panhard rod

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flyingbanana

Member
Posts
92
Location
Southampton england
I've noticed that now that my RRC has been lifted the front Axel seems to be one sided I've been told
I need an adjustable panhard rod.
As money is bit tight can I cut and lengthen and weld up my old one with plenty of strengthen,
its only about 10-12mm shorter any one done this.
I can't see any problems
 
Never lifted suspension to that extent but if I did then I'd be looking at the pick-up points and the radius it creates from them.
The panhard scribes an arc and the ideal vertical tangent line is 90 to the horizontal.
Probably easy to extend the rod with good welding but is that all anyone recommends for a suspension lift, surely there is some geometry adjustment at the mounting brackets to undertake?
 
flyingbanana said:
I've noticed that now that my RRC has been lifted the front Axel seems to be one sided I've been told
I need an adjustable panhard rod.
As money is bit tight can I cut and lengthen and weld up my old one with plenty of strengthen,
its only about 10-12mm shorter any one done this.
I can't see any problems
Click to expand...

I haven't done it, but if I needed to I would (but get someone else to weld, mine aren't up to it yet). I'd slide a sleeve of the same or greater cross-sectional area over the rod, butt join in an insert (10-12mm as you say) and then slide the sleeve over and weld that too.
 
Installed in correct alignment the panhard rod should only be controlling a tension and compression force, no bending.
However, the cycling of stress ranges between compression and tension is a key component of fatigue.
What do those that peddle the kits say? If you bought an off the shelf kit would it simply be a 10mm longer rod (possibly rose jointed) and that's it?
Check first but if you do weld then make sure its good.
Surely if the axle is being forced or held one way now it will still be incorrect when extended and the suspension is at other end of travel.
 
The reason I'd go for a pre-made one from a parts supplier rather than a home made one is the question of liability in the event of an accident. The CPS and insurance companies can and do go after home mechanics. I'm sure 99% of the time it would be fine but I'd still worry. I see the purpose made ones are around the £50-60 mark, so by the time you've bought some bits of metal, a second hand one to practice on etc. and paid someone to weld it, there wouldn't be much saving. Plus with an adjustable one you can centre the axle fairly accurately.
 
Bantam1 said:
Installed in correct alignment the panhard rod should only be controlling a tension and compression force, no bending.
However, the cycling of stress ranges between compression and tension is a key component of fatigue.
What do those that peddle the kits say? If you bought an off the shelf kit would it simply be a 10mm longer rod (possibly rose jointed) and that's it?
Check first but if you do weld then make sure its good.
Surely if the axle is being forced or held one way now it will still be incorrect when extended and the suspension is at other end of travel.
Click to expand...

A Panhard Rod is only ever the right length in one position - if it's the correct length then that is when the vehicle, at a chosen load and at the desired attitude, has the axle laterally central. At any other time the axle is either to one side or the other, and it's the modifier's job to get that length right. It's not a perfect mechanism and you won't see one on anything designed for precise handling.

@Brown makes a very good point though. If you're not well enough qualified to argue and win your case in court, buy ready-made.
 
A better solution would be to ‘move’ one or both of the mounting points by the lifted amount to obtain standard geomtery, then you can use the standard rod
 
Grem said:
A better solution would be to ‘move’ one or both of the mounting points by the lifted amount to obtain standard geomtery, then you can use the standard rod
Click to expand...
That’s exactly what I would have thought too.
It’s a matter of retaining geometry.
 
Grem said:
A better solution would be to ‘move’ one or both of the mounting points by the lifted amount to obtain standard geomtery, then you can use the standard rod
Click to expand...

Ideally yes, but the rod bracket's a pretty difficult thing to recreate in a longer format, and as I pointed out earlier, the rod is only the right length in one position anyway, and the best position would be so low that it would be at risk of occasional grounding.
 
Or possibly the axle mount could be higher.
The greater lever arm on the mount would need better reinforcing too.
I'd say the tangent line is supposed to be vertical at the mean travel point when in use (which may not necessarily be the mid point of the spring travel).
These things tend to be used on bigger axles so the radius they scribe is big and the sideways movement therefore small.
Adding 20mm seems wrong because that 20mm will shove the axle a further 20mm at some point.
 
Bantam1 said:
Adding 20mm seems wrong because that 20mm will shove the axle a further 20mm at some point.
Click to expand...

But that's the whole point of the thread. He's lifted the suspension, so moved the axle down from the chassis, and the standard length rod is now pulling the axle to one side when at rest. He needs the extra to push the axle back to central.
 
And what he’s saying is that because the static angle of the angle is steeper when the suspension compresses when the rod gets horizontal the axle will be the extended amount out of where it should be
 
He may be saying that (because his explanation isn't clear) but if he is it's wrong. I've no idea what he means by the tangent line (tangent to which arc?) or the scribed radius. Radii normally scribe arcs. I've also no idea what your angle of the angle means.

I think he may be trying to say that a horizontal rod is good because the axle doesn't move sideways much. That's true for small suspension movements, and OK on a road car. But as the movements get bigger the axle is moving sideways more and more and always towards the chassis bracket.

Now if the rod isn't horizontal, but at a steepish angle the axle always moves one way as it falls and the opposite way as it rises. And it moves a bit more to the right than the left for a given movement down or up. But as you drive over these big bumps in a lifted LR on off road tyres do you honestly think that you could tell through the steering?

The OP's RR is lifted by about 89mm further away from the chassis than standard (I did the geometry). This has moved the axle right by about 10mm, so he needs about 11mm more in the rod to centralise the axle at rest. If you think through what a Panhard rod actually makes the chassis do as the axle rises and falls the distances they do when you have the abnormally large suspension travel that he has then you wouldn't worry about a few mm here or there.
 
I have now googled and found the following pic on panhard geometry.
panhard.jpg


I don't know how credible the source is but the pic seems to capture the geometry issues we are debating here.
I think you're right Boguing, off-road who cares what position the axle is in as long as it hasn't come loose or destroyed the chassis connections.
I am more concerned for the on road condition, especially if this attracts unwanted attention from the constabulary.
It could of course upset the impeccable handling and control we all enjoy on the road too.
 
boguing said:
Now if the rod isn't horizontal, but at a steepish angle the axle always moves one way as it falls and the opposite way as it rises. And it moves a bit more to the right than the left for a given movement down or up. But as you drive over these big bumps in a lifted LR on off road tyres do you honestly think that you could tell through the s compliant asteering?
Click to expand...
So should he be splitting the difference and not extending by the 10 to 12 mm he think he needs but 5 to 6mm? If it always moves one way, which it will, then when passengers and load are applied it could settle into a more compliant rather than less compliant alignment.
However, without re-positioning the geometry closer to the ideal you are surely restricting movement rather than easing it so why wouldn't you at least try?
I appreciate this is all very theoretical and in practice would have little real benefit on our vehicles but I dont see why it can't be as ideal as possible.
 
It should be set with the axle in the centre when carrying the normal load. Bear in mind that you're still comparing with the perfect horizontal rod, whereas a Landy is already compromised by about 80mm.

If the OP loads this car up significantly he's going to have far greater worries than fine-tuning the rod for it. Nigh on 4" suspension lift remember? Centre of Gravity heading skyward, possibly no castor correction and much worse body roll on the longer springs.
 
boguing said:
It should be set with the axle in the centre when carrying the normal load. Bear in mind that you're still comparing with the perfect horizontal rod, whereas a Landy is already compromised by about 80mm.

If the OP loads this car up significantly he's going to have far greater worries than fine-tuning the rod for it. Nigh on 4" suspension lift remember? Centre of Gravity heading skyward, possibly no castor correction and much worse body roll on the longer springs.
Click to expand...

They do look good though.
Probably higher maintenance than standard though.
 
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