This is a spin off from my "Plans for the Cobra" thread.
Anyway, I am now deciding on what Coil over spring rate for the front.
I am looking at the UPR kit. They offer springs in the following length and rate.

12" length: 200, 250, 350, and 400
14" length: 130, 165, 175, and 350

For the rear IRS I am running a stock 03 Cobra 600lb spring w/ one coil cut to drop it about 1.5".

This is a street car that will probably see some track time with Lman and Mberglo in the coming months so don't suggest some 130 rate spring or such.

 

I'm thinking the 350 or 400 bro....just my 2 cents, as far as the length.....got me...I'd say go 350 for the 14, and if it isn't to your liking, then go 400.....

 

For your suspension questions, I'd refer you to SEARCH on www.corner-carvers.com. Every suspension question concerning Mustangs has been beat to death there. Do NOT post there until you've read the Wiki and understand how the forum works. You will not survive first contact otherwise.

 

I registered, but have to wait for an admin to activate. In the mean time I plan on getting the car weighed, front and rear weights to assist with the decision.

I'm going to try and swing back by around 3p.m. to give you a hand. I figure if you're giving me free room and board in the trailer, the least I can do is lend a hand. I'll call first though.

 

Well I got the car weighed..ugh, she's a pig. All weights were with a FULL tank of fuel. I would be interested to see what she looses on the nose by a k-member/ coil over kit.

Front: 2040 w/ driver, 1940 w/o
Rear: *1680/60 /w driver, *1580/60 w/o
Total: 3700 w/ driver, 3520 w/o

* The scale kept bouncing from XX60 and XX80, i guess you could split it in the middle and say 1670 w/ and 1570 w/o.

I believe this give me a 55/45% balance.

 

Where did you get your car weighed?

 

On the Arsenal. Scales open 24hrs just drive on. If you can get on it let me know and I'll PM you the directions.

 

Spoke to Jason at Maximum motorsports today. He was more than helpful, After speaking to him, I think I will get everything from them. Here were his thoughts.

Get rid of my Steeda HD front swaybar, put the stock 98 back on. (thinking I will cause the car to understeer even more than stock)

Go with Bilstein HD struts to handle a 325 lb spring with a 10" free length.
look to replace front control arms with aftermarket, or at least replace bushings.

I can keep my stock 03 rear springs for now......

More to follow, wife's home now.

 

Yes I can get on...I am active duty Air Force

 

PM'd you.

 

Yea, don't let her know you've discovered Maximum Motorsports! That stuff is more addictive than crack.

 

Decided to keep costs down, Staying with stock arms and Poly bushings. Ordered today, Next Coil over kit.

Sell Eibach sportline springs and recoup some of the cost.

 

Poly bushings came in, need to order the coil over kit now.

 

Have you spoken to anyone about coil over spring rates? They are much different than conventional springs because of their mounting points. I'm curious what rates are recommended for your Cobra.

 

Remember, you're going to need quality camber/caster plates to run coilovers. I hope you're talking to someone at MM.

Coilover rates have a relation to conventional springs. Here's the math for you:

Front Coil Springs = 28% Conventional Spring (ie 600lb springs = 168lb CO)
Rear Solid Axle Coil Springs = 45% Conventional Spring (ie 400lb springs = 180lb CO)
Rear IRS Coil Springs = 66% Conventional Spring (ie 400lb springs = 264lb CO)

Also, keep in mind that CO have a better ride quality than conventional springs, so you can go stiffer than you'd think. I know Fox bodies that have 400lb CO fronts and 225lb CO rears, equating to 1428lb and 500lb respectively.

Here's the article from MM.
<TABLE cellSpacing=0 cellPadding=0 width=616 border=0><TBODY><TR><TD class=pageHeading colSpan=2>Coil-Over FAQs

</TD></TR><TR><TD class=plainBox vAlign=top width="100%">Q. How do I compare a front coil-over spring rate to a conventional spring in the stock location?
A. The spring rates must be converted into wheel rates. The wheel rate is the spring rate measured at the wheel. The conversion is done through the use of what's called the motion ratio. For a stock Fox Mustang front suspension, the wheel rate is 25% of the stock location spring's rate. For example, an 800 lb/in stock location spring has a wheel rate of 200 lb/in. For a coil-over suspension, the wheel rate is approximately 90% of the coil-over spring's rate. For example, a front coil-over spring rated at 350 lb/in would result in a wheel rate of about 315 lbs/in. Note: The exact motion ratio conversion of the wheel rate for a front coil-over suspension is determined by the angle of the strut. That angle is the result of the camber and caster settings, and by the SAI (Steering Axis Inclination).
Q. How do I compare a rear coil-over spring rate to a conventional spring in the stock location on my solid axle equipped Mustang?
A. As with front spring rates, rear spring rates must be converted into wheel rates. The wheel rate for the rear of a Mustang with a solid axle is approximately 50% of the stock location spring's rate. For example, a 200 lb/in stock location spring has a wheel rate of 100 lb/in. For a rear coil-over suspension, the wheel rate is approximately 110% of the coil-over spring rate (because the spring is actually behind the centerline of the axle). Also, because the shocks are mounted more outboard than the stock spring location, the rolling rate of the suspension is mildly increased. This helps to reduce understeer.
Q. How do I compare a rear coil-over spring rate to a conventional spring in the stock location on my independent rear suspension (IRS) equipped Mustang?
A. The wheel rate for the rear of a Mustang with IRS is approximately 33% of the spring rate in the stock location. For example, a 600 lb/in stock location spring has a wheel rate of 198 lb/in. For a coil-over suspension, the wheel rate is approximately 50% of the coil-over spring rate.
Q. Why does a coil-over spring with a higher wheel rate ride better than a conventional spring with a lower wheel rate?
A. Although the front coil-over spring in the above example increases the wheel rate by over 60%, the ride quality will actually improve. A conventional spring located on the front control arm contributes to ride harshness because of friction in the control arm bushings and ball joints. A front coil-over kit eliminates this friction by applying the spring force directly to the spindle and upper strut mount. Coil-over springs are also much lighter than a conventional spring. The resulting reduction in unsprung weight allows the suspension to more easily follow bumps in the road. Rear coil-over conversions provide a similar improvement in ride quality, although it's not as dramatic of a difference as the front kits.
Q. What are my options for adjusting ride height?
A. Ride height can be easily adjusted by changing the position of the lower spring perch (The spring perch is raised or lowered by rotating it on the threaded sleeve). The 5" to 6" range of adjustment is more than adequate when the correct spring is chosen for your application.
Q. I've been told that if I use a stiff enough spring for racing, my suspension will never bottom and I don't need bumpstops.
A. If you are running a spring that stiff, you will be hurting your car's ability to absorb bumps (large or small), which reduces your car's overall cornering grip. To quote Carroll Smith in Engineer to Win, "If you are not USING the bump stops, you are running stiffer springs than you need and are therefore giving away some cornering power." If some type of compressible bump stop is not even installed on the car, eventually a bump will be encountered that is large enough to bottom out something else in the suspension, resulting in damage to the vehicle.
Q. Why do you have different kinds of front and rear coil-over kits?
A. The dimensions and construction features of each manufacturer's strut and shock housings are not the same. This requires subtle changes to many components.
Q.What are the benefits of switching to a coil-over front suspension?
A. Better handling and better ride quality! When the spring is in the stock location on the control arm, the minimum spring rate for performance handling is 700 lbs/in. Better handling can be had with higher spring rates, but ride quality begins to suffer with rates over 850 lbs/in. A coil-over kit allows the use of wheel rates that are much higher than those obtained with an 850lbs/in spring in the stock location. This will dramatically reduce body roll and brake dive. Other benefits include easily adjustable ride height, the ability to do corner weighting, ease of measuring bumpsteer, less weight, and a wide selection of available spring rates.
Q. What springs are available from MM?
A. Standard 2.5" inside diameter coil-over springs are available in 25 lb/in increments between 175lb/in and 600lb/in, and in several standard free lengths. The wide range of springs available means that coil-over suspension systems are easily tuned by swapping springs to balance your car's handling.
Q. Are there any disadvantages of running a coil-over suspension?
A1. There may be tire and wheel clearance issues, depending on the wheel size, back spacing, and tire size. For example, our coil-over kit will not interfere with a 275/40/17 tire on a 17X9 Cobra wheel on an '87 Mustang with '95 spindles. The Konig Villain wheels will require a ¼" wheel spacer for clearance.
A2. Because the upper spring perch lowers the point where the bumpstop contacts the chassis, all non-Bilstein coil-over conversions will reduce the amount of available bump travel (no matter what others tell you). We have seen other kits that reduced the available bump travel by over one inch. To maximize bump travel, we carefully designed the upper spring perch assembly — it provides over ½" more travel than most other kits. Also, our exclusive bumpstop helps regain some of the lost travel because it is shorter and softer than conventional Mustang bumpstops. Don't be tempted to regain bump travel by not using bumpstops. Damage to your car, caster/camber plate, or strut will occur when the suspension bottoms.
</TD></TR></TBODY></TABLE>

 

MM recommended a 275 to 325 rate with a 10" free length.

As for the CC Plates, I currently have 4 bolt caster camber plates on the car, so that shouldn't be an issue.

I had also read the MM FAQ as well as tons of searches on corner-carvers.com. With everything that I had researched I compiled a list of questions to subject them to for clarification. MM was more than helpful, especially since I know JACK about suspension stuff.

I am going with MM's recommendations, I figure they have TONS of experience and I might as well use it vs' learning the hard way on my own.

 

"Wise beyond his years is he" - Yoda

 

Well, I contacted MM again today, Now I am planning on getting the Rear coilover as well, the recommended a 570# spring with a 8" free length for me. The kit requires no modification to the control arm or upper mounting point so it should be an easy install.

 

Finally got around to ordering the rear kit. I got the COP-7 from max motorsports with the 570# springs.

should be here in a couple of days......Now I have to fight with the stock coil springs in the rear. I haven't had good luck with them at all, the spring popped out of the compressor and caught my finger bewteen the frame once, then popped out another time but I was clear of everything. (I learned the first time)

 

Koni Single Adjustables ordered for the rear.