I own a 2007 Mustang GT coupe and live in Metro Detroit with some of the worse road conditions that I have encountered.
I was not happy with the ride or handling of our car as delivered. My dealer suggested and installed the FRPP handling package. Great handling but to me the ride was harsh. I am far from an expert and do not compete in any type of sanctioned racing.

After reading the forums (should have done this first) and seeking the advice of many knowledgeable folks on this forum and others, I realized how little I really knew.

I changed from the FRPP dampers to D Specs and that made a noticeable improvement, Koni sports were not available at the time, but the ride was still not where I wanted it.
I bought a set of Koni's from Sam Strano soon after they were introduced, IMHO I noticed an immediate improvement in the ride quality, the car just seemed more composed and it seemed to handle large road imperfections better.
After talking to Sam and others and after trying a number of lowering springs I ended up back on the stock springs with koni's and frpp swaybars etc. I miss the lowered stance but the ride is closer to what I am looking for.
I have had experience with Koni sports in the past. 16 years and 289,000 miles on an Acura Integra and 15 years and still counting on a Mazda Miata. I know they are totally different cars then a Mustang but the koni dampers have been flawless.
I have been reluctant to post on the forums as I am not an expert by any stretch. I can
just post my amateur findings.
I would like to thank Sam Strano, F1fan, Argonaut, RodeoFlyer,Norm Peterson and a number of others for all of the time and advice.
Sam has been great to deal with, he takes a lot of time on the phone and did not try to sell me anything I did not need, as a matter of fact he talked me out of a few things that were not necessary for my needs.

 

I may take you up on that when I come down to pick up my parts. Of course I'm only running D Specs

 

So you're saying that with those cars and all those miles you only have one set of Konis on them? If so wow.

Well that does it. In a few months when I am ready to do suspension work, I'm slapping down 700ish towards Sam for some Konis.

Do Konis work well with the Eibach pro kit springs? I've been thinking about those since they're progressive springs. I was going to get Steeda Ultralites since they don't have a large drop and I don't want the car looking like a low rider - LOL! But from what I understand the progressive "feature" of the Eibach is a very good thing for keeping the car from banking as much in turns and reduce nose dive under heavy braking. I can get them for quite a bit less than the Steeda springs as well. Also the Eibach doesn't lower THAT much more than the Steeda and from the pics I've seen it looks good (the car's ride height that is).

 

"to-cheap-o"... that's pretty good. too-cheap-o would be even better so i'll use that.

(i once tried to argue the quality of the s197 once until someone whipped out the Fix Or Repair Daily... well now, how do you debate that high-level arguement?!)

your arguement, however, that dspecs sold because they were the only choice for so long is completely hollow and is completely revisionist.

along with the fact that they were the only adjustable it also had to do with the fact that people who had them were completely happy with them and couldn't stop singing their praises! that no one had anything bad to say about them! the reputation that dspecs, specifically, have on this forum and others was earned through performance, value, and quality as reported by owners.

 

a long time ago i recall another long tedious debate where no consensus was ever reached on that issue (progressive springs) as well...

 

Agreed. And frankly because there were no Koni's at the time I needed an adjustable damper to do some tuning, that's how I got to use them. I needed dampers. As I've stated before, more than once, I find the D-spec to be a marked improvement over the Illumina series (never made for S197's). But the quality is still an issue. And once I got my Koni's and could compare back to back I could also feel a difference in the way the car was damped. I then later had both dynoed so I could see if what I felt was also backed up on paper (and I wanted to see how various settings compared.

Far be if for me to say everyone on D-specs should dump them. Some have, and not one I've heard from regrets the swap. That doesn't mean that'll be the case with everyone. I think you could do worse, and as long as they don't break then you've got ok dampers. Think of it this way, D-specs are like an FRPP engine tune. Koni's are more akin to a custom tune done with more care and with a more advanced tuner and better program writer because it's more to the point. D-specs are meant to cover everyone and because of that and the price point they don't excel at anything. Koni's are more premium product. Built better, more R&D, better materials and design. Not everyone wants to pay for that.

 

Yes, the work very well with the Eibach's. In fact because I autox a Shelby GT I'm on Eibach's (they make the FRPP springs). I seem to do ok.

Let me say right here, and right now that I don't know of springs for this car that are NOT progressive technically. In fact the rears have to be. If they aren't they come loose @ full droop, but the rates are such you can't make the spring long enough if you don't have a take-up or tender rate.

And there's the trick. There are linear springs (which if you think about it are still progressive in so far that it takes more force to compress them every further). There are truly progressive springs where the rate rises with even increment of compression in a progressive manner (vs. the linear manner of linear springs). And finally there are what I term dual-stage springs. Two windings with a clear and delinated change over point. The soft end is very soft and does dead with static weight applied, leaving only the higher working rate in play. This is how the Eibach's are.

There are some springs that don't have the progressive look to them, but if the spring is tapered, like a little tornado they too are progressive. If you were to calculate spring rate with math, one factor is the spring diameter. If the diameter changes the rate is also changing. These springs can be harder to make, which is why most go the dual-stage route.

 

All that tells me is that early-on, enough people of varying enthusiast backgrounds found that you could get a better combination of ride and performance from them than with the OE dampers. For some folks and their specific driving environments, that may be enough. At least in some cars, even Illuminas (at a step down from D-specs) are still a big step up over the OE.


With respect to the spring subtopic . . . linear, progressive, and what I guess are technically "bi-linear" springs - each has applications where they are a better choice than the others. Hence there can be no universal "optimum" choice here. You may get a consensus for any given sort of driving, but I don't think you can expect any more than that.


Norm

 

Thank you for the explanation, Sam.

I didn't know any of that.

 

This might have been answered already but I have a question? I have a set of Roush Rear springs and an Adj. Panhard Bar for my 07 GT Vert. sitting in the garage waiting for warmer weather. My question is actually two fold;

ONE: If I replace the rear shocks with any of the ones being debated here, do I need to replace the front struts as well, or can I leave those stock with the springs?

TWO: My driving is easily called "cruising", I'm not a hard cornerer at all and the car is not a DD. Could I get by with an upgraded Non-adjustable shock and save a little money, like the Tokico HP line?

Thanks all