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Discussion Starter #1
Hello, everyone. I'm hoping you could help answer a few questions for me. While rebuilding my 69 XR7 convertible's suspension (front and rear), I replaced the stock setup with the following parts:

PST Polygraphite front suspension
1 inch lowering springs
KYB gas shocks all around
New OE rear leafs
Rear sway bar
1'' front sway bar

And now my car runs like a washboard. It is very, very stiff and beats me up over even small bumps. I havn't hit any large ones yet, and quite frankly fear that eventuality. Also, my rear end is very high in the air, even with the stock spec springs. The car does turn great, though. My mechanic said it would soften significantly over time, and the rear leafs would settle eventually. How much it would settle, however, I have no idea. Has anyone here gone through this change and have any advice on how to handle it? Also, is it the shocks that are making it so stiff or what? Pushing downward on either the back or the front is futile- no bound or rebound. Any help or suggestions would be very helpful.
 

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The Polygraphite does not give at all. The original rubber bushings wear out after twenty years because they actually move. The Polygraphite should outlive you.

I got new springs from Detroit Eaton for my green GTE through Mustang Country in Paramount, CA. They were and are very stiff although they were alledgedly the same spec as original I find it hard to believe. The car rides pefectly if four people are inside.
Fortunately the ass end is not raised up. I have my doubts yours will ever come down.
 

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Try to go to Globalwest.net and see the observations they have regarding suspension systems and Polygraphite. While you are there you can check out what they have to offer. Sorry you already spent the money.
 

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Global West used to sell Polygraphite strut rod bushings, they quit a couple years ago. Probably because a lot of customers were mad about strut rod breakage!

Here's a quote from their website:
"Caution: Too high of a durometer bushing in this location can cause strut rod failure due to too much resistance in the direction of pivot. That is why we prefer rubber in this location over other high density plastics".
 

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Discussion Starter #5
The front coils are 620's from Mustangs PLus and the rears are original type from Mustang Unlimited. Would the front springs be bringing the rear up? Also, on the stiffness, I also bought all new upper,lower a frames, etc. with the polygraphite from PST ($549) to make this setup nice. Had no idea it would be this stiff. I appreciate all comments.
 

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Looks like I'm in for a rough ride as well. I'm in the middle of a similar rebuild on the same model 69 XR7 Convert. I went w/American Pony Midolyne bushings, but the rest of my configuration is similar to yours. The only good thing is I waited on the rear springs. I'll make sure I get the 1" drop rear springs.

I guess this means that low profile tires are probably a no-no. I'll probably stick w/50 or 55 aspect ratio tires.
 

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hmmm thats strange
i had sold my front end rebuild set from PST to logan and he says its pretty good .Perhaps a lil stiff but overall good.Iintend to go with global west suspension on the 70 vert when its in its resto stage
thanks
pat
 

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I've got 620's from Mustangs Plus. They are pretty stiff. I read in M&F that shock choice is important with stiffer springs. They say to avoid one option.

As far as your back end riding high, did you tighten the eye bolts with the full weight of the car on the wheels (did I ask you this in another thread)? If not, this could be your problem. You may have locked an artificial arch in the spring, as I did. The fix is simple. Loosen, then retighten the eye bolts making sure the weight is on the wheels. Afterward, my backend came down to where it's supposed to be.

Steve C.
 

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Same w/ mine
i replaced the rear leafs from PST as well i matched them to the originals and they have a big difference in arch.Once i installed them it sat high but after putting a floor jack to the shock plate and loosening it and tightening it they settled down and have a good level stance .
thanks
pat
 

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To update this thread, my son Jason's mechanic secured the rear sway bar incorrectly. The sway bar was removed and minor adjustments made and the car dropped 3 inches and had a nice firm ride. Several miles down the road now, the car has a firm but not totally stiff ride and I am in the process of duplicating the same type of suspension(although I may go with 500's in the front coils because my back is several years older than his) in my 69 m code conv. project. I am going to try and install the sway bar taken off Jason's car on mine. I bought some brackets from NPD that should position it correctly. We'll see. Sorry this update didn't get posted sooner.

Jim
 

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I believe the shocks are a major part of the stiffness of your ride. I have the same set up with stock springs and it is fairly stiff. Although the low profile tires don't help.
 

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It is interesting to hear from all of these different Cat owners. I too have a 69 XR-7 convert. that I have run in SCCA Solo II events for 10 years+. When I did all the upgrades to the front & rear suspension,I too had some of the same problems. The car has 1" drop in front w/ 1 1/16" bar, 426Lb springs and KYB's. The rear has 428 CJ spec springs and a Boss 302 rear sway bar, 3:50 gears, and KYB's The tires are 235-60-15. The ride is still very stiff. I never had height/settling problems. I agree w/ Royce's statement "The car rides pefectly if four people are inside." Oh, all the suspension is Moog w/ exception of poly swaybar endlinks. The overall suggestion to anybody else considering suspension work, is to take your time, choose carefully, and don't expect things to "soften" much if any!
 

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I once purchased a set of leaf springs and installed them on my old '71 convertible. The car was SO high, it was ridiculous and they were stock rate springs. I took it to my mechanic who removed two of the leafs. That made the car sit at stock height with a ncie cougar type ride. The current owner of the car (a friend of mine) is still very happy with the way the suspension rides, six years later.
 

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I love the PST kit. I don't think my front end is sitting high at all...

I run KYB's and don't find the ride TOOO harsh, it is a bit, but not to an unacceptable degree.

 
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