Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/141063
4 .00 an d 4 .50 x 18 rear kn obbies b ecause these are the most popular sizes in use by the seri ous rnotocrossers.: Th e odyokahazlerborreleboshinarum serious m o t o c ro sse r is to wh om this article is di re cted. Before adequate explanations can be made about th e tire a n understanding of b y Al vin Tamura the p rocess o f m a n u fac t u ri n g would be A h , th os e sexy European useful. The process of building a tire knobbies ...you can almost picture b egin s by starting wit h .th e in side . tire yourself chewing up grassy hills in m aterials and working outward to the France o r b ro adslid ing effor tl essly tread. The soft inne r tire rubber lin er is through Czechoslo vakian mud. But n ow p laced on the cy lin de r first. This inner y ou must ch o o se between these and liner makes the casin g airtight. T h e cord other d iff e ren t brands. After all, th ey lay ers are laid on the cy lin d e r d iagonally ea ch look a little different a nd some are to one anothe r. T h e angle at which more e xpensive than others. So before these cord s are laid determine the y o u p lunk down you r hard-earned cash , stability of the tires road-holding. Rubber c ove re d wi res are laid on the you wan t to make sure the tire y o u buy will give you the b est p e rforman ce. cylinde r to c reate the bead. T hese wire ri ngs keep th e tire shape and diameter First, you m igh t like to consider how fixed. The bead also serves to keep the imporatnt this p ar t of the bike really is. Maybe you'd like to use some of that tires on the rim. The end pieces of th e cord p lie s are wrapped aro und the bead, m o n ey fo r a n ew port job or a trick ca rbo Well, b esi des h oldin g up the rear securing th e bead to the now formi ng tire. of y ou r bike , th e rear knobby is the T he side Walls and tread are then conversion point o f horsepower to added and all parts are pressed together trac tion. There's n o sense in having that 40 h o rse bomb of yours if n one of that . by sending all of i t th rough a set o f tire o r because we ca n acquaint y o u with the basic principles o f tire c onst ru c tio n . When you as k "What si ze tire should I fit on my bike?" a gen eral repl y to the seri ous motocrosser would be to mount a 4 .00 o n a high performance 125cc to average 2 50cc bike and a 4 .50 o r larger on a hig h performance 250cc or la rger bike. On the w hole , a 4 .50 or larger ti re offers the ma xim u m in traction but often this traction is too m u ch for a lower h o rsep o we r bike to pull. Tires are measured in flated a t the -fle x in g poin t o n t heir sidewalls. We m easu red the tires at the wi des t poin t of the tread because we feel that this is the area that counts. After m easu ring we were amazed to fin d th e Yokohama 4 .6 0 to b e over 5 inc hes acros s with several other "4.50s" in the 4.80 inc h range. Be sure to check. the w id t h s of th ese tires with th e clearance be tween swi ngann stru ts. Tire p ro file is kn own as th e asp ect ratio or a ratio between the cro ss section a nd th e h eighth of the tire. On the average tire these dimen sion s are per onnanc e an tire . T hese two inv ersely related which m ean s that a h igh traction tire will h ave lo w tread life an d vice versa. T he rubber is generally b lended b y m a n u fac turer s to give the optimum in p erformance with th elongest tread life. Th is tends to be come a p rob lem wh en tread design is involved. Tall knobs or lugs wi th a soft rub ber c o mpound so metimes resul t in tire .. c h un king" or th e breaking and ch ip p in g of p arts of the lugs . 1\105t manufact u rers , w hen questi on ed as t o th e . type of terrain th eir tire is suitable , gave the response of "general p u rpose" an d w ould not specify if the tir e was best in sand, mud , h ar d pack o r wh at h ave you. This is an ind ica ti on that . mo st tires are n ot specifically created fo r a p articu lar soil co n d i tion, a nd that the ru b ber co m p o sit io n w as blended f or a n ear 5 0ยท 5 0 p er forman ce-l ongevi t y ratio. Notab le e xcep ti o ns were T re lle borg, G oody ear and th e Dunlop 4. 6 0 ; all were d esigned for mud. Ch arac terist ic of kn obby tire tread s are , o f cou rse , the kn obs. These knobs THE REARWEENIE COMPARISON TEST The contenders, from left to right : Goody ear 4.50 & 4.00 ; Yokoha ma 4 .60 & 4.00; Cheng Shin 4.50 & 4.00; Barum 4.50 & 4.00; Pirelli 4.00 ; Full Bore 4 .20 ; Trelleborg 4 .50 6p r. 4.50 & 4.00 ; and Metzler 4 .50 & 4.00. power is applied to the gro u n d . Se cond , it provides stability to th e rear of the bike while corne ring . And lastly, th e p n eum ati c tir e p rovides an air suspe nsi o n fo r a smoothe r ride and fo r pro tec tion of e xpens ive rims , With thes e importan t tire fun ct ion s in mind, c on sid er h ow much attention these often n eglected parts sh ould re ceive . Poor tires c an rend e r the mo st perfec tly p repared motorcycle absolutely useless. Th e b asic reason fo r this ar ticl e is to inform the re ader ab o ut sp ecific fa cts of ge neral c o ns truc ti on and pe rform ance of th e e igh t lead in g accessory rear kn obbies. We will atte mpt t o e xpose the designed applications and th e general po in ts of interest in the c on struc tion of each ti re . We also test ed each tire u nde r co n trolled con di t ions in fo u r ge ne ral categories. The tire sizes tested we re limited to ro lle rs. T hi s ri ng of ru b b e r fa bric an d wire is th en placed inside o f a sem i-w affle iron whe re the fin al shaping and tread formatio n t a kes p lace. The finish ing drum is closed w i th an ai r bag pl aced inside the ti re ri ng. H ea t is ap p lied while the air bag is filled with steam. The pressure o f the air bag p ush es th e tire into the h ea ted m o ld w h ere th e tire is shape d an d th e final tred is pu t on. When the process is comp leted th e air bag is deflated and the finish ed product is released. There are man y facto rs which will co n tro l the amoun t of trac tion a tire will give . Some external' fac tors are the horse power output o f" th e machine, soil conditions, and w eigh t of the ride r an d m ach in e. But the factors we are inves tiga ting are tir e w id th , rubber com position , tread design, cord p lys an d tire weight. We can't choose the best equal. So a lo w p rofile or w id e oval tire is o n e wi th a lower h eigh t than c ro ss section . Two makes claim low p ro fil e or wide oval designs, Yoko hama 4 .6 0 an d Full Bo re . A w id e oval design h as it s advan tages an d di sad van t ages wei ghing even Iy aga ins t o n e an other. A n advantage o f the low profile is th at it pl aces m ore tread flatly on the gr ound su rface . This in tu rn m a kes a slig h tly sharpe r side wall a ng le w it h a li ttle les s side wall fo r t read. A possible disadvantage might be a lack of air cus h io ni ng d ue to the decreased h eighth of t he tire. T he d ifferen ces are small yet dese rve men tion , Rubber co mp o sition is a h igh ly r e g ar d e d secret amo ng tire man ufac ture rs, so little information cou ld be re leased . Wh en dealing w ith rub b e r compositions th ere are tw o factors to be c o nsi de re d. th e a re t h e e s s e n s e of th e ti re's performance . T he treads on all brands tested were no t com p u te r designed, as are many car tire s, but fashioned an d c r e a t e d t hrough trial an d er ro r e xp erimenta ti on. All t he tires tested. save o ne, had a straight ac ross tread p attern with th e de sign repeating itself eve ry tw o rows. T he power lu gs, or th e lugs in th e ce nter of th e ti re, ge ne ral ly deli ver straigh t line perfo rmance . Tires w ith taller lugs will o f fer m ore traction but are again suscep tible to ra p id we ar. T he m o st unu su al d esign s w ere sho wn by th e G o ody ear an d T re lle bo rg 4 .5 0s. Both are very simila r. T he ce nte r lu gs o n both tires a re tall, over I \4 inc hes wi de and spaced a la rger 2 \4 in ches apart. T he Yokah ama 4. 60 also has gian t lu gs sp aced far apart, but the y are n ot very tall. Th is is the diff eren ce be tw een the biggest and the smallest .