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 Post subject: spring rates
PostPosted: July 13, 2006, 11:47 am 
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Location: Lethbridge Alberta
what spring rates are people using?
for everyday road use or for dedicated track car
mine will be somewhere in between.


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PostPosted: July 13, 2006, 1:27 pm 
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A better question is what wheel rates people are using. Or, if you like math, figure the spring rate based on suspension frequency. Low 2cps is a good street/track setup. Quite firm, but not bone-jarring.

For what it's worth, I'm using 320lb springs on the front, while others use 500lb spring. Because of the shock angle and location, the wheel rates are the same.

G

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PostPosted: July 14, 2006, 1:27 am 
We're using 275 lbs/inch springs in the front, and I think 150 lb springs in the back. Seems just about right, although our cars are pretty light... :D


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PostPosted: July 14, 2006, 9:21 am 
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I was going to call TrueChoice and ask them what it would cost to have them build me a set of Koni single adjustable coilovers for my Miata based Locost. I decided not to call when I decided that I didn't have enough information.

I know everyone's car will be different and weigh more or less etc. but I would like to call them and see about a group buy on a set of four. We would need to reach a consenses on what the correct spring rate, shock travel etc. should be. That being said I'm going to sticky this.


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PostPosted: July 14, 2006, 10:20 am 
http://members.cox.net/enderw88/springratetheory.htm

You will need to use Internet Explorer to view the equations.


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PostPosted: July 14, 2006, 11:03 am 
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SkinnyG wrote:
Because of the shock angle and location, the wheel rates are the same.G


The only way for it to be the same is if the spring is mounted 90deg to its chassis support and 90deg to the wheel axis, and be attached at the tire centerline...

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PostPosted: July 14, 2006, 11:50 am 
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So what is the approximate inclination angle for the front coilovers if you go by the book? Anyone?


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PostPosted: July 14, 2006, 12:03 pm 
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kb58 wrote:
The only way for it to be the same is if the spring is mounted 90deg to its chassis support and 90deg to the wheel axis, and be attached at the tire centerline...


If I understand your post correctly, I am not saying the spring rate is the same as the wheel rate. I'm saying the wheel rate between two different cars can be the same despite each car running different spring rates. Am I understanding you correctly?

G

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PostPosted: July 14, 2006, 8:14 pm 
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Ah, okay, my bad... I misunderstood your post.

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PostPosted: August 20, 2006, 7:49 am 
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I ordered 175 rear and 250 front. I`m going to mount the fronts as upright as possible, possibly with a range of mounting holes to experiment.


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PostPosted: August 20, 2006, 11:54 am 
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Mounting the shock closer to the spindle has a greater affect than a more vertical, more inboard location.

G

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PostPosted: August 27, 2006, 1:21 pm 
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Hi. I am using 180lb front and 125lb rear. I do have 28 way adjustable dampening both front and rear which gives a lot of adjustment and also a front sway bar. Driven a little on the road and feels OK, ran 8 Autocrosses and feels good.

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PostPosted: August 27, 2006, 2:44 pm 
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General question here...

Isnt spring weight dependant on car weight?
With different builds and donor/engine choices the weight of the vehicle could vary quite a bit, couldn't it? With the weight variations spring rates might vary.
So without knowing the final weight is it just general knowledge?

Please feel free to school me if I am wrong....

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PostPosted: August 27, 2006, 4:54 pm 
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Yes. A heavier vehicle will feel softer than a lighter vehicle, everything else being equal. The weight affects "suspension frequency" which is a measure of how stiff you want the car to ride. I shoot for low 2 cycles per second.

One philosophy is to run wheel rates that are a percentage of corner weights.

As you surmised, there is no real way of comparing any two Locost spring rates because there are so many variables.

G

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PostPosted: August 27, 2006, 6:27 pm 
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mr.that eyeball guy.d wrote:
General question here...

Isnt spring weight dependant on car weight?


Yes... and no. You can have a Locost that uses 150lbs springs, 300lb, or 1000lb, or whatever, and it will feel exactly the same. The key is the installation ratio.

That term relates how much the spring moves versus wheel movement. If the spring mounting is such that it moves 1/2" for 1" of wheel travel, the spring needs to have 4x the spring rate had it been directly connected to the wheel. When comparing cars, the important thing to compare is wheel rates; spring rate doesn't mean anything.

SkinnyG is right about that rule-of-thumb, that "in general" sports cars have wheel-rates equal to 1/2 that corner's sprung weight. Race cars tend to have wheel-rates equal to that corner's sprung weight.

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Last edited by KB58 on December 15, 2010, 10:37 pm, edited 1 time in total.

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