I bet if I were to replace the bottom 12”/100lb springs with some 16” long springs and the top 12” with some 10” springs the crossover will come in better range of operation.

The shocks have 31” eye to eye.

Threads start at 2.5” and the body only threads down to 10.5”. ( 8” of total thread)

Make sense?

I was kinda thinking that way as well when I looked closer at the shock. l will work on the numbers tommorow and see if I can get something posted. Maybe get some more info before ordering springs incase a change in rate will better suite the machine.
Since your going to be able to use the cross over and like the combined rate. A different combo may work and help in body role at crossover to a stiffer rate.
As you work on this there is few things you can do to help if you get out and ride.
Raise up the bottom out bumper to the shock body and do some turns at different speed on flat ground so bb does not effect the bumper position. Then increase speed until excessive role is felt. Then measure the shaft distance to the bottom of the bumper then rest and test. Then we can see at what rate and position it gets upset. Then we can set the poundage and crossover to help with roll stiffness since there is no low speed adjuster.
This one example of what the math can do.
Once we get some role stiffness in it we can look at front caster and it's effect on the push.

You can also use this method for acceleration out of a cornor and start. Then we can see the effect on the front end weight change. AKA traction forces. We can see if to much is being removed from the front via soft springs or fast valving or both. It would be good to know if when it bottoms out your using how much of the travel. Same trick or remove spring pack and suck it down and see.

I think you can do the same/similar thing with some zip-ties around the shaft.

Hmm.. Getting roll stiffness is going to take me probably 2 weeks. Also is pretty hard for me to do I think unless I do it in my street. I'll try but it may be a few days before I can test that out. Offroad is going to be bumpy and not accurate. I was actually hoping to order better springs before then and install maybe even before my next trip.

I can tell you this; the body roll is really very bad in the rear. Its even causing the front to tilt as well. Almost needs a sway bar its so bad. Same as when it bottoms out as well. Seems like the springs have too much soft give that the machine keeps rolling, and bottoming out seems like the spring is endlessly traveling until the skid hits the ground (2 times then I stopped what I was doing).

need a few numbers
the distance of thread
distance from separator to threads at ride height and fully extended.
I need this for base calculation of COP or cross over poundage at what shaft length.
Thank you

Here is what you have as a base line.
Assuming the there is no cross over to main spring.

Currently the crossover plate can go down another 2"

The other measurement is 4.3" at ride height, and 5" fully extended.

Hope this helps?

Did some numbers for you to start with.
At 7" crossover point. In lbs
COP=3.11
BOP=811

At 5"
COP=222
BOP=922

At 3"
COP=133
BOP= 1022

You cop point is where you go from 44.5 to 100 lbs rate of shaft travel
You spring travel rate per inch is
Top=.556
Bottom=.445

The BOP is based on using full 12" shaft

so if take the 44.5 x 7 this leaves you 5" of shaft left @ 100 + Cross over poundage (COP)

I will next check the spring specs and compare to these numbers for issues.
After wards I will graph it out (plot)
This way we can look at different set ups
I feel the way it is you will need a sooner crossover as long as its not to soon to provide harsh ride
Further testing as discussed will aid in decision.
One issue with the 12" 100 rate and sooner crossover may be a spec issue under full compression.

spec on the 100 main

not good news once you factor in the 3.115 then add 5 for a total of 8.115

I once had a pogo stick when I was a kid. At first I weighed nothing and couldn’t use it. Then I grew a little heavier and was then able to pogo for years. Then one day I stood on it and the thing bottomed out and would not spring me at all.

The pilot feels like a pogo stick with a spring designed for a 10 year old kid but the pilot weighs as much as an adult.

springs are not cheap, I like your idea of making some cross over spacers, maybe some 2" PVC? maybe also check with King and Fox to see if they have such an animal, Dave Co seems to use the same spring rate on the 3 cars I know of and other than bottoming, good reports from all. I have 100/125 on my LT, it dunes good but doesn't do the woops very good, still working on it, I'd check the inexpensive stuff before buying new springs.

I am doing my best to follow along and understand everything you guys are talking about with the springs and crossover and the measurements and calculations. I'm still unsure the solution. Is it as simple as new springs? I'm sure that those shocks are really nice and probably expensive. Is this something that could be retrofitted with a Fox air shock?

Kuma,

Whats wrong with it? Are the 125s too stiff once the crossover pulls the 100 out?

with the 12" spring watch your cross over point if you do any at all the primary spring will block. ouch

Can you see if an 8” 150lb spring on top with a 18” 150lb spring on bottom would work for calculation? Assuming crossover will cut the 150, but until that point the spring load would be —~75 then jump to 150 at crossover.

Or try with a 10” 150 top and 16” 125.

Also I just ordered a foot of 2" Nominal 6061 Aluminum Schedule 40 pipe. It should be 2" ID, 2.35" OD, and 0.150" thick. I'm going to cut it to a 5" length and use it to get the crossover plate in-range with 80/100 springs. I'd like to test this BEFORE I go and order $300+ worth of springs.

I don't think that the springs are rebounding like they should be after hitting the first woop, I have re-valved the rebound, I believe I'm at 30, I have the DSC adjusters which are for compression but it may be possible that they are also restricting the flow back to the shock on rebound? I'm going to try to increase the rezzie pressure to 200 and see if that helps to force out the oil and hopefully doesn't mess too much with the compression.

Rebound is it too fast or too slow? Bouncy or packing? Are you using the crossover plate on your 100/125? Presuming these are 12" springs.

SOOOO I just got off the phone with Polyperformance. They're trying to help me figure out a good spring weight as well. One thing they mentioned which makes sense is I need to subtract the weight of the wheels from the corner weight. Wheels are unspruing - which means when the machine hits the ground, the wheight of the wheels is supported by the ground and not the shocks. My wheels weight 30#ish.

Wheels are "unsparing" = unsprung

Well done as usual adnoh!

Question:Spring Stack length at ride position (Sagged with weight)
20 & 6/16 | 10 & 6/16
Did you mean 10-6/16 in lieu of 20 & 6/16
OR:
Left 20-6/16 and Right 20-616 for stack with weight at ride height.

I would also assume you have some pre-load cranked down on the spring stack.
The spring spacer is ? usually a 1/4 inch i will reread.
Working on it now try to post up something as I go.

have another question see pic.
what you may be able to do if room allows is buy one spring longer and have the two others for dialing in.

worked on pre-load poundage a bit.

please correct me if i am wrong.
I took the extended stack number of:
top: 10-11/16
bottom 10-15/16

= 20-26/16 or 21-10/16 or 21.625

if I add the 1/4" (4/16 or .25) spring spacer the stack has a total length of 21.875"

If we take the 2-12” spring and ad the ¼ in spacer we have 24-1/4 or 24.25”
Now we take the 24.25-21.875=2.375” of pre load on the spring set
At a combined rate of 44.5 x 2.375 we get a pre-load poundage of 105.6875 pounds
Now we can add that to the base line BOP

I took the shocks off and let the machine all the way down. When the rear end skid touched the ground I measured shock mount distance between top and bottom. That number is 19".

So, the machine bottoms out when the 31" shock compresses to 19". The shock when compressed down to the bump stop actually measures 19.25" compressed. This means at full down the shocks are likely hitting the bump stop; but I'm thinking that I'm hitting the ground hard still because of 2 things -

1 the ground between the wheels must be higher than where the wheels are landing. Makes sense on the jumps I was making given that many machines land the same way. The ground looked flat though.
2. The tires may be compressing when all that weight comes down on them, meaning the rear end is getting lower than the bottom of the tires on full weighed compression.


I ordered a hand-full of 1/2" 7/8 shaft bump stops. I'll likely try bottom bump stop adjustment again when I have them - next time I'll do it without springs. Maybe I'll add about 1/2 to a full inch in cases of #1 & #2 above.



I know you are doing calculations, but I went ahead and ordered 4x new springs. I ordered a set of 10" 175lb springs for the top, and a set of 16" 100lb springs for the bottom. Effectively that should give me 68.75lb before the crossover, and then 100lb below it. It should also give me plenty of adjustment setting for the crossover; effective rating should be adjustable between about 1050lb and 1270lb at full compressed and that is including preload.

I can change this order tomorrow morning if I am WAY off. I may also be able to use the new 16"x100lb springs with my current 80 or 100lb spring if I've over-shot.