Outer Limits 4x4 Board

Quick question guys....

Picked up my 16" RadFlo Coilovers for my Lux today, Less coils obviously until i can get truck weight of finished build

Just curious does it matter what brand of Coil you use compared to what brand of Coilover you have?

Have been reccomended to use Eibach, but just wondering once you figure out poundage of truck and give supplier that information so they can figure out correct spring rate, does it actually even matter what sort of coilover you have so long as they know its a 2" x 16" version?

Are all 2" Springs dimensionally the same? ie: are all 2" Coilovers the same when it comes to spring mounting? So in effect i could use whatever brand spring i wanted irrespective of coilover brand because so long as its a 2" x 16" spring it will be good (poundages and spring rates aside for a second)

Cheers guys, i hope you understand what i mean....

I'm not familiar with RadFow coilovers. Mine are Swayaway Racerunners, which for springs are similar to Fox, etc.

Assuming usual convention has been used; 2" will be the piston diameter and 16" the stroke/travel.

Then you will need 2-1/2" springs (the inside diameter is specified & o/d changes depending on wire diameter).

You will need at least 2 springs with a total length of 2 time stroke e.g. 2 x 16" or 1 x 18" + 1 x 14" (18" can be harder to get in 2-1/2").

When you have 2 springs in series like this, the combined spring rate is less than the rate of either spring. e.g. 2 x 16" springs each 200 lbs/inch will have a combined spring rate of 100 lbs/inch.

If you use a dual rate stop, when the slider hits the stop, you then only have 1 active spring and the rate changes to the that of the active spring.

You don't have to have equal rates for each spring, this allows much finer adjustment of combined spring rate and dual rate.

If you know the sprung load (not wheel load) on the front and rear coilovers, and the angle from vertical of the coilover, then you need to decide how much the rebound (down) travel you want in inches.

The rebound travel is the same as the amount of compression of the springs at normal ride height. Then the spring rate required is:

Spring rate in lb/in = spring force in lbs/compression in inches

If the coilover in inclined at an angle, you first divide the sprung load by the cosine of the angle to get the spring force. e.g. if sprung load is 600 lb and inclination of coilover is 10* then spring force is 600 lb/cos 10 = 600/0.9848 = 809 lb

You then need to look at the spring force at maximum compression. This will depend where the dual rate stop is set, which determines how far the lower spring becomes compressed.
Spring force in lbs = spring rate in lbs/in x compression in inches.

When setting the position of the dual rate stop, you need to consider how much up (bump) travel before you want to have a large change in the spring rate (remember spring rate is spring stiffness).

You might also want a tender and or helper spring (see Eibach catalogue).

For more information and online calculators look on this page http://www.swayaway.com/TechRoom.php

Also good information on pirate tech pages.

Edit: Eibach springs are about as good as you can get.

Edit2: I forgot to include spring pre-compression at full extension when I discussed finding the spring rate from ride height above.

Edit3: Another guide (pdf file) for spring selection here http://www.gorancho.com/docs/spring_selection_guide.pdf

Using suspension frequency is probably best way to determine spring rates.

ring the supplier...

Use EIBACH or KING SPRINGS . at least you will get the same pound spring as you order. with dimensions as Bush65 has said.... Lukey

Cheers Luke, will do...

Hey Bush65, that is awesome mate, I'll be honest im still going to have to read that probably another few times to really soak it in, but that is way more than anyone has ever told me before, i was always told it mainly just relates to truck weight and he would figure out the rest...

Your on Lake Macquarie too... I think i need to buy you a beer when i get back from WA in 2 weeks time and pick your brain even more

Elmo wrote:Cheers Luke, will do...

Hey Bush65, that is awesome mate, I'll be honest im still going to have to read that probably another few times to really soak it in, but that is way more than anyone has ever told me before, i was always told it mainly just relates to truck weight and he would figure out the rest...

Your on Lake Macquarie too... I think i need to buy you a beer when i get back from WA in 2 weeks time and pick your brain even more

What I tried to point out is that there is much to consider, and more information than weight is needed to get it right.

With 16" coilovers it is even more of a problem to get your ride height correct.

I didn't say much about spring frequency so added an edit and reference to other places and links for more info.

Spring frequency (SF) is the best guide for selecting the spring rate. SF allows you to measure and compare how spring rate affects handling of different vehicles for various purposes.

SF measures how stiff the suspension is by accounting for both spring rate and sprung weight.

Note that this SF is without the shockies. It is the natural frequency (vibration) of the spring without dampening. Shockies are used to dampen the natural vibration of the spring - they should not be used as a bandaid to make up for a bad choice of SF.

If you will only use the vehicle off road, the SF should be between 1.0 and 1.5 Hz. If it is to be used on road as well, the SF should be higher - 1.35 front and 1.69 rear is about right.

The rear SF should be about 20% higher than the front. The reason is that the front wheels hit the bump before the rears. It is this time delay that governs the choice of higher rear SF.

After the front springs are compressed by the bump, they rebound and after some small time the shockies bring them to rest at the normal ride height. The same happens with the rear springs but there is a time delay to when their cycle starts.

What we want to happen is for the cycles of both front and rear springs to finish at approximately the same time (even though the cycle for the rears starts later). We can achieve this by increasing the SF of the rear springs - higher SF = shorter period of vibration (i.e. vibrates quicker).

If the end time of the front and rear spring deflection cycles don't coincide the vehicle will have a pitching motion that is uncomfortable and adversely affects traction.

Once you have chosen springs with rates that have acceptable SF your problems will start, because you need to get the ride height right with the amount of bump and rebound travel you want.

With a 16" stroke coilovers, you will most likely be looking at setting the ride height with something like 8" to 6" of up travel (bump). This means that at ride height the springs are compressed 8" to 10" - that is most likely not going to happen with your spring rates.

With coilovers, you musn't allow the springs unseat at full extension - you risk loosing the bottom coil seat off the shaft. Probably the best solution is to use helper coils. Helper coils are soft springs wound from flat wire - they compress to a low height. The helper spring will take little of your weight to compress, but take up the slack at full extension.

Faark...

saved to favorites

that was awsome bush65, if only i could get my head around it all

How much would you charge to setup an A frame rear end (long arm kit lowers)with 16" coilovers and 3tube shocks.

cheers smitty
sorry for the hijack elmo..

Na dont be sorry mate, im thinking of asking the same question...

WOW!!! I've never learned so much

You can adjust the coil over to get the desired ride height based on the spring length. My old Fox's had 2 x 12 inch spring on a 14 inch coil over, worked fine and still gave the shock full travel... Otherwise what Bushy said is fine.

Ensuring that there is always pressure on the coils at full extension is key - especially for fast stuff. Most shock failures to the lower sections that I know about were caused by not having enough tension.

what sort of scales do you use to measure the sprung and unsprung weights of each corner of the vehicle ? i dont udnerstand

pinkfloyddsotm wrote:what sort of scales do you use to measure the sprung and unsprung weights of each corner of the vehicle ? i dont udnerstand

If you have good springs like Eibach (accurate spring rates), you can measure how far they are compressed at ride height and calculate the sprung weight from the compression, spring rate and inclination angle of the coilover.

Sprung weight in lbs = Spring rate in lbs/in x compression in inches x cosine of angle from vertical

Bush65 wrote:

pinkfloyddsotm wrote:what sort of scales do you use to measure the sprung and unsprung weights of each corner of the vehicle ? i dont udnerstand

If you have good springs like Eibach (accurate spring rates), you can measure how far they are compressed at ride height and calculate the sprung weight from the compression, spring rate and inclination angle of the coilover.

Sprung weight in lbs = Spring rate in lbs/in x compression in inches x cosine of angle from vertical

ok thanks alot man, im really considering going coilovers, so ive been reading up the coilover bible on pirate the last couple nights, interesting s tuff. cheers


EDIT: my scientific calc is comming up with crazy numbers using your calcs man, if i was to do this to my normal coil springs i got in atm,the cosine angle would just be 0degrees wouldnt it ? also spring compression , my rear springs are 18.1" ,is that exactly how id type it into the calc ? thanks for help

pinkfloyddsotm wrote:

Bush65 wrote:

pinkfloyddsotm wrote:what sort of scales do you use to measure the sprung and unsprung weights of each corner of the vehicle ? i dont udnerstand

If you have good springs like Eibach (accurate spring rates), you can measure how far they are compressed at ride height and calculate the sprung weight from the compression, spring rate and inclination angle of the coilover.

Sprung weight in lbs = Spring rate in lbs/in x compression in inches x cosine of angle from vertical

ok thanks alot man, im really considering going coilovers, so ive been reading up the coilover bible on pirate the last couple nights, interesting s tuff. cheers


EDIT: my scientific calc is comming up with crazy numbers using your calcs man, if i was to do this to my normal coil springs i got in atm,the cosine angle would just be 0degrees wouldnt it ? also spring compression , my rear springs are 18.1" ,is that exactly how id type it into the calc ? thanks for help

If the springs are vertical, then angle is zero degrees and cosine 0* = 1.
If you know the spring rate accurately and measure how much the spring is compressed from its original free length then the force to compress the spring by that amount is rate x compression.

With the stationary vehicle on level ground and a beam axle (not independent) then the force compressing the spring is the sprung weight at that point. Disconnect sway bars and some shockies are gas charged and carry a small load.

Say you had springs that were 300 lbs/in and they had a free length of 18.1 in and at static load were 16 in heigh.
Then the springs have been compressed 2.1 in (18.1 - 16).
The sprung weight is 300 lbs/in x 2.1 in x cos 0* = 630 lb (note x cos 0* has no affect and can be left out when springs are vertical)

Bush65 wrote:

pinkfloyddsotm wrote:

Bush65 wrote:

pinkfloyddsotm wrote:what sort of scales do you use to measure the sprung and unsprung weights of each corner of the vehicle ? i dont udnerstand

If you have good springs like Eibach (accurate spring rates), you can measure how far they are compressed at ride height and calculate the sprung weight from the compression, spring rate and inclination angle of the coilover.

Sprung weight in lbs = Spring rate in lbs/in x compression in inches x cosine of angle from vertical

ok thanks alot man, im really considering going coilovers, so ive been reading up the coilover bible on pirate the last couple nights, interesting s tuff. cheers


EDIT: my scientific calc is comming up with crazy numbers using your calcs man, if i was to do this to my normal coil springs i got in atm,the cosine angle would just be 0degrees wouldnt it ? also spring compression , my rear springs are 18.1" ,is that exactly how id type it into the calc ? thanks for help

If the springs are vertical, then angle is zero degrees and cosine 0* = 1.
If you know the spring rate accurately and measure how much the spring is compressed from its original free length then the force to compress the spring by that amount is rate x compression.

With the stationary vehicle on level ground and a beam axle (not independent) then the force compressing the spring is the sprung weight at that point. Disconnect sway bars and some shockies are gas charged and carry a small load.

Say you had springs that were 300 lbs/in and they had a free length of 18.1 in and at static load were 16 in heigh.
Then the springs have been compressed 2.1 in (18.1 - 16).
The sprung weight is 300 lbs/in x 2.1 in x cos 0* = 630 lb (note x cos 0* has no affect and can be left out when springs are vertical)

ohhh now i get it, thanks so much dude, i wasnt subtracting the free length spring measurment from the static height of the spring, thanks man.