THE SCIENCE OF COR­NER WEIGHT­ING

THE SCI­EN­TIFIC ART OF COR­NER WEIGHT­ING A CAR IS OF­TEN CON­SID­ERED THE REALM OF HIGH-END RACE CARS, BUT IN RE­AL­ITY ANY CAR, RACE OR STREET, CAN BEN­E­FIT FROM A PROP­ERLY SET UP SUS­PEN­SION PACK­AGE AND WEIGHT BAL­ANCE. WE CHAT TO THE GUYS AT J TUNE AU­TO­MO­TIVE TO

NZ Performance Car - - Contents - WORDS: NZPC PHO­TOS: MAR­CUS GIBSON

ALL YOU NEED TO KNOW ABOUT COR­NER WEIGHT­ING AND WHY YOUR CAR NEEDS IT

So what is cor­ner weight­ing you may ask? In the most ba­sic of terms cor­ner weight­ing uses four scales (one un­der each wheel) to cal­cu­late both the to­tal weight of the car and the weight placed on each wheel, which is passed through the sus­pen­sion. Th­ese fig­ures are then used to cal­cu­late the weight dis­tri­bu­tion of the car (we have all heard about a car hav­ing per­fect 50/50 weight bal­ance) so we’ll show you how it’s cal­cu­lated. Weight dis­tri­bu­tion has the abil­ity to make or break the han­dling of your car around a cir­cuit. Springs, shocks, sway bars, wheels, and tyres can all have a pos­i­tive im­pact on han­dling but some­times, with­out cor­ner weight­ing, th­ese mod­i­fi­ca­tions can have a neg­a­tive ef­fect. It’s a sim­i­lar sce­nario to how a high-per­for­mance en­gine pack­age can fail mis­er­ably if you don’t know how to tune the highly-strung com­bi­na­tion cor­rectly, or you over­look the ba­sics. So, let’s think of cor­ner weight­ing as a dyno tune for your sus­pen­sion com­po­nents.

As we in­stall dif­fer­ent sus­pen­sion com­po­nents, com­plete en­gine con­ver­sions, and re­move in­te­rior trim, the weight of the ve­hi­cle can ei­ther in­crease or de­crease and with this comes vari­ance in weight dis­tri­bu­tion. This dif­fer­ence in weight dis­tri­bu­tion can cause the ve­hi­cle to pull to one side, or turn in one di­rec­tion bet­ter than the other. Even the preloads on brand-new coilovers can be dif­fer­ent shock to shock, as can en­gine con­ver­sions such as an RB en­gine into a Sil­via, a K-se­ries into a Honda, or a ro­tary into a BMW. There are two main as­pects to ad­dress in or­der to com­bat th­ese weight is­sues: static weight dis­tri­bu­tion and cross-weight per­cent­age, and when used to cor­rectly dis­trib­ute weight across the ve­hi­cle, it should roll straight on a flat sur­face.

Here we’ll run through the ba­sics of the the­ory and then ap­ply this cor­ner weight­ing to a new Honda Cup­build race car. As you might ex­pect, there are spe­cial­ized tweaks that ap­ply to each rac­ing dis­ci­pline, be it drift­ing, au­tocross, drag rac­ing or cir­cuit rac­ing, but here we’ll deal with the fun­da­men­tals. Through­out this ar­ti­cle we will ex­plain the cal­cu­la­tions needed to find weight-per­cent­age val­ues, but in all hon­esty all cor­ner weigh­ing ma­chines we have used do all th­ese for you, mak­ing life much eas­ier.

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