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Bilstein 7100 custom valving - leaf springs

Location
Smash HQ
To start my rig is a full bodied, full width, not exactly light pig. Around 4500 lbs me in it. I originally started with 255/70 valved 5125s in the rear mounted vertically through the floor. I changed my front end setup and started to get into the go fast thing. I've got the front perfectly set up with some Profender 2.5's but the rear was lacking, specifically in the compression department. I ordered up some Bilstein 7100 short bodies in 360/80 valving.

This improved the rear dramatically but I'm still lacking in the compression. The rear bottoms way too easily compared to the front. I've got about 5" of uptravel and progressive poly bumps.

Researching online it seems most leaf sprung go fast rigs run extremely light on the rebound, something I'm not anywhere near. Would I benefit from dropping the rebound to say a "180"? Or should I bump the compression up to "135" or "160"? Or change up both?

The leaf pack I'm running is a relatively stiff 7 leaf custom pack. I don't think its a spring problem, but more of a heavy crawler trying to jeepspeed.
 
I'm just staring to work on my Jeep's valving but I've raced/tuned more than a few 1400 trucks. Problem number 1 is up travel. I don't know what size bumps you are trying to run though, but when we raced on leaf springs we found 9" of up travel was the minimum we could get away with without living on the bump stops. Since most of our Jeeps ge a total of 14" you'd have to sit really high to achieve that.

You do want light rebound. If your axle can't get down into each bump int he whoops, you will get "packing" which slowly reduces your up travel each bump....very very well known issue for leaf springs. Also I don't speak Bilstein. I speak thickness (.008" or .012") or I speak fox vavle stacks (#40 stack is all .008" shim pack). I can tell you we ran .008s on most of our leaf spring trucks.
 
I had a similar issue at my last race. I'm rookie as rookie can be at this going fast stuff. I knew the rear valving in my rear 7100's was light at 170/60. I was in a pinch and ran them anyway. What a mistake that was. I hit my first whoop section at about 30 mph and my truck wanted to leap frog over itself.

Since then I've ordered new valving shim kits 360/80. The plan is to use the compression shims from the new kit and reuse my rebound stack already in the shocks. This is for the interim. I will post up results if you'd like to hear about them.


I have since my last race, picked up some help from FOX Shox and will be changing over my entire suspension setup over the off season.
 
I had a similar issue at my last race. I'm rookie as rookie can be at this going fast stuff. I knew the rear valving in my rear 7100's was light at 170/60. I was in a pinch and ran them anyway. What a mistake that was. I hit my first whoop section at about 30 mph and my truck wanted to leap frog over itself.

Since then I've ordered new valving shim kits 360/80. The plan is to use the compression shims from the new kit and reuse my rebound stack already in the shocks. This is for the interim. I will post up results if you'd like to hear about them.


I have since my last race, picked up some help from FOX Shox and will be changing over my entire suspension setup over the off season.


Yes I would love to hear the results. I haven't had much time to mess around with mine yet. I'm in the middle of a move but hopefully soon I can start playing around with them.
 
Went out to Silver Lake Dunes this past weekend. The rear sucked. I just spoke with a rep at Bilstein. He said he has been recommending 255/100 with 250 psi. I also ordered some shaft bumps. Hopefully this sorts the packing issue up.

If it doesn't, I'm linking the rear.
 
It sounds like you need leafs, not shocks.


That thought has been in the back of my mind but I'm at the point where if I decide to buy $700 leafs, I might as well link it and drop $700 on some coilovers.

Do you think they're simply not stiff enough?
 
There's more to it than simply not stiff enough, but I think that is part of it yes.

If you look at any performance leaf pack, it is 9-13 leafs. How many leafs is your pack? It is probably 4-6, and they are probably close to 1/4" thick each. A good pack is going to be a lot more thinner leafs so they will travel, bare load, and have a decent rate.
 
There's more to it than simply not stiff enough, but I think that is part of it yes.

If you look at any performance leaf pack, it is 9-13 leafs. How many leafs is your pack? It is probably 4-6, and they are probably close to 1/4" thick each. A good pack is going to be a lot more thinner leafs so they will travel, bare load, and have a decent rate.


It's a 7 leaf pack. I guess I'm just at the point where I invest in $700 leafs or take that money and link the rear. I'm not completely sold on a set of deavers being my end all fix.
 
Thats all a matter of what you want to do. I like the way a leaf spring rig handles. Linked rigs feel and look less stable to me, and add a lot of expense with swaybars to get it right again.

That said, in the end you can get more travel out of a linked rear, with a lot more work and a lot more expense. Depends how far you want to go.
 
Thats all a matter of what you want to do. I like the way a leaf spring rig handles. Linked rigs feel and look less stable to me, and add a lot of expense with swaybars to get it right again.

That said, in the end you can get more travel out of a linked rear, with a lot more work and a lot more expense. Depends how far you want to go.

I'm going to try the valving changes and fab up a quick traction bar. With the anti rock in the front, it's extremely stable now. That loss of stability has been whats been holding me back from linking it.

If it gets better I'll look into springs. I know leafs can work. You make it work, I watched a FSJ on junkyard spring over chevy 63"s make it work in 3' whoops at 70 mph. The reason I'm so quick to ditch them is I have everything already in the garage but the coilovers.
 
you got me curious, what leafs do you run that is a 7 leaf pack?
 
I used to believe that I could put a bastard pack together that would perform decently. I had several over the years that I thought were awesome.

Then we bought our first set of *new* (not retired used) Deavers.

It blew my ****ing mind...
 
I used to believe that I could put a bastard pack together that would perform decently. I had several over the years that I thought were awesome.

Then we bought our first set of *new* (not retired used) Deavers.

It blew my ****ing mind...


That makes me feel a lot better about trying them. Nobody runs them out here so I've never had a chance to feel what they're like.
 
I'm not kidding. We originally built 4643 with a set of used deavers I bought from a friend cheap. After pre-running for our 2nd KOH the rig had lost 2" of ride height, so we sent someone out to fetch us a new set of Deavers and threw them on the night before the race.


Richard and I literally giggled for the first 15 miles, it changed the car so much...
 
I'm not kidding. We originally built 4643 with a set of used deavers I bought from a friend cheap. After pre-running for our 2nd KOH the rig had lost 2" of ride height, so we sent someone out to fetch us a new set of Deavers and threw them on the night before the race.


Richard and I literally giggled for the first 15 miles, it changed the car so much...

Now I'm assuming the G9's are built for a car with no weight in the back so I would be better off getting a custom pack built? Rear bumper, caged, co2, hatch, and spare are back there.
 
You drastically underestimate the weight of a race car.

We ran off the shelf G9's, and weigh 4890, even 50/50 front/rear.
 
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