C10CoryM
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| posted on 13/7/07 at 03:40 AM |
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Little OT: Spring theory
Hey guys,
Ran into something I don't know the answer to. When drag racing people often swap their front springs to improve the speed of the weight
transfer to the rear wheels on launch (then use shocks to keep it up as long as possible).
Thing is, all the drag springs have super low spring rates. Say 220lbs/inch where the OE spring sould be something like 300-400lbs/inch.
Why would the lower rate spring, with the same load rating, extend faster than a higher rate spring?
I can only ASSume it has more to do with spring material/design than ratings. Maybe a thinner, higher temper but lower rate spring just does extend
faster?
Anyone know?
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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nitram38
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| posted on 13/7/07 at 04:22 AM |
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Dragsters go in a straight line (most of the time) and have little reason to turn corners so body roll is not a issue.
Soft front springs will affect braking/dive more than traction issues.
Length of the car might also come into play here aswell.
Maybe firmer shock settings too?
[Edited on 13/7/2007 by nitram38]
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gazza285
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| posted on 13/7/07 at 04:46 AM |
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quote:
Originally posted by C10CoryM
Why would the lower rate spring, with the same load rating, extend faster than a higher rate spring?
It doesn't extend faster, but it extends more . Same as a low rate spring compresses more under load.
DO NOT PUT ON KNOB OR BOLLOCKS!
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C10CoryM
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| posted on 13/7/07 at 05:04 AM |
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quote:
Originally posted by gazza285
It doesn't extend faster, but it extends more.
Ah, maybe. I wonder if thats the case. In a car that isn't able to completely unload the front tires (and extend the springs to full rebound)
the lighter rated spring would extend further, transferring more weight.
Makes sense.
Thanks.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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ChrisGamlin
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| posted on 13/7/07 at 12:39 PM |
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Here's my theory... 
I think its not so much that a soft spring extends further than a stiff spring because all springs have a set free (unloaded) length which you specify
when ordering, its more that with a certain amount of force (the weight of the car) a softer spring will be more compressed to start with, so a longer
(unloaded) spring can be fitted to the car whilst still retaining the desired ride height.
When it then accelerates, the unloading spring will be able to "lift" the front of the car further because of its longer free length,
whereas a stiffer sprung car (with the necessary shorter springs) cannot reach the same height.
[Edited on 13/7/07 by ChrisGamlin]
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procomp
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| posted on 13/7/07 at 01:23 PM |
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Hi Cris's theory above is correct . It is also somthing greatly overlooked on kitcars in general.
Can be helped by fittment of antiroll bar to allow softer spring to be fitted to a kitcar that is being driven hard or trackdayed. Anawfull lot of
kitcars when raised to allow dampers to extend fully leave the springs ratteling around whith no load and top retaining collars about to fall off.
Sorry gone OT. Back to the dragster.
cheers matt
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C10CoryM
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| posted on 13/7/07 at 02:09 PM |
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Yup, makes sense. I know about spring heights etc I just was thinking about it the wrong way. I was forgetting that not all drag cars have enough
power to fully unload the front tires. Softer rated springs wouldn't help any if the front tires are off the ground.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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Uphill Racer
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| posted on 14/7/07 at 10:34 PM |
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Link a third spring into the system to control bump and droop and a new world opens.
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