GT frame technology handbook V.03

GT HISTORY 3

GT TECHNOLOGIES 4

SuspensionPhilosophy

i-DriveExplained 4

AddressingPedalInducedBobbing 4

AddressingWheelTrajectory 5

AddressingFrameDesign 5

TripleTriangle 5

InternalTransmission 5

ForceOptimizedConstruction 6

FRAME TECHNOLOGIES 8

Integratedheadsetsystem 8

Internalheadsetsystem(semi-integrated) 8

Replacablederailleurhanger 9

Replacabledropout 9

Boxedchainstays 9

Forgedframecomponents 9

Buttedtubing 10

Hydroforming 10

Mechanicalforming 10

FRAME MATERIAL 11

Carbonfiber 11

6000&7000SeriesAluminum 11

Chrome-Moly&Hi-TensileSteel 11

FRAME CARE GUIDELINES 1 2

EPILOGUE 13

TABLE OF CONTENTS

Thefollowingisaguidetohighlightandexplainthedifferent

technologiesthatgointoaGTbicycleframe.Itexplainswhy

wedothethingswedoandhowtheriderwillbenefitfrom

them.Thereare3sections:

Section1talksaboutGTspecifictechnology.Theseare

featuresthatweredesigned,engineeredandinsome

cases,patentedbyGTBicyclesforourexclusiveuse.

Section2talksaboutframetechnologiesthatarecommon

totheindustryandexplainswhyGTengineershavechosen

tousethem.

Section3talksaboutdifferentframematerialsthatGTuses

intheirproductsandwhatbenefitscomefromeachofthem.

GTBicycleshasadesignphilosophycalledTechnological.

Thismeansthatanythingwedesignislogicalfroma

technicalstandpoint;everythingisthereforareason.

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GT has produced bicycles to be faster, stronger

and better than any other bicycle on the market.

With over 30 years of design, manufacturing

and racing heritage it’s no wonder that GT

Bicycles frame designs are on the forefront

of bicycle technology.

GT history

4

GT technologies

SUSPENSION PHILOSOPHY

i-Drive EXPLAINED

Pedalfeedbackisoneofthebiggestreasonssuspensionbikeshaveinefficientpedalingcharacteristics.

Pedalfeedbackiscausedbyanadditionalunwantedreactionaryforce that causes the pedals rotate backward during rearwheeltravel.Thisiscausedbytherearwheelgettingfurtherawayfromthefrontchainrings.Thechainneedsmoreslacktomakeup for thisdistance changeandpulls backon thefrontchainwheel.Thiscreatesareverserotationinthecrankset,inturndisruptingtheriderspedalcadenceandrequiringmoreenergyfromtheridertoovercome(SeeFig.A).

With i-Drivetechnology,we’veallowedthebottombrackettomoveseparatelyfromthefronttriangleandreartriangleinawaythatcounteractspedalfeedback.Duringthismovement,thedistancefromthepedaltotheseatdoesnotchange.Forthe most part, pedal feedback is eliminated and the riderdoesn’thavethatextrapedalforcetoovercome(SeeFig.B).

Somesuspensiondesignslockoutthesuspensionuntil theriderhitsabigenoughbumporrelyon“platformshocktech-nology”toincreasepedalefficiency.Inbothofthesecases,activesuspensionhasbeencompromisedtoincreasepedalingefficiency.Withi-Drivetechnologyyougetefficientpedalingandanactivesuspension100%ofthetime.

ADDRESSING PEDAL INDUCED BOBBING

Pedal induced bobbing is an event in which the force ofyour downwardpedal stroke causes the rear suspension tocompressresultinginenergyloss.Thisiscontrolledbyaddingback inasmallamountofpedal feedback,alsocalledanti-squat.Toomuchanti-squat(orpedalfeedback)willlockoutthesuspension;reducesuspensionactionandultimately,alossofpedalingefficiency.Toolittleanti-squatresultsinefficiencylossfrompedalinducedbobbing.

WhatwehaveachievedinaGTsuspensiondesignisanaturalbalancebetweenthedownwardbodymovementcompressingthesuspensionandasmallamountofanti-squatextendingthesuspension.Theresultisaneutral-feelingsystemthatremainsactiveoverthesmallbumpsyetdoesnot“bob”whenpedaling.

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Section 1

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ADDRESSING WHEEL TRAJECTORY

Wheeltrajectoryorwheelpathisimportantbecauseitiscrucialthattherearaxlemoveinthesamedirectionasthebumpforce.Ifthewheelpathdoesnotlineupwiththedirectionofthebumpforce,theriderwilllosemomentumwitheachbumptheyhit.GTsuspensionbikesaredesignedwithasingle,highpivottogivethebikesanarcingwheelpathwhichmovesupandback.Thisallowsthesuspensiontoaccuratelyfollowthebumpforcefrombeginningtoendwithouttheriderlosinganymomentum.

ADDRESSING FRAME DESIGN

Framedesignsthatrelyonmultiplelinkstoattachthefrontandreartrianglesaresubjecttoframeflexandlongtermdurabilityissues.Eachadditionalpieceinalinkagedesignisanadditionalareathatissubjecttoflex.

AlthoughGTsuspensionframeswithi-Drivetechnologyhaveatotalof4pivots,thesuspensionworksasasinglepivot(cantilever)design.Byusingthistypeofframedesign,we’vebeenabletoconstructastiffrearendusingboxconstructionandanoversizepivot.Singlepivotframedesignsaresimple,costeffectiveandtroublefreemechanisms.

TRIPLE TRIANGLE

Bylengtheningtheseatstaystonotonlyattachtotheseattubebutalsoweld

directlytothesidesofthetoptube,GTengineershavedecreasedthesizeof

thefrontandreartrianglesandaddedathirdtriangle.Thisreductioninsize

yieldsamuchstrongerandrigidstructure.

Notonlywillthestrongerframelastlongerthroughyearsofbombingdownyour

favorite,rockyfireroadbuttheincreasedrigiditywillimproveresponsivenessin

pedalingandsteering.TorsionalflexisgreatlyreducedonaTripleTriangleframe

design.

Besides,whatotherbrandcanberecognizedevenifthedecalshavebeenremoved?GT

INTERNAL TRANSMISSION

AnInternalTransmissionframedesignisonethatdoesnotuseaconventional,

externallymountedderailleurtochangegears.Thereareanumberofbenefits

tothistypeofframedesign.

Thefirstbenefitofaninternaltransmissionisthatthetransmissionmassis

housedinthecenteroftheframe.Thisallowsthedesignertoreducetheun-

sprungweightoftherearwheel.Un-sprungweightisthemassonthebikethat

isdirectlyconnectedtothewheelsandswingarm,andnotisolatedthroughthe

suspension.Bydecreasingthismass,itallowsthesuspensiontorespond

quickertochangesintheterrain.

Thesecondbenefitis,nowthattheconventionalrearderailleurandcogsethavebeenremovedfromtherearwheel,thehubflanges

canbemovedoutwardandcenteredonthehub.This,asyouknow,createsastrongerandstifferwheel.

Thethirdbenefitis,bymovingthegearchangingmechanismtothecenterofthebike,youeliminatethepossibilityof

damagingthemostvulnerablecomponentonthebike,therearderailleur.Theshiftingmechanismisnowprotectedwithinthe

frameandhaslessofachanceofbeingdamagedevenduringaseverecrash.

ThemostimportantbenefitofanInternalTransmissionframedesignisthatitwillopenthedoorforfutureframeandsuspension

designs.Bygettingawayfromastandardshiftingmechanism,GTengineerscanimprovenotonlyintheareaslistedabovebutthey

canalsoimproveonthebicyclesperformanceincludingpedalingefficiencyandwheeltrajectories.

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ForceOptimizedConstructionisGTBicycle’sproprietarycompositemanufacturingprocessinwhichtheconstructionofeachframeis

optimizedtogivetheframeexceptionalstrengthandstiffnessintheareasthatneeditmostbutatthesametimeremovingmaterial

intheareasthatneeditleast.Thereare4importantfactorsthatmakeupForceOptimizedConstruction:

Optimized Tube Construction-Forcesenterabicycleframefromboththerider

andtheterrain.Theseforces,push,pull,twist,stretchandcompressevery

tubeontheframeineverydirection.ByusingFiniteElementAnalysis(FEA),

eachtubeonaGTcarbonframeisdesignedwiththeseforcesinmindandthey

aregivenacrosssection(ashape)tocounteractthoseforces.

Monocoque (One Piece) Frame Construction-GTframedesignbeginswithchoosingaconstructionmethodthathasthehighest-

strength-to-weightratioavailable.Lugconstructionaddsweightandcanbeweakerduetothepossibilityofvoidsandpockets

betweenjoints.Thejointscanalsoactasstressriserswhichweakenandeventuallyfail.Monocoqueframeconstructiongives

youastrong,onepieceframewiththelowestpossibilityofconstructionimperfections.

Proprietary Kiting and Sequence Process -Justaswoodandmetalhavea

graindirection,carbonhasafiberdirection.Eachlayerofcarbonfiberused

inourframesisplacedinacertainspotandcertainorientationdependingon

thedirectionofforceonthatpartoftheframe.Thisgivestheriderthemost

compliantandcomfortableridepossible.

TypicalFEAmodelforstudyingpedalingforcesontheframe.

FORCE OPTIMIZED CONSTRUCTION

Apioneerincarbonfiberbicycleconstruction,GTBicycleswasthefirstcompanyintheUnitedStatestoproducethermoplasticcarbon

mountainbikeframesinsignificantquantities.In1996GTBicyclesgloballymarketedtheUSAmadeCarbonfiberLTS.TheSuperBike

II(SB-2),producedincollaborationwithUSACyclingforthe1996AtlantaOlympicGamesisstillthebenchmarkforcarbonconstruc-

tionandaerodynamicdesign.GTBicycles,throughitsextensiveresearchanddevelopmentofcarbonconstructiontechniques,has

numerouspatentsdatingbacktotheearly90’s.

Withametalbicycleframe,thecompositionofthemetalandthemechanicalcharacteristicscannotbeeasilychangedoverthelength

ofthetube.Thiscanonlybedonebyformingorlayeringthemetalatthecostofadditionalweight.Withcarbon,changingtheplace-

ment,thedirectionandthemakeupofeachlayerofmaterialispossible,inturncreatingalighterandstrongerstructure.Thecross

section(theshape)ofeachtubecanalsobedesignedforoptimumstrengthandstiffness.

Twistingforcesputonframetubesduringpedaling.

OUR STORY

OUR REASON

OUR TECHNOLOGY

Proprietary Blend of Fiber Types-Therearemanydifferenttypesoffibersthat

canbeusedtomakeupcarbonfiberframes.GTusesaproprietaryblendof

TR30andTR50fibersindifferentareasoftheframetoincreasestiffnessor

strengthintheplaceswhereitmatters.Again,GTengineersuseFEAtostudy

andcalculateareas inneedofstrengthorsupport togiveyouthestiffest,

strongestandlightestweightframepossible.

This4par tcombinationofbaseconstruction,shapedesignandmaterial/fiberapplicationiswhatForce Optimized Constructionisallabout.

GTengineershaveoptimizedourcarbonframestogivetherideracomfortableridethatisstiffenoughforquickaccelerationsand

responsivesteering,strongenoughforserioususeandyetsuperlightforthatcompetitiveedge.

ThisisForceOptimizedConstruction…

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OUR RIDE

FRAME technologies

INTEGRATED HEADSET SYSTEM

An integrated headset is one that is built in to the frame.

Headsetcupsareeliminatedbymachining thebearingcups

intotheheadtube.

Inadditiontocreatinganeasierassemblytomaintainanda

lighterweight system, thestackheight ismuch lowerwhich

allowsforalongerheadtubetoincreaseframestrength.

INTERNAL HEADSET SYSTEM (SEMI-INTERGRATED)

Aninternalheadsetisaheadsetinwhichthebearingcupsare

recessedwithinthediameteroftheheadtube.

This headset systemallows for amore stylish fork/head tube/

stemjunction.Thedecreasedstackheightinconjunctionwith

aheadtubelengthincreaseallowsforastrongerframe.

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Section 2

REPLACEABLE DROPOUT

ByincludingreplaceabledropoutsonsomeGTmodels,theriderisnotonlyableto

easilyremoveandreplaceadamagedderailleurhangereasilybutcanalsoreconfig-

uretheirframefordifferenttypesofaxlesizesandrearendconnections.

REPLACEABLE DERAILLEUR HANGER

Themostvulnerablepartonabicycleistherearderailleur.Thismechanismhangs

offoftherightsideofthebikeandcaneasilybecaughtonrocks,branchesand

passingcarsifyou’renotlooking.Onceyou’vedonethis,you’veprobablydamaged

thederailleurandquitepossiblystripped,brokenorbentthehangerthatit isat-

tachedto.

Byincludingareplaceablederailleurhangersystemonmostofourmodels,GThas

eliminatedthepossibilityofframereplacementsduetobrokenorstrippedoutde-

railleurhangers.Simplyremovetherearwheelandderailleur,unboltthedamaged

hangerandreplace.

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BOXED CHAIN STAYS

BMXracingisverydemandingwhenitcomestotheamountofflexwhilepedaling

andcornering.Byincreasingthesizeandcrosssectiononthechainstays,GTen-

gineers are able to increase the strength and stiffness of the rear end of the

frame.

Boxed chain stays are a feature in which the stays are made from forming two

halvesofeachstayandweldingthemtogetherasone.Withitssizeandshape,this

monocoquedesigndecreasesflexinawaythatstandardchainstaytubescannot.

FORGED FRAME COMPONENTS

Forgingisamanufacturingprocesswheremetalispressed,poundedorsqueezed

undergreatpressureintohighstrengthpartsknownasforgings.

Theprocessisnormally(butnotalways)performedhotbypreheatingthemetalto

adesiredtemperaturebeforeitisworked.Forgingyieldsagrainstructureoriented

tothepartshape,resultinginoptimumstrength,ductilityandresistancetoimpact

and fatigue. The forging process can create parts that are stronger than those

manufacturedbyanyothermetalworkingprocess.

HYDRO FORMING

Hydroformingisatubeformingprocesswhichusespressurizedliquidto

giveshapetoanotherwiseroundtube.Agiventubeisfilledwithpressur-

izedliquidwhichexpandsthetubeoutwardandfillsamoldofthedesired

shape.

ThisprocessgivesGTengineerstheabilitytocreatecomplextubeshapes.

Hydroformingisusedtoreshapeatubeinordertoincreasestrengthinthe

framedesignandalsotoadduniqueshapesandstyletotubeprofiles.

BUTTED TUBING

A butted tube is a tube in which the wall thickness of the tube changes from one end of the tube to the other. The number

ofwallthicknesschangesalongthelengthofthetubewilldetermineifit’saSingleButted,DoubleButted,TripleButted,etc.,tube.A

buttedtubewillbelighterthanaplaingaugetubeofthesameouterdiameterandhavesimilarstrengthcharacteristics.

Byusingbuttedtubes,GTcanhavetheappropriatewallthicknessforweldingoneachendbuthaveathinnerwallthicknessinthe

middlewhereitisunnecessary;thebenefitbeingalighterweighttube.

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STANDARD BUTTED TUBE DOUBLE BUTTED TUBE

MECHANICAL FORMNG

Mechanicalformingisatubeformingprocessinwhichatubeispressed,

poundedorsqueezedintothedesiredshape.Thisprocessisacosteffec-

tivewaytoproduceuniquetubeshapesfordesignswithrelativelysimple

crosssections.

CARBON FIBER

Onematerialthatisbecomingmorepopularinframeengineer-

ingiscarbonfiber.Thismaterialisproducedbylayeringsheetsof

carbonfiberclothintoamoldintheshapeofthefinalproduct.

Thealignmentandweaveof theclothfibers is important for

thestrengthoftheresultingmaterial.

By using carbon fiber GT designers can create a light-

weight,structurallysoundpar tinvir tuallyanyshape.See

ForceOptimizedContstruction.

6000 & 7000 SERIES ALUMINUM

Probablythemostcommonframematerialchoiceinallofthe

bicycleindustryandadefinitefavoritewithGTengineers.Both

6061-T6and7000seriesaluminumalloysarethemostversa-

tile and widely used aircraft-grade, heat treatable aluminum

alloys.Aluminumalloyshaveaverygoodstrengthtoweight

ratioalongwithimpressivevibrationdampingcharacteristics.

Aluminumframescanbemadelightandstiff,makingsurethe

powercomingfromyourlegstranslatestopowerinmovingthe

bike.

CHROME-MOLY & HI-TENSILE STEEL

GTutilizesavarietyofchrome-molyandhi-tensilesteeltubesets,

rangingfrom100%chrome-molyframestoamixofchrome-moly

andhi-tensilesteeltubesforastrong,yetcost-effectiveframe.

Incrediblylightanddurablebicycleframescanbemadefrom

steel tubing. Manycyclistsprefersteeloverothermaterials

duetothecomfortlevelandridefeelthisframematerialcan

provide.Don’tforget…SteelisReal.

FRAME materials

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Section 3

12

FRAME CARE GUIDELINES

Itiscriticaltoconstantlyinspectyourcompletebike,includingframeandcomponentsfordamageandnormalwearbeforeeachandeveryride.Theridingconditionsandactivitiesthatbikesareusedforhasincreasedthewearonbicyclesandforthisreason,GTBicyclesrequiresthatyouinspectyourframefrequently.

•Visuallyinspectyourframebeforeeachride •Lookforcracksand/orimperfectionsinthematerial •Beawareofanyabnormalitiesinridequalityofyourframe •Abnormalframeflexorshiftingandbrakingperformance •Alwayslistenforabnormalnoisesduringyourride •Soundslikecreaking,tickingandpopping

Ifyoudiscoveranyabnormalitiesinanyoftheabovecategories,orifyourbikehasbeencrashedorputthruabnormalstress,pleaseseeanauthorizeddealerforinspection.

Examplesofdamagingactivities: •Ridercrash •Abruptstopimpacts •Runintogaragewhileincarrack

Ifyouhavecrashedorstressedyourframeinawaythatyou’renotsureifitisdamaged,itisalwayssafesttotakeyourbiketoanauthorizeddealerforacompleteinspection.

CARBON FRAMES Althoughcarbonmaterialhasbeenproventobeextremelystrongandcanbeconstructedintobicycleframesthathaveexceptionallyhighfatiguelife,carbonitselfcanstillbeeasilydamagedwhencrashedorputthruanabnormallyhighstressincident.Adamagedframemaynotshowanyvisiblesignsorthesesignsmaybedifficulttoseewithoutmeticulousinspectionbecausethedamagemaybeunderneaththesurface.

Warning:Damagedcarbonfibercanfailsuddenlywithminimalnoticeandcauseseriousinjuryordeath.

ALUMINUM AND STEEL FRAMES Aluminumandsteelframescantakedirectimpactsverywellandarenotlikelytofailcatastrophicallybutitisstillveryimportanttoinspectyourframebeforeeachride.

OUR POLICY •Warranty–PacificCycleoffersalimitedwarrantyonallofitsframesagainstmanufacturingdefectandmaterials.Anywarranty claimsmustbeplacedthroughavalidPacificCycledealerandmustincludeproofofpurchase.Warrantyisonlyvalidtothe originalowner.Pleaseseethebicyclesownermanualoryournearestdealerformoredetails.

•CrashReplacementProgram-Becauseenoughpeopledolaydowntheircarbonbikesinavarietyofways(racing,drivinginto garageswiththebikeonthecar,others…),thatwouldnotbecoveredunderthewarrantypolicy,PacificCycleoffersacrash replacementprogram.WithavalidproofofpurchaseandaPacificCyclelicenseddealer,wecanhelpreplaceyourbroken framewithanewframeorcompletebikeatareducedcost.Pleaseseeyourdealerformoredetails.

GT: technological

A philosophy of design and engineering that

is guided by sensible rational thought rather

than the latest marketing fad. Technological

design is a system that deals not only with

the end product but with all aspects of the

product life cycle from conception to eventual

obsolescence. Throughout design, development

and manufacturing, GT uses its 30 years of

experience to build bicycles that illustrate a

complete holistic consideration of the product

and its eventual owner. With an increasingly

crowded marketplace the philosophy of Tech-

nological design and engineering marks a clear

path towards products that make sense.

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