few coilover questions

Man y'all are flying down the rabbit hole.....

You don't NEED scales...

You CAN and SHOULD buy/ borrow two matching, KNOWN WEIGHT, used springs regardless of length; but I would buy them 2" over or matching the length of travel of the shock. You may get lucky and they'll be used for final...

Block the front suspension at ride height- where the coilovers mount will be the most precise, put springs on the rear (one per side) adjust to level with slider and pre load stops. Measure the shaft at full extension and at ride height... do a little math, and you WILL know the exact weight that EACH spring is seeing....

Repeat for the front...


Read the spring theory thread on pirate by Zukizzy- aka Wayne izrealson.

.... it may help for you to read it half a dozen times....


With this method you don't have to worry about shock angle or any other variable. Corner weights are not as accurate, because of that variable of shock angle!


Edit: missed scotty's post, but this is the dumb down version...
 
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mcutler said:
Corner weights are not as accurate, because of that variable of shock angle!
Click to expand...

Until you do simple math. :D

The benefit of using springs of known rate (for measuring weight) is that you conveniently sidestep having to deal at all with unsprung mass, which definitely has its advantages.
 
Mac5005 said:
The primary spring (bottom) should be 2” longer than the shock travel so that the dual rate stop nuts are in a useable section of travel in their threads on the shock body.

Generally these crossover rings/dual rate stops are around 2” above the dual rate slider at ride height.

Not all shock bodies are fully threaded, but you want the dual rate slider to at least have a chance to his the dual rate stop rings. The easiest way to have them have a chance at this, is with 2” longer than shock travel main springs, and secondary springs equal to shock travel. This doesn’t work for all shock manufacturers. Some shocks require an even 2” shorter upper spring. Brand, age, size, and shock series/model are all different. This is the closest generalization there is.

You tune the height of these crossover rings to set the position at which the spring rate steps up from the combined rate(both springs active) to only the main spring active.

This can help with body roll/corner handling/bump and g-out control, etc.

Here is an example of spring rate math.

Let’s say you have 250/350 lbs springs. (Primary * secondary)/(primary + secondary)

At ride height the combined rate is 146 lbs per inch. Once the suspension is compressed and the dual rate slider hits the crossover rings, the secondary spring is no longer active.

The spring rate increases to the main rate of 350 lbs per inch.

The basics:

In the same example, let’s say at ride height on a 14” shock, 7” shaft exposed at ride height.

The 250 lbs 14” spring is compressed 5”, and the 16” 350lbs spring is compressed 3.5”.

The actual load at the shock is 1250lbs.

This can also be confirmed by adding the spring compression amounts, and multiply by the combined rate.
8.5” compressed x 146 lbs = 1246 lbs at shock. The 4 lbs “load at shock” difference is due to a rounding issue with decimal points and doesn’t matter.

(this removes the trig problem involving shock angles, removes necessity to have corner weights, removes needs for accurate upsprung weights).

If to get that desired suspension at 7/7 split at ride height or the shock at center of its travel at ride height, required 2” or preload, then you have the correct spring weights.

If you need more than 2” of preload, to achieve that desired ride height position, then the springs are too soft.

If you needed less than 2” of preload to achieve that ride height, then the springs are too stiff.

Variances in weight from left to right are a non issue as you can easily adjust preload by small increments to make up for the difference.

As I have stated several times. Rent/buy/borrow some correct length whatever known rate springs and install. Set to ride height, and measure actual preload. If you do this, and post the results, variables, and measurements I will be glad to help you with the math.

Or

Do some math, or use my calculator or any of the 10 others on the internet, to calculate to correct rate springs with the correct preload and desired ride height position.

This is the easiest, least labor and thought intensive, and probably cheapest way to get the correct springs.
Click to expand...
Didn't you start a real tech page on links and such....??

Me thinks you could publish this knowledge in a condensed gear head approach.

I'd like the first Autographed copy.
 
Fabrik8 said:
Until you do simple math. :D

The benefit of using springs of known rate (for measuring weight) is that you conveniently sidestep having to deal at all with unsprung mass, which definitely has its advantages.
Click to expand...

It's not a side step, it's skipping an unnecessary step. The springs don't give two shits about unsprung weight, has no bearing on spring selection, aside from trying to figure corner weights from a gross weight; which as I stated earlier isn't as accurate, due to the angles of the shocks, as setting the actual load on the spring.



Sent from my SM-G892A using Tapatalk
 
mcutler said:
It's not a side step, it's skipping an unnecessary step. The springs don't give two shits about unsprung weight, has no bearing on spring selection
Click to expand...

That's what I was saying. "Conveniently sidestep having to deal at all with.." is basically saying "skip". That's why it's convenient, and a benefit. :D
 
mcutler said:
It's not a side step, it's skipping an unnecessary step. The springs don't give two shits about unsprung weight, has no bearing on spring selection, aside from trying to figure corner weights from a gross weight; which as I stated earlier isn't as accurate, due to the angles of the shocks, as setting the actual load on the spring.



Sent from my SM-G892A using Tapatalk
Click to expand...
Dave Whitely knows all too well about this!

The angle of the dangle plays enormously with the end result.
 
WARRIORWELDING said:
Dave Whitely knows all too well about this!

The angle of the dangle plays enormously with the end result.
Click to expand...
Especially if the top weighs about the same as the bottom[emoji6]

Sent from my SM-G892A using Tapatalk
 
WARRIORWELDING said:
Didn't you start a real tech page on links and such....??

Me thinks you could publish this knowledge in a condensed gear head approach.

I'd like the first Autographed copy.
Click to expand...

I started a thread a while back, but life got in the way of finishing it.

Lost steam and my stream of consciousness to finish it.

I can’t claim any ownership of any thoughts. I just regurgitate the info from those smarter than me.

I have terrible reading comprehension but I’m stubborn enough to keep reading until I understand it.

If I ever put something together, you’ll get the first real copy.

I’ll help anyone who wants help and has an open mind. I don’t hold any information or knowledge hostage. I’ll share it with anyone who wants to listen or learn.
 
Mac5005 said:
I started a thread a while back, but life got in the way of finishing it.

Lost steam and my stream of consciousness to finish it.

I can’t claim any ownership of any thoughts. I just regurgitate the info from those smarter than me.

I have terrible reading comprehension but I’m stubborn enough to keep reading until I understand it.

If I ever put something together, you’ll get the first real copy.

I’ll help anyone who wants help and has an open mind. I don’t hold any information or knowledge hostage. I’ll share it with anyone who wants to listen or learn.
Click to expand...

I am very visual when it comes to mechanics but extremely adept at following a plot in a story line. I have to re read stuff like you post as gazzillion times and often sketch it out to grasp the whole.

It is why i was a constant sketcher while teaching welding or fab......the booth walls became story boards for all sorts of points.
 
mcutler said:
Man y'all are flying down the rabbit hole.....

You don't NEED scales...

You CAN and SHOULD buy/ borrow two matching, KNOWN WEIGHT, used springs regardless of length; but I would buy them 2" over or matching the length of travel of the shock. You may get lucky and they'll be used for final...

Block the front suspension at ride height- where the coilovers mount will be the most precise, put springs on the rear (one per side) adjust to level with slider and pre load stops. Measure the shaft at full extension and at ride height... do a little math, and you WILL know the exact weight that EACH spring is seeing....

Repeat for the front...


Read the spring theory thread on pirate by Zukizzy- aka Wayne izrealson.

.... it may help for you to read it half a dozen times....


With this method you don't have to worry about shock angle or any other variable. Corner weights are not as accurate, because of that variable of shock angle!


Edit: missed scotty's post, but this is the dumb down version...
Click to expand...


Get out of here with your common sense BS. Can't you see that we're trying to derail a thread?
 
From personal experience, I can say the measured weight using springs will vary greatly depending if your shocks are new or not.

Big difference too if you let the weight settle down on the springs or if you compress them and let them go up to their final position.

Do not forget the nitrogen charge.
 
Bebop said:
From personal experience, I can say the measured weight using springs will vary greatly depending if your shocks are new or not.

Big difference too if you let the weight settle down on the springs or if you compress them and let them go up to their final position.

Do not forget the nitrogen charge.
Click to expand...

While those are valid points. I doubt either will make much difference in JF setup considering the mass he is describing.

Yes the Stiction of the seals makes a small difference, as so does the displacement of the shaft volume, but in most setups, isn’t enough to matter.

To a rig with Uber light sprung mass, it makes a large difference, but I consider that an anomaly setup.

Those small variances can be adjusted with small variations of the final preload.

Once installed, I jump up and down on the rig to get it settled. Also can rock side to side.
As well the shocks should be charged with manf. Recommended psi n2, or 200 psi.

While on this, also make sure no links are in a bind and driveshaft slip joints aren’t binding and holding the vehicle up, when letting the vehicle back down to ride height after spring and shock install
 
Mac5005 said:
If to get that desired suspension at 7/7 split at ride height or the shock at center of its travel at ride height, required 2” or preload, then you have the correct spring weights.

If you need more than 2” of preload, to achieve that desired ride height position, then the springs are too soft.

If you needed less than 2” of preload to achieve that ride height, then the springs are too stiff.
Click to expand...

Where does that 2" of preload number comes from, if you don't mind sharing ?

Mac5005 said:
While those are valid points. I doubt either will make much difference in JF setup considering the mass he is describing.

Yes the Stiction of the seals makes a small difference, as so does the displacement of the shaft volume, but in most setups, isn’t enough to matter.
Click to expand...

It did make a big difference on my rig. Maybe because I have 2 shocks per corner ?

My springs are way off, and I did follow the "correct" way to measure sprung mass with the springs of a known rate.

After driving it around for a couple days, springs have settled and the seals are worn in and the measurements are completely different while following the same procedure.

I have a V8 rig on tons and trailing arms. Not uber light by any means.
 
Mac5005 said:
While those are valid points. I doubt either will make much difference in JF setup considering the mass he is describing.

Yes the Stiction of the seals makes a small difference, as so does the displacement of the shaft volume, but in most setups, isn’t enough to matter.

To a rig with Uber light sprung mass, it makes a large difference, but I consider that an anomaly setup.

Those small variances can be adjusted with small variations of the final preload.

Once installed, I jump up and down on the rig to get it settled. Also can rock side to side.
As well the shocks should be charged with manf. Recommended psi n2, or 200 psi.

While on this, also make sure no links are in a bind and driveshaft slip joints aren’t binding and holding the vehicle up, when letting the vehicle back down to ride height after spring and shock install
Click to expand...

For what it's worth, I could set the jeep or the bronco down 10 times each and get a different height each time on every corner with c/os all around. He has a valid point, especially when if is talking about 400lb-in springs. There's nothing wrong with either method, I just like actually weighing things.

All of that being said, it's still a second gen Cummins and there is plenty of empirical data out there on the web as to where he should start.
 
Since no one read it the first time...
jeepinmatt said:
None of this matters. Youve got 10"+ travel and worn out springs with inconsistent tire pressure. Also, drivers side will be heavier because the diff housing and steering column are on that side. And years of ass sweat in the driver's seat.

Just use the 7600lb weight from the other thread, 3000lbs for the rear, 4600 for the front. Minus unsprung weight, you're at 2450 rear, 3900 front.

Or spend a bunch of time and effort weighing and checking, and then ruin it all with some other ignorant halfassery.
:popcorn:
Click to expand...
 
Bebop said:
Where does that 2" of preload number comes from, if you don't mind sharing ?



It did make a big difference on my rig. Maybe because I have 2 shocks per corner ?

My springs are way off, and I did follow the "correct" way to measure sprung mass with the springs of a known rate.

After driving it around for a couple days, springs have settled and the seals are worn in and the measurements are completely different while following the same procedure.

I have a V8 rig on tons and trailing arms. Not uber light by any means.
Click to expand...



1-2” front preload and 2-3” tear comes from Wayne isrealsen.



As far as two shocks per corner and trailing arms, that’s a slightly different setup with its own anomaly’s.

All of my statements are generalized and all include major anomaly’s.

Also consider that I’m talking about a good all around setup that generally splits the shock travel at ride height. Cone dodgers, rock bouncers, monster trucks, u4 all have slightly different characteristics that are important.

As far as yours bebop, the actual sprung mass, vs compression ratio of the shock, motion ratio, etc all matter.

It definitely matters more to you, as the stiction of double the seals/shocks starts to add up.

Also if running larger shafts starts to matter as far as displacement volume.

This is why if you can get away with smaller shafts, it’s always a good idea, bc of less stiction to affect the dampening, and less displacement volume.

As the stiction amounts and displacement volumes increase, the proportion of those values to spring force, start to increase, making them more important issues.

So what I should have said:

It’s a non issue, until it is. Lol.

This would apply to multiple shocks per corner, larger diameter shafts, relatively light sprung masses compared to stiction and displacement volumes, as well as Uber light rigs with minimal sprung mass.

Most of my points in this thread are to JF Marty and his work on this said dodge?

In my mind, JF is using 2.5” emulsions? On this dodge?

Edit: removed frequency bc it only makes this discussion worse.
 
Last edited:
braxton357 said:
For what it's worth, I could set the jeep or the bronco down 10 times each and get a different height each time on every corner with c/os all around. He has a valid point, especially when if is talking about 400lb-in springs. There's nothing wrong with either method, I just like actually weighing things.

All of that being said, it's still a second gen Cummins and there is plenty of empirical data out there on the web as to where he should start.
Click to expand...

If we are discussing the best, id say install,

Drive around enough with enough action to get the shocks warm, then park on concrete. Then jack up the axles evenly f/r and l/r to get the tires off the ground barely, so links/drivetrain are in no bind and return to the concrete.

Also needs to have driver and passenger strapped in, will all tools and parts, and full of fuel.
 
If we are spit balling that JF need a 400/ in combined rate, and the shocks at 7up/7down.

At zero preload Quick dirty math nets 2800lbs per load at each front shock. So 5600 lbs supported by front shocks at ride height.

(This isn’t 100% accurate just quick easy #’s)
 
Mac5005 said:
In my mind, JF is using 2.5” emulsions? On this dodge
Click to expand...
yes their 14" Fox 2.5s
and I'm reading through all this and trying to grasp all this knowledge and math that I've read here and elsewhere to put it all together in a final starting point.
Mac5005 said:
If we are spit balling that JF need a 400/ in combined rate, and the shocks at 7up/7down.

At zero preload Quick dirty math nets 2800lbs per load at each front shock. So 5600 lbs supported by front shocks at ride height.

(This isn’t 100% accurate just quick easy #’s)
Click to expand...
that's in the ballpark of my figures for starting point. 450lb lower springs, 200lb upper springs to start. That is ballpark enough to get me to be able to mount/mock up everything and see how things look/feel/need. I will be talking to the Accutune guys anyways when ordering springs this week and I'm sure they will give me their feedback on my order as well.

Don't anyone think I'm ignoring the advise here...I am very thankful. I do however struggle with reading comprehension pretty badly. If I was being taught this hands on, I would probably learned all this much easier and quicker since I learn visually (and videos don't always succeed either lol). I just never acquired a comprehension of English language hence why me and school don't work haha.
 
mcutler said:
I would buy them 2" over or matching the length of travel of the shock. You may get lucky and they'll be used for final...
Click to expand...
so this was my initial question in ordering springs...for the bottom to be 14" or 16"?? seems you have confirmed to run longer bottom spring for starting point? am I correct, thank you
 
marty79 said:
so this was my initial question in ordering springs...for the bottom to be 14" or 16"?? seems you have confirmed to run longer bottom spring for starting point? am I correct, thank you
Click to expand...
Yes, 2" longer than shock travel on the bottom, same length as shock travel on the top... most of the time.

Sent from my SM-G892A using Tapatalk
 
mcutler said:
Yes, 2" longer than shock travel on the bottom, same length as shock travel on the top... most of the time.

Sent from my SM-G892A using Tapatalk
Click to expand...
thank you very much, that's what I came up with but was difficult to confirm since not every tech article or video fully covered that aspect of setup.
 
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