impactblue

a friend of mine is arguing with me his track 240sx has 12,000lbs coil overs by megan or some japanese company that you cant look up online. its not street legal due to emissions and the cage inside but he swears that it has that high of a spring rate.
i keep arguing thats impossible since the car wont put that much weight down on it thus it would have no weight transfer...

any high end mechanics or engineers willing to explain this further to me? and if its possible to have on his drift car.
thanks

AU N EGL

maybe 120 lbs

http://www.hypercoils.com/Catalog.aspx

impactblue

nono 12,000 lbs.
ive ran coil overs before on a mustang i had... i ran 250lbs fronts which was equal in spring rate to like a 1000 lbs conventional. a 12,000 lb coil over would be equalivent to 35,000 conventional spring... for something to make use of that pressure per square inch it would need to be like a CAT bulldozer to have effective weight transfer which would be pointless since you cant road race heavy machinery.

again someone please correct me if im wrong here... im not a scientist or mechanic by any means but i have a very broad science backround and what he says makes no sense to me.

BrianCunningham

sounds like the springs NORAD used


http://science.howstuffworks.com/norad.htm/printable

trackboss

They are not measured in lbs.

flink

Mac strut suspension is usually close to a 1:1 motion ratio, so a 12,000 lb/in spring rate
is a 12,000 lb/in wheel rate. Such a suspension would travel about 2mm during normal track use,
which is waaaaaaay less travel than you'd get from compression of the tires so you may
as well just weld up the shocks.

I think your friend is mistaken

Mojave

Many Japanese coilover sets use springs in Metric units. 12K kg/m equals 671.9 lbs/in.

http://www.phase2motortrend.com/tesudrcos189.html

Sounds like your friend is a idiot.

gkmccready

Er, um. Some of the overseas coilovers measure in kg/mm rather than lbs/in ... so a 12k coilover would be 12kg/mm. 12kg ~= 26.45lbs. 25.4mm per inch. You're looking at 672lb/in coilovers.

(Yeah, what Mojave said.)

ghoffman

AU N EGL

/thread

Kubs

impactblue

thanks everyone, i looked it up also a little and other posts above are correct, they are measured in MM.
His shocks are also not some custom japanese ones as he claimed but a chinese brand thats bought and re-labeled so it called be used as JDM.

kinda funny because i was arguing so much it couldnt be lbs/inch, kg/mm works out right =p

Mojave

It's either 12 kg/mm or 12,000 kg/m (just a matter if you use meter or millimeters).

69427

Weight transfer is a result of acceleration, c/g height, and trackwidth/wheelbase. It is not a result of spring rates. Springs merely allow the body to move around (lean or dive) due to the forces against the center of gravity. (You could weld the frame to the suspension, and the weight transfer would still be there.)

waktasz

This makes no sense either.

Mojave

Some of what he said makes sense, some not so much.

On a Mustang, the stock spring location is not around the strut, but rather much closer to the inside of the control arm. When you move the coil to around the strut with a coil over, the motion ratio changes drastically, going from approx 4:1 to almost 1:1.

240sx's use more traditional struts with the spring around around the strut, so there is no motion ratio change, because the spring location did not change when installing a coil over (aka threaded strut or strut with a thread sleeve).


As was said above, body roll is a CONSEQUENCE of weight transfer, not a cause. Even if you replace your shocks and springs with solid tubes, you WILL still and ALWAYS get weight transfer, but the body won't dive or roll because the tube won't move.

When selecting spring rate, a great place to start is to look at the ride frequencies of the front and rear, and balance them for your application. For a sedan with no downforce, 1.5 hz to 2.0 hz is a great place to start, and you always want the rear frequency higher than the front. Running a spring rate that is significantly too high, even if properly damped by the shocks, will greatly reduce mechanical grip and make the car very sensitive to road imperfections.