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Old 12-27-2016, 11:21 PM   #1
Mustachio
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Recommend spring rate for ls1 v8 swap?

Pardon if I sound like a complete idiot asking this question, but I have very little understanding of this subject and whatever I found online was either not comprehensive or too detailed and complicated.

So I'm in the process of doing ls1 swap for my 1990 325is, but I can't seem to figure out what coilovers and what spring rate to go with. I'm planning to drive mostly around town, highway on weekends for some spirited driving. I want the ride to be firm so I can blast around on twisted roads without much rolling but still absorb some potholes.

I know that with ls1 engine, the front wheels "see" about 80# of extra weight if that makes any difference with regards to the spring rate. I have a chance at getting some coilovers at a good price with 8k (448lb) on both. But people usually get more on the rear than the the front due to the cars' geometry. Is that applicable to true coilovers though? Anyone can make a recommendation?

Last edited by Mustachio; 12-28-2016 at 12:08 AM. Reason: Correction
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Old 12-28-2016, 09:38 AM   #2
jpod999
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For E30s you want stiffer springs in the rear when running the stock spring location. For true coilovers I have no idea- you definitely don't want true coilovers in the rear if you aren't planning extensive reinforcements.
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Old 12-28-2016, 12:50 PM   #3
Mustachio
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I'm starting to pice the info together now, stayed up all night reading. Don't think I will go with true coils just because it will be harder to fit a larger wheel in the back.

Some people run 350/450 front and rear and say it's perfect, others say 500/700 is also good for dd. But that seems like a huge difference...I'll see what the "experts" may recommend at GC, although I also read people not being satisfied with the outcome.

Also what length of the spring to go with. I want to ride close to stock in the back, can't stand the "low" scene, sorry dudes. If I understand this correctly it's the length of the spring that determines how high/low the car will be. So if it's not a true coilovers in the back, how the hell can you adjust the ride height?

Last edited by Mustachio; 12-28-2016 at 01:52 PM. Reason: Add
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Old 12-28-2016, 02:02 PM   #4
jpod999
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For typical E30 coilovers the rear springs sit on a threaded adjuster that sits on the trailing arm. You thread this up or down to change ride height in the rear.

I have 560f/670r (10k/12k) and love the way it handled before I pulled the M42. I haven't driven the car yet with the V8 in it so I can't really comment on that front. Your idea to call GC and get their advice is a good one, they know what they are doing.
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Old 12-28-2016, 03:39 PM   #5
Zacm829
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I currently run a GC 375f/475r with my m62 swap and definitely need to raise the spring rates. Mostly in the rear. Car really squats with the added torque. Will most likely end up going 550/650 or around there. I second giving Mark a call at Ground Control he will walk you through the process and provide some good suggestions.
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Old 12-28-2016, 09:58 PM   #6
Mustachio
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Thanks guys, I think 10/12 would be quite adequate. I will post what ppl at GC say would be ideal for an all round application.
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Old 12-29-2016, 02:38 PM   #7
Mustachio
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So spoke to one of GC reps today, he was quite willing to help out with any questions I had and seemed to be very enthusiastic about it. He said with an ls1, around 450f and 700r. They usually put 6" springs on the front and 5" on the back. But after I told him that I would like to have 6" in the back for greater range, considering I don't want to lower the car, he said it's also not a problem.

Last edited by Mustachio; 12-29-2016 at 02:39 PM. Reason: Correction
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