why 620's over stock springs

Discussion in 'Classic Mustangs' started by KreagerM, Dec 16, 2005.

  1. tylerrocks New Member

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    I just dont see how you could make this statment. I have maier 600# an kyb's and I cant stand it.

    Tyler
  2. mdjay Premium Sponsor

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    I ran it for years and loved it...
  3. mdjay Premium Sponsor

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    Also Tyler, those Maier 600# springs are more agressive than the MP 620's...

    There's lot's of people running this set-up and love it.

    I don't know the stance of your car but if you drop the rear, the balance of the car equalizes and improves the ride comfort...
  4. Mosse Founding Member

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    I have 620´s and Kyb´s in front and I´m satisfied with them. I have kyb´s with 5-leafs out back, and have some wheel hop problems, with shelby traction bars. Next I´m going to try different stocks out back, if that could help.

    What happened to those Eibach progressive springs?
  5. 94stroker New Member

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    We have the 620s on my dads car with konis all the way around and that thing is so tight it just takes turns like none other.
  6. hobbyhorse New Member

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    I have the older Eibach progressive rate springs Pro-motorsport engineering used to sell. They still offer this spring by another manufacturer. They are the 480 to 680# competition springs. They ride smooth for everyday driving but have the stiff rate when you lean on them. If you are going to run a conventional suspension setup this probably the direction you need to go. This will keep your feelings in and your kidneys in good shape.
  7. Red Barchetta Founding Member

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    I've seen Mike drive as well and my god is it amazing. But in addition to his driving talent, you also have to look at how his car is setup. The suspension geometry of his car is nothing like ours.

    That's why I said to check out Herb Adam's book. It gives a good base line knowledge to use as a starting point to understand what's going on with our cars.

    Example:

    We can agree that the stock geometry, or even the Arning/Shelby drop do not give us the ideal camber curve. Therefore, *to control the camber changes caused by body roll, you need to limit the roll angle by changing the roll stiffness of the suspension.
    So, with that said, the theory is you run the lightest spring you can get away with. Now, if you're lifting the inside tire (as per your example) then that would be a situation where you would probably want to try less bar and more spring. It doesn't mean to chuck your 500lb springs for some 700's and ditch the sway bar. It's all about tuning. Same can be applied with the rear. You always hear about people who run stiff rear springs and say their car handles like crap with a rear bar. The most likely cause is there's too much rear roll stiffness.

    The other thing about running a stiff spring is that the stiffer the spring, the harder it is for the wheel to follow road bumps and irregularities.

    As I said, it's theory. Not until you start actually putting theory to the test will you know what works best for you. From a tuning perspective, it is much easier to tune with stabilizer bars than it is springs. Adjustable stabilizer bars are the cat's meow and allow you to adjust the roll stiffness quicker and easier than swapping out springs. However, it is possible that even after running through the full range of your bars adjustments...you might end up needing more spring. :D

    And to clarify, I run Maier Racing 620's and a Maier Racing 1 1/8" front bar. I have a Maier Racing 1/2" 3-way adjustable rear bar that I have yet to put on my car. The difference the front springs and bar made are incredible. But there's definitely room for improvement. But before I put the rear bar on, I need to stiffen up the car first. Only then can I get the most out of my suspension tuning.

    * paraphrasing Herb Adams
  8. rbohm Founding Member

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    the two seemingly opposing theories on suspension settup are actually after the same end, getting the roll stiffness front and rear properly balanced for the most neutral handling possible. both theories have their proponents and opponents, but both have been used to great effectivness. there are also those, like me, who allow the fact that there are situations where one theory works better over the other. example;

    on a smooth race track, it is better to use stiffer springs, and tune the suspension with shocks and sway bars.

    on a rough track, or the street, it is usually better to use softer springs, and stiffer sway bars, and tune the suspension with shock valving.

    while i usually subscribe to the latter theory, i can, and have, seen the former one work very well. it all depends on how the driver like the car set up.
  9. mdjay Premium Sponsor

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    Great info guys....

    By the way, Mike runs around Hayward in a race prepped 67 fastback with slicks :)

    I had the ride of my life with him in the 67! I've always felt I was pretty good until I rode with him. He is one of the best susp. tuners/drivers I've ever met.
  10. kwkenf New Member

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    Which KYB's is everyone talking about?

    Gas-A-Just
    or
    GR-2


    Thanks,
  11. kwkenf New Member

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    Please specifiy which ones.
  12. mdjay Premium Sponsor

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    They're all talking about the Gas-A-Just ones.

    The GR2's are soft.
  13. 65ShelbyClone Founding Member

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    I know I am, but further investigation leads me to think that G-A-Js have soft low-speed valving and pretty firm fast valving. Cruising along over rolling bumps my car is like a boat, but hit a speed bump faster than a walking pace and it'll knock fillings loose.....and mine are composite.
  14. kwkenf New Member

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    So would the GR-2's be to soft? Manly driven on weekends only.

    Thanks
  15. Hack Active Member

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    I have 620s in my car, and I love them. I have considered going to 7XX rate springs. I currently have the stock shocks; I'm going to change shocks before I make up my mind on springs.

    Regarding spring rate: if you are racing you want to run extremely heavy springs. There are multiple reasons, but a few are: to limit suspension movement because it's impossible to create "perfect" suspension geometry, and limit suspension movement for aero (you don't want a lot of air under the car so you need parts of the body very close to the road).

    Spring rate on a street driven car is entirely different. I remember a number of years ago reading about that year's Mustang Cobra being set up with softer springs than the GT and actually ending up being quicker.

    Good posts on roll stiffness as well. You want the roll stiffness in the front and rear of the car to be as nearly equal as possible. Otherwise you end up working one tire harder than the rest and your corner speed is reduced.

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