Possible adjustable strut solution?

[FineTooned]

My frustrating quest for adjustable struts for the FiST may have brought me to a potential solution.

CorkSport makes an adjustable strut set for the Mazda2 which is apparently a direct bolt-on for the Fiesta. But it requires the use of Mazda2 springs due to a difference in spring perch size. And they sell a combo of the adjustable struts with Racing Beat lowering springs.

This is really tempting because all the reviews make it sound like a quality product that could provide the improved ride I'm after along with adjustability for track days.

My concern is the 500 lb difference between the two cars. Seems to me, using springs designed for a lighter car could mean an excessively lowered ride height or potential bottoming out. And how would the difference in lower spring diameter make in ride quality?

Any suspension gurus out there who care to weigh in on this suspension mod idea? Would 500 lbs not that big a deal for stiffer performance springs? I mean that's about the same as bringing three passengers along in a Mazda2. What other alternatives are out there without going to a full coilover setup?

Thanks.

 

[iso100]

Why are you messing with the ST suspension struts / springs? Is there a performance issue or do you want the aesthetics of less fender gap?

 

[FineTooned]

I live in an area of the US with really subpar road quality. Earthquake region with underfunded infrastructure maintenance. So the stock ST suspension makes for a bumpy, bouncy, unnerving ride.

 

[iso100]

Have you considered trading it in for a normal Fiesta? You could likely save a bunch of money.

 

[Harvick]

I'm not a suspension expert, but I would say from what you posted the 500 lbs difference is going to be a huge factor in affecting ride quality. In the end you might end up spending just as much to correct the problems with negative camber. I would say save your money and do it right or just get a set of 16" tires which should make the ride quality much softer. During the winter time I run 16" snow tires and I can tell you its a big difference in comfort.

 

[iso100]

I second the idea of 16 or even 15" wheels with taller, more compliant sidewalls. Swapping out the suspension is a bad idea in my opinion... that's what makes the ST an ST and partially why it's won over 20 awards.

 

[FineTooned]

Weird that responses have been so against the idea of upgrading the struts. But everybody goes gaga over getting a Cobb reflash or aftermarket exhaust or removing the sound symposer or cutting holes in their air filter housing. But, ok.

Yes, the stock ST suspension is impressive when on the track or a smooth, recently repaved bit of road. On undulating washboarded, potholed roads, like around where I live, there is room for improvement.

I want to maintain the ST's positive handling traits while remedying the negatives and gain more handling versatility. That's one of the many reasons I only wanted to replace the struts with adjustables while retaining the stock springs instead of going with a full coil over set. Maybe someday Koni will come around.

And yep, I'm already running 16 inch OZ ultralegeras. That definitely helped the ride but there's still room for improvement.

So, my quest continues...

Thanks for the feedback. Your opinions are appreciated.

 

[Tex ST-AR]

I believe Koni will build custom springs at your desired spring rate and struts.

 

[iso100]

The problem with replacing the struts (and hence the valving) but not the springs is that you'll then have stiffer springs that are underdampened. This could cause even more bouncing or ultimately you can wear out the dampers due to overdriving them.

If you go with softer springs but keep the stiffer stock struts that could be an option but you might not feel as much of a difference as you are aiming for.

You really do want your springs and dampers to match.

When I campaigned an 81 Scirocco in SCCA Solo II, we had Koni custom valve our adjustable "yellows" to match the insane 400#/600# spring rates we were running. If we hadn't, the dampers wouldn't have lasted half a season. (The Fiesta ST springs are in the 200# range, for reference)

 

[rooSTer]

I don't think people are against the adjustable struts idea...its the notion of putting on the Mazda 2 springs which are rated for a different weight that may cause an issue with the struts.

 

[FineTooned]

Yeah. The weight difference is what I was concerned about. And would the stiffer M2 springs somewhat compensate for the vehicle weight difference. 20% vehicle weight increase vs. 60% spring weight increase. I'm sure the math is much more complex than just comparing those numbers. I can definitely see how under-damping could be an issue with the extra weight. And what about the height change? I'm sure that can potentially screw up handling.

Any recommendations for info/ websites/ books on how to calculate spring rates and damper rates? I'm finding this stuff fascinating.

Thanks again.

 

[iso100]

I'm thinking maybe purchasing stock Fiesta springs and shocks would be the best idea. Softer ride and more ground clearance. Matched too.