Miks15
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| posted on 30/10/08 at 06:18 PM |
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KPI
Ok so im about to start fabricating my front uprights, i am modelling them on the sierra upright with slight modifcation. This modification having to
be made due to the mouting points of this fabricated part.
So my question is what effect will increasing the KPI have on the steering characteristics of the car?
The top balljoint hole will be moved about 10mm further out in relation to the lower balljoint hole than on the sierra.
Thanks
Mikkel
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m8kwr
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| posted on 30/10/08 at 07:24 PM |
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i thought the kpi was there, so there was no need for excess camber....
But someone may correct me.
usually the kpi is in between 7-9 degrees.
Obviously you know how to measure the kpi, but the scrub radius is import too, it is the distance from the kpi line to the ground to the center line
of the the tire. It is best to have a minimal scrub radius, but this would invovlve putting the upright further into the alloy - then you need to
think about wishbone movement etc.
I just been reading about it...
[Edited on 30/10/08 by m8kwr]
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nitram38
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| posted on 30/10/08 at 08:43 PM |
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If there is a fixed kpi, the way to get around making the scrub angles right, is to change your wheel offset so that the kpi line runs through the
desired point on the tyre.
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m8kwr
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| posted on 30/10/08 at 10:00 PM |
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what if you can not get the kpi to go directly through the center line of your wheel.
Is it best to just try to get it as close as possible?
Trying different outset of alloys, and different size of tires etc.
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nitram38
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| posted on 31/10/08 at 03:45 AM |
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You can have positive or negative kpi but I can't tell you which is which. What I can tell you is that if it is not close to the turning centre
of your tyre tread, you will literally be dragging the wheel (scrub) on one side of the car if you make tight turns (usually on the outside of the
turn).
Some kpi scrub is useful as it helps with grip, but it must be just a little.
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Syd Bridge
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| posted on 31/10/08 at 10:00 AM |
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KPI on a Sierra upright is 13+ degrees. You don't want any more than that.
Scrub is an evil, and is not desirable, but tolerated in small amounts.
Negative KPI????? I'd like to see the car with that. Never been done, to my knowledge.
Cheers,
Syd.
[Edited on 31/10/08 by Syd Bridge]
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m8kwr
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| posted on 31/10/08 at 10:28 AM |
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i found this link off the locost USA forum
LINK
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Miks15
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| posted on 31/10/08 at 11:53 AM |
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Well my upright will be about 16-17 degree KPI. How bad will this be?
The only way to reduce the KPI would be to offset the top balljoint hole, but this then would mean that the two balljoint would not go through the
center of the upright if lookinf face on, i believe this is also bad?
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MikeRJ
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| posted on 31/10/08 at 11:55 AM |
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Out of interest does anyone know what the scrub radius of the standard Cortina upright with original Cortina wheels/tyres is?
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Mark Allanson
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| posted on 1/11/08 at 11:10 AM |
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Massive
 
Rescued attachment Uprt-Cortina-ScrubRadius.jpg
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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