Up Stepping to High Performance
Colour Markings on the Side Wall of the Tyre
Fitting Instructions on the Side Wall of the Tyre
High
performance driving is not a pleasure limited to the owners of exotic
performance vehicles. The popularity and success of the tune-up industry is
ample proof of the widespread interest in driving that "goes beyond
ordinary."
Car
tuners take engine, suspension and tyre modification to the extreme in order to
maximise performance.
Here,
Yokohama gives you a guide to the tyre aspects of tuning, so you can make an
informed and correct choice of tyres and give virtually any car substantially
improved handling.
Please
remember that when driving, your tyres are the only contact between the car and
the road. So for the sake of safety, always consult your local Yokohama High
Performance Tyre dealer for professional advice.
Selection
of the wrong type of tyres can lead to serious accidents.
The
main function of a tyre is to carry the load of the car. Therefore, it is vital
that correct air pressure is maintained. Over-inflation will cause rapid and
irregular wear.
Under-inflation
will damage the tyre structure leading to possible accidents.
Improper
air pressure will not allow the tyre to function within its design. For best
performance maintain the air pressure recommended by the vehicle manufacturer
and/or the tyre manufacturer.
A
major cause of rapid tread wear is improper wheel alignment and balancing.
Abnormal noise, vibration and harshness of steering is a signal that alignment
and balancing may be improper.
Recommended
at 6,000mile intervals, tyre rotation balances tyre wear to increase overall
tread life. High performance tyres are often position specific and should not be
rotated. For vehicles with different tyre sizes front to rear, rotation should
be performed left to right periodically.
1.
Yokohama Brand/Tyre Pattern
2.
Tread Wear Indicator
3.
Speed Rating
4.
Load Rating (not found on Z-rated tyres)
5.
Inner Diameter (Rim Size) 
6.
Aspect Ratio
7.
Tyre Width
8. Construction (Radial)
Performance can be improved without the necessity of changing wheels simply by selecting a tyre with a lower profile. This means maintaining overall diameter while lowering aspect ratio and correspondingly increasing the tyre width. Put simply, a tyre with a lower section height and wider tread has better cornering force and grip, thus improving steering stability.
In
order to attain the maximum performance out of your vehicle, larger and wider
wheels are recommended. Although high performance is our goal,
there are certain safety guidelines that must be observed. This means that wheel
size and type, and tyre height and width must fall within certain limits. When
selecting a high performance tyre the following must be observed.
Wheel
well clearance must be maintained. Failure to do so would most likely severely
cut the tyre when turning, if not lead to a puncture. The vehicle manufacturer
can provide the maximum tyre
width
permissible, or consult us before
you order, use the E-Mail facility to let us know your requirements
With
a constant wheel diameter, overall tyre diameter will decrease proportionately
with aspect ratio. This smaller overall diameter will result in speedometer
error.
It
is often is the case that new wheels are required. This can be for the following
reasons: either a larger rim width and/or larger rim diameter is called for.
When choosing your high performance wheels ensure that they have the correct
offset and pitch circle diameter (P.C.D.) for your vehicle.
Maximising
your car's performance by selecting a lower profile tyre/larger size rim
combination is referred to as "up-stepping." Plus-one or plus-two
tells you how much larger the rim size is. This "up-step" approach to
improving performance came into being for the following reason.
As
explained previously, it is possible to get higher performance without changing
rims. Unfortunately, it is often necessary to increase tyre width to the point
that steering geometry is affected, with the result that a change in driving
style or habits becomes necessary.
So
to fully maximise your vehicle's performance (which includes preserving the
steering geometry) the "up-step" approach is highly recommended. By
fitting a larger rim, increases in tyre section width are properly managed while
correct overall diameter is maintained. This maximises cornering force and grip
without sacrificing any other handling parameters. In fact, all-round
performance is improved.
Aspect
ratio measures section height to section width.
As illustrated, holding section width constant, section height will decrease as aspect ratio decreases. Another way of looking at this is also illustrated. Holding rim diameter constant, overall diameter will decrease as aspect ratio decreases.
The illustrations are vital to selecting the proper high performance tyre as will be explained in the next section.
Road
tyres are given a speed symbol indicating their maximum permissible speed. These
are as follows:
*
Speed rating depends on tyre size.
It
should be noted that the load capacity of the tyre would diminish as the maximum
speed is approached. For expert technical advice, please consult your Yokohama
High Performance Tyre dealer.
Red
Point/Red Triangle Indicates the maximum point of Radial Force Variation (RFV),
the stiffest point of the tyre side wall. This mark should be aligned with the
'L' mark (i.e. the low mark) on alloy wheels when fitting.
White
Point/White Circle In the case of some Original Equipment tyres, this white mark
will indicate the minimum point of RFV, the most flexible point of the tyre side
wall. In these cases, the white mark should be aligned with the 'high' mark on
the wheel, or 180° to the 'L' mark.
Yellow
Point/Yellow Triangle If no 'L' mark is visible or in the case of fitment to
steel wheels, the tyre should be fitted with the yellow mark positioned to line
up with the wheel valve. This yellow mark indicates the lightest point of the
tyre determined under static balancing conditions.
Symmetrical
tread
No indications
Assymetrical
tread
Side facing outwards
Sidefacing inwards
Directional
tread
Arrow rotation
Assymetrical
& Directional tread (Honda NSX)
Indications on sticker on the tyre
Determine
your car's maximum allowable tyre selection width.
Locate
your current tyre size on the TSW Wheel/Yokohama Tyre conversion chart.
Make
a list of all tyre sizes to the right of your current tyres with a similar
overall diameter.
Many
of the listed sizes may require a change of wheels; therefore it is important to
consider the level of performance improvement you desire. Plus-one or plus-two
upgrades offer the best results. Refer to the "Rim Width Guide" to
determine rim width requirements, but please remember your car's specifications
may limit your choice.
Narrow
down the list of possible tyre sizes by removing those with larger section
widths than your car allows. Note: The replacement tyre's load index must be
equal to or greater than the original.
After
consulting us if required, select the most suitable tyre size.
If
you require a wheel change, ask us for the recommended offset value and correct
PCD.
Have
your new set of tyres and wheels properly mounted, balanced and aligned by a
professional.