----- Original Message -----
Sent: Saturday, March 15, 2003 12:25
AM
Subject: RE: hey guys....LONG
Mark,
Softer rates (approx 16%) are better for longer events as there is
less driver fatigue. It does take it out of you with harder
rates.
With
a bit of experimentation you will find what suits your needs best. These
figures are only guides to start with.
Part
of the fun is proving every expert wrong ;-)
A
good result is that I have had an offer to test my Serious suspensions
performance with a Data Logger and shock sensors. Thanks
Andrew!
I am
looking forward to getting set up for the test but it will be a few weeks
yet till I get the time.
DAMN Errol....Glad I asked.....now what was the
bit after ..."here goes" LOL.......
Many thanks for the info.....I plan on running a
variety of spring rates front and back over the next 6 months, once the new
car is up and running. The shocks will have to be upgraded at some
stage....not quite sure what to go for yet.....but I think this time round I
will be spending the xtra $$$$ and get bump and rebound
adjustables.....especially for the front.
Thanks again.
Mark.
----- Original Message -----
Sent: Friday, March 14, 2003 2:00
PM
Subject: RE: hey guys....LONG
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?
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