TTB coil-over spring rates/lengths

[PaulW]

Springs: Top 3.75x8x450, Bottom 3.75x22x450

I am far from a suspension guru, but it doesn't work in my head to call this a dual rate, maybe I'm missing something or naive, but I just dont see the point.

You only get dual rates if you use the crossover nut. The combined rate of the two springs is 225 per inch and when it hits the crossover you have the lower spring rate of 400. Seems like a pretty drastic change to be hitting right around ride height to me but I guess it works. doesnt matter if both springs are same rate to get two rates.

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Mine are not optimum. Static the rig sits on the high rate. I have had to adjust the collar to get the camber near normal. Cause is springs settle with use. The result is those first hits are solid.
I wonder how many guys are running at the low rate at static ride height?
PW
PW

[BajaF250]

I am far from a suspension guru, but it doesn't work in my head to call this a dual rate, maybe I'm missing something or naive, but I just dont see the point.

You only get dual rates if you use the crossover nut. The combined rate of the two springs is 225 per inch and when it hits the crossover you have the lower spring rate of 400. Seems like a pretty drastic change to be hitting right around ride height to me but I guess it works. doesnt matter if both springs are same rate to get two rates.

=======
Mine are not optimum. Static the rig sits on the high rate. I have had to adjust the collar to get the camber near normal. Cause is springs settle with use. The result is those first hits are solid.
I wonder how many guys are running at the low rate at static ride height?
PW
PW

Hey Paul,

I'm running 500/700s which gives me an effective rate (off crossover) of 291. I'm riding on the 291 spring rate at ride height. My problem is I can't get my crossover adjusted down to my needs due to coilbind. So, unless I change my geometry, I have to live with it. (new front end design in works!)

For my application, I'd like my crossover at ¼"-½" at ride height, that gives me the softer rate for the first inch or so and then transition to the primary coil rate. Right now, my crossover is set at about 2½" above the coil slider (again, limited by coil bind) which equates to about 4" of wheel travel... way too much and the result is a very high wheel rate when I'm in the bigger stuff. So, without bypass' I can't control my wheel rate, even with hydraulic bumps, to avoid some pretty hard hits on the stops. The solution for me is to design the front coilover to allow the spring rates I want along with the geometry to allow me to fully utilize the springs dual rates AND employ a bypass shock to control the springs better.

[PaulW]

And change your springs to a lesser values and moving the stop so it operates with smaller deflections is way less expensive than a bypass shock.
Somehting to consider.
From the other thread you rates are highest, and any extra weight probably is not much more than a Bronco?
PW
==========
Hey Paul,

I'm running 500/700s which gives me an effective rate (off crossover) of 291. I'm riding on the 291 spring rate at ride height. My problem is I can't get my crossover adjusted down to my needs due to coilbind. So, unless I change my geometry, I have to live with it. (new front end design in works!)

For my application, I'd like my crossover at ¼"-½" at ride height, that gives me the softer rate for the first inch or so and then transition to the primary coil rate. Right now, my crossover is set at about 2½" above the coil slider (again, limited by coil bind) which equates to about 4" of wheel travel... way too much and the result is a very high wheel rate when I'm in the bigger stuff. So, without bypass' I can't control my wheel rate, even with hydraulic bumps, to avoid some pretty hard hits on the stops. The solution for me is to design the front coilover to allow the spring rates I want along with the geometry to allow me to fully utilize the springs dual rates AND employ a bypass shock to control the springs better.[/quote]

[philofab]

And change your springs to a lesser values and moving the stop so it operates with smaller deflections is way less expensive than a bypass shock.
Somehting to consider.
From the other thread you rates are highest, and any extra weight probably is not much more than a Bronco?

He has different pivots (44HD front end) so the leverage on his shocks is greater, plus he drives harder than most requiring stiffer springs.

[PaulW]

And change your springs to a lesser values and moving the stop so it operates with smaller deflections is way less expensive than a bypass shock.
Somehting to consider.
From the other thread you rates are highest, and any extra weight probably is not much more than a Bronco?

He has different pivots (44HD front end) so the leverage on his shocks is greater, plus he drives harder than most requiring stiffer springs.

========
Sure, so regardless of his need for the higher rate, different springs can address the location of the stop without coil binding. Coli binding is just about coil selection not rate. I still suggest his rate it to high.
PW

[philofab]

And change your springs to a lesser values and moving the stop so it operates with smaller deflections is way less expensive than a bypass shock.
Somehting to consider.
From the other thread you rates are highest, and any extra weight probably is not much more than a Bronco?

He has different pivots (44HD front end) so the leverage on his shocks is greater, plus he drives harder than most requiring stiffer springs.

========
Sure, so regardless of his need for the higher rate, different springs can address the location of the stop without coil binding. Coli binding is just about coil selection not rate. I still suggest his rate it to high.
PW

A lighter spring will hit coil bind faster as it will need more preload or a longer length to hold the truck up.

[BajaF250]

And change your springs to a lesser values and moving the stop so it operates with smaller deflections is way less expensive than a bypass shock.
Somehting to consider.
From the other thread you rates are highest, and any extra weight probably is not much more than a Bronco?

He has different pivots (44HD front end) so the leverage on his shocks is greater, plus he drives harder than most requiring stiffer springs.

========
Sure, so regardless of his need for the higher rate, different springs can address the location of the stop without coil binding. Coli binding is just about coil selection not rate. I still suggest his rate it to high.
PW

Hey Paul,

Actually, my spring rates fit the truck and the way I drive it quite well (with the exeption on the geometry issue). I've gone through quite a few iterations on rates and lengths to arrive at my current setup. This seems to work better than the rest. The bypass addition is not intended to mask the spring issue, but to add spring control where it's needed. The front geometry redesign is to specifically address the spring rates and crossover issues. My approach is to design the front geometry with the proper spring rate and lengths to set up the front end correctly and then add the damping to properly damp the springs.

Plus, I believe my truck is just a little heavier than most of the Broncos (uncaged). The truck weighs in at 7,142 with a front weight of 3,390. Of course, that kind of weight and the leverage factor (I'm running a geometric motion ration of .418) also adds to the spring rate calculation. Plus, as mentioned earlier, I also have an angle correction factor (ACF) of 0.97 added in. These are all factors to consider when evaluating the required spring rates.

My bottom coil is an 18" tall coil and has a solid loat of 5,900lbs which help in slowing down the wheel rate at full bump... if I could go to a 20" coil, I would because it would give me a little higher solid load (which would help with my wheel rates at bump) plus it would bring my cross over in much earlier. But, that would be a custom spring and very costly.

Coli binding is just about coil selection not rate

I understand what you're saying here but it's not purely accurate... spring rate is determined by the mechanical properties of the spring itself and coil bind is determined by the physical limitations of the spring. As an example, a 3.0" x 16" 450lb coil (these are HYPERCOs) coilbind at 7.500" and a 3.0" x 16" 700lb coil binds at 9.570" That's a difference of 2.070" for an increase of 250lb/in rate. The reason being is that the wire diameter and wind count is different.

[PaulW]

Hey Paul,

Actually, my spring rates fit the truck and the way I drive it quite well (with the exeption on the geometry issue). I've gone through quite a few iterations on rates and lengths to arrive at my current setup. This seems to work better than the rest. The bypass addition is not intended to mask the spring issue, but to add spring control where it's needed. The front geometry redesign is to specifically address the spring rates and crossover issues. My approach is to design the front geometry with the proper spring rate and lengths to set up the front end correctly and then add the damping to properly damp the springs.

Plus, I believe my truck is just a little heavier than most of the Broncos (uncaged). The truck weighs in at 7,142 with a front weight of 3,390. Of course, that kind of weight and the leverage factor (I'm running a geometric motion ration of .418) also adds to the spring rate calculation. Plus, as mentioned earlier, I also have an angle correction factor (ACF) of 0.97 added in. These are all factors to consider when evaluating the required spring rates.

My bottom coil is an 18" tall coil and has a solid loat of 5,900lbs which help in slowing down the wheel rate at full bump... if I could go to a 20" coil, I would because it would give me a little higher solid load (which would help with my wheel rates at bump) plus it would bring my cross over in much earlier. But, that would be a custom spring and very costly.

Coil binding is just about coil selection not rate

- - - - -
I understand what you're saying here but it's not purely accurate... spring rate is determined by the mechanical properties of the spring itself and coil bind is determined by the physical limitations of the spring. As an example, a 3.0" x 16" 450lb coil (these are HYPERCOs) coilbind at 7.500" and a 3.0" x 16" 700lb coil binds at 9.570" That's a difference of 2.070" for an increase of 250lb/in rate. The reason being is that the wire diameter and wind count is different.

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Yeah, I know how springs are designed and selected.
Lets compare with my Bronco which is nearly the same weights as your F250 - front and rear. In fact some times I run 7500+ pounds for long trips with both tanks full and extra spare and stuff. A proven setup with no coil bind and 18+" of travel. However as I said it is not optimum, but works just fine and I dont want to deal with another change.
King springs by Eibach: Top spring 3.75x8"x450, Bottom spring 3.75x22'x450Lb/inch
King Shock is 30RS14-1 = 3"x14" with res.
Spring collar set to adjust camber so the Bronco sits on the bottom spring at ride height.
This works with King 2.5" hydraulic bumps set to just touch the heater box with about 1.4" clearance. Meaning hard hits are controlled by the bump not the shock or coil bind.

So what I said is the choice of springs determines whether you get coil bind or not.
PW

[cs_drums]

I have my coils as low as possible and I still need the front end down 1-2". I have 14" king c/o with 14" 350lb over 14" 450lb coils. Can I swap out the 350 with a 12" coil or is there a better rought to take. I really don't want to lift the rear. Thank again guys.

[cs_drums]

route*

[Phoenix0783]

To me it seems that if you replaces the coils with shorter ones, they'll separate from each other before it gets to full droop.

[cs_drums]

To me it seems that if you replaces the coils with shorter ones, they'll separate from each other before it gets to full droop.

Other options?

[hobbyturnedobsession]

Softer spring rate

[hobbyturnedobsession]

Holy crap thats soft!

[Kel Fab Creations]

I've always heard to use a 16 lower and a 12 upper for a 14 shock but that combo still gives you the combined length you have now so IDK. Are you bumped all the way to the frame? I think the only thing you have to worry about with getting shorter springs is that the slider doesnt come off the shock body at droop and that you have enough thread to put a little preload on the top coil holder. Also make sure your not gonna coil bind. The shorter spring will also limit the adjustability of the secondary coil stopper thing. (Whatever thats called.)

[cs_drums]

this sounds like alot of work to get the hiight i want but could i add another slider and a tender with a shorter lowrate coil?

[hobbyturnedobsession]

Are you just trying to lower ride height or is your camber positive?

[cs_drums]

lower ride hieght

[Rmc]

U can run a 12 and a 14, just look into getting a set of tender coils, u set your ride height where u want and when u goto full droop there's enough pressure to keep the springs and slider aligned. There super soft btw and have little to no effect on overall spring rate. This would be used to lower it btw, to raise use a stiffer spring rate and softer valving to get back to where u are now.

[Rmc]

There also called ride heigh coils or triple rate set up.