Studentswill be introducedtothe basics oftireidentificationandhowtointerpretthesidewallmarkings. Maintenanceof atire is as important as knowing its useand application. Studentswillbe instructed onhow to recognize typicaltire wearpatterns and know whena tire should bereplaced.

Lesson Outcomes

The student willbeableto:

•Read,understand,explainand record identificationmarkings on thetiresidewall

•Identify and explain the legaltread depth requirementfor ahighway tire

•Identify anddescribe thedifference betweena conventionaland adirectionaltire

•Identify and describe severalwear patternsof atire andthe probable causes


•The studentswillhavelittleor noprior knowledgeoftires or their use.

•Theteacher is familiar withtheinformation beingtaught.


Aspect ratio: the relationshipbetweenthe height ofthetire’ssidewall andthe tire’s width. Iftheheight ofthe sidewall is 45% of the width,theaspectratiois 45. In thetire size225/45R17, theaspect ratiois 45.

Camber: the inwardor outwardtiltof the topof the tire.Positive camber is when thetopofthetireisangledaway from thecentre ofthevehicle(orcar).Negative camber iswhen thetop ofthetireisangled towardsthecentre of the vehicle.

Directional tires:any tire that hasanarrow onthe sidewall indicating thedirection of rotation.Thetread isdesignedforthe tireto work inone direction only.Mainlydesignedforwetroadconditions. If the tireisput on thewrong sideof the vehicle, then water between thetire andtheroadwill buildupand loss oftractionwill occur.

Sipes: thesmall slits included onthe edgeof atire treadpattern,designedtoincrease traction.

Toe-in and toe-out: These twoterms describewhen thefrontof the tirepointsinward oroutward. Whenthetirespoint inward the car is said tohavetoe-in. Whenthetiresarepointingoutwardthecar is said tohavetoe-out.

Tread depth: the distancefrom thebaseofthetread groove to thetopofthetread.

Treaddepthgauge: ameasurement device used to measure wearand the remaining amountof treadon vehicletires. In theU.S.,the unit ofmeasurement usedin treaddepth gauges is32nds of an inch. Inothercountries, itis millimetres.

Wear bar: aband found betweenthe tread blocks of a tire,designed toindicate when atire iswithin2/32"(1.6mm)ofitstreaddepthandshouldbereplaced.

Winter snowflake designation:themountain/snowflakesymbolfoundonly on thesidewallof winter tires. Wintertires haveadifferenttreadpatternandtread compoundthat maximizetractionduring winter drivingconditions.

Estimated Time

60 minutes(including a question and answersession)

RecommendedNumberof Students

20, basedonthe BCTechnology Educators’Best Practice Guide, workinginpairs


•Sufficient openspaceforeachpairofstudentstomovefreely from stationtostation.

•Workbencheswould be anasset,inordertohavetiresoffthe floor foreaseofinspection.

•Shopfacilitieswith access to compressed air would be an advantage butarenotnecessary.



•Usedtires from atire shopforstudents todiagnose—at least sixdifferent tireswithavariety of types and sizes. The teacher will needto generatearecordofalltire defects andtheircauses.

What Is The Winter TireSymbol?

Winter TireSafetyTips—Transport Canada

Proper TireInflation—CooperTire Canada


1.Groupthe studentsinto pairsandhave them documenttheir names on their handoutsheets.

2.Have students locate andwrite downthe informationrequired as perthehandout.

3.Randomly pick studentsto explain tothe class the sidewall information of the particular tirethey are workingon.

4.Explain the“snowflake” on a tireandwhyitis a winterstandardbelow a specifictemperature of7°Celsius (because therubbercompoundin summertires getstoohard togettraction).

5.Explainhow sipes help grip anicysurface.

6.Demonstratethe useof atread depth gauge, and explain the legallimitof 3 mmof treaddepthfor a highwaytireacross75%ofthetreadwidth.Showthe“wearbar”indicatorbetweenthetreads.

7.Havestudentsindividuallymeasure a tiretreaddepthand record theirfindings on theirownsheets for marking.

8.Havestudentsinflate a tiretothe correct cold pressureaccordingtotheowner’smanual.

If the driver’smanualisnotavailableor the door notice doesnot match the typeor size oftireinstalled,therecommendedinflationpressuretofill a tireshould be about3–5psilessthanmaximumpressure listedonthe tire sidewall. Maximum pressure isdesigned for usewithmaximumload—usually, acar isnotfully loaded.Also, astireswarm up,theairinsidethemalsowarms,increasingthepressure.Thelinkto a “Proper TireInflation”webpageisincludedinthe“Resources”section.

9.Students should be givena randomly selected used tireand be asked to describethesidewall markingsand determine anytreaddefectsand possiblecauses.

Tire Identification and Markings

Figure 1—Mud and snow(P) passenger tire / Figure 2—Directional tire

Figure 3—Directional tire withwearbarindicated;depthgaugeindicates 5mm depth reading.

Figure 4—Siped directional tire / Figure 5—Conventional tire
Figure 6—The winter snowflake designationforwinter-use tires / Figure 7—Winter snowflake designation on tire

Figure 8—All-season tire

Figure 9—All-season symbols

SomeCommonTireWear Patterns and Issues

Figure 10—Centrewear
The tire in Figure 8 was overinflated, causing the centre ringonly tocontacttheroad. / Figure 11—CrackingandbulgingCrackingandbulgingusually comesfromhitting a pothole, curb or fromanolder tire.
Figure 12—Cupping
Cuppinghappenswhenwornordamaged suspensioncomponentscausethetireto bounceas it travels.Badshock absorbersare the usual cause. / Figure 13—Underinflated tire
The insideandoutsideedgesareworndown; themiddle is not.This is a telltale sign of underinflation.
Figure 14—Feathering
Featheringhappenswhen avehicle has aToe In orToeOutalignmentissue.Note theslantedwearandhighpoints on theedgeofeach row of tread / Figure 15—Camberwear
Withcamberwear, thetire wearsonone sideonly.Thisis usually asignof thecamberbeingoutofadjustment.

Figure 16—Positive andnegative camber

Figure 17—Negative cambercar

Figure18—Toeinand toe out

Figure19—Tirewear fromtoe-in or toe-out

Tire Identification Worksheet

Example belowisfor a Goodyear M&S(mudand snow)235/60R15 radialtirewith 8mmtread wearremaining.

Tire# / TireManufacturer / Type / Width / Aspectratio / Diameter / Maximumpressure / Tread depth
1. / Goodyear / M&S / 235mm / 60(%) / 15inches / 35psi / 8mm(5/16")

This space is to document anyobservations made of each tire.