kene

iTrader: (2)

I purchased a brand new, untouched set of stock bc racing rear strut inserts (for an 8kg/mm spring) to have placed on a shock dyno. These are for the 1991-1997 1st gen GS300 or Aristo (jzs147). I left the shocks with FEAL Suspensions of Ontario,calif. and here are the results. I took the picture. The shock was placed at 15 click point (dead center) out of the total 30 click adjustments.

Yes the BC's can go up to 32 clicks, but I was informed by BC over the phone that the highest and last 2 clicks on the stiff setting should be avoided to reduce premature wear.

I did this to gain insight into how the strut performs from factory, and also to get a baseline before I start changing struts shims to achieve different results.

If you are unhappy with your modified springs rates from BC racing, FEAL suspensions can modify your strut inserts to what you desire your ride to feel like for less than half of what you paid for the BC's. This may be something to look at for those who are currently selling their new BC coil overs due to selecting far too aggressive spring rates.







stock BC Racing rear strut dyno graph for 8kg/mm spring pic1
http://imagizer.imageshack.us/v2/150...538/FBPZCy.jpg







stock BC Racing rear strut dyno graph for 8kg/mm spring pic2
http://i119.photobucket.com/albums/o...918_132722.jpg

Please feel free to save, or browse for your records.




Oh and for those interested in doing their own suspension calculations...
The JZS147 (Aristo/GS300) chassis' info is as follows:

curb weight: 3,660lbs
Weight Distribution: 54%-Front, 46%-Rear
Front motion ratio (est. based off of sc300/supra): 0.6058 or 0.6
Rear motion ratio (est. based off of sc300/supra): 0.8235 or 0.82

Corner Sprung weight Front(with 250lb driver): 978.2 lbs
Corner Sprung weight Rear (with 250lb driver): 824.8 lbs
Corner Unsprung weight(rough est.): 55 lbs
____________________________________________
With my weight and my initial spring rate of 14kg/mm front and 12kg/mm rear yields natural frequencies of:
Front: 1.68Hz
Rear: 2.32Hz


This is a big difference between the two. The front takes bumps/dips totally different than the rear of the car. The front feels nice, but the rear(for daily driver) is not my favorite at all...period. So with the 10kg/mm spring I have on the rear now, it is a bit better, and a bit closer to how the front takes bumps, but its still not there. This 10kg/mm in the rear yields a natural frequency of 2.11Hz.

Instead of going to the stock 8kg/mm rear spring (Rear natural frequency of 1.89Hz), I am leaning towards going to 6kg/mm(rear natural frequency of 1.64Hz). This will put the front and rear frequencies close enough to each other so the front and rear takes bumps in the same way. In my opinion I would not have a difference of more than 0.10Hz - 0.15Hz between the front and rear. Granted it can vary from car to car based on the type of suspension arrangement, widths and distances between suspension corners, etc.

Below is a sample graph to give you some insight into the natural frequencies(Front/Rear avg.) of other vehicles and the level of comfort which can vary from person to person. The last 2 on the list are Lotus motorcars. I believe the higher the number on the comfort rating, the less comfortable.





The next huge thing after determining preferred frequencies is your dampers and their respective forces/speeds

I was going to do a whole write up on my use and review of the BC racing 14kg/12kg (front/rear) coil over I ordered, but it may be too much info.

kene

iTrader: (2)

BC racing dyno graph for 8kg/mm spring. From full soft to full stiff.


I finally received the detailed dyno graphs that I wanted. This was the used damper that was exchanged from the rear of my GS300. The thing I find the most interesting is that at clicker setting number 15, the graph plot of the new damper (in the first post above) is different than the graph plot of the used damper in the rebound section. Which leads me to believe there might have been an inconsistency on the rebound side of the piston or shim stack on the "new shocks" dyno graph listed above...

it is late at the moment, so more to come.