# BDS 6" spring rate.....is this right?? **UPDATED**

Discussion in 'The Garage' started by 88K5Jimmy, Sep 4, 2003.

1. ### 88K5Jimmy1/2 ton status

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BDS 6\" spring rate.....is this right?? **UPDATED**

I am using this formula provided by Greg72 (Thanks):

Leaf Spring Rate=(WN/12) x (1000T/L)^3

W=width of leaves
N=number of leavbes in the pack (minus overload)
T=total thickness of pack (minus overload)/total # of leaves
L=length of spring eye-to-eye
12=constant for leaf spring

Here are my calculations:

W=2.5
N=5
T=.4
L=45.5

After putting my numbers into this equation I get a whopping number of 707.741 /forums/images/graemlins/shocked.gif

I then called ORD to see what the ideal spring rate is for a K5 and they said 250-300.

I haven't been able to confirm if my number is right because BDS's contact info is down on their website.

The reason I calculated my spring rate was because of the ride was so rough. I m thinking about taking the overload spring off the bottom of the spring pack and seeing if that makes it ride any better.

2. ### heavy4x41/2 ton status

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Re: BDS 6\" spring rate.....is this right??

No way can you use a standard formula and get the spring rate right on...there are just too many variables (metal variances, teflon pads, what kind of friction/contact the leafs have on the others). You would get a more accurate number by standing on one of the leaf springs while it stands upside-down on the ground, measuring how much it deflects with your weight, and extrapulating that out to 1". Probably be closer than any formula will get you.

I e-mailed BDS a while back and their front 4" lift springs are 425 lb/in.

3. ### Greg72"Might As Well..."Staff MemberSuper Moderator

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Re: BDS 6\" spring rate.....is this right??

The only thing I notice is that the description for "T" is not right.

T = thickness of 1 leaf (in inches)

You could measure a 4 leaf pack and get 1.6" then divide that by 4 to get a "T" value of .40" however.....

Don't feel bad about the numbers, no matter WHO you ask (including spring manufacturers) are all going to tell you different ways to verify the spring rate.

The idea about using a known weight to deflect the spring (and measuring the deflection) is another good way. The hardest part is finding a "repeatable" way to measure.

4. ### 88K5Jimmy1/2 ton status

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Re: BDS 6\" spring rate.....is this right??

[ QUOTE ]
The only thing I notice is that the description for "T" is not right.

T = thickness of 1 leaf (in inches)

You could measure a 4 leaf pack and get 1.6" then divide that by 4 to get a "T" value of .40" however.....

[/ QUOTE ]

That's what I did. My spring pack thickness is 2"/5 leaves = .4

I just got off the phone with BDS and they said the spring rates for their leaf springs weren't available. They said they didn't have them anymore. That doesn't make any sense.

Next step is to email them I guess /forums/images/graemlins/tongue.gif

5. ### marv_springer1/2 ton status

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Re: BDS 6\" spring rate.....is this right??

[ QUOTE ]
The idea about using a known weight to deflect the spring (and measuring the deflection) is another good way. The hardest part is finding a "repeatable" way to measure.

[/ QUOTE ]

I've experimented w/ this....

Get some good heavy beer drinkin' buds over, setup the spring on the floor upside down (like this /\ ) with a shackle on one end. Measure the free arch. Then ask the Big Man to gracefully stand on the spring in the center. Then (this is where everthing can come crashing down /forums/images/graemlins/eek.gif if your not careful) measure how much it's height has been reduced. The divide the Big Man's weight by the change in height. /forums/images/graemlins/deal.gif

[ QUOTE ]
I just got off the phone with BDS and they said the spring rates for their leaf springs weren't available. They said they didn't have them anymore. That doesn't make any sense.

[/ QUOTE ]
Ha...! /forums/images/graemlins/rotfl.gif

Marv

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