azrampage

OK, I have now ordered and received a set of the Vogtland springs (40mm drop) from Stranos. I got the GT set for my V-6 Pony Package for best performance. I'm looking to improve the handling as I venture into local STX classes, so I wanted the best non-coil over springs that would accomplish that purpose.

These will be added to my collection of Konis, camber bolts (-2.5' camber), GT rear sway bar (20mm), Steeda 35mm front bar, and Brenspeed tune. Also have a Mac muffler and green intake filter ......so far. I'm doing just one or two things at a time.

I guess I did not realize when ordering, but these are PROGRESSIVE springs. Upon rechecking, I see that while the picture shows linear, the description mentions progressive characteristics.

Here's the question: Will these in fact do what I need them to do? How do Progressive Springs perform/compete in an autocross settings as compared to linear springs? Will they work well with the Konis?

While I know that the V-6 Mustang is far from the favored STX setup and choice, I have a history of doing better than expected against superior cars. I'd like to continue that habit.

So..... what's the scoop. Will these do as well as the linear models?

Thanks.........

Norm Peterson

Not all "progressive" springs have a rate that varies much over the range of heights that it will see once it is installed. Some springs are wound with two distinctly different coil spacings, and have essentially only two rates. A soft rate that is taken up mostly or entirely just by the car weight (those coils close up solid), and the firmer one (with only the wider-spaced coils still active) that the car normally operates in. It's one way to get some lowering and a firm operating rate without having the spring end up being so short it rattles around loose or comes unseated under some driving or maintenance conditions. You'll have to ask Sam if this is the case with your Vogtland part numbers (I know it is with another brand spring I have for a different car).


Edit - these yours?

Norm

azrampage

Yep.....these are the exact part numbers. Is that a good thing?

That, and thank you for taking the time to look into this. I went out today and took comparative measurements
before installation. Looks like I won't need to use the spring compressor to install the fronts...... :-)

Norm Peterson

Generally, yes. What it means is that the vast majority of your driving uses only the higher rate, so it mostly drives like a higher-rate linear spring. Under conditions of extreme droop, the soft rate portion of the spring "uncompresses" and keeps the spring from coming unseated in the perch - or falling out entirely if not held captive by a shock or strut and the suspension can droop far enough. Handling might get a little more nonlinear once a spring gets into its soft range and the inside corner of the car will roll 'up' a little further than it would if it had a single rate spring, but those effects can't be any worse than what would happen with a spring that became completely unloaded.


Norm

Sam Strano

There is not a rear spring for this car, or actually for any solid axle pony-car I can think of off-hand that is not technically progressive. And that's simply for this reason: If they weren't they'd fall out when the axle drooped.

There are different ways to make progressive springs. Some vary the size of the winding, some vary the distance between coils. Some are progressive top to bottom, some are dual-stage (the Vogtlands and most others are like this).

Norm hit the nail on the head. These are not actively progressive, they are actively linear. You'll notice the one end's coils are almost touching off the car. The weight of the car collapses those and they become dead--out of play. And you are left with a linear working rate spring.

azrampage

This is indeed good news, and what I needed to know. I will probably install this weekend, and am anxious to feel what difference they make.

I wanted the best springs short of coil overs, and I'm hoping these are it. I also philosophically agree with Sam about "stiffer isn't always better", especially on lots (for autox) that are not always smooth.

Stay tuned for a "progress report", and thank you Norm and Sam for educating me on newer spring designs.

myskunk

wrong thread

azrampage

Any advice on how to approach tire pressure with the new springs? Start at what I had before (F:38#, R:36#) and adjust from there?

Or is there a general rule that stiffer springs require either a little more or less pressure?

Also, the car is about one inch lower than on stock Pony/GT springs.

Thanks......

SlideWRX

I'd start with equal pressure front/rear. You're talking auto-x, correct? Or heated track day pressures? I'd target 38 all around and adjust from there.

Norm Peterson

I'd start with what you're already used to. Otherwise you're probably adding at least one "iteration" to the process that may not be helpful to you individually. I think there is general agreement that there should be slightly lower rear tire pressure anyway. Lower rear tire pressure (to a point) tends to dial a little of the understeer out and probably helps rear mechanical grip (which lets you use a little more throttle a little sooner and isn't quite as sensitive to bumpy corners).

I think Sam runs about 4 psi more in the front than in the back in the F-Stock Shelby, which is sprung a little stiffer than the "normal" GT, although I don't remember what his exact numbers are. A search might turn them up.


Theoretically, I would guess that stiffer springs and possibly stiffer sta-bars might call for slightly less pressure, given that most venues are not dead flat and perfectly smooth. That sort of assumes that you're starting with a car that had already been optimized for that particular track, driver, and other things like weather conditions for the softer springs/bars.


Norm