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Discussion Starter · #1 ·
Folks I am new to the site, so forgive me if I ask stupid questions. And I apologize for the really long read. First of all, I recently acquired an early Factory Five car that was built in 1999, I wanted to build one, but my wife convinced me that I should buy one first and see if after tearing it apart and putting it back together I have the skill set to do it then build one....made sense so here I am. The car was built using a 1988 Mustang GT as a donor that included the Mustang wheels. As soon as I got it home, I purchased a 5 lug conversion kit (axles, rotors etc), and proceeded to swap them out and put a set of Halibrand replica wheels on the car (15 inch). While the appearance is 100 times better, after driving the car, I started to get wheel rub inside the rear fenders over harsh bumps. I sent pics to the folks at Factory Five and was told that it appears that the car is a little lower than normal caused by the original springs sagging. So i began checking into what I needed to do and found in the build manual which I was fortunate to acquire that the original springs had to have 1.5 coils removed from the top before installing. Now finally here are my questions.
1. From reading online, it appesars that the 88 Mustang had variable rate springs, is that correct and can I cut them or should I get constant rate springs.
2. How is a cut spring different than just buying a lowering spring that has the same length
3. I also read in the build manual that when installing the springs, "suspension height adjustments are done in the rear by twisting the spring from its normal position on the mount to a position higher or lower"...could my problem be that simple to resolve?
Any responses will be greatly appreciated.
 

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If you're stock springs are sagging, you would make that worse by cutting the spring.

Yes, you could simply turn the spring and raise the rear suspension. That might work, and it's worth a try.

The donor springs should have been cut by 1.5 coils, as the manual states. But, they may have been cut by more than that. If that's the case, you'll have to replace the springs.
 

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Congratulations on your purchase and I hope you love it. Be prepared to spend a lot of time and $$$$ getting it exactly the way you want it. For openers I would suggest tossing the mustang springs and converting to coil overs with 250 Lb rear springs. You'll need a set of traction loc brackets for the installation but they're cheap, easy to find and I have a set if you can't find some close to you. Good luck.

Frank
 

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FFCobra Fanatic
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First of all welcome to the forum. You came to the right place for all the answers! Probably the best solution to your problem would be to replace the Mustang coils and shocks with a set of coilovers. Its a little more expensive now but its that much of an improvement in ride quality and adjustability. The next decision you would have to make would be where to buy them from. FFR sells Koni shocks as does Gordon Levy, Breeze sells QA-1's which are adjustable so you can fine tune to your taste or activity. If you click on the "Advertiser" tab at the top of the page you can find both Breeze and Levy Racing. As for the Mustang springs, they are variable rate and theoretically could be replaced with something like the Eibach Pro Kit. You would still have the same problem of the springs spinning over time lowering your ride height. If you want to, just jack it up and disconnect the shocks allowing the rear to hang down on just the springs, then you will be able to twist them back down to raise your ride height. Good Luck with it!

Mike
 

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Great to have you here. This is where I got my help!

I just finished building a MKIII using a 88 donor and have the same setup...stock 4 link, Mustang coil springs on the rear with 1.5 coils removed. I purchased new springs and after 1000 km had to adjust them 1/4 a turn since things settled. I was very pleased with the way my car handled...I have 17" wheels, four lug. If I were you, cut new springs, install and adjust the height. Upgrades can come later ..... that's my plan!

Rocky
 

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Official OLD GUY
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Yup, that's the ticket

Sounds like your wife is a smart woman . . . save the upgrades for now, see if the springs can be adjusted (twisted) for now. Drive the car for a bit and then, if you really love it and still want to build one from the ground up, that would be the time to go all out on upgrades . . . full coil-over suspension or IRS in the rear, 4 wheel disks on 5 lugs, PS if you lean that way.

Get to know the car, they can be a beast and many have sold because they don't feel they can live with it's little "quirks" and the ever present possibility that the car will get out-of-control before you can blink. These cars are not toys and can you can get in big trouble fast.

Just my 2¢

We are all here to help you spend your money and answer any questions you can come up with along your journey.

Welcome to the madness!!

Doc :beerchug:
 

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Congrats and welcome to the club. I too purchased a pre-owned Cobra, just recently after looking for many years. The price was good, and my wife agreed. My mk3 was also built with doner suspension and 4 lug turbine. As I wasnt to happy with the look of the wheels, I upgraded to 5 lug with 17" SVE 10th Anniversary Cobra wheels. I increased the ride height in the back by turning the coil springs, but havnt road tested yet. Im planing on a coilover upgrade very soon. I still have manual steering and rear drum brakes and Im happy with that area.

Im new to this also, and have learned alot from the people on this forum, dont be affraid to ask questions.
Where do you live? Pa?
 

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My roadster was a strict donor build with new mustang springs. Had all kinds of issues until I changed to coilovers. The best bang for the buck modification on my car!
 

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My roadster was a strict donor build ... The best bang for the buck modification on my car!
Same here. Much better overall ride & handling, no more noticeable body roll or driveshaft hitting the E-brake bracket. Not a difficult mod, either. I got all the info I needed to do it right here.
 

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Cobra Nutcase
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As others have said, toss those springs in the trash and buy yourself a set of coil overs. It is one of the best mods that you can make, and I went with the VPM coil overs.

Rob
 

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Discussion Starter · #11 ·
Congrats and welcome to the club. I too purchased a pre-owned Cobra, just recently after looking for many years. The price was good, and my wife agreed. My mk3 was also built with doner suspension and 4 lug turbine. As I wasnt to happy with the look of the wheels, I upgraded to 5 lug with 17" SVE 10th Anniversary Cobra wheels. I increased the ride height in the back by turning the coil springs, but havnt road tested yet. Im planing on a coilover upgrade very soon. I still have manual steering and rear drum brakes and Im happy with that area.

Im new to this also, and have learned alot from the people on this forum, dont be affraid to ask questions.
Where do you live? Pa?
Brian I live in the Harrisburg area, so not very far away.
Carmen
 

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There is another issue that jacking the coil springs up glosses over. If the rim was backspaced to center the tire, then there would be no rubbing, inside or outside. Since many don't check, they get rims that fit 85% of what is out there, or worse, whatever is on the shelf, then adjust everything else to compensate. Not always for the best.

No doubt the rims chosen look better, but they don't fit better. I've done it, so have many many others. It's really a mistake, and finessing the installation doesn't fix it. Wheel fitment starts with centering the rim in the wheel well, not picking a rim for it's looks. That's actually just window dressing. Yet we get the priorities reversed all to easily.

The next issue is having the widest rubber we can possibly cram under the wheel well. There are limits, and the wider we go, the less we get for the incremental increase in costs. Adhesion doesn't go up as fast as price on tires. It's their sand box, and you have to pay to play. In terms of all year, all weather use, the wider tires suffer more loss of grip in slick conditions than a narrower tire - they let go quicker. And they are usually not chosen for their wet weather ability. It rains in the summer, too.

In cars with these power to weight ratios, tires won't be able to hook up anyway. Many with mildly built motors report spinning them easily, even in higher gears. It still depends on driver skill to prevent it, the car has an abundance of power. Going to a Plus 2, 3, 4 oversize won't stop it. They will just cost more.

If the look of having the perfectly fitting tire in the maximum size is the goal, step back, check the backspacing, order the custom rims. Likely rims in stock won't be the ones you really need. When the clearance is measured in fractions of an inch, then you have to backspace the rim in fractions of an inch.

Don't forget, measure them at full droop and bump, they change camber going up and down, and things aren't always the same.
 

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I've built these cars both ways and for a highway cruiser I prefer the cut down Mustang coils. If I was going to the track I would definitely switch to coil overs but the softer ride of the donor style spring is far better for cruising in my opinion. I do have to have my ride height a bit higher in the rear and have the occasional drive shaft binding on large bumps but I check the drive shaft frequently and so far see no indication of damage. IMHO you should crank up the springs and drive it for a while, get used to the car and see what else you might want to change. You may find that you want to switch to a different rear suspension design and then you can do it all at once.
HTH
Bill


Sent from my iPhone using AutoGuide.com App
 

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Discussion Starter · #14 ·
There is another issue that jacking the coil springs up glosses over. If the rim was backspaced to center the tire, then there would be no rubbing, inside or outside. Since many don't check, they get rims that fit 85% of what is out there, or worse, whatever is on the shelf, then adjust everything else to compensate. Not always for the best.

No doubt the rims chosen look better, but they don't fit better. I've done it, so have many many others. It's really a mistake, and finessing the installation doesn't fix it. Wheel fitment starts with centering the rim in the wheel well, not picking a rim for it's looks. That's actually just window dressing. Yet we get the priorities reversed all to easily.

The next issue is having the widest rubber we can possibly cram under the wheel well. There are limits, and the wider we go, the less we get for the incremental increase in costs. Adhesion doesn't go up as fast as price on tires. It's their sand box, and you have to pay to play. In terms of all year, all weather use, the wider tires suffer more loss of grip in slick conditions than a narrower tire - they let go quicker. And they are usually not chosen for their wet weather ability. It rains in the summer, too.

In cars with these power to weight ratios, tires won't be able to hook up anyway. Many with mildly built motors report spinning them easily, even in higher gears. It still depends on driver skill to prevent it, the car has an abundance of power. Going to a Plus 2, 3, 4 oversize won't stop it. They will just cost more.

If the look of having the perfectly fitting tire in the maximum size is the goal, step back, check the backspacing, order the custom rims. Likely rims in stock won't be the ones you really need. When the clearance is measured in fractions of an inch, then you have to backspace the rim in fractions of an inch.

Don't forget, measure them at full droop and bump, they change camber going up and down, and things aren't always the same.
The wheels I bought were from Factory Five and designed to be used with the setup I have, and I kept the same tire size that was on the car when I purchased it which are a very tame 255/60R15
 

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Two things. 1. build skills. If you want to build one, and have any doubts about your abilites, go to build school. It is a great experience and will let you know if you really want to build. If you just want to own and drive, they can be purchased complete for much less than you can build right now.

2. $$$ You can also think about converting to a 3 link or IRS and resolve the issues the be$t way possible :)
 

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Discussion Starter · #16 ·
Thanks for all the help guys...gotta tell you I just turned the springs just under 1/2 turn and it worked perfectly, changed the ride height just enough, still looks great and we drove about 8 miles on some crappy roads and did not rub at all. Sure beats buying new springs and cutting them. Once again thanks for your help and I am sure I will have more questions:eclipsee_steering:
 
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