TTB coil-over spring rates/lengths

[BajaF250]

The number that matters more is the wheel rate and the curve of wheel rate that increases during compression.

Philo is right, wheel rates are critical. I found that I've increase my wheel rates given more aggressive driving (remember here folks, this is all relative, this certainly isn't a race truck so my sunday morning driving skills are just relative to my situation )... But, since I have higher wheel rates, I've decided to increase my static rate as well as my solid load rate, and I'm doing that by increasing my upper spring to 600 lbs/in which will give me a static rate of 300 lbs/in and then increase my bottom spring length by 2" which gives me a 17% increase solid load force (the resistive force the spring provides fully compressed).

[BajaF250]

Every truck as well as every driver is different. Nice to know that I might be in the ballpark on Bertha. I bought what everyone considers very heavy springs for it (600 & 700 I think). I don't think a 400/500 combo will hold that beast up.

Hey Philo,
Do you know how much BB will weight in the front? I have a sneaking hunch, 500/600 may work, but not if you're going to drive it with aplomb!

[BajaF250]

Just the latest... I dropped by Mirage yesterday after work. I've decided to go with, again if I can, a 12" 600lb/in over a 16" 600lb/in pack. But, Hyperco doesn't make a 12/600. So, apparently, they are going to do an engineering design analysis to come up with build parameters and then decide if they will build them for me (don't think that they are doing this for me... this is a corporate decision to add a new product to their line). But, I should head back Thursday with their decision on the new spring. If so, it'll take about 6-weeks to produce the new spring. So, I'm going to wait to hear back from Hyperco on their production decision and if they decide to produce the new spring, I'll wait for it... if they decide not to produce the new spring, I'll have to go with a 10-600 over a 18-600. I'm concerned that this combo will be too stiff for my application so I really hope they decide to go with the new 12" spring.

[PaulW]

Dual rate of 300 is pretty high which means your shocks will be rebound challanged.
Your front weight is only 200 pounds more than the Bronco and your spring choice is much higher?
Paul
=====

Just the latest... I dropped by Mirage yesterday after work. I've decided to go with, again if I can, a 12" 600lb/in over a 16" 600lb/in pack. But, Hyperco doesn't make a 12/600. So, apparently, they are going to do an engineering design analysis to come up with build parameters and then decide if they will build them for me (don't think that they are doing this for me... this is a corporate decision to add a new product to their line). But, I should head back Thursday with their decision on the new spring. If so, it'll take about 6-weeks to produce the new spring. So, I'm going to wait to hear back from Hyperco on their production decision and if they decide to produce the new spring, I'll wait for it... if they decide not to produce the new spring, I'll have to go with a 10-600 over a 18-600. I'm concerned that this combo will be too stiff for my application so I really hope they decide to go with the new 12" spring.

[SteveG]

Dual rate of 300 is pretty high which means your shocks will be rebound challanged.
Your front weight is only 200 pounds more than the Bronco and your spring choice is much higher?
Paul

I agree that Tom's rates seem a little high (what do I know?), but he also has shorter beams and higher ratios than us D44 TTB guys, so maybe that has something to do with it.

[philofab]

I agree that Tom's rates seem a little high (what do I know?), but he also has shorter beams and higher ratios than us D44 TTB guys, so maybe that has something to do with it.

Bingo. Probably a very close wheel rate. Driver style also has a lot to do with it. Tom is flat out twice as fast as most people I know.

[BajaF250]

Dual rate of 300 is pretty high which means your shocks will be rebound challanged.
Your front weight is only 200 pounds more than the Bronco and your spring choice is much higher?
Paul

Hey Paul,
For comparison, what spring rates are you running?

[PaulW]

Dual rate of 300 is pretty high which means your shocks will be rebound challanged.
Your front weight is only 200 pounds more than the Bronco and your spring choice is much higher?
Paul

Hey Paul,
For comparison, what spring rates are you running?

=========
What Spirit said, and I am not sure? Eibach 450 lb/in (short) & 350 lb/in (long) Low rate 197
Any way my shocks run hot but the bumps work the bottoming so I suspect the rates could be that low. Very little rebound with the low rate. At static the high rate is active.
3.0" King #30RC-R-14, King 2.5" Air bumps. I think Glen said I have 18" travel now with the relieved crossover joint.
3020Lbs front weight 4040 rear loaded for the desert and 50+ gal of fuel and 10 gal on the bumper.
Paul

[philofab]

Softer spring rates require more compression in the shock which equates to more heat being made because the shock is holding the vehicle up at speed rather than the spring. This is why TT trucks sit so low when not moving but "lift" up under speed and power.

[BDKW1]

So what is the correct way to choose the spring stack when the springs and different rates?
I wonder if I still do not understand??
Then here is another question. Why use such high rates. Fat shocks and Hyd bumps should be able to deal with an F250 or a Bronco???

Example with the 600/600 a huge amount of rebound setting will be necessary to control such a high rate as 323

I still say I probably have it all wrong?
Response please
Brian K.?
Paul

300#'s isn't all that stiff. JD Dave's ranger rides on 300#'s single rates in the front. You just have to valve accordingly and take out a lot of low speed damping. On Todd's Bronco we are going to a single rate 400# spring with a tender front and rear. To accomplish this we are going to have to go up to 3" C/O springs with a custom slider.

It's all about what is doing the work, the shock or the spring. Light springs = hot shocks and lots of body roll. Firmer springs = less body roll and cooler shocks.

As it sits, Todd's is kind of a handful cornering due to the amount of body roll. In the rough it works beautifully the faster you go. Hopefully we can improve on a few things without causing any new problems.......

[shockseals.com]

So what is the correct way to choose the spring stack when the springs and different rates?
I wonder if I still do not understand??
Then here is another question. Why use such high rates. Fat shocks and Hyd bumps should be able to deal with an F250 or a Bronco???

Example with the 600/600 a huge amount of rebound setting will be necessary to control such a high rate as 323

I still say I probably have it all wrong?
Response please
Brian K.?
Paul

300#'s isn't all that stiff. JD Dave's ranger rides on 300#'s single rates in the front. You just have to valve accordingly and take out a lot of low speed damping. On Todd's Bronco we are going to a single rate 400# spring with a tender front and rear. To accomplish this we are going to have to go up to 3" C/O springs with a custom slider.

It's all about what is doing the work, the shock or the spring. Light springs = hot shocks and lots of body roll. Firmer springs = less body roll and cooler shocks.

As it sits, Todd's is kind of a handful cornering due to the amount of body roll. In the rough it works beautifully the faster you go. Hopefully we can improve on a few things without causing any new problems.......

Heavy springs need more rebound = heat. It all washes out in the end and everybody likes different set ups.

[BDKW1]

Heavy springs need more rebound = heat. It all washes out in the end and everybody likes different set ups.

The extra rebound is negligible, if you look at the block load on the current 400/500 using the secondary stop, it's not that far off of the 400# single rate set-up. The difference is all in the middle of the stroke. There is actually a lot less spring force as it approaches full droop. 220 versus 110...........

[shockseals.com]

All depends on where the stops are at. A 10 percent change in crossover height(coming in sooner) warrants 3 turns on a reb tube or a full stack increase on a non bypass vehicle, sometimes two stacks up on rebound valving. Thats my experience in the last couple weekends working on a few vehicles spring set ups.

If a tender and single rate was used it would be at least that much change if not more on the above applications.

I didnt take any temp data since the shocks were oversized anyhow and heat wasnt going to be an issue.

adding more to this..
Same but opposite held true for going from a single rate to a dual rate.

[BDKW1]

Well, after another stint in the race truck last weekend, I think I'll be keeping the spring rate a little lower than 400. For some reason it feels like it has way to much high speed. It transmits a lot of the initial hit through the chassis. It's still using all the travel and with the stacks we are running the only conclusion that I can come up with is the stiffer springs. This truck used to ride like a caddy. The Bronco was a good 10MPH faster through some of the whoop sections and way more comfortable.

The main issue we're having now with the Bronco other than body roll is the secondary stops are set so low to keep it from bottoming it gives a little kick as it comes off the round tube. If we could move the stop up to let off as the same time as the tube this wouldn't be an issue..........

[shockseals.com]

Well, after another stint in the race truck last weekend, I think I'll be keeping the spring rate a little lower than 400. For some reason it feels like it has way to much high speed. It transmits a lot of the initial hit through the chassis. It's still using all the travel and with the stacks we are running the only conclusion that I can come up with is the stiffer springs. This truck used to ride like a caddy. The Bronco was a good 10MPH faster through some of the whoop sections and way more comfortable.

The main issue we're having now with the Bronco other than body roll is the secondary stops are set so low to keep it from bottoming it gives a little kick as it comes off the round tube. If we could move the stop up to let off as the same time as the tube this wouldn't be an issue..........

What was the change or changes?

[BDKW1]

On the race truck? Rear went from a 2.5 C/O and a 3" BP to a 3'C/O and a 4" BP. Spring rate went from 400/500 to a single 450 rate. It also had the spares moved to the very rear on either side of the cell and the radiator moved to the rear. Also went from a 44 cell to about a 72........ Only change on the front was the springs. I think the were 500/500, now a single 400.

When we were testing in Barstow Iribe took 2 bleed screws out of the rear C/O and lightened up the rebound stack. Not sure what it has in it as far as the stacks go, I'd have to go look at the notes.


fun problems: When We were getting ready to go test before the race, the front C/O started leaking fluid in the upper cap area. Had a hell of a time figuring out where it was coming from. Turned out that the cap had cracked around the pipe fitting about level with the inside cavity top. If the hose were to tight (which it didn't seem to be) you would think that it would have cracked strait down where it's the thinnest.......

[shockseals.com]

On the race truck? Rear went from a 2.5 C/O and a 3" BP to a 3'C/O and a 4" BP. Spring rate went from 400/500 to a single 450 rate. It also had the spares moved to the very rear on either side of the cell and the radiator moved to the rear. Also went from a 44 cell to about a 72........ Only change on the front was the springs. I think the were 500/500, now a single 400.

When we were testing in Barstow Iribe took 2 bleed screws out of the rear C/O and lightened up the rebound stack. Not sure what it has in it as far as the stacks go, I'd have to go look at the notes.


fun problems: When We were getting ready to go test before the race, the front C/O started leaking fluid in the upper cap area. Had a hell of a time figuring out where it was coming from. Turned out that the cap had cracked around the pipe fitting about level with the inside cavity top. If the hose were to tight (which it didn't seem to be) you would think that it would have cracked strait down where it's the thinnest.......

Pipe thread sucks...not sure why king still uses it.

Not sure why the coilovers dont have pop off valves on rebound at all 4 corners.

The spring jumps were rather large depending on where the x overs were set. Also the increase in gas force per corner with the larger shafts on each unit is roughly 63lbs per every 100 psi per corner granted thats solely an offset to the damping curve...it still needs to be accounted for.

The increased shaft diameters will increase harshness without custom tuning. How many times did the bypasses come off the truck for tuning changes?

[BDKW1]

How many times did the bypasses come off the truck for tuning changes?

Zero....... We are only running 150PSI in the BP's.........

I'm leaning towards the tubes not being in the right place for our set-up. I think the piston sits above the long comp tube. Will have to measure. Also a little skeptical about the tubes ability to flow enough at higher shaft speeds for such a large piston.

Some of the people on the team keep wanting to set the thing on the deck to make it corner better. I tend to like a little more up-travel. The first thing Iribe did when we got there was make us pick it up 2"........

[shockseals.com]

How many times did the bypasses come off the truck for tuning changes?

Zero.......

There's your problem...hope he didnt pay king. Harshness isnt going to go away without pulling those shocks apart.

I wouldnt worry too much about the bypasses being a bit out of place, you should be able to close them off 100% and tune with valving, piston and spring cross over if you really had to.

2" is a shit ton or ride height to add and ride height is rarely operating height.

[Andy Jones]

putting together a set of 14" fox 3.0 coil overs. was wondering what a recommended spring rate would be for a Bronco with a 351w with extended ttb's and 4x4? i was thinking something around 500 lower 450 upper. but now i'm confused on length's. i haven't dealt with coil overs for a very lonnnnggg time!! so i'm a little rusty!
-Andy