spring rate and ppi? same thing?

[spdcrazy]

i'm looking into some other coil's to use. read the tech library about the jeep rancho 6423's. and those have 240 ppi.

saw some on rustysoffroad that look tempting, but they are labeled as 150 lb spring rate

same thing but different wording?

thoughts?

 

[Bray D]

i'm looking into some other coil's to use. read the tech library about the jeep rancho 6423's. and those have 240 ppi.

saw some on rustysoffroad that look tempting, but they are labeled as 150 lb spring rate

same thing but different wording?

thoughts?

Same thing.

ppi = pounds per inch. Just thought I'd throw that out there for clarity.

 

[spdcrazy]

hmm... ok. makes me wonder if the rusty shocks at 150-180 spring rate will hold up my b2.

tech they are the same thing as the rancho 6423's but softer. so they should....

 

[JohnnyU]

PPI, lb/in, etc are just units for the spring rate.

The Rusty's Offroad SPRINGS are WAAAY too soft at 150lb/in for a TTB Bronco. They're arguably too soft for a SA BII as well.

 

[spdcrazy]

PPI, lb/in, etc are just units for the spring rate.

The Rusty's Offroad SPRINGS are WAAAY too soft at 150lb/in for a TTB Bronco. They're arguably too soft for a SA BII as well.

good to know... might have found a pair of terraflex coil's. need to find out which one and for what jeep they were for. we will see!

 

[JohnnyU]

I went through this a couple of years ago. All of the Jeep springs that I found were MUCH too soft for an RBV. Are you running TTB still? I gave up before finding a set of flexy TTB Ranger coils, but I think the Wild Horses or JBG Early Bronco coils were the closest to fitting my specs. Have to done the suspension cycling to determine your free length and ride height? That will help you determine the correct spring rate required as well.

 

[spdcrazy]

no i haven't cycled it fully yet. don't know what i'd do with that info when i got the info anyways. i was just going with the info in the tech library. i assumed that if the rancho's at 240ppi would work. then so should a similar coil for the same model of jeep...

 

[4x4junkie]

Skyjacker's coils are 237PPI, and seem to be much better made than Rancho.

Don't forget about ZJ/WJ coils too (and possibly even JK coils), maybe you can find something usable there as well.

 

[spdcrazy]

Skyjacker's coils are 237PPI, and seem to be much better made than Rancho.

Don't forget about ZJ/WJ coils too (and possibly even JK coils), maybe you can find something usable there as well.

thought youd chime in on this thread.

by skyjacker coil's you mean for a xj? cuz my skyjacker TTB coils are stupid stiff still

 

[JohnnyU]

no i haven't cycled it fully yet. don't know what i'd do with that info when i got the info anyways. i was just going with the info in the tech library. i assumed that if the rancho's at 240ppi would work. then so should a similar coil for the same model of jeep...

[Deep breath]
When you find the lowest point that the suspension can droop without the axleshafts binding (you'll probably have to clearance the beam 'windows' and trim the center slip spline) measure the distance from top of the spring bucket to the spring mounting surface on the axle. This will be your desired free length or unloaded length of your spring, let's say this is 22". Now, you'll also want to take the same measurement at your desired ride height, we'll call this 15". Take the difference between these two (22" - 16" = 6") This will be the distance that the spring compresses, this is important later. We'll also need to know the weight over the front axle of your truck. Lets say that the total weight is 3500#, and 60% is over the front axle, 2100#. Subtract the weight of the tires, rims, and axle and you get about 1800#. Divide that by two (since you'll have two springs supporting this weight (1800# / 2 = 900#). This is the tricky part that many folks overlook. The distance between the beam pivot and the wheel mounting surface is nearly 1.5X the distance between the beam pivot and spring pad. This gives us our "TTB Nutcracker Effect". So we now have to multiply our weight by this ratio (1.5 x 900# = 1350#). This is now the force that the spring will have to excert in order to maintain the desired ride height. In order to determing the most desireable spring rate, you want to take that effective weight or force (1350#) and divide it by the number of inches of compression that the spring sees at ride height (6"), so (1350# / 6" = 225#/") Using these example numbers, I was able to get a desired spring rate of 225 lb/in.
[/deep breath]

You'll need to determine the actual numbers for your specific truck with its specific modifications, but this will give you an idea of what goes into "tuning" the TTB for more flex. Then, you'll have to measure for custom shocks, and probably want to do some rear suspension work as well, but that's a different class.

 

[4x4junkie]

Yep, exactly how it's done (couldn't have explained it better myself).

Find out what your exact requirements are for springs, THEN try to match it up as best you can with what's available.

(yes, I was referring to Skyjacker XJ springs. Their TTB springs are more like 410-450PPI, depending on height)

 

[spdcrazy]

ok i have read things similar to this. but not as in depth. next thing i need to do is clearance the window and figure out what kinda coil free length i need. I have a shop in town that can figure out my exact weight on each corner i think... this might be helpful!

 

[gwaii]

[Deep breath]
When you find the lowest point that the suspension can droop without the axleshafts binding (you'll probably have to clearance the beam 'windows' and trim the center slip spline) measure the distance from top of the spring bucket to the spring mounting surface on the axle. This will be your desired free length or unloaded length of your spring, let's say this is 22". Now, you'll also want to take the same measurement at your desired ride height, we'll call this 15". Take the difference between these two (22" - 16" = 6") This will be the distance that the spring compresses, this is important later. We'll also need to know the weight over the front axle of your truck. Lets say that the total weight is 3500#, and 60% is over the front axle, 2100#. Subtract the weight of the tires, rims, and axle and you get about 1800#. Divide that by two (since you'll have two springs supporting this weight (1800# / 2 = 900#). This is the tricky part that many folks overlook. The distance between the beam pivot and the wheel mounting surface is nearly 1.5X the distance between the beam pivot and spring pad. This gives us our "TTB Nutcracker Effect". So we now have to multiply our weight by this ratio (1.5 x 900# = 1350#). This is now the force that the spring will have to excert in order to maintain the desired ride height. In order to determing the most desireable spring rate, you want to take that effective weight or force (1350#) and divide it by the number of inches of compression that the spring sees at ride height (6"), so (1350# / 6" = 225#/") Using these example numbers, I was able to get a desired spring rate of 225 lb/in.
[/deep breath]

You'll need to determine the actual numbers for your specific truck with its specific modifications, but this will give you an idea of what goes into "tuning" the TTB for more flex. Then, you'll have to measure for custom shocks, and probably want to do some rear suspension work as well, but that's a different class.

nice....this should be stickyed somewhere.

 

[JohnnyU]

Yep, exactly how it's done (couldn't have explained it better myself).

I probably have a PM from you saved in my inbox that says basically exactly what I typed. :icon_twisted:

nice....this should be stickyed somewhere.

I think these is a similar explanation in the Tech Library some place. I would agree, however it seems that no one really reads the stickied threads.

 

[spdcrazy]

that or the get scared like i did! or lazy (again like i was) but i'll just throw the highlift on it and see what numbers i come up with. i can always play with the top bucket, and change my static spring height a bit. thought about building new buckets anyways. heard our can collapse if beat on. tho copykat hasn't had a problem yet.

 

[gwaii]

I would agree, however it seems that no one really reads the stickied threads.

isn't this the truth!

when explaining spring rates,i find that most people get the basic lbs/inch concept,and can usually get the idea of base compression (the difference between full droop and ride height)through-though on this one i like to figure in an inch or two of full droop preload so the spring never becomes fully unloaded-but what most don't seem to get is the leverage effect of the ttb arm(or any suspension arm that is pivoted off the frame and carries the spring,for that matter).it was good to see that specified.
there is one thing to add for those who want to get picky-the main beam does not act as a single piece in this system.it is actually working with the radius arm as a single large swing arm assembly,so to calculate spring leverage you need to draw a line through the two pivots in the system(beam pivot/radius arm pivot)and strike a line perpendicular to this hinge line that goes through the tires contact point on the ground.the distance between the pivot line and the tire that the spring sits at is the ratio you use to calculate spring rate.
by playing with the numbers you can see how extended radius arms can affect the effective spring rate.
longer radius arms stiffen the spring rate.

 

[4x4junkie]

isn't this the truth!

when explaining spring rates,i find that most people get the basic lbs/inch concept,and can usually get the idea of base compression (the difference between full droop and ride height)through-though on this one i like to figure in an inch or two of full droop preload so the spring never becomes fully unloaded-but what most don't seem to get is the leverage effect of the ttb arm(or any suspension arm that is pivoted off the frame and carries the spring,for that matter).it was good to see that specified.
there is one thing to add for those who want to get picky-the main beam does not act as a single piece in this system.it is actually working with the radius arm as a single large swing arm assembly,so to calculate spring leverage you need to draw a line through the two pivots in the system(beam pivot/radius arm pivot)and strike a line perpendicular to this hinge line that goes through the tires contact point on the ground.the distance between the pivot line and the tire that the spring sits at is the ratio you use to calculate spring rate.
by playing with the numbers you can see how extended radius arms can affect the effective spring rate.
longer radius arms stiffen the spring rate.

Exactly.
http://img.photobucket.com/albums/v173/sfr4x4/ttbsymetry.jpg

The 1.5:1 figure is always pretty close though, and seems to work for most people.

I probably have a PM from you saved in my inbox that says basically exactly what I typed. :icon_twisted:

Wondering how old that PM is :icon_rofl:

 

[spdcrazy]

makes perfect sense! i'm using skyjacker arms now, however i'm not happy so i'll be building my own soon!

my local spring shop is working on finding some coils now. and measuring them for me. i'll look into what exactly i need for spring rate, and length and stuff this weekend.

 

[Sasquatch_Ryda]

Wondering how old that PM is :icon_rofl:

I have one of those too :icon_thumby:

 

[spdcrazy]

hey guys. my local spring shop has a machine that compresses a spring and tells you how my PSI it takes to move it. Is there any way to caculate this into PPI? or how can i use this psi measurement in calculating what i need? I was thinking about making new coil buckets top and bottom and adjusting their locations to help fit a different spring. They have plenty of different length springs laying around, so if i can find one that fits my numbers ( still working on, free length could be 21 as the stock buckets sit), i'd like to see what i can do.