Advice for Coilover Spring Rates - 2003 GT - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 6 Old 08-25-2017, 03:22 PM Thread Starter
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Advice for Coilover Spring Rates - 2003 GT

For a 2003 GT

Looking at MM coilover conversion kit for front and rear. Looking for spring rate advice. Use is for open track. Car will only really be driven on the street to and from track events. I was thinking maybe 400 - 450 front (maybe a little too aggressive?) but not sure what a good balance match rate is for rear.
Set up now:
- Body weight is essentially stock.
- Koni yellow single adjustables front and rear.
- H&R sport springs
- MM CC plates.
- Stock front Lower Control Arms's.
- Steeda X2 ball joints
- MM solid mount steering rack mounts.
- Front sway bar Eibach 1.4" OD .
- Strut tower brace.
- Full length subframe connectors.
- Panhard bar
- MM HD rear Lower Control Arms.
- Stock rear Upper Control Arms.
- Stock swaybar in rear (Eibach does not fit with MM's HD lower control arms. Waiting for resolution from MM)
- Wheels and tires - 9" square with BFG 255/40-17 G-Force Rival S

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post #2 of 6 Old 08-25-2017, 04:48 PM Thread Starter
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Well, perhaps to answer my own question....

From the MM website Damper Selection for Coil-over Springs , they say that the appropriate rate for my application is 400 - 425 Lbs. The rear 4-link is determined by subtracting 125 from the front rate.

You guys concur?

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post #3 of 6 Old 08-25-2017, 07:18 PM
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Koni single adj show max rate of 375. I've been told you can run a little more but have to crank the adjustment all the way up. You can always send the struts in and have them revalved to handle more spring.
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post #4 of 6 Old 08-25-2017, 09:07 PM Thread Starter
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I saw that Matching spring rates with dampers on the MM website. However, I cant find any confirmation of this from Koni. Surfing a lot on the web regarding max spring rate and it would appear that the Koni yellow SA are being used with much higher rates without damage.

Does anyone know if there is an official Koni position on this?
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post #5 of 6 Old 09-17-2017, 08:56 PM
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I have 425lb on the front of my fox, track dedicated, and I would not want to drive it on the street.

I would recommend getting a set of H&R super race or Steeda Race springs before you go coil over. Your set up will handle them fine and you'll spend a lot less money. The car will also handle pretty damn close to what your coil over set up would do.

'03 Cobra-529rwhp, '95R #201, '90 GT w/ IRS, 2015 Focus ST, 2012 GT track car
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post #6 of 6 Old 09-19-2017, 10:38 AM
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In contrast, I have 425# coil-overs on the front of my Fox and think it drives perfectly fine on the street; literally zero complaints about the front end ride quality. (Rear end, on the other hand...) I wouldn't tolerate it if the ride quality on the street was poor, because it's only been on a road course a handful of times over the past 15 years - it just wouldn't be worth keeping the stiffer springs on there.

'89 GT convertible, N/A 357W, MM front susp w/425# coil-overs and Koni D/As, MM TA/PB rear setup (Koni Yellows, 390-430# springs), Stoptech 332mm / 12" Baers, MM 6 point rollbar, Maier 1.5" flared fenders & quarters, 18x9.5" front/18x10.5" rear Enkei RPF-1s (street), 18x10" CCW C-10s (track), etc...
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