Softish springs, stiffish dampers - yay or nay? Or, using Focus ST dampers on non ST.

Hey all.

Question, for the Mk3 Focus specifically, on spring rates and damping.

Vogtland's progressive springs are I think pretty well known for having near stock spring rates initially, and then the rate ramps up a bit with compression (Focus fronts, for instance are 115lbs initial, 285lbs final). They also state they make them to work with factory dampers (true a few years on now for both the e30 and the Focus).

Their Focus ST springs are stiffer initally and not such a wide swing from initial to final at 185/220 or something close to that.

I presume the ST is fairly significantly more "damped" given the spring rates.

So, since the STs will be damped more stiffly than their pedestrian counterparts, would the factory ST dampers work well with the relatively "soft" initial spring rate of the Vogtlands?

Why the question? Well, a guy is going to lower his car with Vogtland's and wants to know which way to go. And while my dampers are still fine, you can get the whole set of either the ST units or non-ST handling pack dampers for around $250, so I may upgrade for the h-e-double hockey sticks of it.

I like my Focus an awful lot, but it's pretty much a wallowing pig around the cones (the nut behind the wheel is worse, but isn't likely to change ...), and I wouldn't mind tightening it up at that price.

What sez y'all?

Subaru gained a very good reputation for chassis dynamics and ride quality by going with lots of damping on relatively soft rates.

All that said, lowering + stock spring rates almost always = failure. The rates need to go higher just to make handling stay the same because of the negative effects lowering has on suspension geometry (makes it want to roll more for the same cornering forces) and any kind of progressive rate you could get in the 1" of travel remaining after you lower it is not going to be much different than just slamming into the bumpstop like it was some kid who cut his springs.

You can't really compare to what E30s can get away with because BMWs have acres of suspension travel, FWD cars generally don't because they have to deal with the twin problems of packaging the suspension above the axle, and limitations of how much plunge/angularity that the front CVs can live with.

tl;dr: Up the damping and also up the rate moderately

Knurled wrote: The rates need to go higher just to make handling stay the same because of the negative effects lowering has on suspension geometry (makes it want to roll more for the same cornering forces)

I'm trying to understand this sort of thing without any formal education on the matter, and I think I was making some bad logical leaps in my head. I would have thought that lowering the center of gravity would result in less body roll, so lowering a car would equal better handling of the weight transfer in a corner. Can you fill in the part that I'm missing there? I've been thinking about trying to put some skid plates on the Neon and bring it down an inch or two to try to improve handling, so I'm trying to understand how all this works...

The suspension geometry makes a virtual pivot point called the roll center. Push on the car above the roll center, the car rocks. Push on the car inline with the roll center, the car doesn't roll. Simplified, mind you.

With the kind of suspensions that cars are generally built with, when you lower the car, the roll center drops even faster. So the center of gravity, still in the same spot on the chassis, now has more leverage on the car, so you get more body roll.

Make a suspension where the roll center is above the center of gravity, the suspension will want to lean into the corner like a boat, but you still have weight transfer to the outside because the center of gravity is above the ground. Then Chevy decides to stop putting swing axles on Corvairs and VW stops putting swing axles on their cars too and we don't worry about this anymore.

Lowering a car does generally require stiffer springs, but a bigger problem is the shocks/dampers. Lowering with out changing the length of the dampers will lead to blown dampers in short order. Dampers are designed to have a certain range of motion in both directions from their static position. Lowering changes that static position giving more travel in one direction and less in the other which doesn't help the ride/handling and leads to blown seals.

Progressive springs aren't very popular here as they can lead to a pogo like feeling. I'm sure others can explain it further but the basics make sense. I like the rates of the stiffer springs better.

It depends on what you're using the car for. Since it sounds like you're autocrossing with it, get Eibach lowering springs and ask them what the spring rate is. You can also get custom Eibach springs and get 285 or 300 lb rate springs. You can also go with Ground control springs and sleeves for an inexpensive coilover setup. Progressive rate springs are good for when you can't tolerate stiffly sprung cars on the street. Don't lower your car on factory shocks and struts because they can't handle the altered suspension geometry and blow out quick. They also don't handle as good as performance shocks and struts when lowered.

Yah, the problem with progressive springs is that the dampers aren't also progressive, so the damping is either insufficient after you blow through the travel and get close to the end of travel (ke-boing!) or they are too stiff initially, which is better but negates some of the advantage of a progressive spring rate. Plus progressive rate springs seem to be aimed toward people who want to slam the car for looks but don't want to put decent dampers on it.

The beauty of Vogtland's progressive rates are that the car does not pogo - how they do that, I have no idea, and I've heard, sparingly, mind you, that some mk3 guys have said the Eibachs are a bit bouncy. Others have said it's fine. I do not know Eibach rates.

I'm 1.4" lower on my Vogtlands, and the ride is close to stock; does not bounce or pogo at all.

I can tell you that as you reach full compression on a dip, at highway speeds anyway, they're a bit of a gut punch. Short of that, it's a really comfortable ride.

Blowing out struts on a lowered car I think is as much a change in the frequency of spring oscillations outside the range the strut is designed for as anything else. I know there are other problems going to short relative to strut length, but I'm not usually that low.

On e30s, the general consensus (r3vlimited and e30 tech) was that lowering beyond an inch or so without upgraded struts was a disaster; 1.5" drop Vogtlands on stock replacement KYBs have been on the car for several years/at least 30k miles and they're fine. And on the 320i, I blew out new stockers within a month - H&Rs, with other stuff taking me a 1/2" below what the springs dropped.

I'm a huge fan of Vogtland for those reasons. I digress.

To the original point, I think it's fair to say the more stiffly damped ST struts would be a decent improvement over stock units, and probably a little better than average with aftermarket springs (progressive rate or not...).

Fair assessment?

Lots of people run stiff dampers on stock springs in SCCA autocross since Street class allows pretty much open struts but requires stock springs.

It works, better on some cars than on others.

If I was going through the hassle of changing out the springs and dampers on a focus, I'd spend the extra $100 for a set of Koni Yellow's instead of the ST shocks. They'll be more durable and they're adjustable and in most cases they can be revalved.

drdisque wrote: Lots of people run stiff dampers on stock springs in SCCA autocross since Street class allows pretty much open struts but requires stock springs. It works, better on some cars than on others. If I was going through the hassle of changing out the springs and dampers on a focus, I'd spend the extra $100 for a set of Koni Yellow's instead of the ST shocks. They'll be more durable and they're adjustable and in most cases they can be revalved.

Koni Yellow's are like $275 or $250 a pop - I think rock auto had ST struts, the whole set,for about that or not much more - than 1 strut!

For cheap, I'd switch out my still good struts for a semi-noticeable improvement, but at $500 just for fronts, not so much.

And, pretty sure the fellow for whom I'm trying to find out feels the same way...

Set of Koni's for $748 - http://www.redline360.com/koni-yellow-shocks-ford-focus-st?gclid=CJyyzZSn2sICFUQV7Aod_REAbw

If you end up getting serious about autocrossing the car, you'll want them anyway.

Therein may lie some of the problem - while I love to auto-x, I don't seem to make it as often as I'd like... only about 5 events this year.