I don't think there are any disadvatages to them. I think it was just economics. Eibach and Intrax are bigger operations and could probably produce springs cheaper. Add to that, most people prefer a mild drop to a near 2" drop and Eibach and Intrax appealed to a wider market and out sold the SS springs. I had them on my car for 2 years and loved them. I recently sold them on ebay since I've switched to coil-overs.
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ThrillSHO Racing
93 ATX SHO
UDPs, LPM, 80mm MAF, K&N w/CAI Snorkle, 8mm Taylor wires, Koni Struts, IPT Coil-overs, Camber plates, Adjustable rear control arms, Touque box brace, Poly bushings, 24mm front SB, 26mm rear SB, Shaved Alum SFB, Full-length SFCs, Front & Rear STBs, SS Y-pipe, Borla Cat-back, TransGo Shift Kit, Relocated battery, Five point harness, Five 2" gauges below the CD player, 225/50s on 16x7s, TCE/Wilwood Brakes
Very Low Very Fast