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View Full Version : spring preload from shimming


builthatch
2006.05.25, 08:04 PM
does the rate increase when you shim the front suspension? for instance, i have 4 kyosho .2mm shims per corner and am running the PN purple springs; do you think the shims are effectively increasing the rate so they are like a few steps stiffer?

Sasquatch
2006.05.25, 09:52 PM
Springs are linear, it wouldn't be any stiffer, it's the same rate throughout it's movement, so whether it has no load, or it's compressed halfway, rate shouldn't change. I forgot the equation for springs, learned it earlier this year in Physics, but I know it's linear.

builthatch
2006.05.25, 10:22 PM
Springs are linear, it wouldn't be any stiffer, it's the same rate throughout it's movement, so whether it has no load, or it's compressed halfway, rate shouldn't change. I forgot the equation for springs, learned it earlier this year in Physics, but I know it's linear.

they can be progressive too tho...i mean, i guess it's safe to assume that these are linear because they are so cheap and small and not conical in any way, but....i'm not sure lol

Biff
2006.05.26, 03:33 PM
they can be progressive too tho...i mean, i guess it's safe to assume that these are linear because they are so cheap and small and not conical in any way, but....i'm not sure lol


They can be progressive if some of the coils are wound closer together than others, otherwise they are linear.

Sinister_Y
2006.05.26, 06:44 PM
Everything is correct as stated. However, when talking previously to some mechanical engineers (friends who also have automotive tuning experience) about the spring preloading, they said even though the spring is linear, by using preloading, it actually tricks the car into thinking it is a harder spring during the initial period of spring compression (very short duration). So, builthatch, your viewpoint is shared by others. I personally use that option when the spring is perfect for everywhere (i.e. I have enough steering) on the track except say during/after a sweeper (where I need some additional roll resistance).

Anyway, it works for me. Just try it and see if it makes the car do what you want it to.

SuperFly
2006.07.05, 07:21 PM
I personally use that option when the spring is perfect for everywhere (i.e. I have enough steering) on the track except say during/after a sweeper (where I need some additional roll resistance).

Would you get the same result with a suspension limiter? Are you achieving the additional roll resistance simply because the spring is fully compressed? Just curious...

color01
2006.07.05, 09:32 PM
The suspension limiter would be like a very hard bump stop... it's nicer not to rely on this part because if you've ever bottomed out your real car during AutoX or a track session, you can feel it- it's not pretty.

Spring preload might help in a fast sweeper because it makes the car feel stiffer up front, thus making the response faster, which will get the car to turn at high speed and counter the high-speed understeer these cars are prone to. Just a thought.