Valving and spring rates

Well the jeep is apart and i am going to be putting some 14" coil overs on the front, the jeep has a full traction long arm kit, dana 44 and 33s that will eventually be going to 35s. I love crawling but want to be able to keep up with some of my go fast friends, so i want the best of both worlds. Basically im looking for suggestions on spring rates and valving. Thanks, and a quick pick you so can see how it sits.

I was sure happy with stiff front springs and the poly coil inserts for going fast. I got a pair of coilovers for the front but never put them in.

What do you plan to do for front bumpstops with the C/O's?

What are you going to do to the rear so it can keep up with the front?

The Jeepspeed guys are fast without C/O's and with 10" of travel. Not trying to talk you out of it, but what is your plan to make the C/O's work better?

What steering will you have to handle the 14" shocks?

Just getting the discussion going, and figuring out what all you're doing.

Each shock company uses a different designation for their shock valving, so you can't compare one company's valving to another, unfortunately. What shocks do you have?

For spring rates I'd probably start with something like 200/325 or 200/350. The Deaver Jeepspeed progressive coils are 250/300, but you'll have a lot more travel to work with and can start out softer, but then it would be good to get harder since the Jeepspeed guys mostly run air bumps which add some spring rate at the last few inches of travel. On my buggy, which would be a little lighter than your XJ, I run 12" shocks with 175/300 springs.

Thanks Richard, i really dont know too much about this stuff this is why i started the thread just to get people talking and get ideas started in my head im definitely going to be started with the front for now and the rear will have adjustments too, to be able to keep up with the front. I actually have dave taylors old dana 44 and im gong to be running the heim steering that came with it also.

I don't think the Deaver coils are that stiff, unless they changed them over the past few months. Last time I talked to Deaver about coils they told me 250/200. We run a Rubicon Express coil that has a rate somewhere between those (team secret) and 1714 (current points leader and last year's champ) team runs the same coil.

How are you going to mount those C/O's? You are going to have to cut open your inner fenders and fab some type of upper mount.

Mine spring rate is 175 rear and 200 front and Im satisfied and only have 10" so you with 14" travel Id say you would be fine to but deaver race coils are 225 or 250, I'm not sure if there are any benefits of going stiffer other than being able to land bigger air

How are you going to mount those C/O's? You are going to have to cut open your inner fenders and fab some type of upper mount.[/QUOTE]

Yes i was planning on doing something like this.

On the Deaver spring rates, I was going off of the Currie Jeepspeed coils that were made by Deaver. Currie specs on them were 250/300, but it's been quite a while since I looked.


I can see going to coilovers if you're installing a new front axle. I don't remember if that axle has any coil pockets, or if Dave already had air shocks on it then.

What about bump stops? What are you thinking?

Are you considering air shocks at all? Will this be mostly a DD, or mostly trails, or mostly fast desert stuff? For street and trail, and non-racing desert stuff, the ORI's are a pretty good choice. Since you want to discuss, might as well see what your goals are and talk about how to get there. You need to give us a little more info.

Well it is a dd/trail rig leaning mostly towards crawling but i also want to be able to go fast, about bump stops i was planning on running some air bumps. Dave old axle has lowered shock mounts, just for longer shocks i believe, maybe he will chime in here. Basically im just trying to get ideas and info.

What are the pros and cons of air shocks/Struts?

You need to protect the valves from impacts:doh:

karstic said:

You need to protect the valves from impacts:doh:

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lol haha i was there!

karstic said:

You need to protect the valves from impacts:doh:

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(we really need flipoff smileys)











I'll post up some more comments when I get more time.

On that axle I was running 4.5" rubicon springs with a 3" spacer on top. The spring were to soft for the go fast stuff. I had T&J upper shock mounts(the kind you weld in)on the frame. The axle mounts were moved down so I could run a
12" 7100 remote res short body shock.

It's a nice axle with all the good stuff.

I would run an 2.5 air shock over a coilover anyday. But Hay, that's just me.

Thanks for the input dave, now i have more to look at and more research to do

01 XJ CHEROKEE said:

Well it is a dd/trail rig leaning mostly towards crawling but i also want to be able to go fast, about bump stops i was planning on running some air bumps. Dave old axle has lowered shock mounts, just for longer shocks i believe, maybe he will chime in here. Basically im just trying to get ideas and info.

What are the pros and cons of air shocks/Struts?

Click to expand...

2" coilovers with dual spring hardware, springs, and air bumps and cans are $735 on Poly performance's website. ORI Struts are roughly $600 and include internal bump stops.

Fox shocks come with a set valving, I think it's 80/50, and you can valve them differently, of course, and it's not too hard to do. But you do have to take them apart to change the valving, then refill with oil and recharge the nitrogen. You can adjust the ride height with the c/o with the upper collar, and you can adjust the secondary collar to set the transition from primary to secondary spring rate. Adjusting the transition point can effect the handling and bottoming resistance and it's easy to do. Like a normal air shock, on climbs, drops, and side hills the c/o will extend all the way to maximum extension (pushing off) when weight is removed from weight transfer, effecting stability and performance. To avoid this a triple rate kit can be used, which uses shorter springs and a third (tender) coil that has little to no spring rate. The tender coil applies some pressure to the other springs to keep them in place when the shock extends all the way, usually 4 to 5 inches more than the extended length of the regular springs. This allows full droop but also means there is no spring force for the last 4-5" of extension, so no pushing off. The triple rate slider and tender coil add to the cost.

The ORI struts are air shocks with quite a few added features. The core of the design is that there is rebound air/spring rate as well as compression air/spring rate. The rebound air resists full extension, so no pushing off. They also are incredibly stable since they have air on top and on bottom, basically trying to keep the shock at ride height. Since you can add and subtract air both top and bottom there is a tremendous amount of adjustment available without even removing the shock from the rig. Ride height is set by balancing the air top and bottom, so you can make them stiffer or softer by simply adjusting air pressure. Add a little air to the top, which raises ride height, then add a little to the bottom which brings ride height back down and the shock is overall stiffer. The stability of these things is amazing, doesn't lean on sidehills and corners like a go cart. There also is an external adjustment for rebound valving, just like a Rancho 9000 or Pro Comp MX6. To really fine tune them, the viscosity of the shock oil can be changed to effect valving, and the range of the external rebound adjustment can be moved up or down (stiffer or softer). I have different from stock viscosity oil in both my front and rear ORI's, and the range of rebound adjustment has been changed in the rear. They also function similar to a bypass shock, as there is no valving in the middle couple inches of travel, just air, then the valving (oil) kicks in, and they have internal hydraulic bumpstops for both compression and extension (no limit straps are needed). So, they have both a very cushy ride and great stability.

Coilover spring force as they compress is linear, with a step increase at the transition point between primary and secondary rate. If the primary rate (both springs together) is 100 lbs/in, then the spring force increases by 100 lbs every inch, 3" of compression and the overall spring force is 300 lbs. If the secondary spring (lower spring) is 250 lbs/in, then spring force increases by 250 lbs every inch once the transition is made. For an example, if the primary rate is 100, and the secondary rate is 250, and the transition is made at 3" of compression, and there is 6" of total compression, then the total spring force at full compression will be 300+750 or 1050 lbs . If you moved the transition collar up an inch, then total spring force at compression would be 200+1000, so 1200 lbs.

BTW, the primary rate (rate of both springs together) is calculated by multiplying the two spring rates, then dividing that number by the sum of the two rates. For example, the primary rate of a 200 lb/in top spring and a 300 lb/in bottom spring would be 60000 divided by 500, or 120 lb/in. 200x300=60000 and 200+300= 500. The secondary rate is simply the rate of the lower spring. Once the transition collar is hit, only the lower spring compresses further. So, in this example the primary rate would be 120 lbs and the secondary rate 300 lbs.


Now, on an air shock the increase in spring force isn't linear, it's progressive and actualy exponential. The spring rate is determined by compressed air, and as the shock compresses the air chamber holding the air decreases in volume accordingly and the pressure (and spring force) ramp up very rapidly. The spring force of an air shock at full compression will be many thousands of lbs. This massive ramp up of spring rate and spring force is what gives the air shock it's characteristics, a cushy ride and yet tremendous resistance to bottoming. An air shock is simply a very long air bump. Tuning an air shock (regular, not ORI) involves changing the oil level and the air pressure, and changing the valving (similar to a c/o).

Hope this all helps. I've been cleaning carpets all day and this is a way to unwind and relax.

Not to hijack this thread, but it got me thinking. I have BDS stuff on my XJ with their 4.5 inch LA kit. It feels really stiff to me. I asked them what the spring rates were and they said 240 front, and about 10% over stock for the rears. I feel like the rear is very stiff. I also have their gas charged shocks which should (?) be making the ride feel stiffer. Would my jeeps go fast (recreationally) ability be improved by softer springs, or do I want some better shocks to control the bumps. Will some Bilsteins help me out, or should I start saving up for the Deavers? thanks!

edit: I also have prothanes up front, and large daystar bumpstops in back inspired by threads...and the rear BDS springs are 3-inch springs with 7 leaves (although one is an overload spring)