Side mount camera view. Burnout, etc.

[NashMan]

Brad, it is normal for the rear wheels to toe in when the suspension compresses.. It is a geometry design aspect call Roll Underster. Just like just stated, engineers design rear suspenesion cause the rear wheels to toe in when in compression and toe out when in rebound. The opposite happens in the front typically. The reason for this is that its is understood in automotive safty that understeer is safter (more controlable) then oversteer by most drivers. The impliment this to force the car to never turn ever so slightly less then the drivers asks it to. This makes it far less likely to have to read step out on you.

I doubt that what your seeing has anything to do with worn bushings. A worn bushing would cause excessing deflection while cornering and in you video, I can see the toe change is about the same while going in a straight line as when cornering when the suspension compresses.

Deflection understeer and oversteer is not commenly seen in rear suspension setups cause of the use of twin lower arms instead of a single A are like the front. In front setups, this is a common thing cause of the single lower A arm. Deflection Understeer in the front is set up by putting the steering gear ahead of the axle centerline. If it was installed behind the axle centerline, when the bushing compress due to side loads induced from cornering force, it causes the front wheels to toe into the corner thus causing the wheels to be turned into the corner. By having the steering gear ahead of the axle centerline, when the bushing compress from the side loading, this will cause the front wheels to toe away from the corner thus being concidered as understeer.

The reason the read doesn't do this while cornering is because the toe control is not rigid like it is in the front. Now if you were to put a rigid pivot like a heim joint in only one lower arm in the rear and not the other, then you would see deflection under or over steer depending on which rear lower arm you installed the heim joint in.

One thing to note with rear deflection steer (or deflection toe chance) is that it is oposite of the front with the rigid joint location relitive to axle centerline. Basically, in the front, a rigid toe control member ahead of axle centerline causes deflection understeer, behind axle centerline causes deflection oversteer where as in the rear, a rigid toe control member ahead of axle centerline causes deflection oversteer, behind the axle centerline causes deflection understeer.

thus why the lower arm has a moveble bushings but when they were out it get's pretty sloppy back there

cause if that bushing was soil the knukle whould never move and work the way it's suppost to


cj great right up

 

[tekdeus]

Thanks for the detailed info CJ! After looking at the video carefully again, I do see that the toe in is the most when the rear suspension is at the highest. However, I imagine that new/poly bushings would help a lot, since it does still seem to have more play than it should.

If both wheels toe in under compression, then wouldn't that really screw up launching and acceleration of a car with lots more power? My suspension looks to compress at least 2" under load, and I assume that having both wheels toe in would be more likely to lose traction. What do the Mk4 drag racer's do? Do they set up the rear to toe out with positive camber so that under heavy squat it squares out? How could you maximize the flat straight contact patch on a street car? Stiffer rear springs?