Over the weekend my dad mentioned the change of king pin inclination on cars with beam axles that has been lowered in front extensively. It seems the lower you go with the front of a car the farther forward the king pins tilt. I am having a hard time imagining this and the effect it would or could have on the driveability of a car. Early slingshot rails had front axles that tilted rearward, probably to make the car try to track straight, but never thought much about the effects if the axle tilted forward. I know on motorcycles the neck angle plays huge in how a bike steers. Big angles with long front ends track straight easily, where lesser angled necks turn easier. Would this cause a car to fight straight forward tracking? If so, how would you correct this?
after looking at my sedan in a full side shot...it seems to me that the lower you go the king pins would actually tilt rearward not forward, or am I completely off base on this.
Forward and back in this context is caster angle, not KPI. The further the kingpin [or the imaginary line thru the center of the upper and lower ball joint etc] moves to the rear at the top, the greater the positive caster and the harder it is to steer left or right and the more stable the vehicle usually is. KPI uses the same reference points as above but to "see it" you stand at the front or rear of the vehicle instead of observing from the side.
You are going off of degrees of the ground, but yes, the lower a front end goes, the more the more the degree tilts the tops back in relation to the FRAME.
You are mixing up king pin inclination with caster, I believe. Caster is the amount of angle the king pin or upper a arm angles back in relation to vertical. King pin inclination is a line projected through the king pin from inboard to out board with the angle of line meeting the vertical center line of the tire (ideally) and true vertical met to format the pivot point of the tire. The three angles are referred to as the included angle. If any of the angles are off, scrub radius is produced. Lowering a car at the front causes it to lose caster which can be restored by bending the axle ends back at the top or adjusting the radius rod length top or bottom if dual rods or adjustable ends are used to restore the correct caster angle. By lowering the rear of the car the correct amount, it will also cause the caster angle to set back where you want it. That is a somewhat simplified 2 minute explanation of some of the geometry involved in front end alignment. Several books can explain it better and show drawings for examples. Find a good front end mechanic and discuss it with him too.
I see...thats how I imagined it...the reason I asked is my dads friend mentioned that lowering his cars from time to time set up a high speed shimmy or wobble that corrected itself if the car was raised back to stock height and I was just trying to see this in my head as to what would be going on there. My sedan is about as low as you can get in front but it handles fine at all speeds though the steering is a bit stiff at low speeds which I chalked up to poly tires and a stock A steering box. just curious
Since lowering mine it tracks really good , so good the ****ed steering box doesn't bother me any more, it is a bit stiff to steer though but it's good alround. But sorry, got no idea about the x/ z - pie x dia of the flux capacitor theory behind it. lol
this is why when you set up your front end, you get the ride height as close to where you want it before you set your caster.
LOL Yeah exactly like mine. I can never remember which is Caster, which is Camber. I just ***umed king pin inclination was the tilt forward or back, but I see its actually how it tilts side to side. I guess as long as my car runs straight down the road I should be happy.
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