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Discussion Starter · #1 ·
Where did I go wrong?

When the rear of the GT body is closer to the axle. The panhard is not correct any longer. Panhard works in an arc and bringing the two closer should make your panhard too long. I thought the train was on the tracks so far. I cut the rod and shortened it after taking numerous measurements. Went to reinstall it and I am off double what I removed. I understand I screwed this pooch and can fix it. What I am wondering is how I got here? I keep looking at it and thinking about it and I am lost as to how it is the opposite of what it looks is true. Don't everybody laugh at once even tho it is pretty funny ...now
 

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With the GT on flat-level ground and 150 pounds in the drivers seat, the panhard rod should be installed and torqued to specifications. Why in the world would you want to cut and shorten it? It was designed by the Opel engineers to be a specific length for a given weight. Oh well, can you put some steel slugs back in the tube and weld it back to original length? I sure hope so.

Ron
 

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Discussion Starter · #3 ·
This is not stock it has one of OGTS's front springs, and the back is also lower. This changed the geometry for the panhard rod, it is 3/8 of an inch off. I just can't for the life of me figure out how I went the wrong way. I can make whatever I need, but I just hate to proceed without some idea how I got here. Before the rod was pushing the rear ascew now without it in I can see where it needs to be. I just can't see where I got off track unless as stock somehow the rod was below axle but that can't be. As it sits the rod is 3/4 inch short after taking 3/8 out. I know measure twice cut once.
 

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rod end?

I'd cut one end off entirely and substitute an appropriatly sized spherical rod end for the stock loop. One end being solid won't transmit too much vibration, and you would be able to adjust it after all is completed to the right length. I seem to recall that the ID of the stock tubing is a pretty good fit to be tapped directly, but I can't remember the size off the top of my head.

Do a search here for more info, there were a couple of really good threads on that part of the suspension a while back.
 

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in a right triangle try this formula- A squared + B squared = C squared. A being length from point of attachment on axle to directly under point of attachment to body on other side of axle , B being height between axle attachment and body attachment and C is the dimension your looking for, I think, I'm pretty sure if you can get accurate measurements and have a calculater, this should do it. Good luck with those measurements, I just looked under my GT, not a lot of room
 

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Discussion Starter · #6 · (Edited)
I have a short piece of the tubing and it would be better to weld in a nut. There is not enough wall thickness for that size thread. I still wonder about the geometry, does the panhard need to be longer? Or is something else shifted making for an optical illusion.
Also the panhard is pretty much paralell with the axle.
 

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still has to be a side B to form right triangle no matter how little of it there is. Longer would shift it to the drivers side, shorter to the passenger side. If the body anchor point is even below the axle anchor point, The formula should still apply. HTH
 

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Discussion Starter · #8 ·
Ok thanks Jim in measuring it I found why. Stock is above axle mount. In lowering the back it is now below axle mount more than it was originally above. This is why the panhard went from 30 inches and change to 31.036. I moved it across fulcrum point and gained instead of lost distance. Now knowing this the rear will act opposite of stock. When it sits down in the rear it will pull toward passenger side. Stock would push toward drivers side. I believe roll or twist reaction will still be the same.
 

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Where did you go wrong? Well, first you posted this thread in the wrong heading :) Please try to place posts in a heading that relates to the question. Thanks!

As for the panhard rod, there have been a number of excellent threads relating to suspension geometry on this site. A quick search for "panhard" turned up the following threads, with good discussion and great photos:

http://opelgt.com/forums/showthread.php?s=&postid=1438&highlight=panhard#post1438

And ESPECIALLY

http://opelgt.com/forums/showthread.php?s=&threadid=232&perpage=20&highlight=panhard&pagenumber=1

and

http://opelgt.com/forums/showthread.php?s=&threadid=1623&highlight=Panhard

HTH
 

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Discussion Starter · #10 ·
Ok I did the same search but found no mention of length. Alot of nice ideas but no mention of even a way to calculate a starting point for how long.
 

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If you're going with an adjustable bar, start with stock length. The variation in size needed when lowering the car is VERY small. If you plan to build a bar of the proper length you will need to collect more data which is somewhat difficult to measure. The best/easiest thing will be to build an adjustable bar of stock length and bring it to an alignment shop and have it adjusted...

I'd expect lengthening the bar by 1.036" to cause things to be MUCH worse than where you started.

-Travis
 

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Discussion Starter · #12 ·
Total addition to the bar was only .3, it now sits even in the rear. It just had me wondering when it came up the wrong way. I know it will need to be aligned but at least now it isn't obviously wrong. Until Jim convinced me to measure a different way I kept looking at it as a shift when it came down across the arc. It eluded me that it was now on the other side of the arc center. Then again on a stock setup is the right side mount below the axle mount? If so then I had a major moment going for me. Well at least I had the opportunity to share with you all this experience. If the right mount is lower, don't tell me I feel stupid enough already.
 

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Even .3" seems rather large. Note that if your new bar is NOT adjustable the alignment shop won't be able to do anything with it...

-Travis
 
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