Spring rates needed for new front Viking coilover purchase

mjhcobra · #1 (**permalink**) 10-27-2014, 10:43 AM

Hi guys,
I am making the switch to coilovers on the front and I am going to try the Viking coilovers. They offer the 500# springs as standard and have a 375# option and a 600# option. My EM has the standard Mustang II front end with all stock control arms, springs, and shocks. I will be installing new tubular A-arms (5/8" narrower) to help bring my new front wheels inside the front fenders. With my 428, would the 375# springs be the choice for my setup or the 500# springs?

cycleguy55 · #2 (**permalink**) 10-27-2014, 12:40 PM

If you search the CC site you'll find coilover spring rates have been discussed a lot. Regardless of which way you go, you'll need to know the front weight, and perhaps the rear as well while you're at it - so find a scale.

As a starter I'd read the following thread - it has a few suggestions, including the experience of someone with a 460 (including air conditioning!) and his thoughts the 400# springs may be too heavy and he could have gone lighter.: Coilovers and MII front end

QA1 has a good article on spring rates at Street Performance & Racing Spring Rate Tech | Understanding Spring Rates | QA1 Suspension

QA1's recommendations for Mustang II front ends are as follows, based upon front end weight:
<1350 lbs.: 375 lbs/in.
1350 - 1525: 500 lbs/in.
1525-1700: 600 lbs/in.

Shorter suspension arms may call for higher rate springs, depending upon the geometry.

Your best bet may be to call technical support at Viking, QA1, Heidt, etc.

mjhcobra · #3 (**permalink**) 10-27-2014, 01:37 PM

All sound like good ideas. Would be great to be able to get my weight in the shop without driving to a local scale. I will contact Viking and get their take on my car. Any ideas on what a fiberglass cobra with an FE engine and Top loader would weigh in at? More importantly, what the front end would weigh?

cycleguy55 · #4 (**permalink**) 10-27-2014, 04:16 PM

A few years old, but here's a thread on Mustang II suspension upgrades on EM Cobras: Mustang ll front end upgrade

You might be well served to post your question on the Everett Morrison forum: Everett-Morrison Motorcars -- Speak with Julie and Brett - Club Cobra

You could also look at some of the posts on the EM forum and PM a couple of owners with FE engines.

Dwight · #5 (**permalink**) 10-27-2014, 05:23 PM

Do you have a Co-op or someone who sell feed grain? I used our local Co-op to weight the front and rear and total weight of my Cobra. Just pull the front wheels onto the scale and get a reading. Then pull onto the scale for total weight. Pull the front wheels off the scale leaving the rear tires on the scale.

The Co-op has a 20 lbs increment but should be close enough. Truck scale are another place you might try.
Dwight

mjhcobra · #6 (**permalink**) 10-28-2014, 08:44 AM

Quote:

Originally Posted by cycleguy55

A few years old, but here's a thread on Mustang II suspension upgrades on EM Cobras: Mustang ll front end upgrade

You might be well served to post your question on the Everett Morrison forum: Everett-Morrison Motorcars -- Speak with Julie and Brett - Club Cobra

You could also look at some of the posts on the EM forum and PM a couple of owners with FE engines.

Thanks for reminding me of what I should have done in the beginning. Unfortunately, the EM website does not see a lot of action these days. I will PM some of the guys with the FE motors for comments.

mjhcobra · #7 (**permalink**) 10-28-2014, 08:49 AM

Dwight, the co-op is a good idea. We have several feed stores in Tucson that are closer than the local scales. My car is down now so I am using 2,600 for the total weight, which appeared to be enough for the guy at Viking. Hopefully, I can get the tires in and the front end adjusted for the last time.

cycleguy55 · #8 (**permalink**) 10-28-2014, 09:40 AM

Quote:

Originally Posted by mjhcobra

Thanks for reminding me of what I should have done in the beginning. Unfortunately, the EM website does not see a lot of action these days. I will PM some of the guys with the FE motors for comments.

I guess I wasn't clear - when I mentioned the EM forum, I meant the EM section of Club Cobra (Everett-Morrison Motorcars -- Speak with Julie and Brett - Club Cobra), not the EM Web site (Everett-Morrison Motorcars).

mjhcobra · #9 (**permalink**) 10-30-2014, 07:50 AM

You were clear, it was my post that wasn't. I meant the EM club site as you suggested. That place does not see much action since nobody has a current build except me. The Viking shock rep said the 375# springs should work as long as I run a sway bar. The 500# springs in his mind would lift the front end up and be to stiff. I will run a sway bar, so it looks like 375# springs. The sway bar is the next item to research. From what I have read, I will need to get the new A-arms on and then determine where the bar will connect to the arms. Several guys have used the shock thru bolt and several welded a bung to the arm. I am leaning towards the shock bolt if I can find the correct width sway bar with the ends that layout properly.

cycleguy55 · #10 (**permalink**) 10-30-2014, 12:52 PM

My QA1 springs are marked 465#, though the closest I can find in the QA1 catalogue is 500#. I will say they're quite firm, and my car is most likely a bit heavier than yours, perhaps by more than 200 lb. Given the lighter weight of your, and the FE being 100 lbs. or so lighter than my 460 with iron heads, sounds like the 375# springs will work for you.

I haven't scaled my car, but West Coast Cobras seem to be on the heavy side of the various replicas due to the longer wheelbase, heavier frame construction and heavy fiberglass body. In addition, most of them have 429/460 engines and lot of them have C6 automatics (mine has a Richmond 5 Speed Street manual). The specifications page on Vern Redel's Web site lists the car as 2,850 lbs., but equipment varied quite a bit.

I really need to get mine to a scale when the weather warms up around here.

mjhcobra · #11 (**permalink**) 10-30-2014, 01:36 PM

Are you running a front sway bar? If so, who makes it and is it in front or behind the cross member?

cycleguy55 · #12 (**permalink**) 10-30-2014, 07:07 PM

With the exception of the QA1 coilovers and urethane bushings, my front suspension is full Mustang II - including the crossmember, sway bar, control arms, steering rack and strut rods. I've only had the car since July and haven't taken a real close look at it, but I suspect the sway bar is original Mustang II - connected to lower control arms via links. I also have a rear sway bar - this thing corners FLAT.

mjhcobra · #13 (**permalink**) 10-31-2014, 08:23 AM

Thats interesting that you have coil overs with the stock suspension. I thought that you needed to go with tubular arms for coil overs. My mistake. One guy used a bar from an MGB which has a pretty clean install. I may try that if my measurements work out with the shorter A-arms.

cycleguy55 · #14 (**permalink**) 10-31-2014, 10:09 AM

My QA1 coilovers use the same upper and lower mounts the shocks would use. I have given some thought to tubular arms, but less so after what I paid to have the urethane bushings installed.

Knowing what I do now, it would have been less expensive for me to purchase the tubular arms and install them myself than what I paid to install the control arm bushings. Missed opportunity. Lesson learned.

mjhcobra · #15 (**permalink**) 10-31-2014, 07:00 PM

The Viking Rep got a new manual today for the shocks and determined that a 2,600# car with a 60/40 weight ratio would take 500# springs. This is based on the 375# springs being good for 1,325# front end weight. He also stated that since the M2 spring is conical, the spring pressure is different form that of a "straight" spring. So my narrower arms and coli overs are now ordered. The sway bar will be looked at once the new arms are in. The MGB bar is definitely a consideration as is the TCI bar.