I just don't get it--the way the camber changes during the suspension cycle. I mean I cannot think of any situation in which it doesn't seem wrong!

For instance, you go into a curve, the outside wheel's suspension compresses and forces the bottom of the tire IN TOWARDS the vehicle! It seems to be the complete opposite of what you would want to happen.

Can anyone come up with a situation where this system is beneficial?

This is probably true of any stock IFS. The a-arms move in an arc... starting from neutral, they are going to move the tire closer to the vehicle regardless of whether you're talking compression or droop. Or am I missing what you're asking <img src="/forums/images/graemlins/confused.gif" alt="" />

[edit] The only way the tire would move further away from the vehicle with compression is if the a-arms start out pointing towards the ground slightly (like when you crank the torsion bars). This doesn't provide as smooth of a ride, though; because of the way it changes the distribution of forces going to the spring and going into the frame.

Actually I think he is referring to the fact the the A-arms are not the same length, and therefore not only follow an arc, but also pivots or swings the tire about the center in the case the hub (camber). If the A-arms are the same length and/or appropriately spaced off center the camber will change very little while cycling up and down. They will as you said follow and arc and be pulled in slightly, but the bottom of the tire will not be pointing in toward the vehicle. This all is of-course negating the caster effects on turning the tire.

Yes this is probably true of most IFS systems that I have seen but I am no expert.

Well in that case, I'd imagine contact patch has a lot to do with that decision. By the upper a-arm being shorter, it pulls the top of the tire in more than the bottom of the tire comes in during droop. This allows the a-arms to travel down in their respective arcs while still allowing the tire to maintain a rather flat contact patch on the road instead of riding up on one edge or the other.

Yes if the arms are the same length the tire will stay vertical while cycling.

I think you are correct I am not sure this is what you want in a passenger vehicle. They might do it for contact patch reasons. Besides car manufactures main concern is drivability, safety and most importantly how expensive it is to put things together/manufacture.

The system seems to work well. My tires wear very evenly.
Pete

The only question i have ever had about the Isuzu IFS is why we have to have torsion bars when the Yotas get coils in the front. This seems like a much more stout system than what we have. Much more expensive, but much less to drag on the ground/adjust/screw up....

Just a thought...
-J <img src="/forums/images/graemlins/kewl.gif" alt="" />

from my point of view, torsion bars are much easier to adjust and to lift than coils. If we would have acoils in the IFS, most front works on the trucks would be more complex.

Early IFS Toyotas had torsion bars attached to the upper control arms. That makes Toyotas easier to do diff drop ifs lifts. I dunno if newer Toyotas have coils .... guess I haven't look at one lately.

Yup newer Yota's have coils, started in 95.5 with the Tacoma