help , dropped rear on GN 3", no travel left

Discussion in 'Customs / Lowriders' started by GregInAtl, Jul 5, 2009.

  1. GregInAtl

    GregInAtl Not-quite-so-new-guy

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    OK, I have an 86 Buick GN, I have it lowered a bunch, Moog coil 5385s w/ a coil removed, dropped it right at 3". I have KYB shocks, rear disc conversion, and 20x10s on 275-30s.
    Here's the deal. It has no travel. Its all tire...and there aint much there!!
    The rear driver caliper was hitting the frame, so I notched a vertical slice in it for clearance....test drove it, now its clear but now I have 1" travel.
    Anyone w/ a G-body experienced this? I have seen many regal's lower than this, and something just doesnt add up. The shocks surely have more than 3" of travel...
    Shed some light if you can...
     
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  2. dogshit

    dogshit Royal Smart Person

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    You are where you are. With that much drop they are more for shows. Harsh ride no travel and no traction under boost. I lowered mine an 1 1/2" with the Eibach springs and run a 275/50. Its a lot firmer but not harsh still has sufficient travel and has enough side wall to hook. I could not stand the idea of spining and getting whipped by a slower car with traction. But you will definately get more props at some shows.
     
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  3. GregInAtl

    GregInAtl Not-quite-so-new-guy

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    I know there are G bodies that low w/ travel. The height isn't a problem if there is some travel, the spring rate and tire choice will be the issue then. With no travel I could be on drag radials and have problems. Its just not very low to see, it doesnt look slammed, it seems bizarre that the travel is so limited. I took a long look today, and nothing is in contact (frams to anything, bump stops to anything, and lower arms dont appear to be touching anything either.
    [​IMG]
     
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  4. AnPmc

    AnPmc Apprentice

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    It's real nice, I don't see how Your Car is giving You Trouble, Doesn't Seem that Low at all.
     
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  5. custom442

    custom442 Royal Smart Person

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    those springs have a free load of 167 lb/in which is very stiff even at stock height or 1" lower than stock. Basically you got one of the stiffest springs possible and now is stiffer after the coil was cut.

    You don't see many rear coils close to 200 lb/in on street driven 4 link rears without coilovers -- because you can't adjust them like coilovers

    You can have decent traction at that height, but your geometry has completely changed, time to look into adjustable control arms
     
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  6. GregInAtl

    GregInAtl Not-quite-so-new-guy

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    We are all talking rear susp right?!?!
    What spring could I use to get some ride back and have some travel? I plan on removing spring and shock and dropping the car down, just to see when it begins to bind.....shouldnt that be at bump stop compression?I was considering QA1 coilovers rear only. My frontis fine, I have Moogs up there w/ 2" drop spindles, and its a little stiffer than I want, but it keeps the tires off the liners.
    Thx for the help guys, keep the suggestions coming, I certainly do not know it all! (Obviously)
     
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  7. custom442

    custom442 Royal Smart Person

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    yes, rear suspension. (200 lb/in front coils are way softer than anything ever used on these cars)

    And you might never reach the point where the bump stops come into play with those springs installed because it's so stiff to begin with.

    Rear springs are very particular, we've been through a few threads on here about the rear pigtails and it's hard to find a correct spring for a swap, although it can be done. Cutting pigtails isn't the best idea either. IMO I would look into a drop spring at the height you want. Like QA1 or eibach just as examples (front springs you can do fine with moogs). They might be about twice what you'd pay for a MOOG that's supposed to drop the rear--like using an Abody or monza spring on a g body, but it's worth knowing what the specs are on the spring and that you'll have a driveable ride.

    I would buy drop springs and fully adjustable rear shocks. If you really want to convert to coilover you could, but it's so expensive and not needed unless you have a specific need for perfect geometry (race car).
     
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  8. GregInAtl

    GregInAtl Not-quite-so-new-guy

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    200lb are softer? They feel WAY firmer....I am used to 375 and 400 lb springs in import cars and them riding 1000x better than this big heavy car on 200 lbers.
    what am I missing? I want a comfortable ride, not OEM soft (tiny wire used on the coils) but not a wagon either.
     
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  9. jrm81bu

    jrm81bu Comic Book Super Hero

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    He was saying that 200 lb/in would be too soft for a front spring.
    But as a rear spring thats pretty stiff.
     
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  10. custom442

    custom442 Royal Smart Person

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    Greginatl- here's some info to help explain a little better

    Stock these cars had around 300-350 lb/in in front. In rear, about 100-130. A stock rear susp. set up on these cars will perform best with around a 1.5" drop, which is about the max you can go without changing out other rear susp. components.

    So you could see how a 200 lb/in at a much lowered ride height would cause problems. When you drop the car 3"s you're losing just about any suspension travel. The max you really should go with a coil spring set up on these cars with stock geometry is about 1.5-(maybe) 2" in.

    In a simple way - a 200 lb/in spring at a 1" drop is now 400 lb/in, at 2 inches it's 600 lb/in, at 3" it's now 800lb/in This isn't saying your rate is 800lb/in at all, but spring rate is just a representation of the real world calculation of wheel rate. You can't really tell the wheel rate without linkage ratios, weights, etc.

    But it's not the end of the world - here's what to do for better results (you could even try it with your current springs). Set a correct/decent pinion angle with new adjustable upper arms (adj. lower arms wouldn't hurt either). Also remove the rear frame rail bump stops but keep the stop on the pinion


    Look at this chart: http://bbb-carb.com/moog_Coil_Springs.htm
    note your 5385's have a free height of 12.6". At that free height they have a spring rate of 167.5 lb/in.

    But on whatever stock vehicle they came on, it lowered it to a 9" ride height. The original 167.5 lb/in was then multiplied by 3.6" (free height - install height) to get the 603 lb/in at install height.

    When you cut a coil (depending on the spring) it usually increases the spring rate beyond the amount of lowered height you just cut off ... if that makes sense.

    Also when pigtails are cut, it screws up rates/performance and can have mounting issues, just take a look at a pigtail spring and you can see what I mean by that.
     

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