Let's talk spring rates

I'm planning on the ground control coil conversion for my koni yellows within the next couple of moths and trying to decide on spring rates. I'm running cobb front and rear sway bars and want to dial the car a little more neutral balanced or slightly oversteer biased. right now it's slightly understeer biased but still pretty close to neutral. i'm hoping the proper spring rates will get it dialed just right. i don't run autocross, only full circuit tracks. I also put a lot of miles on my car for work so i don't want anything too hard on the kidneys. suggestions?


Al

 

Not sure about the spring rates, but keeping the stock sway bar and just upgrading the rear can save you money. Too stiff a bar in the front causes understeer, so it's counterproductive to your goal. A good rear bar can make you much more neutral, or even tail-happy if you get a racing bar and go full stiff on it. The point is for the rear bar to be comparatively stiffer than the front for neutrality or rotation. That's how I understand it, anyways. Maybe @Nliiitend1 can chime in.

 

Yeah, I'm happy with having both bars.... Corners flat as a pancake. I could use a slightly stiffer bar in the rear, but figure a slight bias in spring rates might make it perfect. The Cobb sways I have are set on softest front and firmest rear.

Al

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If as little body roll as possible is your main goal, get a very stiff bar for both front and rear and run them in full stiff. If going through corners as fast as possible is your goal, definitely DON'T do that.

 

That's not my main goal.... I'm just saying that I don't think removing the fsb is a good idea. I am very close to neutral, but not quite there. I am thinking with the right balance of spring rates I can get it dialed in perfect. I run full track days, stability in corners is key. I see plenty of guys run super stiff rsbs and no fsb, it's got to be one tail happy car which isn't a great idea in a fwd car... Maybe in auto-x it's tolerable but for full course tracks I don't want that. I'm just trying to find a good spring rate combo to compliment the current setup.

Al

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I think we miscommunicated. I wasn't recommending NO FSB. I was recommending stock FSB and an upgraded/stiffer RSB. Lots of guys who track these cars have had a great deal of success doing so.

 

If the rsb is stiff enough, you can go with a fsb. The Cobb is. The car is far more neutral balanced than stock sways which I really like.

Al

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The RSB isn't stiff enough for most folks. The FSB is stiff enough. That's why many peeps just upgrade the rear. Ultimately, use whatever setup works best for you. But I'm sharing in keeping with the trends I've noticed from those who track/auto-x. @Nliiitend1 and @phate could tell you much more than me.

 

The CS and jbr 1.25 is too light for a fsb in my opinion. But the Cobb is beefy enough to run a fsb. Hotchkiss is another that is crazy stiff rsb that can be paired with a fsb. It's all about balance.

Al

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If you want a stiff rear bar, go with the JBR 250. It think it's by far the stiffest of all.

 

My Cobb rsb is close enough. I would never run a jbr bar because they constantly break. Last thing I need is it snapping on a high speed sweeper sending me into an understeer.

If I need stiffer after springs, it will be hotchkiss.

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Nothing but pleased with my JBR 125. Zero issues for years. If you really want a well suited setup, have you considered the MSM Coilovers, which are essentially KW V3s? I've heard lots of good things.

 

Do you know which spring rates Ground Control is offering you, or are you going with custom rates from the eibach catalog?

 

Sorry for sidetracking the convo regarding bars instead of spring rates. @ConeKiller and the other guys I tagged would be much better, like I said.

Wouldn't having the same spring rate in the rear as the front encourage more rotation since we're like 60/40 weight biased? Just a thought.

 

If changing the front bar was as easy as the rear, most people would do both and swear it's the only way to go just like most actually do about the rear only. But I digress...

 

GC springs for the conversion are all generics out of the ERS catalog. when ordering they initially ask for driving style of touring, aggressive or track, then they later discuss your car and give you a suggestion of rates. I figure they probably have some good input, but I'd also like to hear some input from people on the same platform. The good news is that if I'm unhappy with the rates it's just ~$200 for another pair of springs.

Al

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What's donny's screen name here? (From rpm)

They did a group buy at one point. Perhaps he'll remember what people said about the rates.

 

@Donny@RPM;

 

Hey Al,

I know, I own a set of GC's with "race rate" springs (approx 2.1/2.3 hrtz if I remember correctly).
You should really contact GC and see what rates they recommend for your for the different driving styles.

 

@AlsChopShop; I will be trying out 600 front and 850 rears this weekend at PIR on Konis. I will let you know how it goes.

-Derrick