ASTM F724-94a(2000)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F 724 – 94a (Reapproved 2000)
Standard Test Method for
Outdoor Evaluation of Tire Sidewall Component Cracking
Resistance
This standard is issued under the fixed designation F 724; 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 D 3395 Test Methods for Rubber Deterioration—Dynamic
Ozone Cracking in a Chamber
1.1 This test method covers procedures for evaluating pas-
F 538 Terminology Relating to the Characteristics and Per-
senger car tires for sidewall component integrity and cracking
formance of Tires
resistance, using an outdoor roadwheel.
1.2 This test method evaluates the resistance of tire side-
3. Terminology
walls to dynamic weathering, atmospheric ozone cracking,
3.1 Definitions:
fatigue cracking, or openings of splices within, or of junctures
3.1.1 black sidewall, n—a sidewall on which only black
between sidewall components and cracking at molded sidewall
compounds comprise the outer visible surface of a tire.
elements.
(F 538)
1.3 This test method is useful for evaluating tire black
3.1.2 clinch strip, n—high-modulus or high-hardness com-
sidewalls, white sidewalls, and coverstrips.
pound applied between the carcass and the sidewall in the bead
1.4 This test method is limited to comparative performance
area to reinforce the bead. (F 538)
testing between a “control” sidewall component or assembly
3.1.3 coverstrip, n—a thin layer of black compound which
and one or more experimental alternatives that are built onto
covers the unexposed white sidewall portion of a finished tire.
the same tire (“multisection”) or onto tires that are identical in
(F 538)
all respects other than the sidewall variation.
3.1.4 crazing, n—minute, closely grouped, generally super-
1.5 This test method is not applicable to evaluation of
ficial cracks that usually result from light activated oxidation.
sidewall resistance to abrasion, as may be experienced in
(F 538)
severe cornering or curb scuffing.
3.1.5 flex cracking, v—cracking primarily caused by appli-
1.6 The values stated in SI units are to be regarded as the
cation of mechanical stress-strain cycling. (F 538)
standard.
3.1.6 juncture, n—the interface between two different tire
1.7 This standard does not purport to address all of the
components or different compounds within the same compo-
safety concerns, if any, associated with its use. It is the
nent. (F 538)
responsibility of the user of this standard to establish appro-
3.1.7 juncture cracking, n—a crack with opening originat-
priate safety and health practices and determine the applica-
ing at a juncture between two components. (F 538)
bility of regulatory limitations prior to use. For specific
3.1.8 juncture opening, n—a separation developing in a
precaution statements, see 5.2.
juncture. (F 538)
2. Referenced Documents 3.1.9 rim strip, n—a layer of compound, with or without
fabric reinforcement, that is applied at the bead to protect the
2.1 ASTM Standards:
carcasspliesagainstdamagefrommountingtoolsandfromrim
D 518 Test Method for Rubber Deterioration—Surface
2 chafing during service. (F 538)
Cracking
3.1.10 sidewall, n—of a tire, that portion of a tire between
D 1149 Test Method for Rubber Deterioration—Surface
the tread and the bead. (F 538)
Ozone Cracking in a Chamber
3.1.11 sidewall component, n—an individual part of the
D 1171 Test Method for Rubber Deterioration—Surface
sidewall construction, either a separate compound or a sepa-
Ozone Cracking Outdoors or Chamber (Triangular Speci-
rately assembled piece. (F 538)
mens)
3.1.12 sidewall rubber, n—the exterior rubber layer of a tire
that extends over the sidewall part of the carcass. (F 538)
This practice is under the jurisdiction ofASTM Committee F09 on Tires and is
3.1.13 splice, n—the joint formed either by overlapping or
the direct responsibility of Subcommittee F09.30 on Laboratory (Non-Vehicular)
butting the ends of a given tire component in the course of
Testing.
Current edition approved Dec. 15, 1994. Published February 1995. Originally
published as F 724 – 81. Last previous edition F 724 – 94.
2 3
Annual Book of ASTM Standards, Vol 09.01. 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.
F 724
assembling the tire. (F 538) 6. Sampling
3.1.14 splice crack, n—a crack originating at a splice.
6.1 Asampling plan is not applicable since this test method
(F 538)
is intended for research and development testing only. Test
3.1.15 splice opening, n—a parting of a splice along the
specimens (see Section 7) shall be tested simultaneously with
interface of the assembled ends of a given component.
a control specimen for direct comparison of relative perfor-
(F 538)
mance.
3.1.16 veneer, n—athinlayerofrubbercoveringthesurface
7. Test Specimens
of the tire sidewall. (F 538)
3.1.17 weather cracking, n—distinct surface cracks induced
7.1 A test specimen shall be a given assembly of sidewall
by action of ozone in those areas of sidewall that are under
components, specific as to component formulations, assembly
tension; the cracks usually form perpendicularly to the direc-
cross-section geometry, and preparation procedure. The test
tion of stress.
specimen may cover the entire sidewall circumference of the
3.1.18 white sidewall, n—a sidewall which contains a white
test tire and be compared with a control tire or it may cover a
(or light colored) compound as a part of the total sidewall. section of the sidewall and be compared with a control section
(F 538)
and other test specimen sections built onto the same (multi-
section) tire.
4. Significance and Use 7.2 Atest specimen section shall cover ⁄4 of the circumfer-
ence of the tire sidewall.
4.1 Test Methods D 518, D 1149, D 1171, and D 3395 can
7.3 In multisection tire tests, only specimens on the same
be used to evaluate different aspects of fatigue and weather
side of the tire shall be compared directly.
cracking resistance of sidewall component materials in the
form of test specimens. The present method applies to com-
8. Selection and Preparation of Test Tires
plete tires that are subjected to actual weather exposure
8.1 All test tires shall be approximately the same age and
conditions. The present method is satisfactory for research and
subjected to the same pretest conditions, particularly as related
development purposes but is not applicable to regulatory
to heat and ultraviolet exposure.
statutes or purchase specifications until standard classifications
8.2 Multisection test tires shall have been prepared with the
of state of cracking, similar to those in Test Method D 1171,
test components (for example, varied compounds) having the
can be established.
same cross-sectional profile and dimensions, so as to avoid
extraneous mechanical stress variability between the compo-
5. Apparatus
nents, unless the profile variation is a test variable.
5.1 Outdoor Roadwheel—An apparatus situated outdoors
8.3 The test component surfaces of tires shall be washed
and consisting of:
with water to remove any temporary protective coating but
5.1.1 One or more smooth steel road wheels of specified
shall not be subjected to solvent or other surface treatment (in
diameter. The road wheel(s) shall be wide enough to extend
the process of mounting, etc.) that may affect performance
beyond the test tire foot print width. The road wheel diameter
unless this is a part of the experimental study.
shall be no less than 610 mm (24 in.). Smaller diameter wheels
may produce excessive flexing and premature extraneous tire
9. Procedure
failure.
9.1 Mount a test tire on a rim contour approved by the Tire
5.1.2 Satellite stations for loading several test tires against
and Rim Association for its particular size. For tire-to-tire
the road wheel with known constant force.
comparative tests, rims shall be of the same width.
5.1.2.1 Each satellite station can individually unload and
9.2 Mount the tire with the valve at a convenient reference
withdraw the tire from contact with the road wheel in the event
pointfordescribingthelocationsofcracksorotherdegradation
of an inflation pressure loss or other potentially catastrophic
as they occur.
occurrence.
9.3 Inflate the tire to the selected test pressure at ambient
5.1.2.2 The tire-loading system may be done by any system
temperature. A commonly used inflation pressure is 138 kPa
that provides a constant force to maintain the desired tire
(20 psi). This pressure facilitates the desired deflection of the
deflection throughout the test.
tire (see 9.4.2) with moderate axle loading.
5.1.3 Adrive motor that can drive the road wheel(s), within
9.4 Installthetireonthetestmachine.Givethetireaminute
6 1 % of a set test speed for extended periods of time. A
run at full (test) load to ensure that the beads have fully seated.
commonly used speed is 48 km/h (30 mph).
Unload the tire and allow it to return to ambient temperature.
5.1.4 System for deter
...