Having a blast working on my "old" 99 STS, but since I never drove or rode in one when new am not sure what is normal.

New, nice Michelin tires. Had a leaking rear shock and replaced both shocks and struts with the real thing and had avery good alignment. Shop owner told me he couldn't get it utterly perfect, but I can brake from 40mph down to a stop on a decent road with my hands off the wheel. ZERO error codes reported by my scan tool after 4 months. Before I had the shocks/struts replaced the "Service Suspension System" message would occasionally appear, but would go away after a couple drive cycles.

At times the ride is as smooth as the '71 Fleetwood my grandma hadeven on roads that look far from perfect. On new, smooth roads it seems to float. At other times on roads that look fairly decent, I can only describe the ride as annoyingly busy. On truly rough roads movements are VERY well controlled and appropriately stiff. Body roll is nearly absent even when cornering a high speed.

I've tried a couple times to get the rear end to step out by taking curves on slightly wet (after dry spells)asphalt roads at speeds higher than I EVER considered safe and the "Stability System Active" message has never appeared.

Are these observations valid for any of you who bought one of these cars new? Perhaps something to do with original review comments like, "Not an especially good ride." when comparing to high-end imports that this car was supposed to at least compete with?

 

I have a vette, Fiero, and a Olds Alero to compair to. Mine is also a 99 STS. First thing its a big heavy car so there will be some float, no where near what a car 10 year before it would have had. The biggest differences i notice is not ride but brakeing, after driving the other cars the caddy does feel heavy, like I'm always brakeing to late so i need to get on them more. On any roads with depressed wheel tracks (far to many around here, we have alot of large farm trucks) then mine is "busy" good discription. Rough roads do seem a bit odd to me also, like i have a split second of wheel float or something.. still its an incredibly smooth ride (but then again compairing to a vette, a 20 year Old fiero and a everyday car I'm guessing most any luxery car will feel smooth).

and I dont think i have been inside a car with less noise, its very quiet.

not sure I helped at all, but thouhgt I would put in my 2 cents.

Am susprised you read comments on ride, pretty much every review I have read (that was done when the car was new) compares favorbley to its competitors. I have rode in a few of its compteitors from those years and I would say they feel more "sporty" and that means rougher (BMW,Mercedes(buddy just bought a s class)).. the caddy is more of a Boat on water feel. Never cared much for a luxery car that was trying to handle like a sports car, they are alwasy in the middle of the road on everything, soft, but not soft enouhg, handles, but not good enough to make it truley sporty. Just remeber these are the same reviewers who rated a Mercury tracer/ford escort almost half as low as a Mazda 323 (they are the same car almost, just different sheetmetal). it only matters waht you think of the car. maybe i just have caddy love fest going atm as I love mine.

 

Yes, it did help. Thanks. Your observations seem similar to mine. I too have noticed that momentary thought that "it won't stop" and desire to mash the brakes. When you do actually mash them though it's very well controlled, fast braking and I've yet to feel the anti-lock activatesomething I've definitely noticed in my truck, my cargo van and a light Chevvy I drove for a while. That decent weight, good weight distributionand lots of rubber definitely seem. to help...

Also know exactly what you mean about a luxury car trying to be a performance car and how they normally disappoint on both counts. Of the cars I've owned or driven regularly (76 Grand Prix, 81 Z-28, 86 Thunderbird, 86 Daytona Turbo, 87 Eldorado, 95 Deville, 95 Cougar, 00 Taurus, 03 Regal) the 99 STS is by far my favorite. Not only is it the most comfortable and BY FAR the quietest, but I've yet to find its limits. The ride though is strange compared to others I've driven with active suspension systems (06 Chrysler 300 and 08 Toyota 4-Runner). Perhaps some understanding that the rear wheels are very likely to experience what the corresponding front wheels just experienced has been included...

 

Well the more I drive mine the more I wonder about the rear. At highway speeds on large bumps it feels like the rear wheels are hopping, very strange feeling, never been in another car that does it. Now I am worried I have something wrong. I have no codes and suprisingly the underside of my car is clean, no leaks (even the motor suprisingly). So i have no idea now.. No handling problems with corners, just something different on rough stuff.. Busy, like you said. To be honest its almost like the wheel hopps to the right.. strange. Car that big is hard to crawl under and bang stuff around to see if anything is wrong. Smooth roads or normal roads, its awsome..

 

See why I asked what was considered "normal" for a 99 Seville STS and hoped to hear from an original purchaser?

Have been studying the print service manual and on-line sources regarding active suspension systems and am still not sure if things are normal. As best I can tell, the car makes a gross differentiation between "rough" and "smooth" roads, but I cannot determine how rapidly it changes its mind. Since it also has a gross "aggressive" and "grandma" mode, I wouldn't be surprised if the two are inter-related.

In town, my roads are mainly rough and very hilly. At most times aggressive driving does nothing except waste gas and wear out transmissions... Rural road though are rather like those you see in commercials.

Lots of feedback for the road sensing suspension, so most problems [should] show up as DTCs. Do though check your rear shocks carefully for evidence of leakage.