800836 Prediction ofDriving Traction Performance onSnow Thomas R.Nesbitt TireWheelSystems GeneralMotorsProvingGrounds DonaldJ.Barron Product TestDevelopment GeneralMotorsProvingGrounds Passenger CarMeeting HyattRegency, Dearborn June9-13,1980 400 COW~~\i1a~t41#£ALTH 1i'VARRENITJ,;t\lE?Downloaded from SAE International by Columbia Univ, Sunday, August 19, 2018Theappearance ofthecodeatthebottomofthefirstpageofthispaperindicates SAE'sconsentthatcopiesofthepapermaybemadeforpersonal orinternaluse,or forthepersonai orinternaluseofspecificclients.ThisconsentIsgivenonthecon­ dition,however, thatthecopierpaythestatedperarticlecopyfeethroughthe Copyright Clearance Center,Inc.,Operations Center,P.O.Box765,Schenectady, N.Y.12301,forcopyingbeyondthatpermitted bySections 107or108oftheU.S. Copyright Law.Thisconsentdoesnotextendtootherkindsofcopying suchas copying forgeneral distribution, foradvertising orpromotional purposes, for creating newcollective works,orforresale. PaperspUblished priorto1978mayalsobecopiedataperpaperfeeof$2.50 undertheabovestatedconditions. SAEroutinely stocksprintedpapersforaperiodofthreeyearsfollowing dateof publication. DirectyourorderstoSAEOrderDepartment. Toobtainquantityreprintrates,permission toreprintatechnical paperorper­ missiontousecopyrighted SAEpublications inotherworks,contacttheSAE Publications Division.Downloaded from SAE International by Columbia Univ, Sunday, August 19, 2018800836 Prediction ofDriving Traction Performance onSnow Thomas R.Nesbitt TireWheelSystems GeneralMotorsProvingGrounds DonaldJ.Barron ProductTestDevelopment GeneralMotorsProvingGrounds GENERAL MOTORS hasspecificperformance requirements forthetiresusedonitsvehicles. These requirements areestablished undertheTirePerfor· manceCriteria,orTPC(1)*,system. Oneoftheareas specified underthissystemissnowtraction perfor­ mance.Specifically, eachtirequalified asmeeting TPCrequirements musthaveacertainminimum trac­ tiononsnow.Asnewtiredesignsaresubmitted for approval, theyareevaluated byfullscaletestfortheir snowtraction capability. Testingofalltiressubmitted isalengthyprocesswithnoguarantee ofsuccessful tireperformance. Ifaprediction equation forsnow traction performance wereavailable toevaluate thepotential ofvarioustires,thetestingjobcouldbe greatlyreduced. Additionally, tirecompanies could usesuchanequation atthedesignphasetoascertain thepotential ofanewdesign. Astudytoevaluate snowtraction prediction techniques isreported inthispaper.Thepurposeof thisstudywastodevelopequations whichutilize certaingeometric properties oftiretreadstopredict snowtraction performance. *Numbers inparentheses designate References at endofpaper. _______________ ABSTRACT _ Theamountofperformance testingrequiredto evaluate tiresnowtraction performance issubstantial. Thiscouldbereducedthroughtheuseofasnowtrac­ tionprediction equation toscreentiretreaddesigns. Thedevelopment ofsuchanequation usingfivegeo-metrictreadproperties isdescribed. Simplified versions ofthisequation arealsodeveloped andchecked against tiresofknownsnowtraction performance. These equations provideanobjective methodforestimating thesnowtraction potential ofatreaddesign. 0148-7191/80/0609-0836$02.50 COPYright ©1980SocietyofAutomotive Engineers, Inc.Downloaded from SAE International by Columbia Univ, Sunday, August 19, 20182 Treadpatterns representing variousgeometric treadparameters weredesigned andthenhandcut ontoblanktires.Thesnowtraction capability of eachwasthendetermined throughfullscaletesting. Regression analysiswasusedtotestforthesignifi- cantlinearandquadratic effectsofthedesignpara­ metersaswellastheirinteractions. Ageneralequation usingallofthesignificant parameters andinteractions wasthendeveloped. Simplification ofthisequation wasthenpursuedalongtwopaths:tiredesignequa­ tions,andtireevaluation equations. Thesimplest possiblecombinations ofthedesignparameters were determined forthedesignequations. Theseequations couIdbeusedbyadesigner ashedeveloped anew treadpattern. Theevaluation equa