Just curious on this one (trust me I searched my a$$ off and found everyone was using the 620's, but why.). I'm looking to change mine out because of some tire rubbing issues. I like the ride height I have but the shocks and springs seem to be shot. Any thoughts would be great.
I went for the Lighter coils, and Glad I did (66). The 550s I think they are. Which have the 1" drop to them. I was in a fellow stangers car with 620s and it knocked my fillings loose, and I don't have FILLINGS LOL. Either way, it is a preference, I feel the 500s are firm yet forgiving enough for my driving style. I run a firmer shock (soft coil, firm shock) so all seem to dampen just right to make me happy.!
620s aren't that stiff I also have 5 leafs out back. To me they are a little more than stockers but give you the drop. If you want stiff go to 700 series.
I agree, 620s are all you would want for driving around town. 620+ would be NO fun on the street. Anyways, to answer your question of why?........ For better performance. DUH. why eles? A 620 is a stiffer spring, hence, they will hold the car up better in agressive cornering. IMO, after driving on maier 600's (chopped a little), a soft or adjustable shock is reccomended with 620's. I have KYB shocks and they are st..st..sti..ff!! Tyler
I have since changed to Edlebrocks IAS and they do ride nicer,ive never comapared the handling to the KYB's though
the 620's don't make the ride harsh...ISK is correct- i had bought the 720's by mistake and i didn't find out till after i had cut them and installed them with the kyb shocks. it felt like i had truck springs in my car... i went ahead and changed my shocks first to see if it would help. i went to the summit adjustables and put it on 90/10's to see if it made a difference- IT MADE A HUGE DIFFERENCE!!!! It feel so nice and smooth now- but still works well in the corners... street driven. i put my KYB's on my girlfriends 66 with stock springs and shocks to stop her's from floating like a cadillac.
Thanks for everyones replies. I decided to order the 620's after tons of searching, with so many positive results. I'm not so much worried about the harsh ride I just want to stop the tires from rubbing everytime I hit a bump, or have a passanger in the car. I do like the idea of have a more stable feeling going around turns then what I have now. I already have the KYB shocks that I'll install with the new springs. I can't wait to feel the difference.
I do too and I agree. However, I do not think it is excessively choppy. Stock mushy springs like mine and a stiff shock are a bad match. Hopefully some 620s will be coming my way around the 25th...
the big reason that people use the 620's is that is what shelby used on the GT-350's. the reason he used them was to limit suspension travel in most driving regimes as much as possible to prevent balljoint damage, and to improve handling with bias ply tires. these days with modern radial tires, you dont need springs that are as stiff as the 620's. a 540lb springs does very nicely, especially when combined with a good shock absorber, like the edelbrock ias or the kyb gas adjust shocks. the gr2's are also a good shock to use as they are softer than the kyb's, but still provide good control. one more thing, the stiffer the spring you use, the harder it is for the tire to maintain proper contact with the road surface when things get bumpy. and when you add subframne connectors, you lose the twsting of the chassis, and thus end up with a stiffer ride.
Just curious where everyone bought their 620 springs at. I bought my 620 springs from Mustangs Plus and I hardly think they were stiffer than my stock springs with 1/2 coil cut.
Just because they say 620 springs doesn't mean that is the spring rate. That happens to be the size of the rod used to make the coils. Maier Racing tested those 620's from MP and found them to be in the mid 500 range. The 720's (hence the rod size) have their place with big blocks. The KYB's are not even close as strong as the Koni's. The new custom Bilsteins provide even more dampening. I felt the KYB's were too spongy on my ride in the rear. However I have the Maier 200 race leafs on mine. I went to the Koni's on the rear and they were perfect. The stiffness is usually the spring rate but not the dampening. The shocks should just take the bounce/float out of the springs. Shouldn't increase the spring rate. If you go up in spring rate, you should in turn go up in shock dampening so the springs don't over power the shocks. I'm as guilty as the next guy for lowering the front of my car in the nose for a good rake. For balance tuning, the car should sit more level and the ride feel changes drastically.
As has been said, it's to limit suspension travel. However, what wasn't addressed is you want to limit suspension travel due to the unfavorable stock suspension geometry of our cars. In simple terms, when your suspension compresses, positive instead of negative camber is induced on the outside wheel. The Arning* drop does help with the camber issue, but it's just a band aid for the poor suspension geometry. Conventional theory is to run the softest spring possible while controlling roll stiffnes with sway/sta bars. What's the best combo of spring and bar? Depends on your driving style/preference. That's why they call it suspension tuning. Pick up Chassis Engineering by Herb Adams. It's a good read and really helps you understand all of the different variables involved in suspension tuning. With that said, I'm running 620's with KYB Gas-Adjust shocks on my car. I don't really consider it too stiff...probably because the car flexes so much as is. I still need to do some chassis stiffening before I get my suspension dialed in. Arning* drop: Klaus Arning was the Ford suspension engineer that came up with relocating the upper control arm on the Shelby Mustangs. As they say, there's no glory in engineering.
dang, I knew I hung around here for a reason! Been doing this crap for almost 20 years and here I go and learn something new!
I'm no pro! I just know from what I've seen, driven and discussed. I've heard the contradictory, heavier spring rate and less bar, the driving style pref. quote is key. With more sway bar, you are lifting the inside tire when the body rolls. The sway bar itself is a spring. Most of the racer's that I know tend to go toward the higher spring rate theory and less bar. Especially in the back. Mike Maier seems to do pretty well with the higher spring rate theory. Granted he can drive the **** out of any car We're talkin' race cars here so this is in extreme applications. Street driving applications are more forgiving and you would set the car up more for versatility (ie somewhere in the middle). 600# and KYB's in the front are a nice combo for a SB on the street
620's work find. Your dentist will love you when the 700's series go in! I have used as high as 1100 at the Big D. HistoricMustang www.historicmustang.com
