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 Post subject: Re: spring rates
PostPosted: July 24, 2014, 11:28 am 
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Location: Pemberton, BC
Although it is being done all the time, adjusting ride height with pre-load or a softer spring is not very effective, and should only be used for fine tuning. The only proper way to change your ride height by that much, is to change the mounting position.
The spring should not be loose between the perches. The other function of the spring is to be able to extend the shock in droop and maintain tire traction. To let the shock free fall, so to speak, is not effective. The suspension is compromised if you use a soft spring to lower the ride height. If a certain spring rate is needed to provide the handling you are looking for, then a softer spring will reduce your available shock travel.
However, changing the mounting position may not be practical, so you need to do what you have to. You could also look into a different coil over, that may have the right amount of travel you are looking for, but due to a different construction, might be 1 inch shorter between the mounting holes.
I built my mounting towers with two holes 1 inch apart.


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 Post subject: Re: spring rates
PostPosted: July 24, 2014, 1:33 pm 
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Here's a picture. Not sure if it helps. I don't see how you can control enough variables to prevent the spring being loose on it's perch. Nothing limits the droop travel besides the rod ends (bad) and the shock.


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 Post subject: Re: spring rates
PostPosted: July 29, 2014, 11:15 pm 
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Joined: June 8, 2010, 8:02 pm
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Location: White Rock, BC, Canada
Thanks guys (specifically Chuck who actually answered the question :lol: )

My springs are long because my shock travel is probably long for a locost. 3" bump, 2" extension. I've had cars with minimal wheel travel before and didn't want it again. I have bump stops, and probably add extension bumpers too. Where I went wrong is I didn't weigh my car accurately enough prior to ordering springs. I'll throw the 150lb springs in and see what happens. I'd intended to run soft spring/large ARB setup anyhow. Springs are cheap enough and nice to have different rates around for tuning. If it wants the 200lb springs I might be able to fab a different bracket, but not easily.

Cheers.

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 Post subject: Re: spring rates
PostPosted: July 20, 2017, 4:42 pm 
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Joined: August 8, 2014, 6:08 pm
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Location: Green Bay, WI
I just corner weighed the car and started running through GAZ excel worksheet.
the questions I have are : What is the % of droop you look for? I have 6" of total travel in front 3up 3 down. Rear free travel is 2up 2 down on a live axle. At my ride height that is forced by struts currently. Center to Center on the perches is 12". Same in the rear 12". Front are on 42degree angle rear are 20degree. Right now I have 290lbs on each wheel front
rear is 300. My D1=14 and D2= 20 for the front if been seeing spring rates up tp 700lbs in the front. I don't know where to start with this.
Do use all of the travel available in the program where it gives a box for it? Do you limit it to half of the available travel?. What kind of travel are you guys experiencing
I know I have to add me in the car and add 60lbs for fuel. For a good Riding car with the values I have Are there standards to go by?

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 Post subject: Re: spring rates
PostPosted: July 20, 2017, 5:15 pm 
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Joined: July 4, 2006, 5:40 pm
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Location: Novato, CA
I used that same spreadsheet and pretty much went 50/50 front and rear. Ended up with 350# front, 160# rear. My weight estimates were wrong, too, but the springs have worked out pretty well. Steering is very neutral, but the ride is stiff. On the one hand I never bottom out, which is good, and the car corners very flat, but I feel every bump and a big jolt can bounce me out of my seat.

Springs aren't that expensive and I've often thought about getting a 300#/140# set for a little more comfort, but it's a compromise either way, and it's never been bad enough to actually get me to make the change.


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 Post subject: Re: spring rates
PostPosted: July 20, 2017, 5:38 pm 
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nick47 wrote:
I used that same spreadsheet and pretty much went 50/50 front and rear. Ended up with 350# front, 160# rear. My weight estimates were wrong, too, but the springs have worked out pretty well. Steering is very neutral, but the ride is stiff. On the one hand I never bottom out, which is good, and the car corners very flat, but I feel every bump and a big jolt can bounce me out of my seat.

Springs aren't that expensive and I've often thought about getting a 300#/140# set for a little more comfort, but it's a compromise either way, and it's never been bad enough to actually get me to make the change.

Nick what is your shock angle in the front?

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 Post subject: Re: spring rates
PostPosted: July 21, 2017, 4:28 pm 
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Pretty sure it's 35 degrees. I'll have to dig up the worksheet I filled out when I get home.


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 Post subject: Re: spring rates
PostPosted: July 21, 2017, 5:09 pm 
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nick47 wrote:
Pretty sure it's 35 degrees. I'll have to dig up the worksheet I filled out when I get home.

Not a big deal just curious. We're only 7 degrees apart but I'll bet my front end is much wider.

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 Post subject: Re: spring rates
PostPosted: July 23, 2017, 8:37 am 
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One thing I have noticed is that Bruntons worksheet in D2 is pivot point to center of wheel. The other calculators I found go to center of ball joint. Whats going on here?

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 Post subject: Re: spring rates
PostPosted: July 24, 2017, 8:16 pm 
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is anyone riding on wheel frequencies of 2.0 or higher?

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 Post subject: Re: spring rates
PostPosted: July 24, 2017, 11:13 pm 
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Yes, 2.5 hz, but the car isn't used on the street.


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 Post subject: Re: spring rates
PostPosted: July 25, 2017, 9:17 am 
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So I am looking at Ride frequencies at 1.7(front) and 1.9(rear). The trouble I have is the excel spreadsheet is so different than the shock manufactures in the place you measurements are taken. is this a big deal or not?. I also don't have any idea what these ride like that in its self is frustrating. Once I started putting my numbers in the right spaces for D1, D2. the values made sense. That will make you feel dumb.

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 Post subject: Re: spring rates
PostPosted: July 25, 2017, 10:46 am 
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I agree that the excel sheet doesn't pass the test of reasonableness. I couldn't get it to produce the values that I'm getting with other spreadsheets. I agree with nick47 that around 350# spring is a good place to start. Also, frequencies below 2.0 are a good starting point for a light street car that won't be used at 10/10ths.


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 Post subject: Re: spring rates
PostPosted: July 25, 2017, 9:40 pm 
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Tundra 7 wrote:
One thing I have noticed is that Bruntons worksheet in D2 is pivot point to center of wheel. The other calculators I found go to center of ball joint. Whats going on here?
Center of ball joint = correct
Center of wheel = incorrect

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 Post subject: Re: spring rates
PostPosted: July 25, 2017, 9:58 pm 
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I never entirely understood the logic behind using frequency - its getting shot to hell as soon as you add any sort of damping.

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