BUMP STEER 101

NZV8 - - WORLD NEWS -

Good ar­ti­cle on bump steer, as most older Amer­i­can cars are fairly di­a­bol­i­cal right from the fac­tory. There is one vi­tal thing to note, and that’s the shape of your graph. In bump or com­pres­sion, you must have toe in and not toe out. It’s vir­tu­ally im­pos­si­ble to have zero bump steer, and a wee bit is ac­tu­ally not a bad thing, as it gives the driver some feel and feed­back; that’s some­thing Colin Chap­man noted decades back. If you have toe out oc­cur­ring in bump/com­pres­sion, then you can get some fairly rad­i­cal un­der­steer hap­pen­ing if you’re not care­ful, and it’s too late to make ge­om­e­try changes as you’re sledg­ing in the very first cor­ner. There are some nice sus­pen­sion soft­ware pro­grammes out there, but [for them] to be of gen­uine use you do need to have a sound knowl­edge and some ex­per­tise with sus­pen­sion ge­om­e­try. I have played with race car and street ve­hi­cle sus­pen­sions for a while, and have mer­rily gone down the rab­bit hole all too of­ten. There are a few golden rules you quickly learn, and the com­ments above would be one of them. Steve

Thanks, Steve. Bump steer is an in­ter­est­ing sub­ject once you start look­ing into it. As you say, it’s quite scary just how bad some of the older Amer­i­can cars are. What’s even scarier is that a lot of af­ter­mar­ket sus­pen­sion man­u­fac­tur­ers that peo­ple tend to hold in high re­gard also have bad bump steer–in­duc­ing ge­om­e­try. In this day and age, with com­puter tech­nol­ogy and the level of knowl­edge in gen­eral around the topic, there’s no ex­cuse for it not be­ing taken into con­sid­er­a­tion or for ve­hi­cles run­ning mas­sive tie-rod spac­ers to move the rod ends into the cor­rect po­si­tion, when they could sim­ply have cre­ated the spin­dles right to be­gin with. We hope that the ar­ti­cle has helped ed­u­cate peo­ple about it and en­cour­aged them to ask the ques­tion be­fore buy­ing just any in­de­pen­dent front sus­pen­sion (IFS) set-up purely be­cause they’ve heard of the brand be­fore. Cheers,

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