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Thread: getting grip with your rear suspension

  1. #31
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    Quote Originally Posted by driftke70 View Post
    softer front sway bar stops the the rear end pushing onto a rigid front, and allows the front to absorb some of the action from the rear end.
    Softer front swaybar promotes oversteer. Ie. the opposite of what is desired in this case. This is pretty basic chassis tuning knowledge.

    What you say might be true if the rest of the setup is super fucked up. 9.5kg springs in the rear is pretty fucked up.

    The general consensus in the thread is pretty much on the money.
    Softer rear springs and,
    Less/no rear swaybar.

    I know an engineer who ran an rx3 making around 250hp as a grip car. He found the best setup was
    Stiff front end (both swaybar and springs),
    Soft rear springs, and
    No rear swaybar.

    It might be worth having a look at some of the chassis tuning books available. Carroll Shelby had a good one and there was one called "Competition Car Suspension, Design, Construction, Tuning" but I can't remember who wrote it.

    Here are some guidelines:

    A softer front bar:
    1. Increases front chassis roll.
    2. Increases front grip or traction, while decreasing rear grip or traction.
    3. Slower steering response.
    4. Increases off-power steering at corner entry.


    A stiffer front bar:
    1. Decreases front chassis roll.
    2. Decreases front grip or traction, while increasing rear grip or traction.
    3. Faster steering response.
    4. Decreases off-power steering at corner entry.


    A softer rear bar:
    1. Increases rear chassis roll
    2. Increases rear grip or traction, while decreasing front grip or traction.
    3. Less on-power steering.


    A stiffer rear bar:
    1. Decreases rear chassis roll.
    2. Decreases rear traction, while increasing front grip or traction.
    3. Faster steering response in high speed corners and chicanes.
    4. Increases on-power steering.
    Last edited by af300e; 3rd June 2009 at 07:59 PM.

  • #32
    Senior Member s14seriesII's Avatar
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    Quote Originally Posted by munki View Post
    before you lower your rear rc 3 inches take a look if you need to raise your front rc first. a good rule of thumb is to have a lower rear rc when doing circuit work on live rear axle cars.
    have taken this into consideration.. going to see how the rear peforms this weekend as raising the front r/c has been on a list of things to do but can hopefully wait for the time being as i cant use the normal bolt in rca's so crossmember modification was always planned
    Owner built and tuned 9000rpm 402kw atw 3sGTE - AE86

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  • #33
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    Quote Originally Posted by af300e View Post
    What you say might be true if the rest of the setup is super fucked up. 9.5kg springs in the rear is pretty fucked up.


    ..fix this first before worrying about anything else - no other changes are going to work properly until you go softer spring rate in the rear. Just look at other local quick cars and you will find that rate is way too stiff!
    "go forth young man, and if it has more..... pull fifth"

  • #34
    Senior Member Medwin_3sGTE_AE86's Avatar
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    Hate to say I told you so Mark..... ..... Who am I kidding, I love being right (who doesnt!)

    For those who dont know, I was having a heap of issues too, rear end just too taily. It wasnt so bad that it was uncontrolable, but for what I built my car for (track, tarmac grip) it wasnt on par with what I wanted.

    So, I spoke to real people who have actually done things in motorsport who actually know real facts and figures, (read, not the bunch of forum warriors who's only claim to fame is the ability to spend more time on the net than working on or driving their car, yet profess to know everything there is to know), and their advice was simple, softer rear end setup = more rear end grip.

    9.5kg/mm rear springs! Mark, you may of as well welded the rear end solid. Yeah, in your s14 they might be alright (yes, we all know about the 'quick as IP guys around basky with the drift setup' story) but the s14 weighs a bit more in its fat arse than the 86. I dont know the weight of the s14, but my guess would be that the 86 has only 2/3 (if that) the weight acting on the rear suspension as the s14 does, therefore a 9.5kg in an s14 would be compareable to a 6.5kg in the rear of an 86.

    Not that you're going to listen to anything I or anyone else on here says, but I can tell you that my initial (rear) setup was with custom made 4.5kg/mm springs, whiteline adjustable swaybar on the softest setting and that was far too stiff. Changed to standard springs and no sway bar, world of difference. Equal length trailing arms trialed, tested and setup, and pinion angle calculated and adjusted so it was in the optimum range and the improvement was again, unbeleivable. Redesigned front end, springs and adjustments in shocks, played with setup on whiteline adjustable sway bar, and the thing is great.

    If you're so naive to run 9.5's in the rear, I cringe to think of what the front is set up with (14kg/mm?!) and no doubt set at a height for maximum wank factor, which consequently has no practicality what so ever as it has no room for suspension travel. Wank factor might be great, but you're not going to get it to handle like an IP car with no travel.

    Quote Originally Posted by af300e View Post
    Softer front swaybar promotes oversteer. Ie. the opposite of what is desired in this case. This is pretty basic chassis tuning knowledge.

    What you say might be true if the rest of the setup is super fucked up. 9.5kg springs in the rear is pretty fucked up.

    The general consensus in the thread is pretty much on the money.
    Softer rear springs and,
    Less/no rear swaybar.

    I know an engineer who ran an rx3 making around 250hp as a grip car. He found the best setup was
    Stiff front end (both swaybar and springs),
    Soft rear springs, and
    No rear swaybar.
    Funny that after talking to people and testing and tuning different setups, I ended up with that ^^^ exact setup. You wouldnt beleive the amount of criticism I received when I first suggested softening up the rear to induce more grip.

    Quote Originally Posted by Jase86 View Post


    ..fix this first before worrying about anything else - no other changes are going to work properly until you go softer spring rate in the rear. Just look at other local quick cars and you will find that rate is way too stiff!
    Thing is Jase, Mark seems to think that because he 'ran as quick as the IP guys on the drift setup' in his s14, that the rates used in the 86 being the same as the nissan will provide the same characteristics. That, and that if he let it slip to any of the NS guys that he'd softened up his suspension setup, his wank factor ranking within the tas drifting circles would plummet.

  • #35
    Veteran driftke70's Avatar
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    Quote Originally Posted by Medwin_3sGTE_AE86 View Post

    9.5kg/mm rear springs! Mark, you may of as well welded the rear end solid. Yeah, in your s14 they might be alright (yes, we all know about the 'quick as IP guys around basky with the drift setup' story) but the s14 weighs a bit more in its fat arse than the 86. I dont know the weight of the s14, but my guess would be that the 86 has only 2/3 (if that) the weight acting on the rear suspension as the s14 does, therefore a 9.5kg in an s14 would be compareable to a 6.5kg in the rear of an 86.

    not to mention an irs setup is acting more so on one spring at a time than a live axle rear end, and the lever effect produced by various arms.
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    ^^^
    Roffle, Lmao..

    Geez Mr medwin, you just love starting a shit fight...

    Have to agree with what you say though...

    From my own experience, I have found a softer bum gives more grip, not sure if the total removal of sway bar is helpful though...I would at least run the standard one...

    Regards

    Scott

  • #37
    Senior Member s14seriesII's Avatar
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    haha good to see your back medwin, i was almost begining to miss your short essay style replys

    anyway i will keep running ridiculas springs rates but i will try something as low as a 5.5

    that is all i will keep you all posted when i find some rear traction
    Owner built and tuned 9000rpm 402kw atw 3sGTE - AE86

    Quote Originally Posted by Beau View Post
    4ages are for the scared

  • #38
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    i run 4.5's in the back of my car and it's used for drift, its still on the too stiff side IMO

  • #39
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    Quote Originally Posted by Simon-KE70 View Post
    i run 4.5's in the back of my car and it's used for drift, its still on the too stiff side IMO
    from what i have seen this thing seems to be a good balance of power, grip and lean.
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  • #40
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    i never ran 10 rears dave, running whiteline rear bar and TRD front bar. seems to work well, front seems to be a little stiff as it picks up inside wheel during scando's lol

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