Panhard bar question

[Tyler James Inc]

[MENTION=118730]AssBurns[/MENTION] is that saying that with a 4" lift- with no PH correction- it only shifts the axle over 2.xxmm? Thats less than 1/8". Seems like it should be much more than that- more like the 18mm [MENTION=50342]JayRolla[/MENTION] experienced.
And I actually am running the Bilstein shocks that are made for a 4th gen with a 2" lift. Do you happen to know if the OEM 4th gen rear shocks are Tokico black- comparable to the LC OEM Tokico shocks?
Yeah, I've thought about the travel change with moving them outboard/perpendicular. That's one reason I've been thinking about just lowering the lower mounts. It would be pretty simple to do, so maybe I'll give that a shot first.

 

[AssBurns]

@ Tyler James Inc According to the drawing it is 5.xxmm shift at 4" lift which would be closer to 1/4". Still seems like it's not as much as I would have expected.


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[fourfive]

@ Tyler James Inc According to the drawing it is 5.xxmm shift at 4" lift which would be closer to 1/4". Still seems like it's not as much as I would have expected.

1/4" is about what I got too. My superflex gave me 3.5" of rear lift unloaded & my axle was shifted just about 1/4" to the passenger side with my stock panhard. BUT I was using a tape measure using the edge of my tire and fender flare as my measuring points which may not be the most accurate way to do it. I did measure multiple times though and consistently got 1/4 to 3/16".

I also agree that it's not that big of a shift. It's one of those things that nobody else would notice except the owner (I noticed the 1/4" shift everytime I looked at it).

 

[jkeith.w]

@ Tyler James Inc According to the drawing it is 5.xxmm shift at 4" lift which would be closer to 1/4". Still seems like it's not as much as I would have expected.

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Yeah, it works out to something ridiculously minor when I draw it up - which I why I questioned what an adjustable panhard was actually correcting.

I'm more concerned about any weird effect that a raked panhard bar (which places the two pivots in the rear suspension at different heights and distances from the centerline of the chassis) may have on steering inputs than the seemingly insignificant axle-centering changes. In terms of body roll, what happens when steering left? Does it pivot from the axle end of the bar (low RC)? When steering right, does the body then pivot from the frame side (high RC)? My truck has a tendency to step out under throttle in wet conditions when steering left - how much of that is attributable to an artificially low RC because of my raked bar? What happens in emergency lane change situations (left/right/left) at speed? Or when off-camber/pitched over to the right negotiating an obstacle off-road? Too many unanswered questions for me that I don't have to think about with the bar leveled.

On top of that, I've also noticed that at least one of the popular adjustable panhards have right hand threads at both ends - making it coarsely adjustable. You certainly aren't dialing in small bar-length adjustments/corrections without having left/right threads, so I'm doubting that I could address the axle offset from my ~2.5" lift with any precision with one.

:shrug:

 

[jkeith.w]

so, just saw this on crazydubman's thread:

:wow:

things get weird when both sides droop.

 

[JayRolla]

1/4" is about what I got too. My superflex gave me 3.5" of rear lift unloaded & my axle was shifted just about 1/4" to the passenger side with my stock panhard. BUT I was using a tape measure using the edge of my tire and fender flare as my measuring points which may not be the most accurate way to do it. I did measure multiple times though and consistently got 1/4 to 3/16".

I also agree that it's not that big of a shift. It's one of those things that nobody else would notice except the owner (I noticed the 1/4" shift everytime I looked at it).

After I did the SS panhard and used his adjustment I was still off .4" when I got it aligned.

 

[fourfive]

After I did the SS panhard and used his adjustment I was still off .4" when I got it aligned.

That was probably correct since your rear lift was a little higher than mine. ...and the .4" off center measured by the alignment machine is probably a liiittle more accurate than my tape measure tire-fender flare measurements. That was one of the reasons why I asked in an earlier post if there was a more objective way to measure the "centeredness" of the rear axle instead of eyeballing it with a tape measure.

 

[fourfive]

Yeah, it works out to something ridiculously minor when I draw it up - which I why I questioned what an adjustable panhard was actually correcting.

I'm more concerned about any weird effect that a raked panhard bar (which places the two pivots in the rear suspension at different heights and distances from the centerline of the chassis) may have on steering inputs than the seemingly insignificant axle-centering changes. In terms of body roll, what happens when steering left? Does it pivot from the axle end of the bar (low RC)? When steering right, does the body then pivot from the frame side (high RC)? My truck has a tendency to step out under throttle in wet conditions when steering left - how much of that is attributable to an artificially low RC because of my raked bar? What happens in emergency lane change situations (left/right/left) at speed? Or when off-camber/pitched over to the right negotiating an obstacle off-road? Too many unanswered questions for me that I don't have to think about with the bar leveled.

On top of that, I've also noticed that at least one of the popular adjustable panhards have right hand threads at both ends - making it coarsely adjustable. You certainly aren't dialing in small bar-length adjustments/corrections without having left/right threads, so I'm doubting that I could address the axle offset from my ~2.5" lift with any precision with one.

.25" is pretty minimal. The only time I noticed the rear end wag when I had the stock bar was going over large speed bumps. After centering the rear axle with the adjustable bar, I do still feel a mild wag on large speed bumps but it does feel a little less pronounced. I'd describe it similar to how my 4runner handled with the front end lifted to 2.5" and how it handles after lowering it to 2.25"....there was a mild improvement in the ride quality & smoothness in how it handled & my cv axles look a little less angled.

so I'm doubting that I could address the axle offset from my ~2.5" lift with any precision with one.

SS sends precalculated panhard lengths for various lift heights with his adjustable bars but I also agree with you about the precision aspect because although my rear axle looks centered, I'm wondering how squared up it actually is with my front wheels. I'm trying out different measuring techniques I can do myself to double check SS precalculated measurements. I'm reluctant to have an alignment shop do it since they rarely get the front right.

 

[AssBurns]

[MENTION=28464]eimkeith[/MENTION] check out some dirt track racing forums. They get into that stuff in some serious detail. The panhard bar can stiffen or soften up the suspension depending on the angle it is at. Also they talk about RC and how it effects roll axis and therefore effecting steering/ cornering. That's where I learned a lot on this subject, just because they actually break it down, not because I follow dirt track racing. Also Pirate4x4 has a lot of really good suspension geometry threads.


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[Coward]

This is a fun subject! I need to empty my brain of what I think so here it goes. So I think Keith's first thoughts on the PCK was, what good does an adjustable bar do? And what affect does the angle of the panhard bar have on handling when you lift your truck. So my thoughts are that the bar was designed to be level during driving. That means the general engineered design of the rear suspension in regards to roll center was a level bar. And a level bar means a centered rear axle. So an "adjustable" or longer bar is meant solely to rear-center the rear axle after you lift. Even if it's only off a few millimeters, it's off. With or without a properly centered axle you may be hard pressed to even notice that it will turn better at speed left versus right. The bar at an angle of X degrees after lifting it changes the severity of the centering of the axle. Movement left or right of center is exaggerated now because the bar starts at an angle vs flat. Someone else can work up a drawing. That would make it feel "looser" when you compress the suspension while driving (bumps,dips,turning,etc...) as the axle is moving off center line. Which it does even on a stock vehicle. Again its just exaggerated with an unlevel bar. That's part of the reason some say it feels "more tippy".
Keith's background in road race cars (and I'm guessing here) tells him that a level bar is always best. The dirt track forums will tell you adjusting the height of the bar on either side will change the way the car turns (left). So the PCK gets the rear suspension back to the way Toyota designed it. Nice and flat with a centered axle using a stock panhard bar. It helps correct roll center as well. And it for sure eliminates the exaggerated off centering of the axle while driving. Any change on hitting or not hitting the gas tank is coincidence. For me the reason I ordered them was to help on road driving manners. Just my two cents. Oh and read mark Donahue's book The Unfair Advantage to learn all things suspension (on-road anyway).

 

[Tyler James Inc]

I'm with you [MENTION=28464]eimkeith[/MENTION] as far as the axle being centered not being a major concern of mine. Haven't measured, 'cause I really don't care. I do care about it shifting when equally compressing, as well as handling characteristics.
Since [MENTION=118730]AssBurns[/MENTION] asked about up-travel on the OEM LC/extended billy shocks, I took some pics. Also some pics of the PCK axle bracket clearance to the crossmember. Not very helpful with my lack of up-travel. I did, however, verify outboarding clearance between tire and frame, as well as took a look at the lower mounts again.

"Clearance" shot-

Outboard space shot-

Video- attempting to show its at full bump-
https://vimeo.com/199398709

 

[97Run-Man]

Since [MENTION=118730]AssBurns[/MENTION] asked about up-travel on the OEM LC/extended billy shocks, I took some pics. Also some pics of the PCK axle bracket clearance to the crossmember. Not very helpful with my lack of up-travel. I did, however, verify outboarding clearance between tire and frame, as well as took a look at the lower mounts again.

Are running the sway bars still?


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[Tyler James Inc]

Are running the sway bars still?

I am, yes. But that doesn't affect my up-travel. The shock is "bottomed out".

 

[97Run-Man]

I am, yes. But that doesn't affect my up-travel. The shock is "bottomed out".

Oh! So it's the fact that the shocks are extended length! Isn't that a B. Need them for taller shocks and they shorten your up travel


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[jkeith.w]

and I'm with you; I'd be disappointed in the up-travel - so much unused airspace up there!

 

[Tyler James Inc]

Oh! So it's the fact that the shocks are extended length! Isn't that a B. Need them for taller shocks and they shorten your up travel

Exactly. I get more droop, but with 35's, I better be able to stuff that dang tire up there! Gotta change something.

 

[jkeith.w]

More stuff = more stable while crawling off-camber, no? (lower everything)

 

[AssBurns]

That's crazy how much those shocks limit your up travel! Thanks for posting those shots for us. You can see how little room there is up in the wheel well fully flexed out. Now try to stuff another 2.5" further up and you'll also notice that the more articulation you get the more the tire leans in closer into the wheel well. Almost no room for shocks up there at that point. I'm worried that when I go to 35's that I'll rub my tire on my shock with the wider tire. I need to try to get a picture somehow to show how little room there is between the tire and body at full flex. There isn't even any room to get a decent shot.

 

[Tyler James Inc]

More stuff = more stable while crawling off-camber, no? (lower everything)

I mean, yeah, for sure.
I just don't like limiting the suspension by lowering the bump stops, and I'm not gonna have my shocks take a beating from hitting max bump all the time. I have no problem lowering my bump stops if it's to keep my tire from binding and getting tore up on my quarter panel. I want to maximize travel, so I'm gonna set it up to have enough up-travel to stuff the 35 like I could with the stock shocks-

 

[Tyler James Inc]

[MENTION=118730]AssBurns[/MENTION] that pic makes me horny. Didn't you trim/reweld your quarter to give you more room? I'm thinking that's another tip I need to take from you/your rig. With my wheels being pretty high BS(5", but 9" wide), I think I could do the same. Stuff more, without looking cut out(cause our flares hide it).