B serious

You will reduce your droop (extension) travel as you increase preload. If you over do it, you will have wheel lift on hard cornering.

If you REALLY over do it and add in so much preload that the preload force is more than the car's sprung corner weight force, the car will ride like shit and the suspension will be fully extended with the car sitting on the ground.

I think S2000's put like...750ish LB of force into the rear spring. You'd need like 1.33" of spring preload to equal that.

At 7 turns after spring contact, you're probably fine. I think Tein uses a 2mm pitch? 7 turns is 14mm (.68") of preload if 2mm is the correct pitch.

Also remember....creating more travel using preload means that the wheel will travel further up into the wheel well before the suspension motion stops. Do you have enough room?

DefSport

Keep in mind motion ratio is squared when translating wheel force to spring force. So the Flex Z's with 10 kg/mm, or 560 lb/in springs need approximately 2.5 inch of travel to take up 700 lb of wheel rate(roughly 1450 lbs spring force), which jives with my measurements. 6 turns of preload gives 2" of spring rebound travel, 7 turns is about the same at about 1.9".

DefSport

To continue, 2" of spring travel in rebound is nearing 3" of wheel rebound travel (spring travel * motion ratio). That's quite a lot, probably equal to stock with roughly twice the spring rate.

I'll probably try out 7 turns of preload all the way around (14 mm, 0.55"), which will give another 0.1" of compression travel, and that much less rebound which is probably still plenty for any street driving and especially track driving.

B serious

including the MR, the rear corner puts about 750LB into the spring.

A 560 LB spring will compress 1.33". You added 12mm (0.47") of preload for a 1" free travel, IIRC.

Your original free travel was 2.00"?

2.00 - 1.33 + 0.47 = 1.14"

If the car put 1450LB into the spring, a 560LB spring would compress 2.6". Even with your 12mm preload, your damper would be well into the bumpstop.

2.00 - 2.6 + 0.47 = -0.13".

Edit: my bad. a full weight S2000 with a full tank probably puts about 820-850LB into each of the rear springs. Mine puts in about 750-780.

850LB and 0.47" of preload comes out to about 1" static free travel with a 2.00" initial free travel.

panda25

What would be the recommended settings for a dailyed s2k? Including preload.

B serious

Shooting for like 0.75 to 1" of free travel is probably fine with a 10K spring.
With the Teins, 1" free compression travel also translates to 1" of droop travel. All measured at the shock. To me, that sounds fine for the street.


I'll let Defsport answer more firmly if you're planning on using the same coilover as him.

According to what he measured, 12mm (0.47") of preload will yield about a 1" free travel.

Again...depending on your ride height and wheel/fender clearance specs, you will need to make sure that you have room to allow all that extra compression travel.

DefSport

Isn't the stock rear motion ratio just below 0.7 (I seem to recall about 0.65-0.69)? In which case MR^2 = ~0.49.

Maybe 700 lbs is a tad much for wheel force - unsprung corner weight, probably more accurate to say ~700 lbs wheel force - 150 lbs unsprung weight = 550 lbs (this might be a tad high on the unsprung weight part, I figure some of the suspension arms and axle weight would be supported by the wheel, so I'll be conservative). Which would be more travel used than I measured (550 lbs / 0.49 = 1100 lbs, which is 2" of travel with no preload, 1.5" with 12 mm preload), actual spring force is more around 830-850 lbs according to measurements, which jives with your estimate.

So what's the actual rear MR? I must have it wrong in my info.

DefSport

I recommend 6 turns of preload (12 mm) all around, 9 clicks from full hard on the dampers with the first "half click" counterclockwise from the stop being full hard (that first "half click" can be a little vague, so best to get it off the stop and start there).

8 clicks from full hard is a little busy on rough roads for me, but it might work if yours are generally smooth. 10 clicks from full hard makes the car just float over bumps, but it isn't the most controlled feeling when there are some low frequency undulations in a corner.

For spirited driving on relatively smooth roads I recommend 7 to 6 clicks from full hard.

B serious

According to SBG's measurements, the rear MR (including cosine of shock) is 1.73:1 or .578.

I think the shock angle is 22 deg? IIRC.

So its getting 788LB of force and via the 22 deg angle...it is compressing worth 850LB.

If we can measure the pure MR (no cosine angle factored), we could probably turn that into actual sprung weight.

B serious

I'm surprised someone hasn't:
-Put the car on a lift.
-Loosened all the bushings.
-Removed the shocks/springs.
-Put the car down on some scales until the suspension compresses (chassis still supported by the lift).

That'd give you unsprung weight. Then add in about 1/2 the weight of the shock/springs per corner.