Re: coil over spring ratings
[Re: rebel]
#2503396
06/01/18 11:23 PM
06/01/18 11:23 PM
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Joined: Jan 2005
Posts: 4,243 Charlotte, North Carolina
sgcuda
master
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master
Joined: Jan 2005
Posts: 4,243
Charlotte, North Carolina
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If the old car had 130 lb springs and was heavier than what you have now, I can't see any reason to put in heavier springs. General rule is to use the lightest spring possible to support the car. FYI, my new tube chassis, ladder bar project, I'm starting with 110 lb springs, and may drop lower.
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Re: coil over spring ratings
[Re: rebel]
#2503429
06/02/18 01:16 AM
06/02/18 01:16 AM
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Joined: Dec 2005
Posts: 11,638 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,638
Fulton County, PA
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250? On the rear? May as well run solid suspension unless it weighs 5000#. 12" springs? Mounted behind the axle? Weight on the rear axle?
Last edited by CMcAllister; 06/02/18 01:26 AM.
If the results don't match the theory, change the theory.
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Re: coil over spring ratings
[Re: J_BODY]
#2503431
06/02/18 01:24 AM
06/02/18 01:24 AM
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Joined: Dec 2005
Posts: 11,638 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,638
Fulton County, PA
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So where does “lightest spring” and coil bind on rebound meet happy ground? I would be careful using a light spring on a ladder bar car with any power. Light springs can be used on a lower powered 4 link car to store some energy and help apply the tire or on a ladder bar car with decent shocks to control the housing. Obviously you don't want to get into coil bind, but spring rates are something that can used to help get the car to respond the way you want.
If the results don't match the theory, change the theory.
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Re: coil over spring ratings
[Re: rebel]
#2503524
06/02/18 11:31 AM
06/02/18 11:31 AM
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Joined: Jan 2005
Posts: 4,243 Charlotte, North Carolina
sgcuda
master
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master
Joined: Jan 2005
Posts: 4,243
Charlotte, North Carolina
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You have a tube chassis car, you need light springs. Unless you are using thick wall fence pipe, there won't be enough weight to need anywhere near that kind of spring. I have 200 lb. springs in the front of mine, and right now, they are too much to even start compressing my struts. If you can install your springs, run up the adjusters 1/2" past contact, install the shocks, and have them compress to the middle of shock travel, you should be good. My bet is that your springs aren't going to do that.
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Re: coil over spring ratings
[Re: rebel]
#2503570
06/02/18 01:33 PM
06/02/18 01:33 PM
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Joined: Oct 2007
Posts: 4,209 New York
polyspheric
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master
Joined: Oct 2007
Posts: 4,209
New York
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You can't compare spring rates, even on the same car, unless the attachment points (especially the distance from the wheel) are very close. A coil-over replacing a shock (in the factory mount positions) is different than a four link with its own mounts. Shorter distance spring > wheel: spring acts heavier. Yes, this also affects your roll rate, and sway bar size.
Boffin Emeritus
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Re: coil over spring ratings
[Re: polyspheric]
#2503601
06/02/18 03:03 PM
06/02/18 03:03 PM
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Joined: Dec 2005
Posts: 11,638 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,638
Fulton County, PA
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You can't compare spring rates, even on the same car, unless the attachment points (especially the distance from the wheel) are very close. A coil-over replacing a shock (in the factory mount positions) is different than a four link with its own mounts. Shorter distance spring > wheel: spring acts heavier. Yes, this also affects your roll rate, and sway bar size. True, on an A-arm or independent type suspension. On a 4-link solid beam axle, there is no lever effect. On a ladder, moving the shock closer or farther from the front mounting point and/or away from the rear axle C/L will make a difference in spring rate. Ladder bars are just big A-arms. 98% of the stuff now, that's not 40 years old, is a coilover mounted just behind the axle using a 12" spring. Once you get away from that, things can change. The placement of the shock between chassis C/L and the wheels will affect the stability and roll characteristics. It also reduces the ability to use spring heights and uneven shock adjustments to tune. I'd prefer to see them kept on the center or even outboard of the ladder/4-link mounts. On most set-ups, there are maybe 3 common rates (i.e. 95, 110, 130) that fit in the window between not being able to get the shock compressed to ride height and not being able to hold the car up. The choice depends on a lot of factors.
If the results don't match the theory, change the theory.
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Re: coil over spring ratings
[Re: rebel]
#2503765
06/03/18 01:21 AM
06/03/18 01:21 AM
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Joined: Jun 2005
Posts: 6,257 gulfport, ms, west mi
rowin4
master
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master
Joined: Jun 2005
Posts: 6,257
gulfport, ms, west mi
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I don't think it has ben mentioned but you need to get the car scaled before you really spend money on springs. I had a set of springs that were to stiff, asked the same questions hear. Got a answer that sounded good, bought that spring rate, nope to light. Bought another and another before I got it right. If your lucky you can sell those extra springs for half what you paid for them. Get it scaled when you get it back together, get the proper springs, get the weight set side to side and ride height adjusted. The car will launch straight also.. Like the spoiler, got any close ups of it?
Last edited by rowin4; 06/03/18 01:22 AM.
it's ok to butt heads, just don't do it with a butthead
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Re: coil over spring ratings
[Re: rebel]
#2503781
06/03/18 03:00 AM
06/03/18 03:00 AM
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Joined: Dec 2006
Posts: 4,647 aotearoa
rebel
OP
master
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OP
master
Joined: Dec 2006
Posts: 4,647
aotearoa
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The car came with a different rear wing, i didn't like it so i made this. It's Zeus clipped on for days i need to look in the trunk but it refuels from a hatch in the middle of the trunk as shown.
Last edited by rebel; 06/03/18 03:09 AM.
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Re: coil over spring ratings
[Re: rebel]
#2503818
06/03/18 10:15 AM
06/03/18 10:15 AM
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Joined: Mar 2006
Posts: 9,863 MI, usa
dvw
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master
Joined: Mar 2006
Posts: 9,863
MI, usa
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Its not that tough. Rear weight minus unsprung rear weight. Rear unsprung weight comprises the full weight of rear tires,wheels,axle w/brakes. Then add half of the weight of the shocks, suspension arms, drive shaft. Run the attached formula for shock location, simple math. I approximate the unsprung by removing the tire/wheels. Then put a scale between a jack and the axle housing. Start to jack it up from full droop. When the jack starts to move, read the scale. This will get you close. That all being said CMcAllister is correct. Not a super wide range that works. Most non tube door cars will be 120-140. Lighter tube cars 90-110. The only reason to use a stiffer spring is when you have a ton of power and the chassis doesn't require any assistance to hit the tire. Doug
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