Hey guys, just having a debate with a few friends...
Talking about panhard rods like those fitted to Gemini's and VN-VS commodores...
We all know that if you lower a car with a panhard rod (not watts link) the car shifts to one side as the rod is a solid bar...
But my mate is also saying that when you lower the car it will also adjust the ride height on one side... Im not sure his reasoning behind this... he just said he seen heaps of lowerd gems and they all slant to one side...
I said its just a coincidence and it would have been from sagged springs, badly seated springs or one tyre not inflated as much...
Only way I can see the panhard rod effecting ride height is because the weight of the vehicle is shifted to one side so is lower on that side... But were only talking like a 1-2inch shift and I cant see that causing a noticable height difference..
Can anyone confirm or deny?
Panhard Rod Debate
Started by
_Viper_
, Apr 02 2008 11:26 PM
25 replies to this topic
#2
_82911_
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Posted 03 April 2008 - 07:33 AM
Your mate is right.....It is because of the lateral shifting of the differential, relative to the chassis.The suspension bushes will be binding slightly as well as being out of alignment in the fore/aft plane.This causes the wheel rate (stiffness seen by the wheel) to be greater on one side of the car.
#3
orangeLJ
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Posted 03 April 2008 - 08:46 AM
but cant that simply be remedied by fitting an adjustable panhard bar?
#5
_Viper_
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Posted 03 April 2008 - 05:51 PM
Yea we know fitting an adjustable panhard rod moves the diff back to center... were just having the argument of weather or not the stock panhard rod causes the car to slant over to one side (at normal ride height) when you fit lowerd springs...
I dis-agree with what you said 82911 to a point... If you fitted the lowerd springs and then fitted the panhard rod while the car was just sitting there, there panhard rod wouldnt be trying to twist at all, the only force would be left and right...
I agree that while your driving and the diff is moving up and down the bushes could bind up tho..
I dis-agree with what you said 82911 to a point... If you fitted the lowerd springs and then fitted the panhard rod while the car was just sitting there, there panhard rod wouldnt be trying to twist at all, the only force would be left and right...
I agree that while your driving and the diff is moving up and down the bushes could bind up tho..
#6
_82911_
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Posted 03 April 2008 - 06:01 PM
OK.... look at it this way. The panhard rod puts a side load on the suspension bushes. it is this "offset force that causes the bind. The bind will be greatest on the side that has the panhard rod mounted to the axle as this will be the low point in the panhards arc of rotation. It is this side that will have the greater ride height.
This is true only if you use an adjustable panhard rod as Orange suggested.If you fitted the lowerd springs and then fitted the panhard rod while the car was just sitting there, there panhard rod wouldnt be trying to twist at all, the only force would be left and right...
#7
_rorym_
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Posted 03 April 2008 - 06:33 PM
^^ I looked at the answer...thought about it and agree..if it is a solid non adjustable rod and you lower the car...it will sit strange on one side...the rod is the culprit.....
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#8
_82911_
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Posted 03 April 2008 - 08:06 PM
Something else that might help to explain a little better....
The total stiffness of the suspension is determined by spring rate + any extra rate from binding bushes etc.....
The side load forced on the trailing arm bushes are greater on one side than the other because the diff is pushed sideways by the panhard rod.
This makes the suspension stiffer on one side than the other. It is this that makes one side higher than the other.
Clear as mud hey!
The total stiffness of the suspension is determined by spring rate + any extra rate from binding bushes etc.....
The side load forced on the trailing arm bushes are greater on one side than the other because the diff is pushed sideways by the panhard rod.
This makes the suspension stiffer on one side than the other. It is this that makes one side higher than the other.
Clear as mud hey!
#9
rodomo
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Posted 03 April 2008 - 08:39 PM
So, if 2 identical cars (except car 1 has panhard mounted left to body and right to diff, and car 2 is visa versa) were running around the same clockwise circuit one would handle better than the other, yes?Something else that might help to explain a little better....
The total stiffness of the suspension is determined by spring rate + any extra rate from binding bushes etc.....
The side load forced on the trailing arm bushes are greater on one side than the other because the diff is pushed sideways by the panhard rod.
This makes the suspension stiffer on one side than the other. It is this that makes one side higher than the other.
Clear as mud hey!
#10
_82911_
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Posted 03 April 2008 - 08:54 PM
Yes, correct.
Exactly why Winston cup cars mount their Panhards to the chassis on the left side.
Anticlockwise ovals...........Not the most high tech machines for road racing(Nascar).
Exactly why Winston cup cars mount their Panhards to the chassis on the left side.
Anticlockwise ovals...........Not the most high tech machines for road racing(Nascar).
#11
_Viper_
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Posted 03 April 2008 - 09:14 PM
Hmmk so its the pressure its putting on all the bushes (including the trailing arms) thats making it sit higher eh?
If you pushed that side down tho wouldnt it move down to the same height and hold? or would it push up again...
I still dont quite understand how it would hold one side higher, I understand now that one side would have more resistance to suspension travel due to the extra force on the bushes.
So say you did up your trailing arm mount bolts up supertight which put extra pressure on the bush would this also make it sit higher?
If you pushed that side down tho wouldnt it move down to the same height and hold? or would it push up again...
I still dont quite understand how it would hold one side higher, I understand now that one side would have more resistance to suspension travel due to the extra force on the bushes.
So say you did up your trailing arm mount bolts up supertight which put extra pressure on the bush would this also make it sit higher?
#12
TerrA LX
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Posted 03 April 2008 - 09:35 PM
Just pull the pan hard bar off and see if it settles the car.
#13
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Posted 03 April 2008 - 10:12 PM
It would come back up to where it was before you pushed, because that side has a higher wheel rate than the other side.If you pushed that side down tho wouldnt it move down to the same height and hold? or would it push up again...
Spring rate + rate from bush bind= wheel rate. One side is stiffer so it sits higher.I still dont quite understand how it would hold one side higher, I understand now that one side would have more resistance to suspension travel due to the extra force on the bushes.
If they were rubber bushes and you did them up with the suspension at full droop, then YES.If they were urethane then no.So say you did up your trailing arm mount bolts up supertight which put extra pressure on the bush would this also make it sit higher?
#14
rodomo
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Posted 03 April 2008 - 11:39 PM
If the car was assembled AND all the ride heights were even AND you fitted a panhard that slipped straight on without having to jack the car or push the body across, it wouldn't alter anything until the car accellerated and/or turned a corner.Hmmk so its the pressure its putting on all the bushes (including the trailing arms) thats making it sit higher eh?
If you pushed that side down tho wouldnt it move down to the same height and hold? or would it push up again...
I still dont quite understand how it would hold one side higher, I understand now that one side would have more resistance to suspension travel due to the extra force on the bushes.
So say you did up your trailing arm mount bolts up supertight which put extra pressure on the bush would this also make it sit higher?
#15
_Viper_
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Posted 03 April 2008 - 11:42 PM
Yea thats true. Ok I guess I conceed defeat, and he was right in the panhard rod thats not central will cause a difference in ride height... How much are we talking here tho? like mm's or would it be visually noticable?
#16
rodomo
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Posted 04 April 2008 - 12:20 AM
Stationary, it would depend on how much the body had to be jacked or pushed to fit the rod. Again, if the rod "slips" on (adjustable/custom rod) it wouldn't alter anything.Yea thats true. Ok I guess I conceed defeat, and he was right in the panhard rod thats not central will cause a difference in ride height... How much are we talking here tho? like mm's or would it be visually noticable?
#17
micklx
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Posted 04 April 2008 - 07:35 PM
Does anyone here have the capability to build me a panhard rod ?
The standard bar on my racecar fouls against the 9 inch. The adjustable bars with a bend in them that I've looked at don't quite bend far enough.
The standard bar on my racecar fouls against the 9 inch. The adjustable bars with a bend in them that I've looked at don't quite bend far enough.
#18
TerrA LX
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Posted 04 April 2008 - 07:53 PM
^ Can it be bent further?
#19
_82911_
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Posted 04 April 2008 - 09:36 PM
Yes I can build you one..
Adjustable panhard to suit 9" in commodore?
Do you want it made from 4130 or CDW ?
Adjustable panhard to suit 9" in commodore?
Do you want it made from 4130 or CDW ?
#20
_moot_
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Posted 05 April 2008 - 06:42 AM
theory is correct,but in practise....
have you guys seen how sloppy most gemini diffs are without the panard rod? i doubt that the 10 odd mm that the diff is going to move to one side would bind the bushes.and i'd hate the see thwe diff angle articulate up a driveway with these bushes
have you guys seen how sloppy most gemini diffs are without the panard rod? i doubt that the 10 odd mm that the diff is going to move to one side would bind the bushes.and i'd hate the see thwe diff angle articulate up a driveway with these bushes
#21
_82911_
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Posted 05 April 2008 - 07:27 AM
Of course there is a lot of lateral movement without the panhard fitted.....have you guys seen how sloppy most gemini diffs are without the panard rod?
THEY ARE A 3 LINK.
#22
_Viper_
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Posted 05 April 2008 - 08:59 AM
Yea all gems come with a panhard rod standard... And Lowering can shift it to one side up to like 30mm. I had to get an adjustable one for mine as it was just under 30mm out.
#23
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Posted 05 April 2008 - 11:56 AM
i think you missed my point.my point is that with all that slop,i find it hard to belive that the bushes will bind.Of course there is a lot of lateral movement without the panhard fitted.....have you guys seen how sloppy most gemini diffs are without the panard rod?
THEY ARE A 3 LINK.
#24
micklx
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Posted 05 April 2008 - 04:33 PM
This pic shows why I need a panhard rod with a bend in it.
82911 - I'm not fussed what its made of, whatevers cheapest I guess, the standard one would be staying there if it didn't foul the diff housing. I've chopped out one bush and I guess this is why. While we're at it, I don't suppose you can make me some front castor rod bushes that will give me more +ve castor than std? I've got the adjustable rods atm but they need to come off to meet the Improved Production regs.
Hmmm, must sort out my diff breather too.
#25
_rorym_
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Posted 05 April 2008 - 04:45 PM
The aftermarket ones have a bend in them....look in my thread.
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