RE: hey guys....LONG

[E Smith]

Ben, Here goes, Spring rates relate directly to corner weight and leverage ratio on control arms. To make any sense of spring rates you need to work out the effective spring rate at the wheel. On the stanza/sunny with stock lower arms the ratio is 375mm (pivot to tyre centre) divided by 320mm pivot to ball joint centre =0.853. On this car for example a 360lb/inch spring has an effective rate of  307lb (140kg) at the wheel. If the arms have been lengthened for more camber this rate will vary as the rate become closer to unity.   A good guide for a club race car with good quality race rate shockers, is the wheel spring rate in kg's/cm should be in the range of 16 - 20% of the static corner weight of the car. Eg - at 16% wheel rate 260 kg/0.16=41.6kg/cm or 232lb/in this means a 272lb/in spring;  at 18% wheel rate 260 kg/0.18=46.8kg/cm or 261lb/in this means a 306lb/in spring;  at 20% wheel rate 260 kg/0.2  =52kg/cm or 290lb/in  this means a 339lb/in spring   The heavier the spring,  the faster the wheel movement is slowed during bump. This also means the wheel is pushed back faster towards the road surface during rebound. Race cars use heavier springs to ensure that the wheel is able to follow the road surface at race speeds where these events take milli seconds. To stop the spring energy being transferred to the body of the vehicle the shock has to control the transfer of energy to the spring during bump and as the energy is release from the spring during rebound. It gets rid of this energy as heat.   As you get above 15% sprung wheel to corner weight rate, you need much higher quality damper control as the suspension has lower distances to move due to the higher spring rates. Once you have the spring rate at the wheel, you design your shock for damping at a range of piston velocities typically encountered in the application. BILSTEIN for example use 32.5mm/sec, 65mm/sec, 130mm/sec, 260mm/sec, 520mm/sec as their test velocities.   Usually the shock rate on bump is much less than on rebound. This allows the energy to be absorbed by the spring without lifting the body excessively and the energy is dissipated at a slower rate as the spring returns to normal ride height during rebound. This is why cars with stiff shocks for the spring rate usually sit a bit after a bump if the rebound rates are a bit high.   A good shock should provide consistent damping over a wide range of velocities without being harsh at any part of its range.   Any comments or flames?   Cheers, Feral Errol <http://www.datrats.com.au/> --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/[EMAIL PROTECTED]/ ---------------------------------------------------------------------