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I Think You Can Lower IRS More Cause The Tyres Can Tuck Up In The Guards With Live Axel Cause Your Diff Can Drop Lower Than Your Hubs But Then You Get Bad Camber Wear
i think you've missed some words, cause that doesnt make sense. it almost does,but not quite.
IRS can be lowered until the tyre touches the inner wheel tub, or until the spring cant be made any shorter. lowering a car with IRS will cause more camber wear than normal. this can be rectified to a degree with various camber correction kits.
Live axle can only be lowered until either the tyres touch the inner tub, or the diff touches the floor. you will not get any camber wear on a live axle car.