Bike India – August 2019

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Daimler AG

by bending formed flat sections or extruded ones into a circle and welding the joint,

wire wheels are none the less labour-intensive to assemble. In use, they can require

periodic maintenance to ensure even tension on the spokes. Repairing rim damage is

easier, though, and not beyond the abilities of the home mechanic with a block of

wood and a mallet in markets where low-speed commuting prevails over street racing.

Steel has mostly been the material of choice due to strength and low cost, although

aluminium rims with steel spokes, such as produced by Borrani since 1922, have also

been popular due to their offering of lighter un-sprung weight.

Until quite recently, spoked wheels dictated the need for inner tubes, due to air

leakagearoundeachspokenipple.Inthemid-1990s,BMWfounda wayaroundthat

issuebylocatingthespokesaroundtheedgeoftherim,beyondthepressuredarea,a

systemintroducedonthe 1994 R1100R andGSmodels.Analternative,andperhapsa

moreelegantsolution,wasbeingdevelopedbyothermanufacturers,withthespokes

attachedtothesideofa widercentralflange.Infact,HondamayhavebeatenBMW

toit bya wholedecadeontheirParis-DakarinspiredXL600LandR models.Several

currentbikesalsoutilizethisfeature,includingSuzuki(V-Strom),Triumph(Tiger

1200),andYamaha(XT1200ZSuperTénéré).Butit is mostvisibleontheMVAgusta

Dragster800RR,which,thankstoitssingle-sidedswing-arm,exposestherearwheel

initsentiretyontherightside.Colouringdrawsadditionalattentiontothedetail.

Castaluminiumwheelsarrivedinthemid-1920swiththe

curiousCzechBöhmerland,nodoubtforaddedstrengthona

motorcyclethatcouldaccommodatetwo,threeorevenfour

people.Thesewerereplacedbysteelversionsimmediatelyprior

toWWII,afterwhichcastwheelsdidn’tmakea returnuntil

FreidelMünchintroducedhisMammutat the 1966 Cologne

IFMA.Thatsaid,a magnesiumalloycastingwasfittedonlyon

therear,afterevenstrengthenedwire

spokesontheprototypehadprovedtobe

pronetobreakingduetothehighoutputof

theengine.Thefrontwheel,however,

remaineda regularspokedaffair,albeit

matedtoa 10-inch(25-cm)drumbrake,

whichensuredthespokesremainedshort.

Alloycastingsinthe1970swereinitiallydevelopedforroad

racingduetotheirstrengthandlightness,whilstthefittingof

tubelesstyreswasa furtherincentive.Theabsenceoftubes

offeredadditionalweightsavings,whilealsoreducingheat

insidethetyre.Castingsallowmuchmorefreedomthan

pressingsincreatingtheshapeofthesection,permittinga

deeperouterflangeontowhichthetyre’sbeadcansealitself,

whichis essentialintubelessapplications.

Giventheclearadvantages,castwheelsweresoonintroducedonsomehigherend

sportsbikesand,bythe1980s,werefittedasstandardonmanymodels,including

evenmopeds.Tubelesstyresweremostly,thoughnotuniversally,fittedasthesegave

additionaladvantagesforstreetuse.Inthecaseofa puncture,a tubelesstyrewill

usuallydeflatemoreslowlythanonefittedwithaninnertubeandwillbeeasierto

repair—at leasttemporarily,usinga plugandinflationcanister—withouttheneed

toremovethewheelandjuggletyreironsbytheroadsideinordertopatchtheinner

tube.Notallalloywheelsarelighterthantheirwirecounterparts,though.Thecast

wheelsemployedonthe 1976 YamahaRD400wereactuallyslightlyheavierthanthat

bike’swirepredecessors.

Aluminiumhasusuallybeenthematerialofchoiceforcastings,althoughmagnesium

alloysfromcompaniessuchasMarchesiniofferlighterweight,albeitat a price.Early

castingshadsomeissueswithporosity,especiallysand-castvariants,butlater

technology—forexample,pressureorrotationcasting—hasresolvedtheproblem.

Dueinparttoporosityconcernsandtoretaina certainamountofradialflex,

Hondadevelopedanalternativesolutionusingeithersteeloraluminiumstamped

centresrivetedorboltedtoextrudedaluminiumrims.TheComstarwheelandits

successor,theComcast,becamea regularfeatureonmodelsfromthe49-ccMB5

rightuptothesix-cylinderCBXandGL1100Interstate.Easycleaningwasonebig

advantagewiththepressedversions,whichI canattesttopersonally.

ABOVE: 1894 Hildebrand&

Wolfmüllerhada solidrearwheel

thatactedasa fly-wheelvia

connectingrodstothepistons

RIGHT:Earlymotorcycles,like

this 1902 Duesenberg,followed

thesafetybicycleinadoptingwire

wheelswithinflatablerubbertyres

BELOW:FreidelMünch,testingtheprototypeMammut,

foundthatthehighpowerbroketherearspokes

BELOW:TheproductionMünchMammuthada

rearwheelmadeofcastmagnesiumalloy

BELOW:

TheHondaComstarwheel

LEFT: The first

motorcycles

rolled on

wooden wheels

with iron tyres

Image Copyright:

Münch

Image Copyright:

Münch

Image Copyright:

Honda

http://www.bikeindia.in August 2019 BikeIndia (^43)
Image Copyright:
Glynn Kerr
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