Front Panhard Rod Question

[Gerrha]

Hello,
I have been a member for a while, but since I was busy in tear-down mode for my 97, I did not have too many questions. However, I am now getting ready to start the rebuild and the questions are coming. My first one regards the front panhard rod. I searched and did not find a definitive answer for this.

I am looking at a Dobinsons 0-3" lift package. Probably most of you know that they offer an adjustable front panhard rod as an add-on. Of course, my question is how does this work considering that the non-adjustable OEM rod is curved? I did see that Terrain Tamer offers both straight and curved adjustable panhard rods, so there is something going on here, but I do not understand it.

Thanks!

 

[Delta VS]

First post of this thread should shed some light on the topic for you as well:

Delta Vehicle Systems Panhard Lift Bracket, 3" & 5"

Howdy folks! By now you’ve probably seen @woody's Panhard Lift Bracket (PLB) review thread (Review: Delta VS Panhard Lift Bracket). Whether you have seen the review or not, it’s time for an official Delta Vehicle Systems (DVS) thread on these things now that we have finalized it. We designed a...

forum.ih8mud.com

As always, approach to the problem depends on use. For Landtank, who spends many miles on the highway traveling, having good geometry at ride height is helpful. For someone who spends a lot of time on the trail, lengthening the panhard is going to effect how the right side tire stuffs into the wheel well under articulation, which could be a big issue, depending on wheel choice and tire size.

 

[Broski]

The amount of lift plays a big role.
And leaving the pan hard stock length on a lifted truck will affect how the driver side front tire stuffs.

As soon as you start modifying everything is a trade off

That's why I prefer a lower lift.

I would suggest a 2" lift, you can fit 35- 37" tire with that with minimal modifications.

 

[Delta VS]

leaving the pan hard stock length on a lifted truck will affect how the driver side front tire stuffs.

Please explain your thought process on this.

As soon as you start modifying everything is a trade off

That's why I prefer a lower lift.

I tell people this every day.

 

[Broski]

Please explain your thought process on this.

As you lift the truck the stock PH pulls the axle to the drivers side. How much affect it has on stuff depends on lift height, wheel off set and tire size.

 

[lumbee1]

I have a Dobinson 2.5" lift in the front and installed an adjustable panhard bar just to center the axle under the truck. There was no performance benefit unlike the rear. I have the Delta VS panhard bracket in the rear and it make a huge difference in stability.

 

[NeverFinis]

I am not a suspension expert in any way, but last night I focused on the panhard rods and it seems to me they have a tough job in the suspension. If what I am about to say is incorrect, I hope someone will correct me.

If the vehicle sits immobile, in its OEM state, perfectly aligned, at its design weight, it seems the panhard rods should be neutral, neither in tension or compression. However, if the vehicle gains weight causing the frame to lower by some amount, both panhard rods will then be in compression, which will attempt to push the front axle to the right and the rear axle to the left. Conversely, if the vehicle loses weight causing the frame to rise by some amount, both panhard rods will then be in tension, which will attempt to pull the front axle to the left and the rear axle to the right. This is for a static, immobile situation.

When the vehicle is moving the same process will occur as it goes down the road. The difference being that the panhard rods will be cycling between tension-compression as the vehicle goes over dips and bumps. At high speed on a rough road, the life of a panhard bar is pretty tough.

Now, consider when a suspension lift is added. Doing this with the OEM panhard bars will put both into tension, which will then attempt to pull the front axle left and pull the rear axle right. This matches Landtank's real world observations above. Depending on lift height, it would likely be difficult/impossible to reconnect the OEM panhard bars because they are now too short.

From my outsider thinking, there would be two solutions.

First, is to lower the frame attachment points for both panhard bars. The amount to lower them is that amount which makes them neutral, neither in tension or compression when the vehicle is at rest, perfectly aligned, and at its average weight. This method has the benefit of retaining the OEM geometry, but the lowered attachment brackets are under greater stress than were the OEM attachment points. The other problem is the difficulty in figuring out the exact amount to lower those attachment points and likely they have to be designed individually for each situation.

Second, is to use adjustable length panhard bars. These have the benefit of allowing length adjustment to suit individual lift variations but have the disadvantage of altering slightly the OEM geometry.

Finally, in Landtank's experience, aftermarket adjustable front panhard bars have a higher rate of failure compared with the OEM. I have no experience here, but I accept that. For sure, the life of a panhard bar is really tough, but it seems that someone could make a beefed up front panhard bar that would never fail, but maybe the cost prohibits that.

Sorry for the rambling, but writing the above has hopefully helped me understand (a tiny bit more) about the arcane life of a panhard bar...

Your talk of neutral...

I was just adjusting my Dobinson's adjustable panhard bar yesterday. Dobinson's 2.5" flex coils, @Delta VS 3L arms with new factory bushings installed by them. All the suspensions bushings, front and rear, have been replaced with new factory bushings.

I had adjusted the panhard before, but more things have been stuffed in the truck since then. Fine tuning because the front axle is on jack stands due to R&R and I am waiting on parts.

The Panhard bar was still in a nearly in a neutral position. The axle bolt was easy to remove. I reduced the length of the panhard bar to account for the added weight and it was easy to put the bolt back in. Add people and more gear, and it won't be in a neutral position any longer, but it will be close to neutral.

I would think you would probably wear out the panhard bushings faster the further away you are from neutral. This could also be an issue for the radius arm bushings if they are constantly being pulled in one direction by the Panhard bar. Big deal?..probably not.

 

[mudgudgeon]

If the vehicle sits immobile, in its OEM state, perfectly aligned, at its design weight, it seems the panhard rods should be neutral, neither in tension or compression.

There'll be some minor load on the panhard

When the vehicle is moving the same process will occur as it goes down the road. The difference being that the panhard rods will be cycling between tension-compression as the vehicle goes over dips and bumps.

Yes, this is true if the panhard is stock or lengthened, if the suspension is stock or lifted.
The variables are gross weight of the vehicle, spring and shock rates.

Now, consider when a suspension lift is added. Doing this with the OEM panhard bars will put both into tension

Not really. The static resting position is still static, its just in a different position. The dynamic forces are still essentially the same (barring any variables like mentioned above) loads haven't changed.

If the bolts through panhards and links etc were loosened while the lift was being done, bushings will find a new neutral position
There might be minor tension/compression on bushings while immobile, but really no more or less for stock vs lifted.

A lift increases the angle of the panhard bar. Ideally, you want panhard bars s close to horizontal as possible.
the increased angle increases the effect of bump steer and has an effect on the way the vehicle handles.

I don't see there being any significant change in the load on panhard bars

 

[Gerrha]

I appreciate all of your feedback. There are so many variables that there is no one-size fits all answer for these things. My daily driver is a 2015 F250. I love it, but about 5-years ago, death wobble hit. Anyone that has experienced death wobble at a speed over 50-mph will never forget it. After many $1000s with the dealer, two things were obvious. One, that these suspension systems are really complex, and this coupled with all possible road/driving conditions makes it even worse. Secondly, in my case as in most I think, the death wobble is never completely gone. Mine is under control but lurking in the shadows waiting to jump out and bite.

Thanks everyone.

 

[alia176]

@Gerrha

I say go for a 2" lift, which will prolly net you 2.75" of lift up front until the front end is weighed down, and the springs settle a tad. Your life will be mucho happy, and so will be your wallet. The front panhard rod will be a tad short which will move the front axle a tad to one side but not a big issue in the big picture.

 

[Gerrha]

@Gerrha

I say go for a 2" lift, which will prolly net you 2.75" of lift up front until the front end is weighed down, and the springs settle a tad. Your life will be mucho happy, and so will be your wallet. The front panhard rod will be a tad short which will move the front axle a tad to one side but not a big issue in the big picture.

A 2" lift was my thought from the beginning. I plan to run 305/70R17 tires, which height-wise should be about 1.4" closer to the body than the stock tires. But, I need to factor in planned additional weight of about 175-lbs/spring in the front and 300-lbs/spring in the back.

 

[alia176]

A 2" lift was my thought from the beginning. I plan to run 305/70R17 tires, which height-wise should be about 1.4" closer to the body than the stock tires. But, I need to factor in planned additional weight of about 175-lbs/spring in the front and 300-lbs/spring in the back.

additionally, one has to deal with front DS vibrations, crappy caster, twitchy steering, etc, once they hit the 3" lift mark. It's a whole can of $hit when one surpasses the 3" mark.

 

[Broski]

additionally, one has to deal with front DS vibrations, crappy caster, etc once they hit the 3" lift mark. It's a whole can of $hit when one surpasses the 3" mark.

^^^^ This

 

[Delta VS]

As you lift the truck the stock PH pulls the axle to the drivers side. How much affect it has on stuff depends on lift height, wheel off set and tire size.

100% agree that as you lift the vehicle, the axle gets pulled to the left side (of a LHD vehicle). This, however, does not effect stuffing tire into wheel well since the axle is still rotating around the same point with the same length arm (the panhard rod). Only once you change the length of the panhard does it start to effect how the tire will fit the wheel well. The ONLY thing lengthening the panhard does it correct RIDE HEIGHT front/rear tracking. Something that has significant benefits for someone who spends a lot of time on the highway. As soon as you move from ride height though, you start to have geometry issues, however small they might be. One more reason I tell people every day to stay at or below 3" of lift.

100% agree that wheel offset and tire size will effect the ability of tire to stuff into wheel well also.

A 2" lift was my thought from the beginning. I plan to run 305/70R17 tires, which height-wise should be about 1.4" closer to the body than the stock tires. But, I need to factor in planned additional weight of about 175-lbs/spring in the front and 300-lbs/spring in the back.

My recommendation to customers is to always get rig set up the way it's going to be driven 95% of the time, THEN make your spring choice, put 500 miles on it, THEN correct suspension geometry. Either that, or be ready to purchase other springs (as well as corrective measures) as QC on springs these days is spotty at best, and your build is likely to go tangential on at least one aspect, effecting the final build.

 

[Broski]

100% agree that as you lift the vehicle, the axle gets pulled to the left side (of a LHD vehicle). This, however, does not effect stuffing tire into wheel well since the axle is still rotating around the same point with the same length arm (the panhard rod).

In theory I would agree, and in a stright up stuff (Both tires up at the same time) this would hold true.
But IMO and my experience once lifted, and in articulation drivers side up the pan hard is still further down in the ark pulling the axle to the drivers side affecting Stuff.

 

[Kabanstva]

The issue is a lot of these lift kits is just a shot in the dark how much lift you’re actually gonna end up with. My Dobinsons MRA 2.5” kit yielded a hair over 3” of lift with full armor, winch etc.

Do the springs settle a noticeable amount over time or no?

 

[alia176]

The issue is a lot of these lift kits is just a shot in the dark how much lift you’re actually gonna end up with. My Dobinsons MRA 2.5” kit yielded a hair over 3” of lift with full armor, winch etc.

Do the springs settle a noticeable amount over time or no?

They do, and with extra winch+bumper, that also helps with the process.

 

[landtank]

I'll just jump in and hopefully add some thought.

First, the only acceptable solution for the front is an adjustable PH. Anything else and you will get bump steer and most sane people don't want that.

On my first truck I got the MAF rear panhard drop bracket. It did it's job, with the stock panhard the bar was flat and axle centered.

On the second truck I used adj bars front and rear and honestly I can't tell the difference. On road there really isn't much movement in the back and off road I have 2" bump stops in the rear so rubbing is virtually non-existent.

Dobinson 4" flexi-coils, 17x9 0-offset rims and 315/70r17 tires. Bigger tires or less bumpstop will effect performance