Rear Coil Over Spring Rates

[JV106]

1990 GT Convertible - full weight, will probably relocate battery to the trunk and have a sub in the trunk in the future.

I want it to hook up well on the street, ride well on the street, look good, and most importantly not rub the tires on minor bumps.

Right now it sitting on Eibach drop 1.5" drop springs, 17" cobra R's, Nitto 275/40's on the rear 255/40's up front. The drivers side rear tire is getting into the fender to the point where it's cutting up my brand new tire on mild bumps. Passenger side is doing it too but it's minor in comparison.

Did it worse when I took 100 lbs worth of my little girls around the block in the back seat.

I want to do coil overs just on the rear for now and hopefully eliminate the problem.

What height spring and spring rate should I run?

[onjacks]

Have you rolled the fenders yet?

[JV106]

No sir, Late Model's website said they'd fit so I was hoping to not have to. Body work is something I'd prefer to not take on myself and I'm not ready to have all the paint and what not done yet.

[onjacks]

Eastwood fender rolling tool can be rented on Craigslist. Or here. It really needs to be done on any mustang with wide tires that's dropped. It won't mess up the paint and prob cost less than changing springs. Going with a stiffer spring rate will kill comfort.

[Trick Pony]

If you're just doing the rears the handling is going to be imbalanced if you change up the wheel rate. Are you planning to do the fronts later or not at all?

[JV106]

I do plan to do the front later and I didn't know it would cause an imbalance. My logic was to have an adjustable ride height to not tear up these tires until I get ready to continue with suspension and body work. Right now I'm scared to drive it for fear of cutting them up and I just got the damn thing put back together...

[fastwhite99gt]

They recommended 10" tall 150lb/in springs for my rear coilovers, I'd probably go a bit stiffer since yours is a drop top.

[JV106]

I called maximum motor sports - as mentioned doing the rear only would create a dangerous imbalance. So I can either roll the fenders as mentioned or get a wheel with a different back spacing. I think the springs are installed incorrectly so I'm going to look into that 1st, change the shocks and struts, change the bushings and hope for the best.

[Trick Pony]

I called maximum motor sports - as mentioned doing the rear only would create a dangerous imbalance. So I can either roll the fenders as mentioned or get a wheel with a different back spacing. I think the springs are installed incorrectly so I'm going to look into that 1st, change the shocks and struts, change the bushings and hope for the best.

Another alternative would be to get a coilover that gives the same wheel rate as the Eibach springs you have in the rear to maintain the handling balance.
The factory spring location puts wheel rate at 50% of spring rate. With coilovers it's 110%. If you can find out what the spring rate of your current springs is, you can figure out the equivalent coilover.

[White90GT]

What about the Maximum Motorsports lower control arms with the adjustable spring perch? That's also something to consider.

As far as fender rolling, you're only rolling the very inside lip of the fender so that the sharp edge doesn't contact the tire. I've done mine simply using a crescent wrench on the lip and bending it upwards and in. Just go slow and don't bend a lot at one time so as not to crack the paint.

[JV106]

Any tricks to getting the control arm bushings out, the oval ones are giving me fits.

[HECDOGGIE]

I will be running 12" 200lb coilover springs on the front, based off the content in this thread , it is highly suggested i run rear coilovers as well? Or is that only true when running rear only ?


Hector

[Trick Pony]

As long as you can get the wheel rate you want you don't really have to run coilovers in the rear just because you run them up front. On mine I am still running coilover type springs in the stock location out back with the MM adapters. They are offered in 25 lb/in increments and lighter than factory springs too.