ASTM F1112-00
(Test Method)Standard Test Method for Static Testing of Tubeless Pneumatic Tires for Rate of Loss of Inflation Pressure
Standard Test Method for Static Testing of Tubeless Pneumatic Tires for Rate of Loss of Inflation Pressure
SCOPE
1.1 This test method covers the determination of the rate of inflation pressure loss resulting from air diffusion through the structures of tubeless tires under constant temperature conditions. The testing is done under static conditions, that is, nonrotating, nonloaded tires.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F 1112 – 00
Standard Test Method for
Static Testing of Tubeless Pneumatic Tires for Rate of Loss
of Inflation Pressure
This standard is issued under the fixed designation F 1112; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 This test method covers the determination of the rate of 4.1 Test tires are mounted on rims, fitted with calibrated
inflation pressure loss resulting from air diffusion through the precision pressure gages, inflated to the desired pressure, and,
structures of tubeless tires under constant temperature condi- after a period of stabilization, are monitored for inflation
tions. The testing is done under static conditions, that is, pressure as a function of time under static, constant tempera-
nonrotating, nonloaded tires. ture conditions.
1.2 The values stated in SI units are to be regarded as the 4.2 Measured inflation pressures are normalized to the
standard. The values given in parentheses are for information nominal test temperature and one atmosphere barometric
only. pressure for calculation of pressure loss rates.
1.3 This standard does not purport to address all of the 4.3 Two or more tires per construction are tested for
safety concerns, if any, associated with its use. It is the pressure loss rate over a period of two to six months. High
responsibility of the user of this standard to establish appro- precision in the data may allow shortening the test. See 9.6,
priate safety and health practices and determine the applica- 10.5, and Section 12.
bility of regulatory limitations prior to use. 4.4 The pressure loss rate is calculated as percent loss per
month at the nominal test temperature.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
F 538 Terminology Relating to the Characteristics and Per- 5.1 Inflation pressure retention is an important property of
formance of Tires tire performance because underinflation can adversely affect
F 1082 Practice for Tires—Determining Precision for Test tire rolling resistance, handling, structural integrity, and tread
Method Standards life.
5.2 This test method is useful for research and development
3. Terminology
evaluation of the effects of tire component formulations and
3.1 Definitions: geometry on inflation pressure retention. Testing for rate of
3.1.1 inflation pressure loss rate, n—rate of change of
pressure loss under static conditions is practical because of the
normalized inflation pressure, determined from the slope of the following:
linear portion of the log pressure versus time curve.
5.2.1 Tires in normal use are predominantly at rest, and
3.1.2 measured inflation pressure, n—gagepressureofatire 5.2.2 Relative air diffusion rates of various tires in normal
measured at a given time under ambient temperature and
intermittentroadservicewillcorrelatewithstaticrelativerates,
barometric pressure. to a first approximation. The relative air diffusion rates of
3.1.3 normalized inflation pressure, n— measured pressure
differenttiresmaynotbequitethesameunderdynamicflexing
ofatireadjusted,accordingtotheidealgaslaw,tothenominal as when tested statically, but the difference is believed to be
test temperature and one atmosphere external barometric
small.
pressure. 5.3 The results from this test method are not suitable for
inferring tire inflation retention under severe service condi-
tions, such as heavy cornering or impacts, that might cause
ThistestmethodisunderthejurisdictionofASTMCommitteeF-9onTiresand
significant air loss at the tire-rim seal.
is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-Vehicular)
Testing.
Current edition approved May 10, 2000. Published May 2000. Originally
published as F 1112 – 87. Last previous edition F 1112 – 95.
Annual Book of ASTM Standards, Vol 09.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1112–00
6. Interferences Bourdon tube gages have been satisfactory. Stable, high–pres-
sure electronic pressure transducer systems can be satisfactory,
6.1 Ambient temperature excursions greater than 63°C
and they can be read remotely, avoiding entry to the test
(65°F) for several hours may significantly alter both the air
chamber.
diffusion rate through the tire and the driving force inflation
7.11 Inflate the tire-rim assembly outfitted with the pressure
pressure, thereby causing variability in the rate of tire pressure
gage to the desired starting pressure and test for leaks by
loss. Some temperature variations can result from inconsistent
submersion in a water tank, up to the base of the gage, for at
air currents around racked tires, or from spatial temperature
least 30 min.
gradients in static air spaces. The effects can be significant
7.12 Afterconfirmingthatthetire-rimassemblyisfreefrom
where heat generating tests such as laboratory road wheels are
leaks, fit the valve or adapter opening with a sealing cap, and
operating intermittently in the same room.
keep the tire in the same orientation to avoid causing new
6.2 Other causes for inconsistent results are minute leaks in
leaks.
the tire, rim, valve, or gage assembly; as well as varied service
7.13 After the leakage check, condition the tires at the test
or other heat history of the test tires.
room temperature for 48 h; then adjust to the starting test
pressure. Replace the sealing cap on the valve or adapter. If a
7. Sampling and Preparation of Test Tires
pressure drop of more than 3 kPa (0.5 psi) occurs over the
7.1 All of the tires in a sample should have the desired
conditioning period, recheck the assembly for leakage accord-
producing plant and date codes and similar storage and service
ing to 7.11 and, if necessary, remount. Greater than 48 h
temperature history.
conditioning may be necessary for some tires such as high-
7.2 Tires must be free of molding or other defects, particu- –pressure compact spares, whose growth can affect early
larly on the bead area and innerliner surfaces. inflation loss results.
7.3 New tires should be used for evaluation of construction
8. Test Chamber
or compound variations.
8.1 The test chamber shall be controlled to provide a mean
7.4 Minimum recommended sample size is two tires for
ambient temperature that is within 60.6°C of the nominal test
each type of tire or treatment being tested.
temperature and with overall variation within 63°C (65°F)
7.5 MounttesttiresonT&RA-approved,paintedsteelrims
over the course of the test.
in like-new condition. Rims must have clean, smooth surfaces
8.2 Nominal test temperatures currently in use are: 21, 24,
in the bead seat areas, particularly in the vicinity of the weld.
30, and 38°C (70, 75, 86, and 100°F).
Rim flanges must be free of sharp edges or scuffs that could
8.3 Air in the test chamber should be forcibly circulated to
damage the tire during mounting. Both bead seats of test rims
minimize spatial temperature gradients.
must be checked with a calibrated disc tape (ball tape) for
properdiameteraccordingtoT&RAYearBookspecifications.
9. Procedure
7.6 Acommercial bead-rim lubricant shall be applied to the
9.1 Place the test tires in the test chamber so as to allow free
tire bead areas and rim before mounting. Vegetable oil or
air circulation around them and easy visual access to the
soap-based lubricants are recommended.
pressure gages. The tires shall not be moved during the test.
7.7 Mount the tire on the rim according to the practice
9.2 Record inflation pressures, concurrent ambient tempera-
recommended by RMA. Do not exceed 275 kPa (40 psi)
tures, and barometric pressures daily for two weeks. Tap the
inflation pressure for seating beads. Use of sealants in the
gage lightly prior to each reading. Tires shall be considered to
bead-flange area should be avoided since it can prevent proper
besatisfactorilyconditionedwhentheslopeofthelogarithmof
seating.
the normalized inflation pressure versus time relationship
7.8 The rim shall be outfitted with either two serviceable
becomes constant.
valves or a single valve to which is then attached a metal “T”
9.3 The test shall be continued if replicate tires agree with
adapter that permits permanent attachment of a pressure
eachotherwithin6kPa(approximately1psi)inflationpressure
measuring device (gage) to one opening and inflation through
after two weeks. Otherwise, recheck the suspect assembly for
the other.
leaks according to 7.11, and restart the test.
7.9 A sealing tape such as TFE-fluorocarbon or a 9.4 Inflation pressure readings and concurrent ambient tem-
room–temperature curable epoxy shall be used on all threaded perature and barometric pressure readings shall be recorded at
connections in the valve-adapter-gage assembly. least once per week during the remaining test period. Continu-
ous monitoring of ambient temperature is desirable to ensure
7.10 A pressure measuring device (gage) shall be perma-
that the tire is at equilibrium temperature when its pressure is
nently connected to the adapter (or valve) to continuously
measured.
sense inflation pressure. The device should be selected so that
9.5 Correct inflation pressure readings, P , to the nominal
the pressure will always be in its working range of 40 to 90 %
test temperature and one atmosphere barometric pressure
of full scale. The device should be readable to 2 kPa (0.25 psi)
(101.3 kPa, 14.69 psi) by using the equation in 10.1.
and accurate to 61 % of full scale. Devices shall be calibrated
before and after each use with a reference device whose
calibration is traceable to the National Institute of Standards
Available from Ametek Corp., U.S. Gauge Division, 900 Clymer Ave.,
and Technology (NIST). The pressure measuring device must
Sellersville, PA 18960. U.S. Gauge Dial model No. 37694 has been found
maintain this accuracy over the duration of the test. Quality satisfactory.
F1112–00
9.6 A commonly used test duration is 180 days. The test 11.1.1 Total test duration in days,
period may be shorter or longer depending on the precision 11.1.2 Projected inflation pressure, if applicable,
level of the data. Twice per week measurements are recom- 11.1.3 Average ambient temperature and range over test,
mended if shorter term projections of performance are in- 11.1.4 Initial inflation pressure,
tended. See also 4.3. 11.1.5 Actual and “best fit” final inflation pressure, and
11.1.6 Starting date.
10. Calculation
11.2 Also report the manufacturer, line, size, production
10.1 Calculate normalized pressures from the formula:
plant, and date code for each tire.
11.3 An example treatment of test data is given inAppendix
P 5 ~P 1 B ! ~T /T ! 2 B (1)
1 1 2 1 2
X1.
where:
P = normalized inflation pressure, kPa,
12. Precision and Bias
P = measured inflation pressure, kPa,
12.1 The precision and bias section has been prepared in
B = measured barometric pressure, kPa
accordance with Practice F 1082. Refer to Practice F 1082 for
B = reference barometric pressure (one atmo-
terminology and other statistical calculation details.
sphere = 101.3 kPa),
12.2 An interlaboratory test was conducted in 1985 using a
T = measured temperature,°K, and
set of used uniform tire quality grading (UTQG) Course
T = nominal test temperature,°K.
MonitoringTires (CMT).This set of ten tires was furnished by
NOTE 1—Temperature in kelvins equals celsius plus 273.15.
one of the participating laboratories.
12.3 Five laboratories participated in the interlaboratory
10.2 Fit the data to a model of the following form:
test. Each laboratory tested two tires following the test proce-
bt
P 5 P e (2)
o
dure as outlined in this standard.Thus, there are only 5 degrees
of freedom (df) for repeatability (r) and four df for reproduc-
where: ibility ( R). These low df for r and R are not optimum for a
P = normalized pressure, kPa, good reliable estimate of overall precision.
P = initial pressure, kPa,
12.4 The tire air pressure loss rate was measured simulta-
o
b = loss rate per day at the nominal test temperature, and
neouslyforeachofthetwotires(perlaboratory)at22 60.8°C.
t = test time, days.
This loss rate, as specified by this test method, is expressed as
10.3 Aleast squares fit can be obtained after transformation
( B 3 3000) in units of percent per month (or 30 days) at one
of the model equation to the following form:
atm (101 kPa) barometric pressure. A test result is the value
obtained for (B 3 3000) for one tire and one test on that tire.
ln P5a1bt (3)
12.5 The precision results, given in Table 1, show that the
repeatability is equal to the reproducibility. For this (small df)
where:
interlaboratory test, the variation among the five laboratories is
a =ln P
o
no greater than the pooled tire-to-tire variation within the
The model is derived from a relationship that expresses
laboratories. The rather large relative repeatability of 35 %
pressure loss as a function of pressure only:
may be indicative of variations in the test samples themselves.
dP/dt5bP (4)
There is no independent way to verify this due to the age
Thus, pressure loss in absolute units will vary as the actual dependency of diffusion rate measurements.
nominal pressure changes, but a loss rate can be expressed by 12.6 Table 2 lists the actual test results. Inspection of the
the constant, b. table shows the lack of agreement between duplicate tire
10.4 The calculated loss rate constant, b, will be in units of results within any one of the five laboratories. It also shows
1/day. This number will typically be a very small decimal; it is how the level of agreement among the laboratories substan-
convenient, and perhaps more intuitively meaningful, to ex- tially improves by taking averages. The within-laboratory
press loss rate as a percent per month. This is done by single tire standard deviation, S , of 0.24 is twice the between-
r
multiplying b by 3000 (which is 100 % 3 30 days/month). laboratory single tire standard deviation of 0.12 (adjusted for
10.5 Calculations of loss rate and predictions of future the “averages of two basis” by multiplication by 2).
=
pressures can be made from any point in the test.The accuracy 12.7 Repeatability—Therepeatability, r,ofthistestmethod
of such predictions will depend on the appropriate-ness of the has been established as 0.68. Two single test results, that is,
model as well as the precision level of data obtained that, in loss rate in percent/month at 1 atm (101 kPa), obtained under
turn, will depend on factors such as the following: normal test method procedures, that d
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