Handling Effects of lowering panhard mount at axle?

paulevans76

paulevans76

Well-Known Member
Joined
Mar 21, 2005
Location
York, SC
I've got a y-link radius arm setup on the front of my rig, and the panhard mount and high steer stuff limit my uptravel and keep my ride height higher than ideal. Ideally, I could lower the rig an inch or two and keep or increase uptravel. I was thinking about options and I'd like any feedback y'all might have.

Currently, the panhard mount is on top of the axle, pretty much right under the frame. Almost totally flat and parallel to the drag link.

One option would be to move the axle side panhard mount to a lower spot on the axle, and move the drag link and tie rod down to match - either to underside of the high steer arm, or mount to the original steering arm.

My fear in doing so is that this may negatively affect handling. I like to be able to drive a couple hours to the trail and back, so street manners matter. Currently street manners are marginally acceptable so I don't want to make them worse.

From what I've found, the higher, flatter, and longer you can keep your panhard, as well as parallel to drag link, the better. I don't think I'd be moving my roll center much if I'm just moving the axle side mount lower. The current angle is basically flat, my radius arms a pretty much flat at ride height, but the rig is tall and heavy, so body roll is pretty pronounced.

Other options would be to go to a SUA leaf set up, but that really would be a shame and I'd lose a lot of under axle clearance.

Any opinions?
 
It sounds like you know what you are doing. Any pictures?
 
That's the beauty of the internet :D I can figure out how to sound like I know what I'm doing, but I am hoping someone more experience in actually tweaking suspension can give me an idea of what, if anything might happen if I make those changes.

I'll grab some photos and get em posted up asap
 
The bar height (the height of the bar ends) is really what sets the roll center height. The length and horizontal angle have to do with the motion of the axle in bump and droop, like whether the left/right axle travel is symmetric and how much lateral axle movement there actually is.
 
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IMG_20190514_195501.jpg
Pretty tight in here

Upper mount:
IMG_20190514_195512.jpg

Lower panhard mount, right under the frame
IMG_20190514_195534.jpg

So I guess my main question would be, if I can figure out how to move some things around in order to gain a little uptravel and room to lower it a little maybe, as long as the basic rules are followed, i.e. keep panhard parallel to drag link, etc, if my roll center moves a little and the angle of the bars get a little steeper, it shouldn't have a drastic negative effect on handling, right?
 
Chris_Keziah said:
What's your current up travel? Any particular reason your trying to lower you rig?
Click to expand...

I've got about 3" maybe 4" uptravel with the fresh springs, but I expect them to sag a bit as they break in over the next few months. Mainly want it a lower for stability factor as well as wanting to fit it in the garage some day without having to put it on little 31" rollers. It has a 3" body lift that the PO installed and then built a lot of shit around prior to the SAS (gas tank lift, armor, etc) that I'm eventually going to cut down to 1.5". I'm also going to be adding a cage this year, probably a hybrid interior with a exterior halo around the roof, which will probably lower the rig a tad for me on it's own, but also add to the top-heaviness. So a bit lower COG and having more uptravel in general would be nice. I like crawling but I also like being able to go fast-ish when it makes sense to do so.

I'm also juggling future mods like hydro assist that will depend on nailing down where the tie rod is going to be.
 
paulevans76 said:
I've got about 3" maybe 4" uptravel with the fresh springs, but I expect them to sag a bit as they break in over the next few months. Mainly want it a lower for stability factor as well as wanting to fit it in the garage some day without having to put it on little 31" rollers. It has a 3" body lift that the PO installed and then built a lot of shit around prior to the SAS (gas tank lift, armor, etc) that I'm eventually going to cut down to 1.5". I'm also going to be adding a cage this year, probably a hybrid interior with a exterior halo around the roof, which will probably lower the rig a tad for me on it's own, but also add to the top-heaviness. So a bit lower COG and having more uptravel in general would be nice. I like crawling but I also like being able to go fast-ish when it makes sense to do so.

I'm also juggling future mods like hydro assist that will depend on nailing down where the tie rod is going to be.
Click to expand...

If it were me I'd pull in the shop, pull the springs, steering, and track bar. Set the bumps to your desirable up travel and set it the rig down on the bumps and build the steering and track bar from there. From looking at the pics I don't think you're going to gain much, a sway bar will help your stability more than lowering it an inch or so.
 
Chris_Keziah said:
If it were me I'd pull in the shop, pull the springs, steering, and track bar. Set the bumps to your desirable up travel and set it the rig down on the bumps and build the steering and track bar from there. From looking at the pics I don't think you're going to gain much, a sway bar will help your stability more than lowering it an inch or so.
Click to expand...

Smart-that sounds like a plan. Or at least a plan to see if it's doable and worth it to monkey around with it. And I reckon I shouldn't anticipate any drastic changes in handling, should I end up moving the drag link and panhard a little.

And I do agree, a sway bar is on the wish list. I keep my eyes out but seem to miss the good deals on used ones.
 
paulevans76 said:
View attachment 293463
Pretty tight in here

Upper mount:
View attachment 293464

Lower panhard mount, right under the frame
View attachment 293465

So I guess my main question would be, if I can figure out how to move some things around in order to gain a little uptravel and room to lower it a little maybe, as long as the basic rules are followed, i.e. keep panhard parallel to drag link, etc, if my roll center moves a little and the angle of the bars get a little steeper, it shouldn't have a drastic negative effect on handling, right?
Click to expand...


Lowering the panhard would lower the RC,

It would result in a longer roll moment, which will result in increased body roll compared to current setup.

You may not notice effects or my be substantial. Hard to quantify the effects without really going in depth.

Can always add/tune a sway bar if it gets silly

I say go for it. The increase in uptravel is always a benefit for ride quality. It gives the shocks more time to absorb the energy of a bump.

You know what to do, keep drag link and panhard equal length and parallel angles.
 
Mac5005 said:
It gives the shocks more time to absorb the energy of a bump.
Click to expand...

Are you actually talking about more shock travel and not more time? Shocks don't care about time, they only care about velocity. If they have more shock travel to dissipate energy at a certain velocity, that is what I assume you're talking about.
 
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Fabrik8 said:
Are you actually talking about more shock travel and not more time? Shocks don't care about time, they only care about velocity. If they have more shock travel to dissipate energy at a certain velocity, that is what I assume you're talking about.
Click to expand...

Travel (=) time

Can’t always substitute travel for time without a position sensitive shock.

Takes a given displacement to slow the force, which equals more time (travel in this case) with more uptravel.

I had it worded as intended. More up(travel) gives more available time to dissipate the force before hitting bump stop or frame.

None of the semantics affect the OP question.
 
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Mac5005 said:
None of the semantics affect the OP question.
Click to expand...

That part is absolutely correct. ;)

Mac5005 said:
Takes a given displacement to slow the force, which equals more time (travel in this case) with more uptravel.
Click to expand...

I think I see what you're saying now; You're saying you're underdamped at some velocity. You don't have enough damping force at that velocity, so you need extra displacement to buy enough extra time to compensate for the lack of proper damping force at that velocity.
 
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Fabrik8 said:
That part is absolutely correct. ;)



I think I see what you're saying now; You're saying you're underdamped at some velocity. You don't have enough damping force at that velocity, so you need extra displacement to buy enough extra time to compensate for the lack of proper damping force at that velocity.
Click to expand...


Not pertinent to OP.

And no, that’s not what I’m saying.

I’m generalizing that as an effective substitute for extremely tuned valving for a specific setup, an increase in uptravel is effective in increasing ride quality.

Again off topic, and not beneficial to this thread. :facepalm:
 
Mac5005 said:
Lowering the panhard would lower the RC,

It would result in a longer roll moment, which will result in increased body roll compared to current setup.

You may not notice effects or my be substantial. Hard to quantify the effects without really going in depth.

Can always add/tune a sway bar if it gets silly

I say go for it. The increase in uptravel is always a benefit for ride quality. It gives the shocks more time to absorb the energy of a bump.

You know what to do, keep drag link and panhard equal length and parallel angles.
Click to expand...

It will increase body roll which will make it feel more top heavy ..... and make it tend to oversteer.
How much is a guess.
As stated you can tune the the sway bar.
You can also tune a panhard bar by raising or lowering one side or the other if the mounts are adjustable.
BUT .... (there is always a but) when doing this once you go past roll center handling changes are more drastic to the high side of the panhard bar.
That being said .... preference is for a flat, parallel to draglink panhard bar.
 
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