Quote:
Originally Posted by xlr8or
David,
With the lower arms being so much longer than the uppers, won't that cause a lot of camber gain in bump and droop?
Also, is the oil filter as close to the chassis as it appears in the photo? |
Yes, the
oil filter is very close to the chassis, but you are looking at the bottom of an "I" beam so it looks closer than it actually is.
Actually, suspension geometry is an extremely complex problem. I will attempt to explain it without getting too technical. I am pretty good, but frankly, if you really want to get extremely technical, I will have to get Thomas to chime in--he is an extraordinarily gifted mechanical engineer...I just know how to make things.
You want your control arms to be as long as possible (think F1 or Indy car). The reason for that is--for a given wheel displacement (movement) the camber change is minimized. Camber change is when the top of the wheel moves in or out relative to the bottom of the wheel when looking at the wheel from the side of the car. In most cars, you want negative camber--ie, the top of the wheel moves IN as the suspension compresses UP. If you think about it, as the car leans into a turn and loads the outside tire, you want the top of the wheel to camber IN so the tire contact patch stays FLAT on the road. If there were no camber gain, then the wheel would tip up on its edge as the car leans and you would loose contact patch area and hence grip.
This is a gross simplification of the kinematics of suspension. There is a LOT more that goes into this. The angles of the control arms have a great effect on camber gain as well--especially the upper control arm as it is shorter. (This is what is known as the classic SLA or short arm long arm suspension that is always talked about in the car mags.) If the upper control arm is angled steeply up, then its relative length is "shorter" as it has already started to swing through the steep part of the circle.
As such, our upper control arm is only slightly angled UP (wheel end if HIGHER) than the frame end).
Now, caster, bump steer, Ackerman angle, static camber, roll centers, jacking, squat and dive, wheel rates, and a million other things come into play here. We literally spent hundreds an hundreds of hours messing with the suspension points to get all of this optimized. Of course, everything has its own set of trade offs as well, so what may work well on a smooth track (lots of static negative camber) may stink on the street--where we have to avoid pot holes, speed bumps, road gators, and boogey men who have wandered into the road.
I hope I haven't confused you and that I answered your question.
David
