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? For the coilover crowd

2322 Views 28 Replies 10 Participants Last post by  bnine
What size and rates are you running. Most I've seen on a full bodied tj are running 12" shocks with 10" 250ish over 12" 350ish with triple rate tenders.
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A 14" coilover would be ideal, especially if you could get them setup with equal amounts of up and down travel.

As for the spring rates, I have no clue.
14's in the front, 12's in the rear. Otherwise you've gotta cut into the tub or hood, and still can't get anymore uptravel. I'm just working on the rear for now. The front end will come later.
I'm running 14" 250/300 in the front and 12" 150/250 in the rear. My springs in the front are the standard 12" over 14" but to get my ride height as low as possible, with the rate I went with, I did 12" over 12" in the rear. It rides nice, but I think I may re-valve the shocks one of these days.
That's what I was told. If I wanted it low without tri rate I'd have to run a really soft spring. Then it may be softer than I cared for.

Mouse, Murphy, inline6, etc where yall at buds?
14s front and rear.

No cutting into the tub or hood required. About 5-6" of up travel. Could have more, but that would just be more ride height.

I tried these rates first, according to a bunch of spring calculators:
250/150 front
200/125 rear
Blue Coil Springs
To squishy for the street, I was into the bump stops all the time. I was also always into the second rate, the 125 and 150 would always be compressed. Triple rate option did not work either, for the ride height I wanted.

Then I made some guesses and ordered the second set of springs.
Now I run, dual rate only.
350/225 front
300/200 rear
Eibach springs
I may have them a bit different, but you get the idea.
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Mine is 14 front and rear with 5.5" up on both ends. No cutting the hood or the tub. 200 - 300 springs on both ends as the weight with the 103 wheelbase is 100 lbs lighter in the rear than the front. Perfect ride and feel for me :)
Melmo said:
Mine is 14 front and rear with 5.5" up on both ends. No cutting the hood or the tub. 200 - 300 springs on both ends as the weight with the 103 wheelbase is 100 lbs lighter in the rear than the front. Perfect ride and feel for me :)

Everyone to post here has their rates backwards.

No offense, its a very common misconception to go with lighter rates in the rear, and is accpetable for PURE crawlers.

For what we do, onroad/offroad, trail riding, hill climbing, technical crawling, etc etc, you want a slightly higher rate in the rear.

Some express it as a ratio compared to the front.

For example, a ratio of 1.2 would look as follows.

Front combined rate of 100 x 1.2 = 120lbs/inch rear rate.

Baja commonly uses a 1.6 ratio.

Pure crawlers use around 0.90

KOH and and other mixed application crowd favor something in the middle around 1.2

So take inlines front rate of 350/225 and calc the combined rate.

350 x 225
350 + 225

136 lbs/inch

Multiply x 1.2 for the rear comes to 164.34

Now you essentially experiment with numbers until your get your desired rate, of a close approximation of it.

Lets try 375/275

I get 158.65 lbs/inch

You can fine tune from there.

Once you have that dialed in, you want to valve your rear shocks slightly lower then your front. Unless you have a perfect 50/50 bias, then you could leave them equal.

The softer valving will help with smother running over mid and high speed terrain, but the higher spring weight will support weight transitions better.

When we climb, hit whoops, accell on corner, so much weight is tranfered to the rear of the vehicle. The additional spring rate back there helps compansate for that weight transfer.

Thats why the Baja run such a high ratio. If they didnt, the back end would sink to hard every time they went into a whoop, and then the front end would lurch forward after. Basically turning the truck into a bucking bronco.

If you make those subtle changes to your set up, you will feel a noticeable difference in handling and performance.

Just as an example, when my good freind competed at KOH, he had a tuning day with King. He runs a 1.2 spring ratio, and equal valving front and rear.

All king did was dial down the rear valving by about 1 setting, and Joey grabbed about 10-15mph more through the same section.

Essentially this is the basics of a good all around setup.

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Hey Man, good to see you around these parts again. Hope you've been doing well. How did the wife's new rig turn out? Any pics? Hope you drop by more often as you have time. Take care of yourself, and have a very Merry Christmas.

Best of Luck,

Yes it does bud. I appreciate your input. Thats why I'm asking, to get a ball park of where to start. My buddies rig(trying to keep it simple one ton tj [Rkik] on pbb) I'm comparing to runs 12" 200 over 14" 400 on the front and 10" 250 over 12" 350 on the rear with tri rates. His is dialed in and just embarrasses alot of other rigs that have way more money in them. He's got 5.5" stretch in the rear and 8" in the front. I'm looking at another inch or so on the rear, but undecided.

I almost died laughing when that guy on pbb questioned your knowledge pleading leafs were better and you didn't know your stuff. Please come back with your knowledge more often, this site needs yall to stick around.
I have thought about swapping them front to back to see how it rides. All a bunch of experimentation on my part.

bnine, good info

So if I reversed them I would go to a 120 - 136 or close to the desired rate of 144 for the 1.2 ratio. If I understand correctly.

Now the real question, what spring rates should I run?. What are the good rules of thumb to determine the lbs/inch ratio needed.
Thanks bnine, that is great info!

Let me make sure I am understanding you correctly using my exact setup as the example. Not all this information will probably matter but since I don't know for sure what will and won't I'll give it all to you.

Wheel Base = 103" = +7" rear and + 3" front
Front weight = 2,400 lbs
Rear weight = 2,280 lbs
FOA 2" x 14" Coilovers valved Light compression, medium rebound
2" Air Bumps
5.5" up travel
8" down travel (limit straps 1/2" short at each corner)
Lower Springs 16-300
Upper Springs 12-200
Front LCA length = 38"
Rear LCA length = 36"
Three Link + Panhard Front
Upper triangulated four link rear

The following is based on the triaged 4 link calculator ver 3.1 and an estimated CG height of 40", with 500 lbs front and 400 lbs rear unsprung weight:

Static anti-squat = 85%
Roll Center = 26"
Roll Axis = 0
Instant Center X-Axis = 69"
Instant Center Y-Axis = 24"

Continued in next post...
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300 x 200
300 + 200

120 lbs/in x 1.2 = 144 lbs/in or

300 x 275
300 + 275

143.47 lbs/in correct?

Then, does the adjustment of when the dual rate stop come into play calculate into this as well? I currently have my rear dual rate stop comming in at about 3" of compression, along with the 2" air bump whereas the front dual rate is about 1" later. Or does that not really matter at all?
inline6 said:
Now the real question, what spring rates should I run?. What are the good rules of thumb to determine the lbs/inch ratio needed.
I actually used the calculator on FOA's website to come up with my rates. I think it worked out pretty well, maybe give it a try
This is turning out to be a good thread. :D thanks guys
sleepsontoilet said:
This is turning out to be a good thread. :D thanks guys

Getting some good tech here. I'll be keeping an eye on this one for some future changes.

Thanks bnine, Inline, Melmo for your info here-this will be very useful for many folks I'm sure.

Sleeps-good luck, hope you get what you need.

Best of Luck,

I am definitely tagging this thread. :)
Im definately no expert. I have a basic understanding at best, via some trial an error with me and some freinds and a lot of advice from the more informed folks like Blaine.

Spring wise it really depends on the individual user and the rigs application. Pure crawlers love those low rates. 150/250, 140/275 etc etc.

Desert folks favor the higher stuff. 375/425, 250/375, etc etc.

Personally I tune springs like a swaybar. I try for as much rate as possible without sacrificing articulation. Like a swaybar, you crank it up until you lose some travel, and then dial back just a bit.

The numbers of course will change from rig to rig based on weight.

For my rig, I've found that to be in the middle road. Right now I am still a bit soft with 175/250 up front, and 275/200 in the rear. I think I can take everything up about 10-15% and still get away with it. I switched to FOA's last year, and the tuning in my suspensions was severely thrown off from the previous set up. Mostly due to some really soft valving.

Your rig sounds similar to mine Mel. I will probably finish with rates closer to your. If you want to experiment with that rear rate, I would suggest keepimg some variation between the top and bottom rate.
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