I have a 99 with the Selective Real Time Dampening option. According to the owners manual, as I read it, you can adjust it wherever you want but SRTD automatically adjusts based on road conditions, steering wheel angle and speed, regardless of where you have it set. I think it does because when ever I get above about 80 mph. It appears to stay in the performance mode. A very harsh stiff ride no matter where I set it. No change from one setting to another. At lower speeds it seams to adjust just fine. I am an old man I just like to listen to tunes and cruse along on the freeway at 80 mph. without feeling every bone-jarring joint in the concrete or crack in the asphalt. Does anyone know if I am reading this right and if this is the way it is supposed to work and if so is there any easy way to disengage this option. See excerpt from the owners manual below.

This switch is on the center console. Turn it to select the suspension characteristic of your choice.
TOUR: Use for normal city and highway driving. This setting provides a smooth, soft ride.
SPORT: Use where road conditions or personal preference demand more control. This setting provides more “feel,” or response to the road conditions.
PERF: Use for performance driving. This setting provides a tight, firm ride and precise response to road conditions.

You can select a setting at any time. Based on road conditions, steering wheel angle and your vehicle speed, the system automatically adjusts to provide the best ride and handling. Select a new setting whenever driving conditions change.

 

I have SRTD on my 97 vette as well. However, I find that there is a huge difference between the tour mode and the performance mode. Everything feels different. Everything from the steering to the ride quality. For me it doesnt matter how fast I am going it always seems to feel really different. The performance setting definetely increases the sharpness of every bump and crack but touring tones these way down. I have Michelin Pilot A/S ZP on mine and that made a huge difference. There is also the fact that the noise out of the rear compartment is pretty common on all corvettes. I think GM made some changes to the SRTD system between 97 and 98 (recalibrated the system) so it may be different from your 99. I will say that everyone i talk to says they cant feel a difference between the different settings (at least for F45). As far as turning the system off. It is possible, and there was a post floating around here a while go that showed exactly how to do it with a TechII. However, they were turning off the F45 option because they put on Bilstein, Z06, or some other performance shock (these shocks typically are stiffer so its the opposite of what you would want. Although you could put regular corvette shocks on instead.)

 

My car came with F45, but I replaced the shocks with Bilstein sports (which made it ride rougher, but handle better).

I think different tires will help the ride more than anything else.

I've had Michelin runflats, Toyo Proxes on Z06 wheels, goodyear non-runflats (275 front, 315 back) on Grand Sport wheels, and now have Kumho non-runflats in stock sizes on stock wheels. All of them were an improvement in ride quality compared to the stock Goodyear runflats I originally had.

Everyone says the goodyear runflats get harder when they wear in terms of traction, but either the sidewalls get stiffer too, or they are just stiffer to start with. Goodyear has the longest drive-when-flat rating of any runflat, so maybe the sidewalls are stiffer. I'd say next time you buy tires try different runflats, or non-runflats.