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So apologies for a long post but maybe others will find this helpful.
I was always interested in the daily ride and handling effect of a true rear coilover suspension on an s197 sra versus the oem style setup. But it's hard to find much in the way of true apples to apples comparisons. Before and after reports are usually in the context of wholesale changes to dampers, spring rates, wheels, etc.
Note I'm only focusing on rear spring location and its effect on daily driving ride and handling. Car is a daily driver '11 GT that sees 5-10 track events a year. But I'm only talking about the street side of things here.
So I swapped out rear FRPP P springs (~200 lbs, progressive?) with Bilstein monotube sport shocks and the stock 24 mm bar, and installed lightly used Cortex Koni street coilovers with 200 lb linear rear springs and Koni 30 rebound adjustable monotube dampers (4 settings). I took rear bar off completely. I set the Konis to 50 percent damping. (Settings are 0 (softest), 20 percent, 50, and 100.) I have an adjustable PHB and stock LCA and UCA. Ride height is similar between old P springs and new coilovers. (Cortex is very slightly lower.)
So similar spring rates, similar quality monotube dampers (Bilsteins reputationally maybe a little better?), move the springs outboard, and get rid of the rear bar. One variable is that I don't know how the damping rate of these Koni 30s set at 50 percent compares to my old Bilstein sports.
Result is holy cow, the rear axle is way, way better controlled on rough roads in daily driving. My old setup was a lot better than stock but I still was getting extra up and down movements on a lot of bumps, particularly in corners with lots of broken or uneven pavement coming at the wheel fast. All of which created an annoying skittishness in any corners that weren't nice and smooth. The new setup just eats this up by comparison. It is a nice, smooth, taut but not harsh ride, with a noticeable single up and down movement for each bump. The rear tracks way, way better and doesn't step out nearly so much. In fact it doesn't really step out at all as far as I have see thus far, in really quick but sane public road speeds. The improvement is way more than I expected.
Compared to the improvement from stock springs and dampers to the P spring/Bilsteins, this feels like about the same level of improvement again. The rear end is noticeably more stable, more comfortable, and faster around rough pavement corners.
I'm no engineer but I suspect most of the improvement is due to moving the spring outboard, with the corresponding decrease in unsprung weight. It just feels like a lot less weight flopping around back there, and I think if you do the math it kind of is.
I respect that "ride and handling" is subjective stuff but this is not confirmation bias or a placebo. The improvement is significant and real.
I hope this might be helpful to anyone considering a similar swap.
By the way I have to give a shoutout to PLexo50 on here, great seller and thank you!
I was always interested in the daily ride and handling effect of a true rear coilover suspension on an s197 sra versus the oem style setup. But it's hard to find much in the way of true apples to apples comparisons. Before and after reports are usually in the context of wholesale changes to dampers, spring rates, wheels, etc.
Note I'm only focusing on rear spring location and its effect on daily driving ride and handling. Car is a daily driver '11 GT that sees 5-10 track events a year. But I'm only talking about the street side of things here.
So I swapped out rear FRPP P springs (~200 lbs, progressive?) with Bilstein monotube sport shocks and the stock 24 mm bar, and installed lightly used Cortex Koni street coilovers with 200 lb linear rear springs and Koni 30 rebound adjustable monotube dampers (4 settings). I took rear bar off completely. I set the Konis to 50 percent damping. (Settings are 0 (softest), 20 percent, 50, and 100.) I have an adjustable PHB and stock LCA and UCA. Ride height is similar between old P springs and new coilovers. (Cortex is very slightly lower.)
So similar spring rates, similar quality monotube dampers (Bilsteins reputationally maybe a little better?), move the springs outboard, and get rid of the rear bar. One variable is that I don't know how the damping rate of these Koni 30s set at 50 percent compares to my old Bilstein sports.
Result is holy cow, the rear axle is way, way better controlled on rough roads in daily driving. My old setup was a lot better than stock but I still was getting extra up and down movements on a lot of bumps, particularly in corners with lots of broken or uneven pavement coming at the wheel fast. All of which created an annoying skittishness in any corners that weren't nice and smooth. The new setup just eats this up by comparison. It is a nice, smooth, taut but not harsh ride, with a noticeable single up and down movement for each bump. The rear tracks way, way better and doesn't step out nearly so much. In fact it doesn't really step out at all as far as I have see thus far, in really quick but sane public road speeds. The improvement is way more than I expected.
Compared to the improvement from stock springs and dampers to the P spring/Bilsteins, this feels like about the same level of improvement again. The rear end is noticeably more stable, more comfortable, and faster around rough pavement corners.
I'm no engineer but I suspect most of the improvement is due to moving the spring outboard, with the corresponding decrease in unsprung weight. It just feels like a lot less weight flopping around back there, and I think if you do the math it kind of is.
I respect that "ride and handling" is subjective stuff but this is not confirmation bias or a placebo. The improvement is significant and real.
I hope this might be helpful to anyone considering a similar swap.
By the way I have to give a shoutout to PLexo50 on here, great seller and thank you!