KPI

[Nitesh]

Hi guys, Could you please tell me whats the KPI range you prefer for your cars. Is 0 kpi an acceptable value?

[Ben Beacock]

Do a search on "KPI" and "scrub radius" and there is a good discussion a while ago. KPI is generally not wanted in FSAE(positive camber on outside tire when turning), so zero is a great number. However, I'd hazard a guess that your scrub radius is really high to acheive that.
We're at 1deg of KPI and 8mm of scrub radius(static) with 1 deg of camber and KPI follows camber in our case.

[jack]

our kpi is the same as our static camber, so if we have 1 deg. of negative camber, we have 1 deg. kpi. this makes the uprights much easier to make. i suspect alot of other schools do this.

[MikeWaggoner at UW]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by jack:
our kpi is the same as our static camber, so if we have 1 deg. of negative camber, we have 1 deg. kpi. this makes the uprights much easier to make. i suspect alot of other schools do this. <HR></BLOCKQUOTE>

Huh? How do you change your camber? Are you adjusting it inboard? Are you using threaded rodends?

[Charlie]

Depends on your reference plane.

[Big D]

I have sent a question similar to this thread to the Mark Ortiz chassis newsletter, asking whether eliminating KPI, and/or scrub radius is a good idea in some applications. Bear in mind that all these things effect the nature of your car.... KPI gives a self-centering effect, but so does camber...but camber+scrub radius gives weight jacking when you turn, maybe you want that, maybe you don't... and if so, how much of it? It is quite the juggling act. I suggest you try juggling chainsaws, or swords first to get a feel for it. http://fsae.com/groupee_common/emoticons/icon_wink.gif

Pending Mark's answer, I do agree with Ben that 0 KPI is a good idea.