A new thought on Panhard drops

[J-money$$$]

I know this comes up over and over. And I have repeatedly said I dont like them, But I came across another piece of information that was quite surprising to me.

I am currently working out a 3 link design for the rear of my truck. Its time for a change and the stock brackets are toast. Anyways I was planning on keeping the stock track bar mounts for now. I have been using the 3 link calculator that can be found on pirate.

The thing is our 4 link with a panhard operates similarly to a 3 link due to the lack of triangulation and reliance on a panhard/trackbar for axle location. So in this design the Roll Center Height is based mainly on the center of the trackbar (height of the trackbar right in the center of the axle) . This Roll Center Height is basically the imaginary axis your trucks suspension rolls over on. So the higher the RCH the more stable the truck feels. Actually you want to have a RCH right around the center of gravity height. (top of bell housing is a good guess)

So when dropping the FRAME SIDE with a panhard drop mount you lower the Roll center height by about 1" Technically causing more body roll. Compare this to if you raised the panhard mount on the axle side you could raise the Roll center height by an inch.

And if you were to run an extended trackbar you keep it the same.


This is just how it works out on paper. Our rear suspension has horrible roll oversteer and causes even more body roll. So if this few inches of difference makes a noticeable effect is unknown but would be cool to find out. It obviously would have more of an effect with more lift due to the the RCH height further from the center of gravity height. All I know is I cannot get the right RCH iI want without cutting off the trackbar mounts

 

[ryankmasuda]

I know this comes up over and over. And I have repeatedly said I dont like them, But I came across another piece of information that was quite surprising to me.

I am currently working out a 3 link design for the rear of my truck. Its time for a change and the stock brackets are toast. Anyways I was planning on keeping the stock track bar mounts for now. I have been using the 3 link calculator that can be found on pirate.

The thing is our 4 link with a panhard operates similarly to a 3 link due to the lack of triangulation and reliance on a panhard/trackbar for axle location. So in this design the Roll Center Height is based mainly on the center of the trackbar (height of the trackbar right in the center of the axle) . This Roll Center Height is basically the imaginary axis your trucks suspension rolls over on. So the higher the RCH the more stable the truck feels. Actually you want to have a RCH right around the center of gravity height. (top of bell housing is a good guess)

So when dropping the FRAME SIDE with a panhard drop mount you lower the Roll center height by about 1" Technically causing more body roll. Compare this to if you raised the panhard mount on the axle side you could raise the Roll center height by an inch.

And if you were to run an extended trackbar you keep it the same.


This is just how it works out on paper. Our rear suspension has horrible roll oversteer and causes even more body roll. So if this few inches of difference makes a noticeable effect is unknown but would be cool to find out. It obviously would have more of an effect with more lift due to the the RCH height further from the center of gravity height. All I know is I cannot get the right RCH iI want without cutting off the trackbar mounts

I'm confused

 

[Nelsonmd]

Have you read the excerpt on this on Sonoran Steel's website? They basically say the same thing.

Have you thought of making a custom watt's linkage for it? I haven't researched the difficulties of a watts linkage, but if you are doing custom work anyway, it could solve the problem of sideways motion at high flex.

 

[catalina34]

Have you read the excerpt on this on Sonoran Steel's website? They basically say the same thing.

Have you thought of making a custom watt's linkage for it? I haven't researched the difficulties of a watts linkage, but if you are doing custom work anyway, it could solve the problem of sideways motion at high flex.

I made a post not too long ago asking why no one uses a Watt's linkage and most of the replies were expense and the pan hard set up is "good enough". Watt's would certainly provide better manners though.

 

[1985taylor1925]

I havent seen the thread on pirate. What exactly is a three link? Does that mean you eliminate the two smaller swing arms in the rear, and then mount one centered to the rear axel?

 

[t4r4life]

wow never thought of that. i did feel more roll once the drop went on.

 

[J-money$$$]

Have you read the excerpt on this on Sonoran Steel's website? They basically say the same thing.

Have you thought of making a custom watt's linkage for it? I haven't researched the difficulties of a watts linkage, but if you are doing custom work anyway, it could solve the problem of sideways motion at high flex.

No I have not read much on sonoran steel's site.


Watts links do provide a higher roll center, and better stability. But they are pretty complicated builds. And getting everything just perfect would take some serious tuning. IMO moving the gas tank an double triangulated 4 link solves a lot, But then again im trying to keep overall costs to a minimum and swapping the tank location is pricey.




They there are a lot of compromises when your setting up suspension.


1985taylor, yeah pretty much.


And to those of you confused, Hey link suspensions can be confusing at first. I was just surprised what a difference a panhard drop would do to the RC compared to if you raised it on the axle side.

 

[Nelsonmd]

No I have not read much on sonoran steel's site.


Watts links do provide a higher roll center, and better stability. But they are pretty complicated builds. And getting everything just perfect would take some serious tuning. IMO moving the gas tank an double triangulated 4 link solves a lot, But then again im trying to keep overall costs to a minimum and swapping the tank location is pricey.

Here's the page: 4Runner - Fully Adjustable Trac/PanHard Bar (1996 to 2002) - $175.00 : Sonoran Steel, Sonoran Steel Custom Metal Fabrication L.L.C. Custom Toyota Truck Parts

It makes sense, and it is good to hear your experience that you definitely noticed the lower roll center.

As for the double triangulated systems, do you need beefier links to handle the added stress? The panhard is robust because the bar is in near direct compression, but the double triangulated links are in pretty oblique compression, so see higher overall forces. I havn't looked into suspension setups, so I'm being a noob here, but I googled this and found pics of double triangulated systems, and it seems some the links are at wide angles, and some they are at shallow angles. The shallow angles I would think cause some pretty high stress.

Also, just curious here, but do the upper and lower links need to have the same radius (i.e. effective length)? It seems the uppers are usually shorter, and I would think that would cause the axle to twist during flexing. Maybe it only looks like the uppers are shorter...

 

[1985taylor1925]

I made a post not too long ago asking why no one uses a Watt's linkage and most of the replies were expense and the pan hard set up is "good enough". Watt's would certainly provide better manners though.

I had never heard of this before. I just looked it up. That is awesome! Im going to do that to my truck one day, when I have the tools. It seems like that would have more limitations on axel extension for you guys who do more serious off roading though.

 

[MDST]

Very interesting!!

This topic made ​​me remember this:

http://www.toyota-4runner.org/3rd-gen-t4rs/101489-panhard-bracket.html

 

[fire931]

To the OP.. You are correct on your assumptions. By lowering the frame side you are lowering the roll center. Raising the axle side is a much better solution and typically when building custom 3 links you will see guys try and make the axle side bracket as tall as possible for this very reason. The problem with doing that on the stock setup is if you look closely there's a cross member directly above the panhard bar. So when you stuff the drivers side tire it would contact that cross member if it were any taller. I thought about raising mine 1 1/2" since that's how far I extended my bump stops down but don't think it's really worth the trouble, especially since there will be a 4 link going under the rear soon enough.

 

[fire931]

Very interesting!!

This topic made ​​me remember this:

http://www.toyota-4runner.org/3rd-gen-t4rs/101489-panhard-bracket.html

That would be the correct way to do it!