The R6 and A6 have been developed
to improve wear and consistency without any sacrifice of performance.
In many cases, the performance will even improve over previous models.
The new tire models are an evolution in the continuing effort to
provide the best tire for racers.
- Tire Break-In Procedure
- Tire Temperature Recommendations
- Chassis Setup Recommendations
- Tire Pressure Recommendations
- Things to Consider
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 A6s, but be sure to
reset them to the correct operating pressures before your first
autocross run. As you compile autocross runs on your new A6s, 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.
Roadrace/track
applications
Vehicle size |
Recommended Hot Pressure |
Cold Pressure |
1800-2200 lbs. |
34-37+ |
26-31 |
2200-2600 lbs. |
35-38+ |
27-32 |
2600-3000 lbs. |
37-41+ |
27-32 |
over 3000 lbs. |
38-43+ |
27-33 |
+Higher pressures will improve the performance capability but will
require a more sensitive feel to take advantage of the increase.
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.
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