Quote:
Originally Posted by Angel67
I would also note that so far I quite like my setup which uses 3 Group N bushings - one each in the toe and trailing arms, plus one on the inboard side of the lower camber arm (the rest being balljoints except for the normal bushings on the outboard side of the M3 upper arms). Since the Group N bushings are very stiff, they provide not only additional spring on compression but also additional rebound, below normal or static height. Above static height, they work against the metal spring, pulling the suspension back to static height. I have a 521 lb spring and say about 180 lb equivalent spring rate from all the bushings. So on compression, below static height, together they add up to about 700 lb, but above static height the effective spring becomes around 340 lb. This helps the sway bar do its job and the car levels very quickly...
So there is a reason besides rules to use Group N...
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Stay tuned
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The other point to keep in mind is that the very stiff Group N bushings seem to provide anti-pitching benefits. Since they work against the spring above static height, they tend to pull down the rear end on braking, which fights against pitching. Sway bars do nothing in this context and stiffer metal springs only make it worse - they contribute to pitching. My current setup gets about 35% of its effective spring from Group N (and other) bushings, so that adds about 50% to the effective spring on compression below static height, and removes about 50% above static height. At the equivalent of 180lb per corner, it's like throwing 360lb in the trunk as soon as the rear end lifts by one inch on braking. It's a very nice effect. 35% feels very good. Would be interesting to test higher percentages. I would think one could get at or above 65% with a fuller set of Group N (I have 3 per corner, and can easily go to 6 per corner, and possibly 9 per corner - the parts are available so it's just a question of finding the right balance between metal spring and bushings).
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Stay tuned!