E36 True coilover conversion spring rates

[Nolimitz77]

Hey guys, I finally installed my Nitron coilovers on the car a week ago and took the car out to test car at a local track. The suspension is good but certainly not optimized(spring rate wise) so I need some recommendations - see specs below.

Car

96' 328i(competing in time attack)
2613# with full tank and w/o driver
Relatively stock M52
3.15 LSD
4 point roll bar
(M3 style)Nitron R1+, 2way with niton camber plates
(M3 style)Racing dynamics F27/24R swaybars
245/40/17 RS3's(might move to 255 Rivals)

Settings

Camber: 3.2F/1.75R
Toe: 1/8F - 1/16R
Springs: Nitron 850F/550R
Caster: 6.5 Degrees
Ride Height: 3/4"F - 1"R(tire to lip)
*not the most accurate meauserment but thats what I know off the top of my head*
Droop: 4"F/5"R


When I originally ordered the Nitrons, I was planning on switching to R-comps but plans changed and I am now staying on streets. The car certainly has too much spring for the tires and some google searching somewhat confirmed that, so I am here to ask what some of you with true coilovers setups are running. During testing, my car felt like it turned in very good, neutral mid-corner and just spins the inside wheel on corner exit even with the LSD which did not give me a real feel for what the car would do.... Steady state steering is a bit on the loose side and IMO, is another sign that the rear springs are too stiff. The main issue though is spinning the inside tire, if the corner is perfectly smooth, I could put down around 80% power but the track is fairly bumpy and most of the time I was waiting far too long to get the the inside wheel to hookup. I removed the rear bar after the first run but it did not help as much as I thought it would. Unfortunately my day got cut short due to a cooling issue due to a rad mod I did.

Before taking the car back for testing, I am thinking of taking the rear springs(550#) and move them to the front and purchase 400# springs for the rear, lowering the rear of the car and adding increasing rear camber to 2-2.25 degrees to correct the steady state issue. Hopefully the additional rear droop I get from lowering the rear of the car will also help with putting power down.


Thoughts, suggestions and comments?

[macming]

Due to the drastic difference in rear leverage ratio, your coilover rear spring weight is worth close to 1.25x in the stock location.

I'd make subtle changes instead of dropping the spring weight in half. Maybe start with 400 or 450 in the back.

[Cody Overcash]

I run 1000 front 400 rear on an e36 with full coilover nitrons that equates to around 1000 front 1000 rear if the rear wasn't a full coilover. Stock '97 M3 front bar and 325 rear bar. Ideally I'd up the rear to 450 and ditch the rear bar . . . .

Lower your rear spring rate. When your fronts are 850 I'd probably try 400 on the rear with no rear bar.


full coilover rear vs stock location
450 = ~1117
400 = ~993
375 = ~930
350 = ~870

[dradernh]

Among my measurements are:

On-track weight: 2893#

Front Coilovers

Tenders 171
Mains 1599
Bar 38mm, hollow

Rear Coilovers

Helpers 71
Mains 343
Bar 32mm, hollow

It's very stiff, and only the aero allows it to stay hooked-up, which it does very well. I run R1s and R1-Ss on it.

[Nolimitz77]

Thanks for the input guys, I will try 400# in the rear first and leave the fronts alone for now. How do some of you adjust your rear droop when the rear shocks do not have a shock body length adjuster? I was speaking with a shop I deal with and he suggested we use aircraft grade cable from the trailing arms to the chassis. He has done this many times before with great success so I can't exactly argue against it, just seems a little strange to me.

[Nolimitz77]

Update: Event 1 and 2 of the OTA time attack series was held at Canadian Tire Motorsports Park at their DDT track and it was first shakedown since changing the rear springs and other minor setup changes. I decided to go with hypercoil 400# in the rear with a 4" helper spring to keep them in check when at full droop since we also lowered the rear end another 1". Lastly, we changed the rear camber to 2 degrees to help with steady state stability. At the track, the car was fantastic and did everything I needed it to do, only requiring some front dampening changes to help deal with the bumpy 2.4km DDT track. Also, this was my first time here and even though I was still trying to figure out the track, I won my class(GT2), broke the class lap record by 1.1 seconds and finished 3rd(61 cars total) on raw time behind two C5 Z06's. Event 2(Day 2), I started to get the track figured out and won my class for the second time, reset the class record by 2.1 seconds and again finished 3rd overall to the same two vette's. To say I am happy would be a complete understatement!

- - - Updated - - -

Here are some video's: http://youtu.be/bAa9O3JYH0g (Day 1), http://youtu.be/g2n6gpYLi94 (Day 2)