king-pin inclination

[Backyard racer]

aside from setting scrub angles.. does the kpi actually do anything in regards to steering and handling.

what i mean is there a difference between say 5* or 10*??

hope i explaned this correctly.

luke

[philofab]

Too much and the tire flops from side to side and you end up on the edge of the tire when steering... no traction there. Thats why a lot of manufactures run large wheels with the the whole knuckle inside the wheel. Less KPI can result in better handling as long as you keep your scrub radius down.

[151fab]

When cornering, the inclination also angles the wheel/tire out. This might promote traction by aiming the contact patch to counter tire deformation. It also might counter the lessening of the contact patch area due to the dive inherent in off road suspensions but that is usually dealt with through your camber curve. In any case I think "tuning" your inclination would only be useful on a auto-cross type track. The strength benefits of moving your pivot points to as close to the centerline of the wheel and subsequently reducing your inclination as much as possible far out-way any other issues. ...my .02$

[philofab]

I failed to mention you need a little bit of KPI to keep the wheels straight when you let go of the wheel.....

[Backyard racer]

thanks for the quick answers.

kinda what i was thinking.

luke

[KitRacer]

What would be the maximum angle you would want to run? Say with a 35" tire

[philofab]

Wheel scrub is more important... go with whatever angle puts the scrub at zero. If you can, aim for 5 to 10 degrees of KPI with less (5) being better.

[D.Mavis]

So the more KPI you have the more the car ride height raises when the wheels are turned. I've heard that this is what gives the steering a self centering feel at very slow speeds, like in a parking lot. The weight of the car is essentially resisting the turning of the wheels from straight ahead. At some speed weight and traction the self centering effect of a given amount of trail (Caster plus mechanical and pneumatic) will swamp out the self centering effects of the KPI. That speed could be so slow that KPI self centering is irrelavent?

I think one of the previous posters got it wrong though, they were thinking of caster not KPI?. The more KPI you have the more positive camber gain (the wrong way) you get on the more hevily loaded outside tire, opposite for the inside. This makes your outside contact tire ride more on its outer edge which makes for a small contact patch. The more caster you have the more negative camber gain you get on your outside tire during a turn. This helps the shape of the contact patch.

As far as scrub radius goes, The more you have (positive) the more steering feedback you have, too much is not good, you could break your thumbs, at worst, or it could just be tireing to drive. But with major amounts of power steering and driving on dirt there probably isnt much feel anyways, so maybe it doesnt matter. I agree with whoever said that its probably important in an autocross car but not so much in the desert. Just look at ford I beam style front suspension, its sure works well offroad for how "wrong" it is on paper. Just my opinion!

[151fab]

I think one of the previous posters got it wrong though, they were thinking of caster not KPI?. The more KPI you have the more positive camber gain (the wrong way) you get on the more hevily loaded outside tire, opposite for the inside. This makes your outside contact tire ride more on its outer edge which makes for a small contact patch. The more caster you have the more negative camber gain you get on your outside tire during a turn. This helps the shape of the contact patch.



Your right, I was definitly wrong. Sorry for the mix-up.:o