1973 OPEL GT-R run flat

WHEELS AND TIRES3G- 55
WHEELS AND TIRES
CONTENTS
Subject
DESCRIPTION AND OPERATION: (Not Applicable)
DIAGNOSIS:
Car
RoughnessandVibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .AbnormalTireWear
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAINTENANCE AND ADJUSTMENTS:
Demounting and Mounting Tubeless Tires
. . . . . . . . . . . . . .Wheel
andTireBalance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAJOR REPAIR: (Not Applicable)
SPECIFICATIONS:
Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page No.
3G-55
3G-58
3G-6136-6236-62
DIAGNOSIS
CAR ROUGHNESS AND VIBRATIONinflation pressures and perform tire inspection, in-
cluding removal of any foreign material on tire tread
or wheel large enough to upset balance.
Possible Causes
To assist in the diagnosis and correction of some of
the more stubborn cases of tire vibration and rough-
ness conditions that may be encountered, the follow-
ing information is offered:Tire inflation pressure recommendations are very
important at all times and particularly so on all ride
complaints. Raising or lowering tire pressures to
“improve” mileage or traction should not be at-
tempted.
VIBRATION, or a quivering motion condition, no-
ticeable by feel through the steering column, steering
wheel, floor
p&n, or by hood and fender shake, usu-
ally originates from the front wheels and tires. Front
end vibration, when caused by unbalanced front
wheels, can be generally felt as steering wheel “nib-ble”.Next, road-test the car with the owner, if possible,
and have the owner explain the specific ride disturb-
ance.After road-testing, raise car on hoist and proceed to
isolate the offending tire/wheel assembly.
Reproducing the Disturbance
A vibration felt through the seats as a side-to-side
disturbance can usually be attributed to the rearIn an attempt to reproduce the disturbance ex-
wheels and tires.perienced in the ride, a wheel spinner can be used on
the front wheels of the car.
Both front and rear vibration can be noticed mainly
at highway speeds, usually over 60 mph.The rear wheels may be spun by placing car in
“Drive” with engine running.
ROUGHNESS, noticeable primarily at speeds be-
tween 40 and 65 mph, can be felt (and occasionally
heard), and is due to certain irregularities in the tire.
Roughness usually sets up a “trembling” feel or a
shuddering effect.When spinning rear wheels, never exceed a speedom-
eter speed of 35 mph with a standard rear axle assem-
bly, or 75 mph on one with a positive traction rear
axle. Excessive speeds may cause damage to the rear
axle assembly.
Road-Test With Owner
When a ride complaint is encountered, first checkJack up both rear wheels by placing the jack under
the differential housing. Spin one wheel and tire with
the opposite wheel held from rotating by holding the

3G- 581873 OPEL SERVICE MANUALTire Wear IrregularitiesAn additional cause of vibrations may sometimes be
tire wear irregularities. These can also produce noise
disturbances, and can be generally corrected by
rotating the tires, Figure
3G-6. Before proceeding
further, locate and correct the cause of the irregular
tire wear. See Figure
3G-7.Use the criss-cross method of rotation of tires only
when all four tires are equally worn. In some in-
stances, it may be necessary to put the truest running
assemblies (those with the lowest tolerances) on the
front of the car.
Wheel Nut Torque end Tightening SpecificationsDuring all wheel installations, it is important to use
the correct procedures for installing wheel nuts and
torquing them uniformly and in proper sequence.
This is important in order to avoid possible distor-
tion of the brake drum or disc, and to minimize
damage to lug and nut threads and wheel stud holes.
To assure uniform tightening of wheel lug nuts, the
following procedure is recommended:
1. Install wheel lug nuts in a criss-cross pattern and
tighten just enough to seat wheel against hub. This
assures proper piloting of the wheel on its hub.
2. Tighten lug nuts uniformly to proper torque of 65
Ib.ft. using criss-cross pattern.
An impact wrench should not be used, as uniform
torque control cannot be maintained.
Summary of Diagnosis end Correction of Tire and
Wheel Vibration1. Inflate all tires to recommended pressure and
road-test car with owner to define problem.
2. Spin front tire/wheel assemblies with wheel driv-
ing equipment. Rear wheels may be spun with tires
off the ground and with one wheel held at a time. The
offending tire may cause vibration that may be felt
by touching the bumper or fender. By process of
elimination, determine offending tire/wheel assem-
bly.
3. Check for tire/wheel unbalance. Balance, if neces-
sary.4. Check each tire/wheel assembly on the car for
radial runout on the tire tread. Wheel and tire assem-
blies exceeding
.050 inches may be considered as
offending assemblies. Offending tire/wheel assemblyshould be deflated and the tire repositioned (indexed)
180 degrees from original location.
5. After repositioning, rebalance tire/wheel assembly
(static and dynamic preferred).
6. Test drive and evaluate correction.
The following procedure should be used to determine
cause of roughness or vibration with car in operation
at various speeds:
I. Jack up all wheels having jack support rear end of
car at center of rear axle housing.
2. With transmission in “Drive”, run engine at vari-
ous car speeds to note speeds at which vibration or
roughness occurs.
3. Remove rear wheels and run engine again at the
critical speeds noted in step 2. If roughness is gone,
the condition is caused by unbalanced wheel and tire
assemblies.
4. If roughness still exists with rear wheels removed,
remove rear brake drums and repeat the running
test. Elimination of the roughness indicates out of
balance brake drums.
5. If roughness still exists with brake drums
removed, run engine with transmission in “Neutral”.
Elimination of the roughness indicates that propeller
shaft is out of balance. Continued roughness indi-
cates an out-of- balance engine.
ABNORMAL TIRE WEAR
General Operating ConditionsAssuming that there is no misalignment condition to
cause abnormal wear, the life of tires depends largely
upon car operation conditions and driving habits.
Tires wear at a much faster rate in some localities
than in others because of road and operating condi-
tions. Some types of roads are much more abrasive
than others. Tire wear is also dependent upon the
number of hills and mountains which the car must
go up and down, the severity of grades, the number
of starts and stops, driging speeds, the amount of rain
and snow, and prevailing temperatures. Tire
wear
increases rapidly with speed, temperature, and loadon tire. Tires used at low speeds, in cool climates, or
with light loads will have longer life than tires used
for high-speed driving in hot climates with heavy
loads.
Driving habits have a very important hearing on tire
life. A careful driver may obtain much greater mile-
age from a set of tires than would be obtained by a

36. 601973 OPEL SERVICE MANUAL
severe or careless driver. Rapid acceleration and de-celeration, severe application of brakes, taking turns
at excessive speed, high-speed driving, and striking
curbs or other obstructions which lead to misalign-
ment are driving habits which will shorten the life of
any tire.hiaintenance of proper inflation pressure and peri-
odic interchanging of tires to equalize wear are
within the control of the driver. Underinflation
raises the internal temperature of a tire greatly due
to the continual friction caused by the flexing of the
side walls. Tire squealing on turns is an indication of
underinflation or excessive speed on the turns. A
combination of underinflation, high road tempera-
tures, and high-speed driving will quickly ruin the
best tire made.
High speed on straight highways or expressways nor-
mally causes more rapid wear on the rear than on thefront tires, although cupping of front tires can result
if the tires are not periodically switched from wheel
to wheel. Driving turns and curves at too high a rate
of speed causes the front tires to wear much faster
than the rear tires.
An inspection of the tires, together with information
as to locality in which the car has been operated willusually indicate whether abnormal wear is due to the
operating conditions described above or to mechani-cal faults which should be corrected.
The various types of
abnormal tire wear and their
causes are described in the following paragraphs.
Shoulder or Underinflation Tread WearWhen a tire is underinflated, the side walls and
shoulders of the tread carry the load, while the centerof tread folds in or compresses due to the low inter-
nal air pressure. This action causes the shoulders to
take all of the driving and braking load, resulting in
much faster wear of shoulders than of the center of
tread. See Figure 3G-7. For maximum results in han-dling, riding and tire life, tire inflation pressures
should never be allowed to go below the specified
minimum pressure.
Continuous high-speed driving on curves, right and
left, may produce tread wear very similar to underin-flation wear and might very easily be mistaken for
such. Side thrust when rounding turns causes wear
on the sides of tire tread. In making a turn to the left,especially at high speeds, the outside shoulder of the
right tire and the inside shoulder of the left tire take
the side thrust and naturally receive the most wear.
The only possible correction is to advise slower
speeds on curves. Do not increase tire inflation pres-
sures beyond specified limits, as this will cause centeror over-inflation wear. See paragraph below.
Canter or Overinflation Tread Wear
Excessive wheel camber, either positive or negative,causes the tire to run at such an angle to the road
surface that one side of the tread wears much more
than the other. See Figure
3G-7.When tire inflation pressures are maintained within
the specified limits, the tire will make a full contact
across the entire width of tread, thereby distributing
the wear evenly over the total surface of the tread
area.
Cross or Toe Tread WearWhen the front wheels have an excessive amount of
either toe-in or toe-out, the tires are actually draggedsideways when they travel straight down the road
and cross wear or scraping action takes place rapidly
wearing away the tread of tires. This cross wear con-dition will usually produce a tapered or feathered
edge on the ribs of the tire tread. See Figure
3G-7.In most cases, this can be detected by rubbing the
hand across the tire tread.
If the tapered or feathered edges are on the inner
sides of the ribs on one of both sides, it indicates thatone or both tires have excessive toe-in, while the
same condition in the outer sides of ribs indicates
excessive toe-out. Usually, excessive toe-in causes
excessive tire wear on the outer edge of the right
front tire and toe-out causes tire wear on the inner
edge of the left front tire. See Section 3C for toe-in
correction.Cornering wear caused by high-speed driving on
curves (see following paragraph) sometimes has the
appearance of toe wear. Care must be used to distin-guish between these two types of wear so that the
proper corrective measures will be used.
Side or Camber WearExcessive wheel camber, either positive or negative,
causes the tire to run at such an angle to the road
surface that one side of the tread wears much more
than the other. See Figure
3G-7.The amount or angle of the camber wear will be
governed by the amount of positive or negative cam-ber. Tire tread wear very similar in appearance to
camber wear may be caused by driving on turns at
excessive speeds. This “cornering” tread wear (see
paragraph below) cannot be corrected by change of
camber angle.
Adjustments for specified camber are covered in Sec-
tion 3C.

WHEELS AND TIRES3G- 61Cornering Tread WearThe modern independently-sprung automobile al-
lows the driver to negotiate turns at a high rate of
speed with a greater feeling of safety. This fact is
responsible for a comparatively new type of tread
wear that can easily be mistaken for toe or camber
wear.When a car is making a turn, the tires are supposed
to be rolling in a circle. When the turn is made at
high speed, however, centrifugal force acting on the
car causes the tires to be distorted sideways and to
slip or skid on the road surface. This produces a
diagonal cross type of wear, which in severe cases
will result in a fine or sharp edge on each rib of the
tire treads.
Cornering wear can be distinguished from toe or
camber wear by the rounding of the outside shoulder
of the tire and by the roughening of tread surface in
this section denoting severe abrasion. See Figure
3G-7.No alignment or tire pressure cahnge can be made
that will relieve cornering wear. Only the driver can
effect a cure and that is by slowing down on curves.
Heel and Toe Tread WearHeel and toe wear is a saw-tooth effect with one end
of each tread block worn more than the other.
The end which wears is the one that first grips the
road when the brakes are applied. High-speed driv-
ing and excessive “se of the brakes will cause this
type of irregular tire wear. This type of wear will
occur on any type of block tread design. See Figure3G-7.
Heel and toe wear is not so prevalent on the rear tires
because of the propelling action which creates a
counteracting force which wears the opposite end of
the tread block. These two stresses on the rear tires
wear the tread blocks in opposite directions and re-
sult in more even wear while on the front tires, the
braking stress is the only one which is effective. This
may be counteracted by interchanging tires.
A small amount of irregular wear, slightly
saw-toothed in appearance, at the outer segments of tires
is a normal condition and is due to the difference in
circumference between the center and the outer
edges of the tire tread. This saw-toothed appearance,
however, will be exaggerated by underinflation, im-
proper toe-in, or both.Cupped or Scalloped Type Tire Wear
Cupping or scalloping is associated with wear on acar driven mostly at highway speeds without recom-
mended tire rotation. Factors which promote cup-
ping include underinflation, incorrect toe-in setting
or camber setting, and steady highway speeds on
smooth, paved surfaces as opposed to gravel or
rough asphalt.
The following recommendations suggest action that
may be taken to help prevent cupping.
1. Rotate tires as recommended in Figure
3G-6.2. Frequently inspect front tires for irregular wear
due to underinflation, improper toe-in setting, or
camber setting. Regardless of the original cause of
cupped tread wear on either front tire, no alignment
or balance job, however perfect, can prevent future
excessive wear of the spots. Once a front tire acquires
flat or cupped spots, additional wear will continue at
a rapid rate. At the time of correction, however, the
cupped tire should be interchanged with a rear tire
on which the tread runs true. The cupped tire will,
to a certain degree, true itself on a rear wheel.
Although not normally the cause of cupping, the
following factors can contribute to the problem.
Looseness of parts in the suspension system, such as
worn steering knuckle ball joints, loose wheel bear-
ings, inoperative shock absorbers, and any excessive
looseness throughout the steering system all tend to
allow the front wheels to kick around and, if any of
the wheel alignment factors are incorrect, irregular
spotty tire tread wear of one type or another may
result.
Wobble or runout of a tire, either front or rear, due
to bent wheel or to tire being improperly mounted
will cause uneven wear.
MAINTENANCE AND ADJUSTMENTSDEMOUNTING AND MOUNTING
TUBELESS TIRESDue to “se of symmetrical rims, tires must be
mounted over the narrow rim shoulder i.e., over out-
side rim flange.
When demounting a tubeless tire “se care to avoid
damaging the rim-seal ridges on tire beads DO NOT
USE TIRE IRONS TO FORCE BEADS A WA Y
FROM WHEEL RIM FLANGES.
When tire is removed, inspect it carefully to deter-
mine whether loss of air was caused by puncture or
by improper
tit of beads against rim flanges. If im-
proper fit is indicated, check wheel as follows: Do
not reuse dented rims.

REAR AXLE49.23
Adjusting end Fitting SpecificationsPinionBearingPreloadWith
NewBearings. . . . . . . . . . . . . . . . . . . . . . . . . .7-13Lb.In.
Preload With Reused Bearings
__.._..I...................,.................,,...................,,............ 5-8 Lb.In.
Pinion Depth Setting
.002” to -.OOl’ from pinion marking using following selective shims:
Number of Notches
Thickness In.in Circumference.0097Flattened on One Side
.00980
.01081
.01182
.01283
.01384
.01485Clearance Between Differential Side Gears and Case Max.
,000” on the Opel 1900 andManta and
,006” on the GT using the following selective shims:
Thickness In.
1900
,039.04
1,043,045,047,049.05
1,053,055
GT
.0394
.0433
.0473Number of Notches
in Circumference
0
1
2
.05123Max. Permissible Axle Shaft Bearing Seat Radial Runout
.._......................................... ,002”Max. Permissible Rear Axle Shaft Flanze Lateral Runout . .
,004” at Lareest Flange Dia.
Max.Permissible Lateral Ring Gear R&out
._.._,,.........._.....,........................... T . . . . . . . . . . . ...” ,003”RingGearandDrivePinionBacklash
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,004”-.008”
Differential Side Bearing Preload New, Bearings
- 20-30 Lb.In.; Used Bearings - lo-20Lb.In., using following selective shims:
Thickness In..0059.0069
.0079
.0089
.0098
.0108
.0197
.0433Number of Notches
in Circumference
0
1
;
4
5
8
7
Torque SpecificationsUse a reliable torque wrench. Specifications are for clean and lightly-oiled
threads.

5B- 121973 OPEL SERVICE MANUAL
A = BRAKE ON
THE RUBBER FLUID SEAL TIGHTLY GRIPPING PISTON
IS DEFLECTED IN DIRECTION OF PISTON TRAVELAFRICTION PAD
BRAKE DISCRUBBER FLUID SEALBRAKE
IICALIPER
IPISTON
I
CE BETWEEN RUNNING CLEARAN
FRICTION PAD AND BRAKE DISC
B = BRAKE OFFBTHE PISTON IS RETRACTED BY THE AMOUNT OF
RUBBER FLUID SEAL DEFLECTION. THIS AMOUNT
IS EQUAL TO RUNNING CLEARANCE.SBZZ
Figure 58-22 Rubber Fluid Seal -Automatic Piston Retractiondraulic pressure, and the friction pads and pistonsmove away from the brake disc, leaving a small run-
ning clearance. The brake disc can now rotate freely.
The amount of brake travel is dependent upon the
amount of running clearance. For this reason therunout of the brake disc should be checked, besides
bleeding of the brake system and adjusting the rear
brake shoes, when the pedal free travel is too great.during braking, the rubber seals in the annular
grooves of the brake caliper bores deflect laterally in
the direction of piston movement. See Figure
5B-22,View (A). The seal remains deflected for the duration
of the braking operation. After braking, the caliper
bores are relieved of hydraulic pressure and the rub-
ber seals resume their normal position, thus pulling
or retracting the pistons. The distance traveled by
the pistons is equal to that of the running clearance
between brake disc and friction pads.
The running clearance between brake disc and
fric-tion pads is attained as follows: When the pistons in
the caliper halves are moved towards the brake discThe shifting of the pistons in the direction of the
brake disc due to friction pad wear has no effect on
the running clearance. The running clearance re-mains the same in all piston positions.
DIAGNOSIS
DISC BRAKE TROUBLE DIAGNOSIS
ConditionPulls
Possible Cause
I. Incorrect tire
pressures.Correction1. Inflate evenly on both sides to
the recommended pressures (see
Owner’s Manual).

DISC BRAKES58.17a tine cut file.Do not use any solvent except dena-
tured alcohol. Do not use a
metaIJic scraper too/.8. With a punch, drive one dowel pin from inboard
side through caliper and friction pads to stop. Install
new cross-shaped retaining spring under installed
dowel pin, then install second dowel pin. Loose tit-
ting dowel pins must be replaced.
9. Before operating vehicle, depress brake pedal sev-
eral times to adjust friction pads to brake discs.
Check brake fluid level and add fluid as necessary to
bring level up to “MAX” on reservoir.
Car owners must be informed that a break-in period
exists for new friction pads, and that they must avoid
unnecessary, forceful braking during the first 125
miles after installation of new friction pads.
Checking Brake Disc for Lateral Runout1. Remove front wheel assembly.
2. Remove front wheel bearing hub cap and spindle
nut cotter pin. Tighten spindle nut until all free play
is removed from wheel bearings.
3. To check disc runout, use Dial Indicator Set
J-
8001. Attach dial support C-clamp to an upper ball
joint attaching bolt as shown in Figure
5B-27. Posi-
tion dial indicator button against brake disc
l/2 inch
from outer circumference.
Figure 58-27 Checking Brake Disc Lateral
Runout4. Rotate disc, reading maximum dial indicator
movement. Maximum permissible runout is
,004
inch.5. If runout exceeds
0% inch, remove disc and hubassembly and true disc in a suitable disc turning
lathe, following manufacturer’s instructions. The
depth of cut on each side of disc should be just deep
enough to get a true flat surface.
6. After truing disc on both sides, check thickness
with a micrometer. A disc with a thickness of less
than ,394 inch is liable to warp after hard braking
and, therefore, must be discarded.
7. Reinstall brake disc and hub assembly, removing
all play from wheel bearings. Repeat runout check.
If runout still exceeds
,001 inch, replace brake disc.
8. Adjust front wheel bearings.
9. Reinstall front wheel assembly.
MAJOR REPAIR
REMOVING AND INSTALLING BRAKE CALIPER1. Remove left or right front wheel and remove fric-
tion pads from brake caliper.
2. Loosen brake line to brake caliper union nut sev-
eral turns. Unscrew brake caliper plus brake hose
bracket from steering knuckle. Remove it from brake
disc and swing it sideways. Then unscrew brake pipe
from brake hose and remove brake caliper and brake
pipe (bent pipe). To prevent brake fluid loss, close
brake hose with a plug.
3. Prior to installation,check contacting surfaces of
the brake caliper and steering knuckle to make sure
they are free of any burrs and dirt.
4. Install brake caliper on steering knuckle and
torque attaching bolts to 72
lb.ft. See Figure 5B-28.CAUTION: This disc brake
cah@er attachments fas-
tener is an important attaching part in that it could
affect the performance of vital components and sys-
tems, a,ld/or could result in major repair expense. It
must be replaced with one of the same part numberor with an equivafent part, if repfacement becomes
necessary. Do not use a replacement part of Jesser
quaJity ‘or substitute design. Torque vafues must be
used as specitied during reassembly to assure proper
retention of this part.
5. Attach brake pipe to brake hose.
6. Install friction pads and replace wheel.
REMOVING AND INSTALLING
BRAKE DISC
1. Jack-up and support front of car and remove front

98-26 1973 OPEL SERVICE MANUAL
greater than the opposing pressure in the power ele-
ment. Therefore, the valve remains closed. When the
compressor is started, it will reduce the pressure and
temperature of the refrigerant in the cooling coil to
a point where the vapor pressure in the power ele-
ment becomes the stronger. The seat then moves off
the orifice and liquid starts to flow through the valve
orifice into the cooling coil.
The purpose of the power element is to help deter-
mine the quantity of liquid that is being metered into
the cooling coil. As the temperature of the low pres-
sure line changes at the bulb, the pressure of
the
vapor in the power element changes, resulting in a
change of the position of the seat. For example, if the
cooling coil gets more liquid than is required, the
temperature of the low pressure line is reduced and
the resultant lowering of the bulb temperature
reduces the pressure of the vapor in the power ele-
ment, allowing the seat to move closer to the orifice.
This immediately reduces the amount of liquid leav-
ing the valve. Under normal operation, the power
element provides accurate control of the quantity of
refrigerant to the cooling coil.
To employ our tire pump analogy once more for
clarity, it is the same situation that would exist if you were inflating a tire with a very slow leak. Providing
you pumped the air into the tire as fast as it leaked
out, you would be able to maintain pressure even
though the air would merely be circulating through the tire and leaking out through the puncture.
To Sum Up
So far, we’ve discussed only what each unit in an air
conditioning system does. We’ve learned that the
evaporator is the unit in which liquid refrigerant
soaks up heat from the air, the compressor is a pump
for squeezing this heat out of the vapor, the con-
denser is a radiator for getting rid of the heat, and the
thermostatic expansion valve is a device for regulat-
ing the pressure on the refrigerant. Now, let’s
find
out how the temperature of the cooled air is con-
trolled.
METHOD OF TEMPERATURE CONTROL
To achieve temperature control, the compressor is
run intermittently, automatically turning on and off
as necessary to maintain proper temperature.
Thermostatic Switch
The compressor can be started and stopped au-
tomatically through the use of an electro-magnetic
clutch and a thermostat affected by variations of temperature.
The job is usually done by a gas bulb thermostat (Fig.
9B-21).
Figure 9B-21 Thermostatic Switch Schematic
With the gas bulb type of thermostat, a highly expan-
sive gas is sealed into a metallic bulb which is located
in the air stream as it leaves the evaporator. A small
tube leads from the bulb to a bellows operated switch. As air temperature rises, the gas inside the
bulb expands, travels through the tube to the bellows
and closes the electrical switch that engages the com-
pressor clutch.
Of course, as soon as the compressor starts running,
the temperature begins to go down. As the air being
cooled gets colder, the gas in the thermostat bulb
begins to reduce the pressure on the switch bellows.
This
Ilips “off’ the switch and disengages the com-
pressor clutch.
REFRIGERANTS
No matter how scientifically refrigerating machinery
is built or how
efftciently it runs, it alone cannot
remove heat. The only thing that carries heat out of
a refrigerator cabinet or an automobile is the sub-
stance we call the refrigerant.
There are many refrigerants known to man. In fact,
any liquid that can boil at temperatures somewhere
near the freezing point of water can be used.
But a boiling point below the temperature at which
ice forms is not the only thing that makes a good
refrigerant. A refrigerant should also be non-
poiso-
nowand non-explosive to be safe. Besides that, we
want a refrigerant that is non-corrosive and one that
will mix with oil.
Since Nature did not provide an ideal refrigerant,
chemists went to work to see if they could do any
better. They did! But it wasn’t as simple as that.
At first, they tried to improve existing natural refrig-
erants. But after exploring innumerable trails along