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post #1 of 6 Old 11-13-2010, 09:20 PM Thread Starter
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Need advice on Spring rate

I currently run a 92 gt with FRPP B springs and Tokico Blues with Adjustible lowers on the rear. I just ran my last track day yesterday and my car slid all over the place. Found my rear shocks were blown out. But anyway so thru the winter befoe next season, I will be adding coil overs, Koni SA's, 5 lug conversion with 94 spindles and 03 cobra brakss. Since I feel that I am really pushing the car more then before, I notice alot more body roll and lean in the turns. My question is I dont understand wheel rates and I need to know what spring rate for front and rear to get. Mostly track car very very little street driven, maybe 100 miles a year on street. Im going to keep my MM adj XD lowers in the rear, so the spring will not be a coilover spring. What do you all suggest. I have heard of people going higher then375 on Koni SA's. How much stiffer will the car be with a coi over rate at 375 and rear at something else.

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post #2 of 6 Old 11-13-2010, 10:30 PM
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The wheel rate for your B springs is 106.25 - 132.5 lbs/in front and 100 -150 lbs/in rear. A 375 lbs/in coil over spring has a wheel rate of 337.5 lbs/in. I've used 375 lbs c/o springs and the street ride was not unpleasant IMO but a little soft for my tastes on track. Generally, if you use the 100 lbs/in spring rate difference on C/O's front and rear, then you're looking at a conventional rear spring of 600 lbs/in and the 375 lbs/in front C/O to get the same wheel rates as a front and rear C/O setup of 375lbs/in F and 275 lbs/in R. So to paraphrase in three words - call maximum motorsports.

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post #3 of 6 Old 11-14-2010, 01:31 AM
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I suggest joining corner-carvers and using the search function for a month. There's a ton of info over there about what various rates and setups people run.

I personally run 425# front coilovers with koni yellow SAs and I have a variety of sway bars to tune with. However, I also have SN-95 front control arms, 94-95 spindles, 17*9s with 275s, etc. I.E., there are a lot of options out there, it's a good idea to call MM and to research corner-carvers (and here).
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post #4 of 6 Old 11-15-2010, 08:23 PM
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One can search without joining, but one can't get pics and the search access is more cumbersome. FWIW, my 86 is primarily street car with 300# C/Os in front on HD Bilsteins and conventional H&R Super Race (280-300 progressive) on the rear with HD Bils, a PM3L, MM PHB and adjustable sway bar. Front ride quality is just a tad stiff for DD duty IMO, but the rear seems a little light and underdamped with the PM3L and HD Bils. But I'm still working on sorting this combo. I just received my MM adjustable LCAs today, so hopefully I can get this thing dialed in with the correct rear springs.

Last edited by qtrracer; 11-15-2010 at 08:26 PM. Reason: added stuff
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post #5 of 6 Old 11-16-2010, 03:14 PM
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I'm right in the same boat with the rest of you. I've got a completed 8.8 sittin on a pair of jackstands, brand new Detroit Truetrac, 3:73's Cobra disc conversion, UPR adjustable U&LCA's new bushings, MM PB in the box waitng to get installed, yet I still can't decide on Springs / Dampers. Vari-Shock has very good info on thier site on calculating spring rates, but you gotta have the dampers and springs to do the calculations, price is attractive for a set of SA with springs ( 600 ) plus 100 for adjustable mounts, but I don't know if their mounts will work with the PB. Obviously MM has good info and items. I was looking at a set of the MM sport dampers, and a set of springs in the 275 300 lb range as a jumping off point. I have the MM full length SF connectors, and I'm planning an 8 point cage, once I get the rear end back in the car.
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post #6 of 6 Old 11-16-2010, 03:34 PM
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Originally Posted by RJankow661 View Post
UPR adjustable U&LCA's new bushings, MM PB in the box waitng to get installed,
If those UCA bushings are spherical, you're gonna want to re-think your combination, or spring rate will be the least of your worries.
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