Quote:
Originally Posted by LibertyHill
I've been on the fence with these because it seems to me the arms really only locate the wheel and define the geometry of suspension movement. All wheel hop should originate from rotational movement of the diff case transferred by the axle due to soft diff mounting in that axis of rotation.
Something like an old-school long-arm "pinion snubber" seems like the most efficient solution but I haven't snooped around the area to see if this is doable, or even to see what the diff mounting looks like. The size and the mass of the subframe/bushings shouldn't be a component because the hop frequency would be too high.
Any thoughts on this theory?
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I don't know how I missed this but I did... This information is not overly accurate.
Soft cradle and differential bushings are huge contributors to wheelhop. Yes the frequency of wheelhop is much high because the slip and grip of the tires is happening much quicker that the oscillation of the cradle/diff bushings, but that oscillation is in many cases the initial cause of wheelhop. Beyond that, once wheelhop starts, the cradle and diff are moving around so much that the tires can't physically get traction for long enough to drive out of it. When you limit or eliminate that cradle or differential oscillation from soft bushings, there is less movement to initiate wheelhop, and less oscillation to prolong it. You also have less movement in the links because the entire assembly is moving less. And you get less dynamic rear wheel alignment change, which gives you a more consistent tire contact patch. All of this leads to more traction.
The downside is, when you add harder cradle and differential bushings, performance goes up but so does NVH. This means more noise in the driver's compartment.
Trailing arms help in a different way. The factory links are made from very thin stamped steel with soft bushings. These links are so flimsy the you can pretty much twist them by hand. Imagine how they move with the amount of torque these cars make... By adding rigidity to the links and firmer bushing, you reduce the link and bushing deflection. This reduces rear spindle rotation as power is applied to the chassis. When the spindle rotates (similar to wheelhop in its speed and frequency) there is spring back due to the rubber bushings. This can cause the tire to load and unload, causing wheelhop. The more solidly you can mount the links, the less spindle rotation and wheelhop there will be.