To answer the question, you will have a gap between the spring and upper spring seat at full rebound with 8" springs. I corrected my gap with some Hypercoil spring helpers. With a 10" you would probably be OK.Like the title says Why would I want an 8" 10" oe 12" spring in the 325# range?
Im getting MM coilovers and plan on the 325-350# range for springs. I want a great cornering street car.
you will have a gap between the spring and upper spring seat at full rebound with 8" springs
You are correct sir. However, having the same car, same setup and same length spring I speak from experience. With the MM coil overs there isn't enough threaded collar to prevent this from happening with an 8 inch spring in his desired rate, even at standard ride height. With a 10 inch spring you can make it work. Had this been a Honda or a Nissan or F-Body he was asking about, then I wouldn't have a clue. I this instance I do have a clue.With C-C down I was bored and looked through here a bit. I tired, but I just couldn’t leave this technical error alone.
Spring free length in a coil-over application has nothing to do with whether or not the spring will go slack at full droop. I know it seems like it should and lots of people apparently think it does, but it doesn’t.
Car weight, ride height, and spring rate all have an effect. Spring length doesn’t…
I actually found that going to coil-overs on my then street-only car made a huge difference in ride quality. I was using the exact same Koni dampers, just went from conventional springs to D&D coilover sleeves. I was pleasantly surprised how much better it felt, despite the fact that I was actually running a higher wheel rate than I had been with the conventional springs.That being said I would also question the reasoning to run coil overs on a street car. There are many other things youcan do to improve street manners that would be a more effective use of your money. A good set of dampers along with a set of quality springs goes a long way. From my experience a PHB cures a lot of the handling woes of a Mustang by making it much more predictable.
With the MM coil overs there isn't enough threaded collar to prevent this from happening with an 8 inch spring in his desired rate, even at standard ride height.
I'm not quite sure what you are driving at. The man asked about using an 8, 10 or 12 inch 325# spring with MM CO's on his 03 Mustang. I said the 8 inch would not be long enough without helpers, that a 10 inch would be a better choice. How you can infer that my response dealt with anything other than that specific application is beyond me. Yes, you can use different length springs if you are willing to purchase additional pieces to make it work. Shorter struts, travel limiters or helper springs are all options. But with stock suspension travel up front, 8 inches is not long enough no matter the spring rate, car weight or ride height without other parts added to the mix.Huh??? If you run out of threaded collar, you can't get it to the ride height that you want. What does that have to do with the point I was trying to make?
If you use a spring spacer with the 8" coil-over spring so that you can get the ride height you want with the available threaded collar, the fact that it is an 8" spring is still not going to have anything to do with whether or not the spring goes slack at full droop.
It seems that your main argument is that by using spring spacers, you can avoid an 8" spring going slack on suspension droop.
If I have 12.5" between the upper and lower perch at full droop, then a 10" and a 12" spring will be slack at full droop while a 14" spring will still be in compression. Seems pretty simple to me.What??? My argument is that spring length has nothing to do with a spring going slack at full droop. If an 8" spring goes slack at full droop in a certain application, a 14" spring is also going to go slack at full droop in the same application. A spring spacer also has nothing to do with a spring going slack at full droop.
There's no terminology issue. Assuming each or your 10", 12", and 14" springs are the same rate, the spring perches are going to be different distances apart in each case. By assuming a fixed distance between the perches, you're ignoring the fact that coil-overs have an adjustable lower spring perch, and it's not going to be at the same location on the coil-over sleeve when you have springs that have the same rate but different lengths. Basically, your example doesn't make sense.If I have 12.5" between the upper and lower perch at full droop, then a 10" and a 12" spring will be slack at full droop while a 14" spring will still be in compression. Seems pretty simple to me.
EDIT: Mr. Hidley beat me posting, guess there is a terminology issue.
It has nothing to do with the spring being 8" long. That's Richard's point, which you still seem to be missing. At a given corner weight (say, Jack's 1000#), if I use an 8" 325# spring and a 10" 325# spring, they're both going to compress the same amount: 3.08". To get the same ride height with both springs, the 10" spring's lower perch must be 2" lower. So when I jack the car up, the 8" and 10" springs both have the exact same 3.08" of extension, and if the strut has more droop travel than that, the spring will lose contact with the upper seat.Glenn said:So what does all that have to do with the fact that an 8 inch 325# spring on a Mustang will separate from the seats at full droop?
Ok, I will put on my dunce cap and go sit in the corner now. The light bulb just popped on. I was looking at the forest instead of the trees.So yes, you are correct, an 8" 325# spring will lose contact with the upper spring perch at full droop. But so will a 10" 325# spring, and so will a 12" 325# spring. That's all that Richard has been trying to tell you.