Bsi bs au 050 1 2 2 1991 (1999) iso 9112 1991

BRITISH STANDARD AUTOMOBILE SERIES BS AU 50 1 2 2 1991 ISO 9112 1991 Tyres and wheels — Part 1 Tyres — Section 2 Commercial vehicle tyres — Subsection 2 2 Method of measuring tyre rolling circumferenc[.]

ISO 9112:1991

This Bri shStan ard, ha ing

b en pre ared u der the

directonof the Automo ile

Stan ards Policy Commi e ,

waspublished u der

theauthoriy f the

Stan ardsBo rdan

comesinto fect on

2 No emb r1 9

© BSI1 -1 9

The prep ration of this BritishStand rd was entrusted b the Automobi e

Stand ards Pol cy Commit e ( AUE- to Tech ical Commit e AUE/4, upon

which the fol owing bod ies were represented :

Ag ricultural Eng ine r ’ Association

Automobi e Association

British Industrial Truck Association

British Pres ure Gaug e Man facturer ’ Association

British Rub er Man facturer ’ Association

Bus and Coach Cou ci

Dep rtment of Transport

Freig ht Transport Association

Institute of Roa Transport Eng ine r ( Incorporated)

Motor Cy cle Ind ustry ’s Association of Great Britain Ltd

Motor Ind ustry Resear h Association

National Ty re Distributor ’ Association

Retrea Man facturer ’ Association

Roa Haulag e Association Ltd

Roy al Automobie Club

Society of Motor Man facturer ’ an Trad er

Am endm ents is ued sinc publ cation

© BSI 1 -1 9

i

Pag e

National foreword

This S bsection of this Part of BS AU5 has be n prep red u d er the direction

of the Automobi e Stand rds Pol cy Commit e It is identical with

ISO91 2:19 1 “Tr uck a nd bus tyr es — Method o mea sur ing tyr e r oling

cir cumfer enc — Loa d ed new tyr es”, publ shed b the International Org anization

for Stand rd ization ( ISO) Other Parts of this stand rd are:

— Pa r t2: Whe ls a nd r ims;

— Pa r t3: Va lve

Cros - referenc s

The Tech ical Commit e has rev iewed the prov isions of ISO420 -1:19 8 to

which reference is ma e in the text and has decided that they are ac epta le for

use in conju ction with this stand rd

N T I is antcip ted that the ful prov isions of ISO4 0 -1 wil b implemented in a future

re ision of BS AU5 -1.2.1 when rev ision work now taking lace in ISO has b en completed

A British Stand ard d oes not purport to includ e al the neces ary prov isions of a

contract User of British Stand rd s are responsible for their cor ect a plcation

Com pl anc with a British Standard does not ofitself confer im m unity

f om leg al o l g ations

© BSI 1 -1 9

1

1 Scope

This International Stand rd specifies the method

for measuring rol ng cir umference and rev olutions

per u it distance ( kiometre) for new tyres, u der

load ed cond itions, mad e for use on trucks and buses

The v alues th s obtained are not intended for use as

lev els of per ormance or qual ty

This International Stand rd a ples to al truck and

bus ty res

The fol owing stand ard contains prov isions which,

throug h reference in this text, constitute prov isions

of this International Stand ard At the time of

publcation, the edition indicated was v ald All

stand ards are subject to rev ision, and p rties to

ag re ments b sed on this International Stand rd

are encourag ed to inv estig ate the pos ibi ty of

a ply ing the most recent edition of the stand rd

indicated below Member of IEC and ISO maintain

reg ister of cur ently v ald International Stand ards

ISO420 -1:19 8, Tr uck a nd bus tyr es a nd r ims

(metr ic s r ie ) — Pa r t1: Tyres

3 Definitions

For the purposes of this International Stand rd , the

fol owing d efinitions a ply

3.1

revolutions per unit distanc

n mber of ty re rev olutions ( and portions there f)

that oc ur when the ( axle) centre of the ty re is

mov ed ex ctly the u it distance of1km, u der the

cond itions specified below

3.2

roling circum ferenc of tyre

distance that the ( axle) centre of the ty re mov es in

one rev olution of the ty re u d er the cond itions

specified below

4 Principle

The measurement method consists of d riv ing a

ty pical v ehicle equip ed with the test ty res on the

driv e a le, on a straig ht, lev el, p v ed road at a

constant spe d, and counting the number of ty re

rev olutions ( or portions there f) that oc ur whie

trav er ing an ac urately measured d istance

5 Mea sur ment requir ments

5.1 Test cour e

The test cour e shal be a lev el, straig ht section of

smo th, dry roa suraced with either asphalt or

conc ete p v ement of medium roug hnes The

long itudinal and transv er e g ra ient of the roa

shal be at most1 % The leng th ofthe cour e shal

be5 0m or long er depending on the ac uracy of the

test equipment as specified in5.4

The leng th of the test cour e, ex res ed in metres,

shal be measured to within0,1%

5.2 Weather during test

The ambient temperature shal be betwe n5°C

and3 °C; howev er, an asphaltic surace shal be

suficiently co l that the sur ace is not tacky The

wind spe d shal not exce d3m/s

5.3 Test spe d

For ty res with a spe d sy mbol

— G( 90km/h) an a ov e, the test spe d shal

be7 km/h±2 km/h;

— below G or with a ma imum spe d marking

lower than9 km/h, the test spe d shal be

a proximately7 %±2km/h of such a spe d

NOT 1 W hen tyres are not marked wih a sp ed symb l, the

test should b at7 km/ h±2km/ h

5.4 Test equipm ent ac uracy

The minimum n mber of impulses per rev olution

shal be16 The ov eral er or in the

rev olution-cou ting eq uipment including start and

stop er or shal not exce d0,1 %

6 Vehicle for mea sur ments

6.1 Test vehicle and tyre positions

The v ehicle shal be representativ e of the siz used

with the ty re siz being tested

The v ehicle shal hav e only two a les Since most

spe d ometer and od ometer are actuated f om the

driv e-shaft, the test ty res shal be fit ed to the d riv e

a le For four-whe l driv e v ehicles, one a le shal be

diseng ag ed

Ty re siz s that are normal y used as duals on d riv e

a les shal be tested as duals

6.2 Test lo d

The load on the driv e a le shal be8 % of the

ma imum rated ty re loa ( 80% of ma imum d ual

loa rating for tyre siz s normal y used as duals on

d riv e a les) times the n mber of ly res on the a le,

within±2 %

The ty re ma imum loa ca acity is the v alue

cor esponding to the load index moulded on the

sidewal of the ty re

NOT 2 W hen not so marked, the tyre man facturer lierature

should b consulted for the ma imum lo d ca aciy at the sp ed

in icated b the sp ed sy mb l ratng f the tyre

The loa on the other a le should be as obtained

with normal load distribution

7 Tyr s and rims

7.1 Test tyres

7.1.1 The ty res shal be a matched set of the same

siz desig nation, ty pe, and brand hav ing inflated

unloa ed overal d iameter within0,5% of each

other

7.1.2 For future comp risons with other ty res,

record the ov eral diameter of the new ty res This

shal be measured as specified in ISO420 -1

7.2 Tyre inflation pres ure

The inflation pres ure of the ty re at ambient

temperature shal be that pres ure cor esponding to

the ma imum load ca acity ( ma imum dual load

ca acity for ty re siz s normaly used as duals on

d riv e ax les) specified b the man facturer

7.3 Tyre break- in

Prior to the test, the ty res shal be cond itioned b

ru ning at least 15 km at an av erag e spe d of

a proximately7 km/h at the load and inflation

specified in6.2 and7.2 respectiv ely

After break- n, the ty res shal not hav e more

than10% los of trea depth

7.4 Test rim s

The rims shal be of the siz and ty pe a prov ed b

the ty re man facturer for use with the test ty re in

hig hwa serv ice.In the a sence of such information,

the rim nearest or equiv alent to the stand ard iz d

measuring rim shal be chosen

8.1After the ty res hav e be n broken in as indicated

8.3 Driv e the v ehicle at the test spe d for

a proximately6 min to warm up the ty res After

warm-up, the inflation pres ure shal not be

rea justed: the test is ru with pres ure buid-up to

simulate normal serv ice cond itions

8.4 Ru the test immediately at the test spe d

specified in5.3 ov er the test cour e specified in5.1

This req uires an a proach road at both ends of the

test cour e to al ow the cour e to be entered at the

test spe d

Acceleration, braking , an ste ring shal be kept to

an a solute minimum d uring the measurements

8.5 Record the n mber of rev olutions ( and portions

there f) of the rig ht test whe l an the left test

whe l that oc ur ov er the test cour e

8.6 Repeat the test to a total of trav er ing the cour e

twice in each d irection

8.7 I the n mber of rev olutions for each whe l on

the second ru difer f om the fir t run in the same

d irection b more than0,2 %, repeat the test u ti

two runs are obtained in each direction with the

n mber of rev olutions within0,2 % for each whe l

9 Calcula tions

9.1 Accuracy

A calculation is ma e for each of the eig ht rea ing s

( i.e.four ru s for each driv e whe l that comply with

the ac uracy req uirements of8.7

The eig ht calculated fig ures are then av erag ed to

obtain the rated v alue The rev olutions per u it

d istance( se 9.2) and the rol ing

cir umference( se 9.3) are then rou ded to the

nearest u it

9.2 Rev lutions per unit distanc

The number of ty re rev olutions per u it d istance is

d etermined b div iding the measured rev olutions

( an portions there f) b the measured distance

trav er ed in the test Th s the n mber of

rev olutions per kiometre is g iv en b the ex res ion:

where the test cour e leng th is ex res ed in metres

9.3 Roling circum ferenc

The rol ng cir umference is d etermined b div iding

the leng th of the test cour e b the n mber of

Measured rev olutions

Test cour e leng th

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3

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© BSI 1 -1 9

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ISO 9112:1991

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