, but can chip or scratch fairly easily. It is
easy to inspect painted wheels for structural damage, such
as bends or cracking.
Powder coating looks like paint, but is actually a plastic
coating baked onto the wheel. The process is slower and more
expensive than painting, and is usually done only as an after-sale
refinish. Powder coating provides excellent corrosion and is
easily maintained. It is thicker and slightly heavier than
paint, but is stronger. It can, however, stretch and conceal
hairline cracks that would show with other finishes.
Anodizing is a treatment applied to aluminum in which the metal
is oxidized and dyed, forming a hard surface resistant to further
corrosion as well as scratches, nicks and abrasion.
Its thickness
is usually less than one thousandth of an inch, allowing the
base metal’s luster to shine through and exposing its
surface preparation, which must be perfect. Anodizing can fade
in UV light if the wrong process is used. Quality, defect-free
anodizing is difficult and expensive, especially with darker
colors. Maintaining anodized wheels is easy, but they can be
badly damaged by incompatible chemistry.
Polished, bare-metal wheels are the most maintenance-intensive,
requiring frequent cleaning and polishing. A polished finish
looks best on forged metal centers and rolled rims, with their
dense metal structure. Polished surfaces may be more true to
the original shape than those that have been chromed. They
are easily nicked or scratched and provide no corrosion protection
other than the resistance of the metal itself. In recent years,
diamond-cut lips have become possible, with the final machining
process leaving a surface perfectly true and so smooth it needs
no polishing to shine.
Polished wheels are sometimes clear coated with paint or powder
coat, in order to protect against tarnishing and provide some
nick and scratch protection. Lower-quality clear coats can
yellow, fog, or lose their gloss with time and exposure to
ultraviolet light. No clear coat will be quite as lustrous
as chrome or bare, polished metal.
Chrome plating is a hard, durable finish with excellent corrosion
resistance, most noted for its shine. Chrome of Type 1 is most
often used for wheels. It has a bright appearance, and provides
maximum corrosion resistance. Type 2 chrome has a deeper, satin
luster, and is more expensive, considered an “engineering” plating.
Proper chroming includes layers of copper and nickel under
the chromium, adding non-structural weight to the wheel. Initially
and after each intermediate plating step, the surface is polished.
Crevices can be filled and high spots softened, changing the
contours and losing the crispness of details. In extreme cases,
the surface can look wavy.
The final appearance of chroming depends very much on the base
metal, whether it is a quality casting or forging with good
metal structure and uniform surface, or a low-quality casting
with poor surface quality. Better base metals require less
polishing, keeping the surface details crisper and forms truer.
The porosity of a low-quality casting promotes hydrogen embrittlement
during the chroming process, whereas higher quality castings
and forgings with denser metal are more resistant to it.
A recent technology advance is chrome-like paint or powder
coating, which provides nearly the appearance of chrome. A
range of colors is possible, including anthracite, charcoal
and “black” chrome looks. These coatings have the
advantage of lower cost, light weight, environmental friendliness
and no effect on the metallic structure. They can be applied
at the wheel factory, with the resulting benefits of quality
from process control. Perfectly applied, they provide superb
corrosion resistance. BBS’ finish warranty on its chrome-like
painted wheels is significantly longer than on its chromed
wheels.
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