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Tire
Break-In Procedure
Proper break-in will not affect initial performance but will
increase the competitive life of the tire.
The procedure
can be broken down into phases.
1st phase:
The initial run
2nd phase: The length of the time the tire is allowed to "cure"
The
Initial Run Heat Cycle
R6
Roadrace
The first
laps for the tire are critical for setting up the durability
and competitive life. The first session should consist of
no more than 10-15 minutes of running. The early part of the
session should be run at an easy pace, with the speed gradually
increased until the end of the session. The final lap should
be run at the fastest possible speed. The intent is to achieve
maximum tire temp on the last lap. At this point the car should
be brought in and the tires allowed to cool at a normal rate.
During
the initial run-in process, the inflation pressure should
be 3-5 psi higher than you would normally use. The best progression
would have the driver taking 4-7 laps to accomplish this break-in.
Each lap should be approximately 7-10 seconds a lap faster
than the previous lap. The goal is to have the tire temp as
high as possible on the last lap without "shocking"
the tire during the warm up laps. In essence, no wheelspin,
late braking, or sliding. The last lap should be at, or very
close, the maximum possible.
A6
Autocross
For autocrossing,
the A6 does not need the same break in procedure as the R6.
The A6 needs a minimal scuff-in session before the first autocross
run. This “session” can comprise of simply driving
around the event site at minimal speeds on the A6 set of tires.
By scrubbing off the newness of the tread (no or minimal shininess
remaining) prior to your first competitive run, the A6 tires
will be more consistent in handling, grip and responsiveness
on the first run. If this is not completed, running on un-scuffed
A6 tires on your first run may result in the tires not gripping
properly, or feeling like they “skate” over the
course surface. You are welcome to run 3 – 5 psi higher
when scuffing in a new set of A6’s, but be sure to reset
them to the correct operating pressures before your first
autocross run. As you compile autocross runs on your new A6’s,
they should become more consistent in run times.
"Cure"
Time
After completing the initial run phase, the length of time
the tire is allowed to set is possibly more important. The
barest minimum for this process to be beneficial is 24 hours.
(Not "the next day"). Any less than this is a waste
of time. The best situation would allow a week before using
the tire again.
Proper
tire management is a difficult process. To accomplish this
almost always requires a second set of wheels. The payoff
is greatly increased competitive tire life.
Following
the recommended break-in procedure will require a lot of planning
to make it work. The benefits to doing it right include greatly
increased tire life as well as consistent performance and
durability under stress. Please make an effort to educate
your team on the importance of this. It can save you a lot
of money.
Tire
Temperature Recommendations
For best
performance the expected temperature range will vary from
track to track. Generally, optimum traction will be generated
when the pit lane temps show 180-200 degrees for the R6 in
Roadrace applications, and 140-150 degrees for the A6 in an
Autocross application.
Note:
Use of static infra-red pyrometers is an inaccurate method
to monitor tire temps.
Chassis
Setup Recommendations
For optimum performance the Hoosier P-Metric radial tires
require about 3 degrees of camber. There will be a trade off
in maximum performance to maximize wear. Generally, 1/2 degrees
less than optimum will result in the best compromise for wear
and speed. Less than 2.5 degrees can result in excessive wear
on the shoulder junction.
The Hoosier
tires typically offer better performance with spring/shock
rates higher than previous brands you may have run.
Tire
Pressure Recommendations For Competition
Traditionally,
Hoosier tires have often required higher pressures than other
brands. This has changed with the A6/R6.
One characteristic
of the tires is the tendency to "skate" initially
(when inflation pressures are correct). It is important to
resist lowering the pressure to attempt to eliminate this
feeling. Dropping the pressure too far may improve the "feel"
of the tire however it will also lower the performance and
increase the wear rate.
Autocross
applications
For autocross
applications, your starting pressure for the first run should
be within 1-2 psi of the recommended hot pressures shown above.
After the first run and each subsequent run, keep resetting
the pressures back to your target hot pressures before taking
the next run. This way your tires are at the proper pressure
during the bulk of every run you take.
The above
chart is a general recommendation which is intended for a
standard configuration vehicle (i.e. front engine, rear wheel
drive). Factors which can radically affect your pressure set
up would include front wheel drive, independent rear suspension,
rear engine, McPherson vs. control arm front suspension.
Front
Wheel Drive
Vehicles configured with FWD are probably the most difficult
application for a tire setup. The combination of steering,
braking and accelerating on the front tires, combined with
higher corner weights for the front positions produce a harsh
environment for the tire. These vehicles will typically have
a strut type of suspension which limits camber gain. All these
factors result in conditions which require the tire do more
work than a simple chart for pressures can accommodate.
In severe
cases front tire pressures for FWD vehicles can run in the
48-52 psi (hot). In cases where the tire size is limited to
a relatively small tire, the required pressure can run even
higher. The front to rear pressure differential on FWD cars
can have extreme ranges of inflation, depending on the driver
preference, suspension tuning, and track configuration.
Independent
rear suspension
With IRS and proper geometry up front, tire pressures can
be reduced from the recommendations listed above. When there
is adequate camber gain and good roll control, the Hoosier
radial tire will perform very well at the reduced air pressure.
This results in a bigger "sweet spot" and easier
control at the limit.
When
tuning at reduced pressures use the following formula to determine
the minimum safe pressure: Divide the total vehicle weight,
including fuel and driver, by 100 to arrive at the minimum
safe pressure. Example: Your car weighs 2750 lbs. as raced.
The minimum safe (cold) pressure is 27.5 psi.
Extreme
care should be taken when tuning at reduced pressure. Tire
damage can occur that is not visible to external inspection.
Vehicles
equipped with independent rear suspension (IRS) have a distinct
advantage over non-IRS cars when using radial tires. This
is true for two reasons. First, it is possible to setup some
amount of static negative camber on IRS suspensions, if needed.
Second, the IRS geometry can provide the proper camber gain
to achieve the dynamic camber needed for a radial tire. This
is a great benefit because it then becomes possible to better
address front tire grip when the rear of the car can be optimized
closer to the tire's potential.
THINGS
TO CONSIDER
These tires are molded to their designed tread depth. They
do not require shaving to be prepared for competition use.
Due to
extremely light construction, Hoosier tires have a much lower
polar moment than other radial tires. This translates to a
very low rotational mass, which is a good thing for performance
applications. The down side to this feature is that the tires
do not resist "spikes" in braking force as well
as a heavier tire might. As a result, there is a tendency
for drivers to "flatspot" a tire the first time
really getting to the limit. Vehicles equipped with ABS will
benefit from its use. If you do not use ABS it is recommended
that you make an effort to minimize stabbing the brakes until
you have some experience with the feel of the tire under hard
braking.
The light
construction also provides less protection from impact damage
and punctures. Off course excursions or running over debris
on the track will likely result in tire damage.
The tires
are not directional. Once some wear has occurred it may be
desirable to flip the tire on the wheel in order to even out
the wear and maximize tire life.
Wheel
Widths
Wheel width dramatically affects wear and performance of the
Hoosier P-Metric radial tires.
There
is about a one inch window of optimum width. The trick is
to figure out that window. A good rule of thumb to use for
determining proper width is to use the tread width of the
tire. Measure the tread width. Plus or minus 1/2 inch from
the tread dimension will indicate the proper rim sizing. It
is possible to use narrower wheels, but at a sacrifice to
shoulder wear and cornering power.
"Measured"
rim vs. "Recommended" rim
In our printed product catalog and on our website tire specifications
you will see two columns of information regarding rim dimensions.
In most cases, the "measured rim" and the "recommended
rim" will be the same. However in the case of DOT tires,
the information may appear contradictory.
The reason
for the differences lies in the Department of Transportation
requirements for publishing tire dimensions on any tire that
carries a DOT certification. Each tire size has a specific
rim that must be used when taking measurements for tire comparison.
This is intended to allow consumers a consistent way to compare
tire sizes between brands.
With
respect to the Hoosier P-Metric line, the recommended rim
size will typically be wider than the DOT standardized wheel.
The fact
that a tire will "fit" on a rim is not an indication
that it will work effectively in that condition. Radial tires
are extremely sensitive to wheel widths. The performance characteristics
of the tire can change significantly within the recommended
range of application. Mounting a tire on a rim that is outside
of the recommendation is not a good idea.
Driving
Style/Braking
Driving style has also shown to significantly effect tire
wear. Drivers who achieve their speed by "tossing"
the car run the risk of increased tire wear. Radial tires
develop their highest cornering power at relatively low slip
angles. Smooth, tidy driving yields faster lap times and better
tire wear.
The braking
feel of the Hoosier R6 tire is very vague at the threshold.
This is particularly true for "sticker" tires. Drivers
need to develop a sensitivity for the limits under braking.
This takes time and practice. Failure to apply this will result
in flatspotted tires.
Particular
care needs to be taken when selecting brake pad compounds.
It is possible to have a pad that is too aggressive. This
will make it very difficult to develop good braking fell for
threshold braking.
Rain
Tires
The Hoosier D.O.T. Radial tires are extremely good in dry
conditions, however they do not make very good wet weather
tires. Having dedicated rain tires available will be necessary
for your team to be properly prepared. Hoosier makes a D.O.T.
approved bias-ply tire called a "Dirt Stocker" that
has been proven to be far superior to any competitors tire
as long as it is a steady "wet" condition. Check
with your Hoosier representative for size availability.
Hoosier
Racing Tire also offers a D.O.T. Radial Wet tire. This tire
has a molded tread of symmetrical design. Check the product
catalog for the available sizes. The compound for these tires
is intended for wet weather use only.
Hoosier
also offers a non-D.O.T. radial rain tire based directly on
the P-Metric R6 tire. The tread depth is 8/32" and the
pattern is the same tread design found on the R6. They have
been allowed in BMW Club racing and many other sports car
clubs as well. Mounting instructions can be found in the “Road
Racing FAQ” section of the website. The list of available
sizes can be found in the "road racing/tire specs”
section of our website.
When
using rain tires, always increase your starting air pressure
2-4 psi over your dry tire pressures
Any
questions about kits, parts, installations or services are
welcome. Contact Bishop by phone at 866-867-8324 or
e-mail bishop@bishopsales.com
and we will respond promptly. If you're in the neighborhood,
then drop by the shop at 1130 West 15th Street North Vancouver
BC and we will gladly give you a tour of our facilities, but
beware – there may be a Monster and ferocious horsepower
beasts in our shop when you visit! We really love to share
the fun with other performance enthusiasts who want to take
their cars to the next level of performance, appearance and
handling!
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