Coilover.... Tech help!

[Lawrence]

Current setup - 40" MTRs, 16" C/O (250/350 I think w/ ~7" shaft showing) up front, ~4" coils+shocks in the rear.
What I'd like to do - Go with 37" MTRs and lower the front a couple of inches to level the ride (currently front high and arse low).

So, the PO told me I could go with 250/250 springs to drop the front a bit since it would have softer springs. I then talked to Polyperformance and they suggested that I go with shorter springs and a tender coil.

But I thought, why not switch to 14" C/Os instead? That should drop the ride some, right? Well, Poly is telling me that it is not as simple as getting a shorter coilover and said that in order to run 14"s, I would have to change things and redo the mounts. This is where I get confused.

In the rear, if I want to drop the ride a couple of inches, all I have to do is to get shorter coils and shocks, adjust my bumpstops, and no relocation of shock mounts or spring buckets is necessary. So, why wouldn't the same theory work up front by getting 14" coilovers with the same spring rates?

[NAILER341]

Welcome to hell Lawrence.
I have been battling coilover decisions since I put them on there. Dont do the 250/250 swap as this will do away with your dual rate.

I have done this in the rear of my jeep, and plan to go back to 250/300 or 250/350 to keep off of the bump stops, and use a tender to keep the height where I want it to be.

as far as moving the mounts, I kind of see where they are coming from. You would have to test it with the shocks you want to use.

it is the shock body swinging within the bucket on the frame that is the concern. The shorter shocks will have more swing and may crash into the bucket. The only way to know is to test it.

Why are you going down to 37's from the cool-guy 40's? You have the power to move the big tires and the axles to support them....

[dirtman13]

I went with the shorter upper spring to lower mine and it worked fine. I did add the tender spring to keep tension on the coils. I’m running a 14” shock with a 16” lower and a 10” upper. If your only wanting to lower a couple of inches that should work for you. If you go with a tender spring you would need a 4" smaller upper to gain 2" of lowering. What size are your uppers and lowers now?

IMO adjusting ride height by changing spring rate is not the way to do it. If the Jeep handles good now you will affect that by changing spring rates.

[Lawrence]

Welcome to hell Lawrence.

No kidding, I read Pirate's 4x4 Coilover Bible Part 1 and Part 2 and my head hurts.

as far as moving the mounts, I kind of see where they are coming from. You would have to test it with the shocks you want to use.

it is the shock body swinging within the bucket on the frame that is the concern. The shorter shocks will have more swing and may crash into the bucket. The only way to know is to test it.

When you explain it like this, it makes sense, I think! I feel I am getting somewhere.

Why are you going down to 37's from the cool-guy 40's? You have the power to move the big tires and the axles to support them....

The places where I'd like to go wheel are 1,000+ miles away and 37s are cheaper to replace than 40s. Also, the 40s rub badly in the rear, I think 37s would be a better fit in the wheel opening. If I find someone to trade, I'll do it, otherwise I'll keep the coolness.



Besides, it appears that I am definitely not in the cool guys category, but rather in the idiot-who-can't-pay-attention one instead as it appears that I have tender springs after all.

I went with the shorter upper spring to lower mine and it worked fine. I did add the tender spring to keep tension on the coils. I’m running a 14” shock with a 16” lower and a 10” upper.

What's the ride height eye-to-eye measurement on your setup?

If your only wanting to lower a couple of inches that should work for you. If you go with a tender spring you would need a 4" smaller upper to gain 2" of lowering. What size are your uppers and lowers now?

Yes, the front end is a little high compared to the back and I don't even have a rear bumper and spare on right now, so I'd like to level the rig out a bit so it doesn't look back end heavy.



So, here are some measurements I just took at ride height:
Eye to eye ~31.5"
Helper spring ~0.5"
Top spring ~10.5" (250lbs)
Bottom spring ~13.75 (350lbs)
Shaft ~7.5" showing

Here is the part I don't get... If I get a spring that is 2" shorter, this will lower my effective height by that same amount and I will now have 5.5" of shaft showing. Wouldn't this create problems and bottoming out? More pics here.

[dirtman13]

First that is one nice looking Jeep.

Here is the part I don't get... If I get a spring that is 2" shorter, this will lower my effective height by that same amount and I will now have 5.5" of shaft showing. Wouldn't this create problems and bottoming out?

Yes it could especially if your rate is set up on the light side(Soft). My front has about 6" of shaft showing and I don't get in to my stops unless I'm hauling @$$ through some big woops. Your bump stop postion also comes in to play here. Do you have any? I can't see them in your pictures.

Top spring ~10.5" (250lbs)
Bottom spring ~13.75 (350lbs)

This is with weight on the springs. You need to see what they are with no weight on them.

The hope would be your at 18 lower and 14 upper. Then you could easily go to a 12 upper and lower your front 2". As long as the bumps are adjusted.

Edit: I just look at your other pics and see the ridged stops. That makes things a little harder.

[Lawrence]

First that is one nice looking Jeep.

Thanks man, I do like it and I have to learn to feather the gas pedal though. Loads of power.

This is with weight on the springs. You need to see what they are with no weight on them.

I lifted the Jeep ghetto style until the limiting straps were fully extended



With the springs uncompressed, I took the following measurements

Eye to eye ~37.5"
Helper spring ~0.75" (1" on the right side)
Top spring ~13.75" (250lbs)
Bottom spring ~16 (350lbs)
Shaft ~13.5" showing

The hope would be your at 18 lower and 14 upper. Then you could easily go to a 12 upper and lower your front 2". As long as the bumps are adjusted.

So, could I go with 12" upper springs and keep the 16" lowers and therefore reduce the ride height by a couple of inches? This would reduce my uptravel to ~5.5" (from 7.5") and I could extend my bumpstops accordingly. Any negatives to doing that? I assume that I would also have to get shorter limiting straps, right?

[dirtman13]

Eye to eye ~37.5"
Shaft ~13.5" showing

According to Sway Away this is your shock.
Travel16"
Ext. Length 40.57"
Comp. Length 24.05"
Those are eye to eye. My 14" shocks are close to 13" at full droop.
Looks like your losing 3" of full droop.

So, could I go with 12" upper springs and keep the 16" lowers and therefore reduce the ride height by a couple of inches? This would reduce my uptravel to ~5.5" (from 7.5") and I could extend my bumpstops accordingly. Any negatives to doing that? I assume that I would also have to get shorter limiting straps, right?

Personally I think you could go to a 12" upper. Remember your stops are to prevent damage to the shock on hard hits at full bump. They basically prevent the shock from collapsing 100%. If your limit straps are set right you shouldn’t have to adjust them at all. Limit straps do the same thing as stops just protecting the shock at full extension. Changing to a short spring will not affect this.

Like Erik said. Welcome to hell. It's all about trial and error and it will take a while to get them dialed in. My Jeep has been done for over a year and I'm still tweaking the suspension. I'm close but still working on it.

[Tumbleweed13]

But I thought, why not switch to 14" C/Os instead? That should drop the ride some, right? Well, Poly is telling me that it is not as simple as getting a shorter coilover and said that in order to run 14"s, I would have to change things and redo the mounts. This is where I get confused.

In the rear, if I want to drop the ride a couple of inches, all I have to do is to get shorter coils and shocks, adjust my bumpstops, and no relocation of shock mounts or spring buckets is necessary. So, why wouldn't the same theory work up front by getting 14" coilovers with the same spring rates?

After looking at your pics, I noticed you have shock hoops, not buckets. It seems that shorter shocks wouldn't hit since its not surrounded by a bucket. Granted I'm new to coilovers. Just seems logical to me. VERY nice Jeep btw.

[Lawrence]

According to Sway Away this is your shock.
Travel16"
Ext. Length 40.57"
Comp. Length 24.05"
Those are eye to eye. My 14" shocks are close to 13" at full droop.
Looks like your losing 3" of full droop.

Correct on the measurements and I do agree that it seems I am not fully drooping. Perhaps the limiting straps were chosen a little short to allow for stretching over time? But, do I really want to droop some more if my springs are "unseating"? Is there a benefit to drooping so much that the springs are dangling freely (i.e. too much droop)?

Personally I think you could go to a 12" upper. Remember your stops are to prevent damage to the shock on hard hits at full bump. They basically prevent the shock from collapsing 100%. If they are set right you shouldn’t have to adjust them at all. Limit straps do the same thing as stops just protecting the shock at full extension. Changing to a short spring will not affect this.

It seems to me that I would have to extend the bumpstops to prevent the shock from collapsing since I will now have a shorter spring, and that I will have to shorten the limiting straps to prevent droop to the point where the springs are "unseated".

After looking at your pics, I noticed you have shock hoops, not buckets. It seems that shorter shocks wouldn't hit since its not surrounded by a bucket. Granted I'm new to coilovers. Just seems logical to me. VERY nice Jeep btw.

I am new to coilovers too and there are things that I don't understand. I got to think some more (perhaps not a good thing) about Erik's statement:

it is the shock body swinging within the bucket on the frame that is the concern. The shorter shocks will have more swing and may crash into the bucket. The only way to know is to test it.

I do have hoops and the frame is notched for clearance, but here is the part that confuses me and hopefully I can make sense of the mumbo jumbo that is in my head and explain it clearly:

My eye-to-eye @ ride height is 31.5" inches currently. Let's say I want to lower my front by 2" and, regardless of the method, my ride height is now where I want it and it comes in @ 29.5" for argument's sake. I can achieve this by 1) keeping my 16" shock and switching the upper spring to a shorter one or 2) by switching to a 14" shock and setting it up accordingly. So, why would there be a difference in the way the shock swings in the mounts? In other words, for my hypothetical eye-to-eye ride height, why would it matter if I achieve it with a 14" or 16" shock?

Don't get me wrong, keeping the 16" shocks would be the cheaper option for me and I am not looking to get rid of them just because, but I wonder if it is the best option if I am not taking full advantage of the shock capabilities by shortening my uptravel and limiting the droop. It seems to me the 14" could be a better fit... What am I missing?

[dirtman13]

Correct on the measurements and I do agree that it seems I am not fully drooping. Perhaps the limiting straps were chosen a little short to allow for stretching over time? But, do I really want to droop some more if my springs are "unseating"? Is there a benefit to drooping so much that the springs are dangling freely (i.e. too much droop)?

That is what you tender spring is for. The small upper spring that you measured at .5 in. (Mine is 2")Once you have everything set you want to fully extend your shock and adjust the upper preload adjuster so that the tender coil keeps pressure on the springs preventing "unseating". Also I don't see limit straps stretching 3". I set mine 1" short to allow for stretching.

It seems to me that I would have to extend the bumpstops to prevent the shock from collapsing since I will now have a shorter spring,

You want to adjust your bump stops so that the shock does not bottom out on hard hits.

and that I will have to shorten the limiting straps to prevent droop to the point where the springs are "unseated".

Your limit straps should be set to prevent the shock from fully extending possibly causing it damage. The tender spring is set up to control "unseating".

[aw12345]

Correct on the measurements and I do agree that it seems I am not fully drooping. Perhaps the limiting straps were chosen a little short to allow for stretching over time? But, do I really want to droop some more if my springs are "unseating"? Is there a benefit to drooping so much that the springs are dangling freely (i.e. too much droop)?

The limit straps aren't to short, by the looks of things they are mounted inwards of the coil over mounts which will give you the correct amount of droop on one side when the front is fully flexed. Since current setup works, I think Polyperformance and Chuck gave you the answer you are looking for, use a shorter upper spring and a tender coil on top of that and call it good. The bump stops and limit straps are set to where they need to be so leave them alone. In the end this way you end up with less uptravel and more down travel and the ride height you want, nor will switching to 14" coilovers gain you anything but a lighter wallet

[Lawrence]

Art and Chuck, thank you very much. I had difficulty visualizing it and I was hung up on a couple things, but the light bulb finally went on.

It did not occur to me that the bumpstops and limiting straps were set for the shock length, in this case the 16" shock, and that running a shorter spring doesn't matter since the shock remains the same. I also was hung up on the uptravel thing and erroneously thought that a 14" shock with 7" uptravel (purely hypothetical number) would be "better" than my 16" with now 5" uptravel, I felt I was "losing" something by reducing my uptravel.

So, thanks for the quick lesson in coilovers, now onto finding the right spring combo.