what are the major ride differences between these two !?
Im considering either the STS or the prokit springs to put on my koni DA shocks .. i like the spring rates on both sets, i prefer the STS drop .. but im wondering how the progressive Vs linear spring rates affect ride quality and handeling

thanx

 

I'm wondering the same thing. I have ST progressive springs right now, they are 5yrs old and I want to switch. I am not into comfort at this point and a progressive spring seems to have a loose feel. I am getting Koni SA on the front with Eibach Pro Kit springs, but is it true that the 93-97 springs are progressive 300-600lbs, but when you go to the 98-02 springs that they are linear 600lbs?

My thoughts are that linear wouldn't have that loose feel like the progressive when the spring is working in the 300-600lb range. The linear has no range other than a constant 600lbs. Am I completely off on this?

So for track use it would seem a better feel for what you are doing at high speeds would lead you towards a linear spring. You do need one stiff shock to handle this though.

Thoughts anyone?

 

i think i know less than you do about coil springs but i recently switched from the stock linear springs on my 97 to progressive slp/eibach off a 2000 SS. It feels like the car has much more body roll while cornering now. Maybe i should have put highperformance shocks on it too? it does still seem to stick to the road but it doesn't feel as good as linear in my opion (from a racing aspect). From a daily driver aspect it's a bit smoother and makes for a better ride quality. I'm thinking about updating the sway bars to see if it will decrease the body roll and still keep the nice ride.

 

If you left the stock shocks on there, you are doing a big injustice to the springs. The stock shocks are the weakest link in the f-body suspension. I would change shocks before doing anything else if you are looking for better handling. Of course, as difficult as the fronts are to change, you might as well do springs and shocks at the same time and get it over with. I think you'll find that progressive springs will handle really well when matched to a good shock. As a comparison, my Firehawk rode as good or better than either of my other f-bodies (which had stock springs/shocks), and definitely outhandled them both. This was with the SLP Level II suspension (now sold as Level I from SLP). However, since I'm not the type to be satisified with "good enough", I just put Konis on the front and it made a very noticeable difference. While the ride is just slightly harsher than the SLP suspension, the Konis make a noticeable difference in handling. Body roll is much reduced and the car has a much more "controlled" feel when it hits a bump. Also, it has noticeably reduced front end lift during acceleration and dive under braking. I personally like the SLP springs as they don't lower the car into the weeds (only about .5-.75" from stock vs. 1.5" with regular Eibachs), and the spring rates seem to be a very good compromise to me. They start at the stock rate and go significantly higher:
front springs: Eibach 300-450 lb/in
rear springs: Eibach 115-185 lb/in

Anyway, back to the original question. If all you are doing is running on a smooth roadcourse, then sure a linear rate spring would be great. However, how many people use their car solely for roadcourse use, and only on smooth roadcourses? I would venture to guess that on many bumpy/rough roadcourses a progressive rate spring might actually outperform a linear rate spring as it will absorb the bumps better.

 

yeah, i ended up putting new DeCarbons on when i changed springs since i didn't have the money. now i'm wanting to update shocks/struts too. i'm not sure what the spring rates are on my SLP springs, probably the same as yours i guess. do you recommend the Koni's over the Bilsteins?
Sideways_into_3rd, not trying to steal your thread, just trying to learn.

 

Yes, I would definitely recommend the Konis. The most popular setup among all the road racers and autoxers is the Konis SAs up front and Bilstein HD or Bilstein 3rd gen shocks in the rear. I ended up getting the Koni DAs, but that was a screw up on SLPs part (got them for less than SAs) and was originally just planning on SAs. I can tell you right now that the only time you would possibly use the DAs capabilities would be on a roadcourse. For me that's great, as I usually attend 8-10 roadcourse events a year. Here's my picks for shocks from best to worst:

Koni DA front & rear: very expensive, but absolute best

Koni DA front, Koni SA rear: again very expensive, but a better value. I don't know of anyone that runs DAs on the rear and actually uses the second adjustment

Koni SA front & rear: still a little expensive, but a good value for adjustable front and rear.

Koni SA front & Bilstein 3rd gen rears or Bilstein 4th gen HD: probably the most popular setup for serious drivers. Most autoxers like this setup because the Bilsteins on the rear are very similar to the base setting on the Koni SA in the rear (what most people end up running). The difference between the 3rd gen and 4th gen HDs is that the 3rd gen valving is supposed to be a little stiffer. So, for more street use, the consensus seems to be go Bilstein 4th gen HDs

Bilstein HDs front and rear: good value and great performance.

SLP Bilsteins: much better than stock handling, and ride that equals or beats stock. Only use these if using the SLP springs.

Stock Decarbons: Poor. I would use these only on a street or street/dragstrip car. I would definitely not recommned them for autox or roadcourse use.

HAL/QA1: good for there intended purpose, which is street/dragstrip use. I would NOT recommend these for even aggressive street handling.

Edelbrock IAS: worse than stock. expensive and they are reported to fail often. Also don't seem to improve handling any over stock.


One other option you could go for, is to try the Koni SAs in front and the SLP Bilsteins in the rear. I'm going to try keeping my Bilsteins in the rear for a while. If I don't like how it handles with that setup, then I'll probably switch over to Bilstein HDs in the rear (unless I find another good deal on Konis )

 

if you're gonna spend the money on Koni DA, you might as well get the Ground Control adj coil over kit w/ linear springs. 500 lbs seems to be popular.

i got the eibach pro-kit w/ koni SA. like the look, but not the feel

 

Linear springs used properly do not ride any harder than progressive springs. Often they ride better, sometimes worse. It's all about the rate of the spring chosen and in the case of progressives when the rate get stiffer.

Progressive springs are nice on paper, but in real life have some shortfalls. First not all progressive springs are truly nice and progressive. For example, an LT1 Pro-kit is 377-600, but the softer end of the spring is gone the mintue you put the car on the ground. They are, in practical terms, never 377 lb/in springs. Next, how do you know where the spring rate changes? Is it @ 1" of compression or 3? How much does it change in say 3" of travel? These are things that you kind of need to know if you are serious about a suspension. And lets' not forget shocks are spring dampers. They are meant to damp energy stored in a compressed spring. Stands to reason a spring that is greatly varying rate is kind of hard to damp properly. You might get the softer end right, but then you are underdamped at the stiff end. You might get it right at the stiffer end, and be wholly overdamped at the softer end, etc.

 

sounds very complicated... i think i will keep my slp/eibach springs and buy either 4 bilstein HD's or the Koni SA/Bistein setup along with either some Y2K vette wheels and probably the Firestone tires.