[stretch]

Summary:

Some lowering springs for the STI are defective because the coils bind in normal use. Coil bind happens when all the coils of a spring are stacked on top of one another and the spring cannot compress any further.

Usually, the paint will be chipping off the tops and bottoms of the coils were binding is occurring, but careful measurements are the only accurate way to know for sure. If you are experiencing coil bind, contact the manufacturer and ask for a redesigned, free replacement for your defective springs.

Tentative list (please help confirm its correctness):

Defective:

• RCE Yellow's prior to July 2007
• possibly Tanabe GF210, Cobb
• certain Ground Control configurations
• early Crucial springs
• AST Sportline-1 Coilovers (tophat absorbs bump stop)
• Whiteline G2 coilovers

OK:

• Swift
• Prodrive
• JDM "Pinks"
• RCE Yellow's Rev. 2
• RCE Black's
• newer Crucial

Unkown:

• Tein
• Eibach
• Perrin
• others...

Full text:

Well, I took a look at RCE's lowering springs and stumbled upon what may be a MAJOR problem, and worse yet the problem may apply to many other lowering springs, too.

The stock springs use ~14mm (.54 inch) thick coils and there are 4-5 winds depending on where you measure. The bottom coil is ground down specifically to add more travel, but add in the various rubber spring insulators and the stock springs will be coil bound when compressed to a length of roughly 2-3/8 inches at its smallest point. At that point it can't compress anymore.

Now, a completely unloaded stock strut has roughly 7.5 to 8 inches of space between its upper and lower spring cups, depending on where you measure (it's larger in one end to allow the extra half wind of coil). A stock strut has nearly six inches of stroke, but realistically can't use all of that because the bump stop displaces some travel. Realistically, the stock struts have about 5-1/8 inches of usable travel since the stock bump stops will not compress further than 3/4 inches.

Follow me here: if an unloaded strut has 7.5 inches of space between its upper and lower spring cups, and it can compress 5-1/8 inches, we're left with 2-5/8 inches between the spring cups at full compression (slightly less on cut bump stops).

Now, the stock springs can only compress to about 2-3/8 inches, so they are right on the verge of being coil bound at full compression. Being on the verge of coil bound is fine.

But then there's lowering springs. Lowering springs generally have more winds to them than the stock springs. They do this because to lower the car, they must be start out very soft and thus be very progressive. Progressive springs often use extra winds in the coil to become softer. There simply is not any room for these extra winds of coil!!!

I saw some RCE springs, and they looked like they had about half an inch of travel before being coil bound. Looking now at a photo, the springs have six coils- one more than stock- and each coil looks thicker (but I can't confirm, I didn't have calipers handy then). Half an inch prior to bind, if indeed that estimate is accurate, is HORRIBLE. The paint was chipping off on the bottoms of the coils supporting that coil binding is happening frequently. This rapidly deteriorates the springs themselves, but even worse, leads to incredibly sloppy handling and chassis wear as bumps are transmitted directly to the chassis. No wonder so many people like those fender braces. I've seen lowered STI's kind of jackhammer around an autocross course and while I thought this might have been from hitting the bump stops, this is a much more likely cause since the impact would be much more sudden. Becoming coil bound results in an instant seize of suspension compression and is horrible for the chassis.

If indeed this is happening- and I'd like other owners to confirm before getting all heated- then this is a horrible, embarrassing problem that shows an extreme lack of engineering. Whereas the bump stop thread highlighted what was more or less a ride quality and handling issue, I would question the safety of running springs so close to coil bind. I suspect some other lowering springs have this same problem, and it basically means the whole bump stop issue does NOT MATTER because those springs are becoming coil bound! Hell, increased strut travel wouldn't even matter because your springs aren't allowing you to use what you have! There is no excuse for an OE replacement spring to become coil bound on an OE strut, and I'd personally ask for my money back upon discovering such a thing. Such springs are, in my opinion, defective.

As with all my posts, please don't take my word for it. I only saw one car, but the problem there looked fairly obvious on both sides of the car. Please: those with lowering springs (of all brands), could you please take a picture through whatever fender gap you have and look at your springs at your ride height? Take pictures, post 'em up, and confirm this problem (or lack thereof) yourself. Or, if your springs aren't yet installed, measure the diameter of the coils and count how many there are. The spring should be able to compress to 2-5/8" or less.


Edit: Swift, JDM Pink, and Prodrive springs all use the same number of coil winds as the stock springs (or less) and should be OK, but measure the coil diameter to verify!

Edit 2: evilSTi7 reports the Tanabe GF210's binding too!

Edit 3: MTR shows Tanabe GF210's not binding

Edit 4: Racecomp says new, revised design will not coil bind.

Edit 5: Racecomp is replacing all RCE "Yellow" front springs free of charge.

[lackskill]

Makes sense why RCE doesnt recommend cutting the bumpstops now. Makes perfect sense. So we dont get much more bump stroke on stock struts/springs and cut bumpstops either then, do we?

[SWortham]

Stretch, when I had the RCE yellow springs they seemed to work fine most of the time. The only situations where they didn't were over especially large bumps where the suspension would in fact bottom out and I'd feel it through the chassis. I could never reproduce that effect on any road course or autocross though. It only happened over the extremely rough "rally" roads near my house I like to drive on.

This would explain why it felt so harsh when the suspension did bottom out. And this was a big reason why I re-installed the stock springs. Although it wouldn't surprise me too much if many RCE spring owners have never experienced this.

[MGizzle]

I think RCE recommened not cutting the bump stops because that is what every OEM Damper supplier will tell you. They are there for a reason and one of them very much being safety. I would also imagine that the bumpstops adding to your spring rate is a lot more cost efficient than paying for thicker rod springs. But, I am still researching this bumpstop issue with a few OEM's myself so I am not 100% on this.

However, I don't think that lowering springs will make your suspension bottom out or cause the springs to coil bind. Taking your stock spring and cutting a coil off will increase your springs rate significantly, especially the less coils you have. Increased spring rate means more force to move the same amount. In the end, to bottom out your suspension it will need about the same force on a stock or cut spring. However, the shorter spring being stiffer, it will pick your car up more so travel wise with respect to the ground you might have more travel than stock. The same concept is applicable with lowering springs. They are a lot stiffer so if you get your damper to move the same amount as on your STOCK set up, you are hitting bigger potholes or you are rolling more.

I agree that some companies that make springs don't think about this stuff but it is not that hard to get right. A spring tester will within seconds give you more information and displacements about springs than you can imagine. It would flag coil bind if it was a serious problem.

Also, cutting your bump stop will cause coil bind a lot sooner if there is concern of coil binding.

[05_GD7]

I'm a bit of a suspension newb, but what's the definition of coil bound?

When one single coil hits another? Or when the entire spring is compressed to the point where it won't compress anymore?

[D1SMember]

I would like to hear more about this...I've been interested in getting the RCE Yellows. I know they just came out with the black springs which are supposed to be a little more of a gentle ride. I guess I'll have to put a little more thought into the springs I get. Any suggestions?

[MGizzle]

Give RCE a call, they sound like reasonable guys. Ask them to TELL you what the limits of the springs are. Every spring manufacturer has them. If not, don't buy them because they don't know what they are doing.

They will tell you stuff like free lenght, possible installed lenght, AND solid height. Solid height is very bad and you should have more travel before solid height than your strut travel. If they don't want to give you this stuff, calculate it. Ask them for dimensions (diameter of rod, coil number, ground or cut, etc.) and plug them into the equations. They are very easy and are available anywhere.

[stretch]

I'm a bit of a suspension newb, but what's the definition of coil bound?

You reach coil bind when all the coils in the spring compress enough to sit on top of one another. At this point, the spring cannot compress any further.

Originally Posted by lackskill

So we dont get much more bump stroke on stock struts/springs and cut bumpstops either then, do we?

You're so well into the bump stops on lowering springs that I don't think the RCE spring coils smacking one another would be blatantly obvious. But if you cut your bump stops- especially if you trimmed two of the four progressions- I bet it'd be really obvious.

Since cutting your bump stops would actually lower the car further (you're putting more weight on the springs that would've been held up by the bump stop), you'd be riding around even closer to being coil locked. Furthermore, without the bump stop there trying to prevent the spring from compressing, you're going to bottom out with more force. All that force goes right into the chassis, ouch. If Ohlins are built to OE dimensions, they won't help this issue at all, either.

[evilSTi7]

boy am i glad i have coilovers

I can tell you for a fact my 04 spec Tanabe GF210's were coil bound. Every coil on the top and bottom had the paint scrapped off and had become rusted.

[cpunlamd]

Originally Posted by evilSTi7

boy am i glad i have coilovers

I can tell you for a fact my 04 spec Tanabe GF210's were coil bound. Every coil on the top and bottom had the paint scrapped off and had become rusted.

Thats crazy!

[lackskill]

just another reason for me to ditch the stock suspension and go CO, I guess.

[La Mer]

Maybe this is why RCE are creating non lowering "black springs"?

[lackskill]

Originally Posted by La Mer

Maybe this is why RCE are creating non lowering "black springs"?

they are still lowering, but not as much as the Yellow. Think prodrive-ish height.

[stretch]

Originally Posted by evilSTi7

I can tell you for a fact my 04 spec Tanabe GF210's were coil bound. Every coil on the top and bottom had the paint scrapped off and had become rusted.

Crap, so this really isn't an isolated issue. A spring company should know better than that! I mean, that's all they do! I guess one can't assume competence from any company nowadays.

Did you call Tein about this issue? To me, that constitutes a defective spring and I'd want a fixed spring or my money back. Seriously.

Swift, JDM Pink, and Prodrive springs all use the same number of coil winds as the stock springs (or less) and should be OK, so long as the coils aren't too thick.

[Rootus]

Originally Posted by lackskill

just another reason for me to ditch the stock suspension and go CO, I guess.

... or choose springs that don't exhibit the behavior, like JDM STI pinks.