F1Fan

Hi Mustang3GT07,

You will likely tear off or scrape that fancy new Roush bumper cover the first time you drive out ofa driveway with the Sport Lines installed. BIG MISTAKE!

Regarding long tubes, how well they are tuckedupvaries with the source of the long tubes and the merge collector and exhaust coupling. Old stylelong tube headers use the 3 or 4 boltflange couplings and these scrape the ground. Newer style as seen on JBA and a few others are smooth clamped slip fits allowing the headers to actually be tucked upABOVE the frame rails giving you maximum ground clearance and no hanging exhaust parts.With the JBA long tubes when used with their catted H-Pipe the whole thing is up inside the frame rails with nothing hanging below the rails, not even the cats.

HTH!

Mustang3GT07

Wow thats for all the info. I will be going with the pro kit then. But i was also really interested in steedas comp springs or there sport springs. How are they and whats the difference between the both?

F1Fan

Hi Mustang3GT07,

The Eibach Pro Kit springs areexcellent springs and wereand remain my number one choice for a good all around high-performance sport spring kt. They have as high a springrate as I would recommend for use on the street so they still ride welland they let the car sit at the perfect ride height.The problem for my use is that I haveto drive through manyunderground highrise building driveways in downtown Los Angelsandthe car is too low fora couple ofthem when I have people in the car. These areregular clients so I neededmoreride height to avoid this problem.

The Steeda Sport and Competition springs are also both excellent springs with a taller ride height and solved my occassional driveway scraping. Theregular Steeda Sport springs are softer than the Competition springs and this lets them ridenoticably better than the Competition springs. Not surprisingly, the Steeda Competition springs ride slightlybetter then the Eibach Pro-Kit springs with less pitching motion on certain freeway sections that happen to havethe wrong length between expantion joints even though they havesimilar working spring rates in front. The difference inride and pitching may bedue to the linear spring design of the Steeda springs vs.progressive design used by Eibach and the lower rear spring rate Steeda uses on their Competition springs.

I used todevelop high-performance and roadracing suspension components for German production cars and still have access to spring and damper test and measurment equipment and a couple of years ago I started measuring some of themost popular sport springs on the market at the time. Of the streetable performance springs on the market Steeda Competition and Eibach Pro-Kit springs are the stiffest springs and are about the same rate within the normal working range of compression. All of the other Sport springs I measured hadsignificantly lower spring rates than these two obviously performance oriented spring sets. Steeda's regular Sport springs and H&R Sport springs both measured about the same 20% higher spring rate overstock front springs and 20% higher raterear spring ratein the normal workingrange at normal rideheights. Both theEibach Pro-Kit and Steeda Competition springs are about 35%-40% stiffer thanstockin front and about 38% and 28% stifferrespectfuly, at the rearthan the stock springs. These comparisons are all based onthe productionsprings I pulled out of myS197GT coupe. The S197GT convertable springs are slightly softerdue to the slightly more flexible chassis they have towork on.

I like the idea behinda progressive springdesign but in all the years of evaluation, testing and designing suspension components I have had an easier time of making straight rate springs work than progressive rate springs. I think there is just too much variance in vehicle weight and unsprung weight to make a progressive rate spring work well out in the wilddue to the need forhigher precision when designingprogressive springs. A linear spring has no such problems, you can load them up or lighten the load in the car and the spring rate is very predictable nomatter theload, unsprung mass or ride height which makesfinding a reasonable damping rate a little bit easier and less fiddly.

I'm liking the Comps from a performancestandpointbut the car is not nearly as low or aggressive looking as on the Pro-Kit springs. Where the Pro-Kit springs had the car looking sleek and ready to pounce theSteeda Comps have the car looking bulkier and athletic. I may go back to the Pro-Kit springs somedaywhen I loose or dump the downtown clients but at the moment or another year at least until the contracts run out the Compswill need to stay in the car.

HTH!

Aziraphale

Anyone know where the BMR springs stand?

Oh, and 07SCGT, how can it be a trailer queen when it can't get on the trailer

F1Fan

Hi Aziraphale,

Why not call and ask them what their workingspring rates are font and rear? All they can do is say no.

HTH!