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| Coilover spring rate question (Page 1/1) |
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Xenoblast
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DEC 29, 06:36 PM
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I have a stock 87 GT with stock sized wheels, and I was wondering what spring rate I should get for the front and back in the future. I am thinking maybe getting 1 1/2 inch lowering 300 lbs front springs, and maybe 350 lbs for the coilovers in the back with KYB shocks all around. My usage of the car is daily driving on generally well-maintained roads, and going on spirited drives on twisty roads.
Do you guys think this seems like a good setup for my usage? If not, please give advice on what I should do. Thanks.
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olejoedad
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DEC 29, 11:35 PM
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Blacktree
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DEC 29, 11:59 PM
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Those spring rates will cause noticeable oversteer. If you're using 300 lb/in front springs, then rear springs around 200-220 lb/in would be more balanced. Also, it might be wise not to surpass those spring rates with KYB shocks and struts. The KYBs might not be able to handle anything stiffer.
You may be wondering why I suggest a softer rear spring. This is due to suspension design. The rear struts attach directly to the suspension knuckle, and the spring is on the strut. So the rear spring acts directly on the knuckle. But the front springs are mounted on the control arms, away from the steering knuckle. As a result, the front springs have less mechanical advantage over the suspension. So the front springs need to be stiffer to get the same wheel rate. If the front springs are about 1.4-1.5x as stiff as the rear ones, the wheel rates will be balanced.
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Xenoblast
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DEC 30, 12:35 AM
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| quote | Originally posted by Blacktree:
If you're using 300 lb/in front springs, then rear springs around 200-220 lb/in would be more balanced. |
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On the page for a coil over kit by West Coast Fiero's, it states that the stock spring rates for a 84-87 Fiero GT are 208 lbs in the front, and 250 in the back. Is this wrong? It would seem like I'm just making the front stiffer and keeping the back the same. Or is that the idea?
https://westcoastfiero.com/...wcf-fullcoiloverkits[This message has been edited by Xenoblast (edited 12-30-2020).]
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cvxjet
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DEC 30, 12:52 AM
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I have an 85 with 88 rear subframe/suspension....Arraut recommended 300 lb springs on the rear coilovers.....I have stock GT 86-87 front springs. The car handles relatively neutral. Calculate from that. [This message has been edited by cvxjet (edited 12-30-2020).]
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Blacktree
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DEC 30, 01:26 PM
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| quote | Originally posted by Xenoblast:
On the page for a coil over kit by West Coast Fiero's, it states that the stock spring rates for a 84-87 Fiero GT are 208 lbs in the front, and 250 in the back. Is this wrong? It would seem like I'm just making the front stiffer and keeping the back the same. Or is that the idea?
https://westcoastfiero.com/...wcf-fullcoiloverkits
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The front is probably right. But the back is probably more like 150, not 250.
To put things in perspective, the spring rates for the '88 Fiero are approximately 206 lb/in front and 142 lb/in rear. I doubt the pre-88 are much different. Because the vehicle's weight distribution is basically the same.
I'm sure someone will interject with "yeah, but the '88 suspension is different". Yes, it is. But look at where the springs are mounted. Their mounting locations are virtually the same. So their mechanical advantage against the suspension will be very similar.
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Will
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DEC 31, 08:55 AM
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IIRC the '84-'87 cars have about 20# more spring rate in the rear than the '88's do.
If you're on stock size tires, the stock spring rates are going to be pretty good. My '88 Formula with Konis, spherical bearing sway bar end links and spherical bearing lateral links in the rear suspension handles incredibly well for what little I've done to it. It has the factory rear sway bar and is on stock staggered-size wheels and tires.
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Xenoblast
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DEC 31, 11:17 PM
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| quote | Originally posted by Will:
If you're on stock size tires, the stock spring rates are going to be pretty good.
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I am going to install a rear anti-roll bar on my car before I go for coilovers. My car already handles pretty well, but I wish it was stiffer all around. I also wanted to lower my car 1 1/2 inches, which buying new springs on all sides can accomplish (I dont wanna cut my springs or anything like that)[This message has been edited by Xenoblast (edited 12-31-2020).]
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