Civl19303_II.qxd


1.  Introduction

The Saudi Arabian Standards Organization, SASO, is
the sole standardization body in the Country. The Ministry
of Commerce, in association with SASO, has established
a comprehensive certification program termed the
International Conformity Certification Program. It is a
combined assessment program, which deals with a pre-
shipment inspection and a certification scheme. Based on
these inspection guidelines, various consignments are
allowed into the country. It applies to approximately 66
categories of products, and includes new tires for all kinds
of imported automobiles (Ministry of Commerce, 2001).
_____________________________________________
*Corresponding author E-mail: nratrout@kfupm.edu.sa

SASO Standard No.448/1986 deals with the methods
of testing that are performed on tires in order to obtain a
conformity certificate (Saudi Arabian Standard
Organization, 1986a).  SASO Standard No. 447/1986, on
the other hand, documents the values of these tests that
have to be satisfied (Saudi Arabian Standard Organization,
1986b).  These standards have been in effect since 1987
and are similar to the U.S. Federal Motor Vehicle Safety
Standard No.109   (National   Highway   Traffic,   2001).
This federal  standard specifies the tire dimension and lab-
oratory test requirements  for bead unseating resistance,
strength, endurance, and high speed performance that are
applicable to all passenger car pneumatic tires manufac-
tured after 1948.

The objective of this paper was to examine the conform-
ity of imported tires with SASO standards and to assess
their physical characteristics based on these standards.

ring Research 1 (2004) 01-06rnal of EngineeThe Jou

Conformity of Physical Characteristics of Imported Tires
with Government Standards: A Case Study

N.T. Ratrout*1, S. Anwar Basha1, H. I. Al-Abdul Wahhab1 and K. A. Al-Ofi1,2

1 Department of Civil Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
2 Research Institute, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia.

Received 19 March 2003; accepted 7 July 2003

Abstract: The Saudi Arabian Standards Organization, SASO, has established a set of tests that all passen-
ger car tires have to pass in order to be allowed into the Country. These tests are: visual inspection, dimen-
sion measurement, bead unseating, tensile strength and elongation, aging, endurance, and high speed per-
formance tests. This paper describes the application of the first five tests on eight different brands of tires
that are taken to represent the categories of “frequently failed” and “infrequently failed” tires in the coun-
try. The results showed that the dimensions of almost all the tested tires were somewhat different from
those documented in the SASO standards. On the other hand, all the tested tires passed the bead unseating
and strength tests. All tires in the “frequently failed” category failed the tensile strength test. In contrast, all
tires from the “infrequently failed” category passed this test. The average values of the test for these two
tire categories were statistically different at a 95% confidence level. 

Key words:  SASO tests, tire tests, bead unseating test, tires in Saudi Arabia.

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SASO Standard No. 448/1986 describes eight tests for
passenger car tires, namely visual inspection, dimension
measurement, bead unseating, strength, tensile strength
and elongation, aging, endurance, and high speed perform-
ance. This paper summarizes the results of the first five
tests that were conducted on abroad sample of imported
tire brands. The remaining three tests (aging, endurance,
and high speed performance) are still in progress. 

2.  Experimental Design

Four infrequently failed tire brands and four frequent-
ly failed tire brands were selected (Ratrout et al., 2002).
This categorization was based on observing the brand of
failed tires (blow out or tread separation) along four major
roads in Saudi Arabia during three months in the summer
of 2001. The number of failed tires for each brand togeth-
er with its market share along the four roads was used as
rates to rank the tire brands. The highest and lowest four
ranks were selected for this research. It should be empha-
sized that because of the limited tire sample size in the pre-
vious project, the term of frequently and infrequently
failed tires should only be taken as a rough measure for
segmenting the tire population into two main categories.
Consequently, sampling from both categories, simultane-
ously, should increase the probability of covering a wide
spectrum of tire properties and characteristics.

The four infrequently failed tire brands were termed
as brands A, B, C, and D, while the other four frequently
failed tire brands were referred to as brands E, F, G and H.
Three tires from each brand were subjected to the testing
program. All tires were radial, new, and less than six
months old at the time of testing. With the exception of
brands E and F, all tires were of the size 225/70 R15. This
size is currently the most frequently used size in the
Country. However, brands E and F of this size are not
imported (Ratrout et al., 2002). Consequently, the next
most frequently used size, namely 205/65 R15, was select-
ed for these two brands (Ratrout et al., 2002). 

3.  Test Procedures

The visual inspection test recommended by SASO
Standard No. 448/1986 (Saudi Arabian Standard
Organization, 1986a), requires the tire to be visually
inspected by the naked eye, for any cracks or cuts in the
tread or sidewalls.  Information and markings molded on
the tire that are required by SASO Standard No.445/1986
(Saudi Arabian Standard Organization, 1986c), were
checked.  

The dimension measurement aimed to compare the
actual overall width and diameter with the standard values
given in SASO Standard No.445/1986 (Saudi Arabian
Standard Organization, 1986c).  Each tested tire was
mounted on a measuring rim and  to the pressure specified
in the standard, and allowed to stand for 24 hours at room

temperature (23 ± 2°C). Before conducting the measure-
ments, the pressure was adjusted to the original values and
the tire width was callipered at six different points spaced
equally around the circumference. This was done using a
Vernier caliper having an accuracy of 0.05 mm. The aver-
age value of these readings was reported as the section
width. The maximum outer circumference was measured
with a typical steel tape and then the value was divided by
π to obtain the overall diameter.  These values were then
compared with the SASO standard (Saudi Arabian
Standard Organization, 1986c).

The bead unseating test evaluates the tire resistance to
unseating the tire bead from its rim when subjected to lat-
eral forces such as during severe turning movements. For
the tire sizes tested in this paper (section widths 205 mm
and 225 mm), this force should not be less than 11,350 N
(Saudi Arabian Standard Organization, 1986b). The tires
were washed and dried, mounted on a clean rim and inflat-
ed according to the proper pressure specified in the stan-
dard at ambient temperature. A material testing machine
(INSTRON) was modified to host the tire-wheel assembly
horizontally. The testing machine had a force measuring
accuracy of 0.5%.  The   load   was   applied  through the 
unseating block (shoe)  to the tire sidewall at a rate of 50
mm/min, Figure 1. The load was increased until the bead
unseated or until the load of 11,350 N was reached,
whichever happened first (Saudi Arabian Standard
Organization, 1986a). For each tire, a sample of six read-
ings was taken at six equally spaced points around the cir-
cumference.

The strength test evaluates the strength of the reinforc-
ing material in the tire. According to the previous SASO
Standard 447/1986, the bearing energy for the tires tested
should not be less than 294 N.m. Each tested tire was
mounted on an appropriate rim and inflated to the proper
pressure as specified in the standard. The material testing
machine (INSTRON), which was used in the bead unseat-
ing test, was modified to support a cylindrical steel
plunger of 19 mm diameter with a hemispherical end,
Figure 2. The plunger was forced into the tread as near to
the centerline as possible at a rate of 50 mm/min. The dis-
tance the plunger moved was reported by an external lin-
ear transducer capable of providing an accuracy better
than 0.1 mm. Five measurements of force and penetration
were taken at points equally spaced around the circumfer-
ence of the tire. The breaking energy was calculated
according to the following formula:

[1]

where:

W = Energy at break, N.m
F =Force at break, N
P =  Perforation at break, mm

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310
2

−××= PFW



The tire was considered to pass the test when the break-
ing energy was not less than 294 N.m. If the plunger
reached the face of the rim without any break occurring
(plunger bottoms out), the tire was also considered to pass
this test.

The tensile strength and elongation test was conduct-
ed using a test specimen of the shape and dimensions
shown in Figure 3a and was taken from each tested tire
using a press mold, Figure 3b, in the direction of the cir-
cumference. The specimen was clamped between the two
jaws of a material testing machine (LLOYD LR300K),
Figure 4, and stretched at a rate of 500 ± 25 mm/min. The
testing machine had a force measuring accuracy of 0.5%.
The stretch in the specimen was reported by an internal

extensometer resolution having an accuracy better than
0.005 mm. The tensile strength and elongation were calcu-
lated according to the following formula:

[2]

and 

[3]

where:
T = Tensile strength, kg/mm2
L = Maximum load, kg

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Figure 1.  Bead unseating test

Figure 2.  Strength test

A
LT =

 Elongation = 100
1

12 ×
−
I
II

 Average  
Diameter (mm)  

Brand Size 

Tire 
1 

Tire 
2 

Tire 
3 

Standard•• 
(mm) 

A 697 697 697 696 
B 689 689 689 696 
C 693 693 698 696 
D 

 
225/70 
R15 

682 682 689 696 
E 632 632 634 ** 
F 

205/65 
R15 631 631 634 ** 

G 679 687 679 696 
H 

225/70 
R15 679 679 695 696 

Table 2.  Tire diameter

* SASO Standard No. 445/1986.  No tolerance limit given in  standard, 
**No standard exists

Average Tire Width 
(mm) 

(% Coefficient of 
Variation)  

Brand Size 

Tire 1 Tire 2 Tire 
3 

Standard• 
(mm) 

A 
232 
(0.2) 

232 
(0.2) 

232 
(0.2) 220 

B 
229 
(0.4) 

229 
(0.4) 

229 
(0.3) 220 

C 
220 
(0.4) 

220 
(0.4) 

221 
(0.3) 220 

D 

 
 

225/70 R15  

229 
(0.2) 

229 
(0.2) 

229 
(0.2) 220 

E 
214 
(0.3) 

214 
(0.3) 

214 
(0.3) ** 

F 
205/65 R15  211 

(0.3) 
210 
(0.5) 

210 
(0.3) ** 

G 
224 
(0.2) 

231 
(0.2) 

231 
(0.2) 220 

H 
225/70 R15  235 

(0.2) 
235 
(0.2) 

235 
(0.2) 220 

Table 1.  Tire width

A
LT =

 Elongation = 100
1

12 ×
−
I
II

 

*  SASO Standard No. 445/1986.  No tolerance limit given in  standard, 
**No standard exists



A = Cross section area of test specimen, mm2
I1 = Standard length

I2 = Length at breaking
To pass the SASO standard, the tensile strength of the

rubber should not be less than 1.2 kg/mm2 and the elonga-
tion should not be less than 300% (Saudi Arabian Standard
Organization, 1986b). It is interesting to note that the unit
used in this test was kilogram rather than Newton.  This is
inconsistent with the SI system and other SASO tests.

4.  Results

Visual inspection of the tires revealed that all of them
were free from cracks or cuts. All information required by
the SASO standards, namely designation of dimensions
and construction, designation of tire rim diameter, desig-
nation of load and speed, country of origin, date of manu-
facture and batch number, were present (Saudi Arabian
Standard Organization, 1986c). The width measurements

of the tested tires, Table 1, showed that the coefficient of
variation within each tire width measurement never
exceeded 0.5%. This indicates that the width of each tire
was uniform around its circumference. The diameter
measurements  in Table 2  show that almost all tire brands
had some degree of discrepancy with the SASO standard.
The standard does not specify the values for tires of width
greater than 195 mm under the 65 series. Consequently,

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40mm20mm40mm

5
m

m

2
5

m
m

100mm

1
0

m
m

1
0

m
m

R
25

m
m

R
11

m
m

5
m

m

Figure 3a.  Dimension of the tensile strength and
elongation specimens

Average Tire Unseating Values ( N) 
(% Coefficient of Variation)  

Brand 

Tire 1 Tire 2 Tire 3 
A 11,900 

(0.41) 
11,870 
(0.93) 

11,530 
(0.41) 

B 11,540 
(0.74) 

11,410 
(1.52) 

11,660 
(1.63) 

C 11,570 
(1.52) 

11,760 
(1.02) 

11,880 
(1.27) 

D 11,480 
(1.34) 

11,460 
(1.38) 

11,760 
(1.66) 

E 11,750 
(1.61) 

11,890 
(1.41) 

11,590 
(1.40) 

F 11,680 
(1.65) 

11,530 
(1.72) 

11,930 
(1.39) 

G 11,670 
(1.62) 

11,900 
(0.85) 

11,810 
(1.69) 

H 11,930 
(2.07) 

11,480 
(1.53) 

11,460 
(1.57) 

Table 3.  Tire unseating

Brand I-IV:  Frequently failed brands

Figure 3b.  Shape and mold of the tensile strength
and elongation specimens

Elongation (%)   
Tire 
Brand 

 
Tensile strength 

kg/mm2 (% 
Coefficient of 

variation)  

Tread samples**  
(% Coefficient of  

variation)  

Sidewall 
samples 

(% Coefficient 
of  variation)  

 
A 

3.21 
3.25 
3.28 

(1.1) 
331.9 
291.3 
  56.7 

(65.5) 
702.0 
911.4 
911.4 

(14.4) 

 
B 

2.80 
2.82 
2.84 

(0.7) 
584.2 
593.8 
562.3 

(2.8) 
498.4 
464.3 
475.0 

(3.6) 

 
C 

2.34 
2.36 
2.37 

(0.6) 
392.2 
272.3 
390.8 

(19.6) 
416.1 
416.0 
462.5 

(6.2) 

 
D 

1.37 
1.33 
1.31 

(2.3) 
113.8 
113.5 
   50.1  

(39.7) 
400.4 
402.7 
325.2 

(11.7) 

 
E 

0.81 
0.81 
0.86 

(3.5) 
161.3 
     6.4 
241.0 

(87.6) 
532.7 
506.8 
506.3 

(2.9) 

 
F 

1.19 
0.90 
0.77 

(22.6) 
296.4 
240.0 
313.9 

(13.6) 
405.9 
316.4 
375.7 

(12.4) 

 
G 

1.02 
0.98 
0.93 

(4.6) 
341.7 
295.1 
295.0 

(8.7) 
513.8 
521.2 
521.2 

(0.8) 

 
H 

0.51 
0.53 
0.53 

(2.2) 
  41.0 
  88.4 
  66.0 

(36.5) 
511.1 
582.8 
578.2 

(7.2) 

Table 4.  Tire tensile strength and elongation

**  The large variation in the elongation is due to the existance of groove
on samples



there were no standard values with which brands E and F
could be compared. However, the average discrepancy for
the remaining tires was 7.5 mm and 9.0 mm for the diam-
eter and width measurements, respectively. Surprisingly,
the SASO dimension standards do not mention any toler-
ance values for tire dimensions, hence almost all the test-
ed tires did  not comply with these standards. Clearly, this
is impractical from an engineering point of view. The stan-
dard should have some tolerance to account for the accu-
racy of measuring instruments and other random errors.

The bead unseating test was easily passed by all tire
brands, Table 3. It is also interesting to notice that the
results in Table 3 show little variation within, and
between, different brands. The coefficient of variation
within brands was less than 2.1%. The average value for
all brands (i.e. 24 tests) was 11,685 N with a coefficient of
variation equal to 1.5%. The U.S. National Highway
Safety Administration  reported that the bead unseating
test and strength test seem to be ineffective in differentiat-
ing between radial tires and that these tests are more use-
ful for bias ply tires (National Highway Traffic, 2002 ).

In the strength test, the results for all tires were so
good that the plunger reached the bottom (rim surface)
without breaking the reinforcement material in the tread.
This seemed to be consistent with what is being reported
in the U.S. The National Highway Traffic Safety
Administration has recently reported that this strength test,
which was originally designed for evaluating the strength
of bias ply tires, was not so effective in testing radial tires
(National Highway Traffic, 2002). They also reported that
“because of the belt package, radial tires far exceed the
strength requirements of the test and many times the
plunger bottoms out on the rim instead of breaking rein-
forcement material in the radial tire” (National Highway
Traffic, 2002). The U.S. Rubber Manufacturer Association
members also reported conducting about 19,000 strength
tests on radial tires, none of which failed (National
Highway Traffic, 2002).

The results of the tensile strength test for our study,
Table 4, show that the variation  within each brand is
small.  The coefficient of variation was less than 5% for all
brands except brand F.  The latter had a value of 22.6%,
Table 4. Brands A–D (infrequently failed) passed the
strength requirement of 1.2 kg/mm2. On the other hand,
none of the frequently failed tires (brands E-H) passed this
requirement. The average strength was 2.44 kg/mm2 for
the infrequently failed tires and 0.82 kg/mm2 for the fre-
quently failed tires. These two averages are statistically
unequal at a significance level of 0.05%, Table 5.

The elongation test results for the tread samples was
inconsistent and the variation within brands was high. The
coefficient of variation ranged from 88% for brand E and

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100mm

Tire Groove
A

A

B

B

Section A-A Section B-B

5mm5mm

Varying depth based on the Groove

Figure 4a.  Longitudinal cross-section of the tensile
strength and elongation test

 Infrequently 
failed tires 

Frequently 
failed tires 

Mean (kg/mm 2)        2.44        0.82 
Variance         0.551        0.04 
Observations       12      12 
Pooled variance          0.298  
Hypothesized mean 
difference  

        0   

Df      22   
T Stat        7.27  
P(T ≤ t)  one -tail 1.4 x 10−7     Reject H o 
T Critical one -tail       1.72  
P(T ≤ t)  two -tail 2.8 x 10−7     Reject H o 
T Critical two -tail       2.07  

Table 5.  T-test analysis for tensile strength test

Figure 4b.  Tensile strength and elongation test



2.8% for brand B, Table 4. A possible reason for this vari-
ation was the fact that the cross-sections of the samples
were not uniform due to the existence of the groove in the
tire tread, Figures  4a and 4b. This resulted in a non-uni-
form strain along the sample length. With the exception of
brand B, none of the brands passed the required 300%
elongation value in all of the three tire samples tested.
Only 33% of the tested tires passed this test. More specif-
ically, 50% of the tires in the infrequently failed brands
category, and 17% from the frequently failed brands cate-
gory, passed the elongation requirements.

5.  Conclusions

The dimensions of almost all the tested tires were at
variance with the SASO standards. The average difference
was 7.5 mm and 9.0 mm for the diameter and section
width, respectively. However, it is not known whether
these differences are acceptable from a safety and opera-
tional point of view. It might be beneficial for the standard
to include some tolerance value for the dimensions, to
overcome this shortcoming.

All the tested tires easily passed the bead unseating
and the strength tests. Both tests seem not to be stringent
enough for radial tires.

The infrequently failed tires passed the tensile strength
test with an overall average value of 2.44 kg/mm2.
Whereas, none of the frequently failed tires was able to
reach the 1.2 kg/mm2 strength required to pass this test.
The overall average tensile strength of these frequently
failed tires was 0.82 kg/mm2.  This  was statistically dif-
ferent from the average value of the infrequently failed
tires at a 95% confidence level. Consequently, this tensile
strength test seemed to be useful in the screening of
imported radial tires.  The elongation test results were
inconsistent for the tread samples because of the existence
of grooves in the tire tread.  Due to the erratic elongation
results, another set of specimens were taken from the side-
wall of the tire to avoid the effects of the groove. The
results of these specimens appeared to be more consistent
and to have less variation within brands. The coefficient of
variation was less than 15% for all the tested brands, Table
4.  The use of sidewall specimens to measure the elonga-
tion gave better results. In this case, some adjustment to
the specifications may be needed to determine the allow-
able minimum value since all results passed the minimum
required elongation of 300%.

6.  Recommendations

Our research study indicated  that the SASO standards
need to be critically reviewed and updated. Dimension

standards should be completed for all tire sizes and rea-
sonable tolerance in the dimension standard should be
considered. All units in the SASO standards should be
consistent and should follow the SI system. The bead
unseating test and the strength test are not stringent
enough for radial tires. The merits of these two tests for
radial tires should be studied and appraised. In the tensile 
strength and elongation test, it is recommended to use the
sidewall specimens in measuring elongation and to adjust
the passing minimum value accordingly.

Acknowledgements

The authors would like to acknowledge the financial
support of King Abdulaziz City for Science and
Technology and King Fahd University of Petroleum &
Minerals.

References

Ministry of Commerce & Saudi Arabian Standards
Organization, 2002, "International Conformity
Certification Program for Exporting Countries:
Comprehensive Procedures and Guidelines," August
2001 (www.iccp.com).

National Highway Traffic Safety Administration,
Department of Transportation,  2001, "Federal Motor
Vehicle Safety Standard No. 109; New Pneumatic
Tires," Code of Federal Regulations, Title 49, Volume
5, Revised as of October 1, 2001 from the U.S.
Government Printing Office via GPO Access
(http/frwebgate.access.gpo.gov).

National Highway Traffic Safety Administration, 2002
"Notice of Proposed Rulemaking: Federal Safety
Standard; Tires," Docket No. NHTSA-00-8011,
Federal Register: March 5, 2002
(www.nhtsa.dot.gov/cars/rules/rulings/tread/MileSton
es/ 66FRPg10049 .html).

Ratrout, N.T. et al., 2002, "Tire Failure - Reasons and
Consequences," 1st Interim Report, King Abdulaziz
City for Science and Technology, 1423H.

Saudi Arabian Standards Organization, 1986a, "Passenger
Car Tires, Part 3: Methods of Test," SASO Standard
No. 448/1986, Riyadh, Saudi Arabia.

Saudi Arabian Standards Organization, 1986b, "Passenger
Car Tires, Part 2: General Requirements," SASO
Standard No. 447/1986, Riyadh, Saudi Arabia.

Saudi Arabian Standards Organization, 1986c, "Passenger
Car Tires, Part 1: Nomenclature, Designation,
Marking, Dimensions, Load Capacity and Inflation
Pressure," SASO Standard No. 445/1986, Riyadh,
Saudi Arabia.

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