03-01-2005, 03:44 PM | #1 | ||
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Talking with MM...
...this is what the guy said about rear coilovers:
Quote:
Quote:
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1998 Mustang GT Coupe - World's Slowest Racecar 2005 Toyota 4Runner SR5 V8 2013 Volkswagen Jetta Sportwagen TDI |
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03-01-2005, 07:24 PM | #2 | ||
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Re: Talking with MM...
I had always heard to skip the rear coil-overs on the IRS cars, but this was of course before MM started to get involved. But it makes sense considering some people were running a 1100lb conventional spring in the rear!
When you say soft springs, please don't be confused with them actually being soft. Coil-Over Math Wheel Rate = Spring Rate * (Motion Ratio)^2 Conventional spring motion ratio is 1/4 (.25) Coil-Over spring motion ratio is 9/10 (.9) Your car has 600 in-lb Front / 600 in-lb Rear springs. So lets get the class started. 600 * .25 = 150lb wheel rate with a Conventional Spring They are probably going to recommend a 375lb front spring, so lets try that one first: 375 * .9 = 337.50lb wheel rate with a Coil-Over Spring. See the difference? Quote:
337.5lb / .25 = 1150lb conventional spring to do the same amount of work. I'm willing to bet that they will recommendation of 375/375 or even 375/400 for your car considering the IRS has a longer moment arm than a stick axle. Quote:
If you look where your conventional springs mount, they are very close to the control arm attachment points. From "Statics and Dynamics", you should remember this causes a great deal of load forces on the bushings in these locations. (You know, resultant force increases as you move towards the point in question) These forces in turn cause static friction on the bushings and create bind. Whenever you migrate to coil-overs you are reducing the static friction and causing less bind on the bushings. In doing this, you allow the bushings to do their job which is allow the Control Arm to move freely. The spring is also allowed to do its job more efficiently because its not fighting the bushings (static friction) as the arm moves up and down. With the system working in harmony, you get a better ride with awesome handling potential. One last thing; I would suggest skipping the Bilstein "Sport" Valved shocks that they sell with the kit because at 375lb you are at the limit of the rebound valving. I am experincing this problem right now with my car. I'd look into either: the Race Valved Bilsteins or Koni DA's. Hope this helps!
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03-01-2005, 08:26 PM | #3 |
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Re: Talking with MM...
Thanks for the reply, Nathan. The wheel rate and control arm bushing stuff all makes perfect sense.
I figured the springs wouldn't be soft, as in Crown Vic soft or even stock Mustang soft, but softer than most people think they need to be. It seems there are some guys out there who think the springs need to be so stiff they might as well have welded a big steel cylinder in place of the springs. I was going to simply have my stock Bilsteins modified to use with the coil overs. This may be a temporary setup for a while until I go to the Race Valved Bilsteins.
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1998 Mustang GT Coupe - World's Slowest Racecar 2005 Toyota 4Runner SR5 V8 2013 Volkswagen Jetta Sportwagen TDI |
03-01-2005, 08:29 PM | #4 | |
Im gonna show her my...
Join Date: Dec 2004
Location: Somewhere providing FREE tech support.
Posts: 4,269
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Re: Talking with MM...
Quote:
__________________
I heard it on the internet, so it must be true. "I believe that a person's moral compass can be determined by how he references free men the right to defend themselves." T. Nugent "An armed society is a polite society. Manners are good when one may have to back up his acts with his life." R. Heinlein "Never argue with an idiot. They drag you down to their level, then beat you with experience." -Unknown |
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