OK, so I'm getting ready to order some suspension parts for my 1970 fastback and I need some front and rear spring advice. I plan on using 245-45-17 tires all around. Up front, for now I am going to stick with stock control arms with a 1" shelby drop on the top arm, 1" front and 3/4" rear anti-sway bars. The pictures below show a 69 with the stance that I am trying to achieve. Up front I was thinking about 620's and 5 leaf mid-eye's in the rear. I think this will get me close to the stance I'm looking for. I want the car to handle well, but I don't want it to have an unreasonably uncomfortable ride either. For those that have this combo, how does it ride? Also, does anyone have an opinion as to whether this combo will get me close to the stance in the pictures?
IMHO 620 coils are to stiff for any one who makes the statement "I want the car to handle well, but I don't want it to have an unreasonably uncomfortable ride either. " 620 are very stiff, I know I had a set on my 64.5 and I hated them. I live in NW MT so it is ALL curves and hills and... potholes so for me handling is not just the ability to hit a corner at 90+ miles an hour but to also be able to enjoy the ride. Best advise I ever got was to get a set of coil springs that were stock or stock performance if Ford offered a slightly stiffer spring for your application, then cut off 1/4 of a coil and use a performance shock such as kyb gas adjust. Cutting the coils not only shortens the springs but also increases the spring rate. KYB Gas adjust are really great shocks. They will turn even an old sagging set of original 40-year-old springs in to something drivable because there stiffness automatickly increases as speed increases. The 5 leaf mid eye is a good selection but not if your after the stance in the picture. There is quite a bit of distance between the rear tires and the rear fenders, more like normal eye 5 leaf springs. Also keep in mind that when you replace your spring both front and rear the car will sit high for the first couple of weeks to a month. For some reason Mustang settle slowly over time. The Shelby drop is a good option 1" should be sufficient, make sure your bump stops are intact and in good shape. The front sway bar is a good idea but for a street car I don't think I would put on a rear sway bar. Some people like them but as a whole they really change the way the car drives and more importantly how you must drive it. If you already have it, I would start with out it and see how you like the car then if you want a little more try the rear sway bar. I know more people that have installed one and then taken it back off than people who have installed one and kept it.
Most importantly regardless of part selection GET A PERFORMANCE ALIGNMENT NOT TO FORDS SPECS Print out this sheet and take it to the alignment shop:
Please align to these specs “1967-1970 Mustang, Falcon & Cougar Performance Alignment with Shelby drop”.
These specifications are in order of importance.
1. NO more than .25 degrees difference between driver’s side and passenger’s side.
2. +2.0 to +3.5 degrees caster.
3. -.5 to 0 degrees camber. No positive camber, please. There is no problem having a slight variation from driver’s side to passenger’s side to account for the crown in the road.
4. 1/16" to 1/8” toe in
If you run into any problems attaining these specs, please call me (your phone number here).
Also even if they are new I would rebuild the UCAs for extra caster and improved motion and greasibility. I can give you more info on that if you are interested.
Hope all this helps if you have any questions please don’t hesitate to ask.
< Message edited by Daze -- 1/15/2008 7:50:35 AM >
Regarding the front springs, I have to decide soon because the old front suspension parts are long gone. I had also heard that the 620's were very stiff and is why I wanted feedback from users. It sounds like they are stiffer than I want. I basically want good handling, but want to be able to drive the car without being beat to death. Does anyone know what the stock spring rate for a 1970 Fastback is? Also, what do you think of the Contour 550# rate springs that NPD sells? How about the progressive rate springs that are out there?
In the back, I can always just leave the springs I have in there for now and decide later. All I know right now is that the car sat too high with the springs that came with it. Granted I don't know really what they are but with stock shackles it sat higher than I want. My guess would be that they are stock springs I have right now. I will measure the free arch and count the leaves to see what is there. Those pictures I posted are from Mustang Monthly and near as I can tell from some of their articles, that car had the mid-eye leaf springs. I could actually stand to have it sit a little lower than the pictures, but I don't want to go too low to start as I could always get another 1" from lowering blocks. I know some don't like lowering blocks at all, but for 1" I can live with them.
For control arms, strut rods, etc., I plan on stock style replacements control arms, roller spring perches, and home brew adjustable strut rods for now and later on I plan to build a set of tube style control arms with roller pivots.
I have a 69 Mach 1 that will also be getting a suspension refresh after the 383 Dart project is finished. I too am looking at the Shelby drop, already have KYB shocks, and need new rear springs.
Daze, do you have an opinion on best place/manufacturer for 4.5 or 5 leaf stock eye springs?
I can tell you where I got mine and that is NPD. At the time they had the best selection and price, however all of the Mustang supply places seam to have them and when it comes to leaf springs for a mustang one is as good as the next assuming that everything is equal like # of leaves or eye position. I have talked to a lot of different Mustang owners who have purchased things like springs from all the different venders and there doesn't seem to be any quality differences in springs so what I would do is order from the vender that has the combination you want at the best price sum total for springs and shipping. IMHO
Posts: 2031
Joined: 9/5/2006 From: Barossa Valley, South Australia Status: offline
I live in an area like Daze only the hills are waaaay smaller and the potholes can be so big that we find lost English backpackers in the shady side.
FWIW, I went too stiff all round chasing better handling and it backfired on me. our roads are too rough and the car tends to skip around on the bumps. I have plenty of travel, but the set up is just too stiff and the "compliance" is just not there. In short, its a pig to drive at speed.
I have now found a local guy who is great with older suspension setups. His thinking with cars like mustangs is to go reasonably stiff in the front due to the engine weight and reasonably soft in the rear to allow compliance and travel without skipping around. My rear sway is coming off!
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Suspension questions - 
