MEDC 9 (3861) P 2
TANZANIA STANDARD
DRAFT TANZANIA STANDARD
MEDC 9 (3861) P 2 – MOTORCYCLE AND SCOOTER TYRES - SPECIFICATION
TANZANIA BUREAU OF STANDARDS
1
0. Foreword
The motorcycle and scooter tyres are currently very useful on running motorcycle in
our country, in this regard the need of putting forward the right specifications to
harmonize the performance is of paramount importance. The standard is set to
provide safe operational performance for motorcycle and scooter tyres and to place
sufficient information on the tyres to permit their proper selection and use.
In the preparation of this draft standard, the assistance derived from the relevant
publications of the International Organization for Standardization and the Bureau of
Indian Standards.
1. SCOPE
1.1
This draft standard prescribes the requirements and methods of
sampling and test for motorcycle and scooter tyres.
1.2 Performance of on road requirement of the tyres is not covered in this draft
standard.
2. REFERENCES
For the purpose of this draft standard the following reference shall apply
TZS 4: 2009 - Rounding off numerical values
ISO 37: 2011 -Methods of testing vulcanized rubber - Determination of tensile stressstrain properties.
ISO 24153:2009 - Random sampling and randomization procedures
ISO 4223 – 1: 2002 - Definitions of some terms used in the tyre industry
Part 1: Pneumatic tyres.
MEDC 9 (3642) - Motorcycle tyres and rims (Code-designated series) -- Part 1:
Tyres
MEDC 9 (3643) - Motorcycle tyres and rims (Code-designated series) -- Part 2:
Tyre load ratings
ISO 4249 – 3: 2010 - Motorcycle tyres and rims (Code-designated series) -- Part
3: Rims
ISO 6054 – 1: 1994- Motorcycle tyres and rims (Code-designated series) –
Diameter codes 4 to 12 – part 1 - Tyres
ISO 6054 – 2: 1990 - Motorcycle tyres and rims (Code-designated series) –
Diameter codes 4 to 12 – part 2s
- Rims
ISO 5751 – 1:2004 – Motorcycle and rims (metric series) – Part 1 – Design
guides
2
ISO 5751 – 2:1983 – Motorcycle and rims (metric series) – Part 2 – Tyres
dimension and load carrying capacities
ISO 5751 – 3:1983 – Motorcycle and rims (metric series) – Part 3 – Range of
approved rim contour
3. DEFINITIONS
For the purpose of this draft standard, the definitions given in ISO 4223 part 1, shall
apply.
4. REQUIREMENTS
4.1
Tyre size designation
The tyre size designation for motor cycle and scooter tyres shall be as given
in ISO 5751 and ISO 6054
4.2
Dimensions
4.2.1 The dimensions and profiles of tyres shall be compatible with appropriate
rims.
4.2.2 When measured in accordance with the method described in Annex A, the
overall width and overall diameter shall comply with ISO 6054 and ISO 5751
4.3
Load ratings
The load carrying capacities and speed categories of tyres shall be as given
in ISO 4249 – 2.
4.4
Tyre endurance
When tested in accordance with the method described in Annex B, the tyre, when
cut and examined shall show no evidence of broken cords, separation of tread, ply,
cord or bead or cracking of the tread or sidewall rubber exposing the cord fabric
4.5 Tyre strength
When tested in accordance with the method described in Annex C the tyre shall
comply with the static breaking energy requirements given in Table 1.
3
TABLE 1 - Requirement for static breaking energy
SI
No.
Tyre size
designation
Speed
category
Maximum Test
speed
inflation
Km/h
pressure
kpa
Requirement for static
breaking energy, Nm,
min
Nylon
(1)
i)
ii)
(2)
As in ISO 5751
and ISO 6054
a)Standard load
b) Extra load
(3)
(4)
Rayon
(5)
(6)
(7)
L
120
220
34
20
L
120
280
45
27
As in ISO 5751
and ISO 6054
a)Standard load
P
150
220
34
20
b) Extra load
P
150
280
45
27
4.6 High speed performance
When tested in accordance with the method described in Annex D, the Tyre, when
cut and examined shall show no evidence of broken cords, separation of tread, ply,
cord or bead or cracking of the tread or sidewall rubber exposing the cord fabric.
4.7
Skid depth
When measured in accordance with the method described in Annex E, the skid
depth shall comply with the values given in Table 2.
4
Table 2 – Requirement for skid depth
S/
No.
Nominal
section
width, in
(1)
(2)
i)
2.25
ii)
2.50
iii)
2.75
iv)
3.00
v)
3.25 and
Above
4.8
Speed
category
Maximum
speed,
km/h
(3)
(4)
L
P
L
P
L
P
P
P
120
150
120
150
120
150
150
150
Requirement for skid
depth, mm, min.
(5)
3.0
4.2
3.2
4.2
4.0
4.2
4.2
5.2
Physical properties of tread and sidewall rubber
When tested in accordance with the method given in column 5 of Table 3, the tread
and sidewall rubber shall comply with the requirements given in columns 3 and 4.
Table 3 – Requirement for tread and sidewall rubber
S/N
o.
Characteristic
Requirements
Method of test
Tread rubber
(1)
(3)
Sidewall
rubber
(4)
(2)
(5)
i)
Tensile strength, MPa, min.
12.4
6.9
ISO 37
ii)
Elongation at break, per cent,
min
400
400
ISO 37
4.9.
Life span of the tyre
Tyre covered under this standard shall have shelf life of not more than five year
since manufacturing date.
5
5. MARKING
The tyres shall be marked legibly and indelibly with the following on both
sidewalls
(a)
(b)
Tyre size designation as given in ISO 6054
Load carrying capacity and speed symbol as given in ISO 4249
(c) Name of the manufacturer and/or registered trade mark including the country or
origin, and
(d)
Batch or code number and.
(e) Manufacturing date
6. SAMPLING
6.1
Lot
In any consignment all the tyres of the same size and type and belonging to one
batch of manufacture or supply shall constitute a lot.
6.2
Scale of sampling
6.2.1 Samples shall be tested from each lot for ascertaining its conformity to the
requirements of this specification.
6.2.2 The number of tyres to be selected from a lot shall be in accordance with
Table 4.
Table 4 – Scale of sampling
Number of tyres in the
lot
Number of tyres to be
selected
(1)
(2)
Up to 200
201 to 1 000
Over 1 000
3
6
9
7
6
6.2.3 Tyres shall be selected at random.
6.3
Number of tests
6.3.1 Each tyre selected as in clause 6.2.2 shall be inspected for marking (clause 5)
and dimensional requirements (clause 4.2).
6.3.2 The sample selected as in clause 6.2.2 shall be divided into subsamples of
equal size. The tyres in one subsample so obtained shall be tested separately for
tyre endurance (clause 4.4), the tyres of another subsample shall be tested
separately for tyre strength (clause 4) and the tyres in the remaining subsample shall
be tested separate for high speed performance (clause 4.6).
6.3.3 One tyre shall be selected from the lot and tested for to requirements given in
clause 4.7 and clause 4.8.
7. METHODS OF TEST
Tests shall be carried out as prescribed in Annexes A to E of this draft standard.
8. CRITERIA FOR CONFORMITY
A lot shall be declared as conforming to the requirements of this draft standard if the
following conditions are satisfied.
8.1
Each tyre examined as in clause 6.3.1 satisfies the relevant requirements.
8.2
The tyres tested as in clause 6.3.2 satisfy the relevant requirements.
8.3
The tyre tested as in clause 6.3.3 satisfies the relevant requirements.
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ANNEX A
MEASUREMENT OF DIMENSIONS
A.1 Preparation and conditioning
Mount the tyre, on the specified rim and inflate to the pressure recommended for the
maximum load for the size and type. Allow the tyre to remain in this condition for a
minimum of 24 hours at room temperature. Check the inflation pressure and
readjust if necessary, to the original value.
A.2 Procedure
A.2,1 Overall width
Caliper the mounted tyre (see A. 1) at six points, spaced approximately equidistant
from each other all around the circumference Measure the linear distance between
the outermost positions over the twoside walls. Calculate the arithmetic mean of the
six readings to the nearest millimeter
NOTE
All measurements should be taken over the maximum width to include any elevation due to protective ribs, bars,
engraved sidewall markings or decorations
A.2.2 Overall diameter
Measure the outside circumference of the mounted tyre (see A.1) at the outermost
surface of the tread, which is normally at a position along the circumferential
centerline of the tread region Calculate the overall diameter as follows:Do = C/π
where,
Do is the overall diameter in millimetres; and
C is the circumference of tyre tread in millimetres.
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ANNEX B
DETERMINATION OF TYRE ENDURANCE
B.l
APP ARATUS
Apparatus as shown in Figure 1, with a flat, smooth-faced steel drum(test
wheel) having diameter of 1710 mm with a tolerance of +1 percent and a surface
width more than the tread width of the loaded tyre.
Figure 1 – Apparatus for tyre endurance test
B.2
Preparation and conditioning
Mount the tyre after ensuring that it exhibits no visual evidence of tread, sidewall, ply,
cord or bead separation, broken cord or cracking, on a test rim of appropriate size
and inflate to the appropriate pressure MEDC 9 (3643) (clause 6). Condition the
tyre/rim-wheel assembly at room temperature for a minimum period of 3 hours.
Readjust the tyre pressure to the original inflation pressure immediately before the
test
B.3
Procedure
B.3.1 Press the mounted tyre (see B.2) against the test wheel. Run the tyre at each
of the test load specified in Table 5 for the corresponding duration at the relevant
speed.
NOTE
At the end of each run recorded the inflation pressure. Record the first reading of the inflation pressure 3 hours
after the start of the test. If the subsequent readings of the inflation pressure fall below the first reading, rectify
the cause of the pressure drop and adjust to the fist value while the tyre is at the running temperature. No
corrective action is necessary if there is a normal rise in the inflation pressure. Record the inflation pressure
immediately after completion of the test.
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Table 5 – Test loads and speeds
Tyre size
designation
(1)
Speed
category
(2)
Maximum
speed,
km/h
(3)
Test
Speed
Km/h
(4)
(5)
(6)
48
As in
MEDC
(3643)
120
Stage 1
Load
Kg
As in
MEDC 9 (3643)
L
As in
ISO 6054
Test
Inflation
Pressure,
Kpa
Stage 2
Duration
h
Stage 3
Load
Kg
Duration
h
Load
Kg
Duration
h
(7)
(8)
(9)
(10)
(11)
7
Increase
By 8 per
cent
Increase
By 8 per
cent
24
9
16
P
150
As in
MEDC 9 (3643)
64
As in
MEDC
(3643)
9
4
Increase
By 8 per
cent
Increase
By 8 per
cent
6
24
B.3.2 on completion of the test cut and examine across section of the tyre for broken cord, separation of tread, ply, cord or bead or
cracking of the tread or sidewall rubber exposing the cord fabric
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ANNEX C
DETERMINATION OF TYRE STRENGTH (PLUNGER TEST)
C.1. APPARATUS
Apparatus as shown in Figure 2, consisting of a cylindrical steel plunger with a
hemispherical end (8 ± 0.2 mm in diameter) and a device to force this plunger into
the tyre at the specified rate of travel.
Figure 2 – Apparatus for tyre strength test
C.2 Preparation and conditioning
Mount the tyre, inflate and condition as in B. 2
C.3
Procedure
Force the plunger rod into the tyre tread of the mounted tyre/rim wheel assembly,
perpendicularly over a tread element at the centre of the tread or as near as possible
to it avoiding penetration into tread groove at a rate of travel of the plunger 50 ± 3
mm per minute until the tyre breaks. Measure the force and penetration at break a
points nearly equally spaced around the tyre circumference, necessary after
repairing broken points and re-inflation.
If the plunger is stopped by the rim (bottoming of the plunger again the rim) at all 5
11
points, the tyre is deemed to have passed the test regardless of the energy value.
C.4
Calculation
Static Breaking Energy, Nm = F x P x 10¯3
2
Where,
F is the arithmatic mean force at break in Newton and
P is the arithmatic mean of penetration at break or bottoming milimetre
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ANNEX D
DETERMINATION OF HIGH SPEED PERFORMANCE
D1 Apparatus
As given in B.1
D.2 Preparation and Conditioning
As given in B.2.
D.3
Procedure
D.3.1 Press the mounted tyre against the test wheel with the force specified in Column 4 of Table 6. Run the tyre for the breaking
period given in Table 6. Allow to cool to room temperature for period of not less than 2 hours. Adjust the inflation pressure to
initial value. Run the tyre successively at the speeds given in columns 9, 11 and 13 of Table 6 for the relevant periods given
therein.
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Table 6 – Test loads and speeds
Breaking in period
Tyre
size
designa
tion
Speed
Category
Test
Inflation
Pressure
Kpa
Load
Kg
Maximum
Speed,
Km/h
Duration
h
Speed,
Km/h
Stage 1
Duration
h
(7)
(2)
(3)
Stage 2
Speed,
Km/h
Duration
h
(9)
Stage 3
Speed,
Km/h
Duration
h
(11)
Speed,
Km/h
(13)
(5)
(6)
120
2
64
1/2
90
1/2
100
1/2
110
150
2
80
1/2
120
1/2
130
1/2
140
(8)
(10)
(12)
(4)
(1)
As in
ISO
6054
L
P
As in
MEDC 9
(3643)
90% of
the load
given
in
MEDC 9
(3643)
D.3.2 On collection of the test, allow the tyre to cool at room temperature for about one hour. Cut and examine for broken cord
separation of tread, ply, cord or bead or cracking of the tread sidewall rubber exposing the cord fabric.
14
ANNEX E
MEASUREMENT OF SKID DEPTH
E.1 Procedure
Mount and condition the tyre as in A.I. For circumferentially groove, types, measure
to the nearest 0.01 mm the depth of the tread groove nearest to or on the tread
centerline of the tyre at six points equally spaced around the tyre outside
circumference. (see Figure 3).
For tyres with tread having cross grooves only and no circumferential grooves,
measure the depth of the tread groove just outside the point of intersection of radius
above the groove base and that through the tip end of the cross grooves blending
into the base of the grooves (see Figure 4) Do not take into account any
subsidiary shallow grooves at or beyond the cross grooves towards the centerline
of the tyre tread.
Figure 3 - Skid depth for circumferentially grooved types
Figure 4 - Skid depth for cross grooved types
15