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Spring weight
johnnybizzle1986 - 21/1/14 at 12:45 PM

Hi Guys,

Currently building a Locost with ZZR1200 engine, I have some SPAX shocks with no springs....

there is probably a topic relating to this somewhere.... so can anyone recommend spring weights, This one will be a Fast road car, with possibly a track day or two, the roads in sheffield are poor and I think too stiff will either break me or the car.

Can anyone help, because this will have to be the next purchase

Regards Jon

drt - 21/1/14 at 03:12 PM

quote:
Originally posted by johnnybizzle1986
Hi Guys,

Currently building a Locost with ZZR1200 engine, I have some SPAX shocks with no springs....

there is probably a topic relating to this somewhere.... so can anyone recommend spring weights, This one will be a Fast road car, with possibly a track day or two, the roads in sheffield are poor and I think too stiff will either break me or the car.

Can anyone help, because this will have to be the next purchase

Regards Jon


I forecast this will be a long thread
A good start;

WR = (MR)² . C . ACF
WR Wheel Rate (lbs/in) or (N/mm)
C Spring Rate (lbs/in) or (N/mm)
MR Motion Ratio
ACF Angle Correction Factor (cosine of your spring inclination from vertical)



MR = d1/d2
(motion of the wheel vs motion of the spring)



WR = ( SF / 187.8 )² . SprungWeight
WR Wheel Rate (lbs/in) or (N/mm)
SF Suspension Frequency (cpm)
Sprung Weight Vehicle corner weight - unsprung weight



Suspension frequency will have to be chosen,
Road cars are around 0.8 - 1.4Hz (but Lotus elise also)
Race cars 2.0 - 2.5Hz
Race cars with a lot of aero 5-6Hz

I would recommend staying around 1.4 mark,
Opinions may vary ^^

Hope it helps