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Thread: Spring Rates

  1. #1
    riojin
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    well ive been doing some research on spring rates. the theory is the ratio between front and rear should be about 3:2 to 4:3 ie 6kg:4kg to 8kg:6kg. but sway bars add to the compression rate. looking at TRD sway bars, they add 107% to the front and 71% which if the springs are the same rate in steel will change the rate to approx 3:2.

    i currently have 8kg front standard swaybar and 6kg rear 18mm rear sway bar.

    therefore i am planning on buying some springs both with 8kg a compression rate. also buying TRD swaybars of 24mm (+107%) front and 16mm (+71%) rear. so itll be in theory approx 16kg:13kg. this is the setup that Keiichi Tsuchiya is/was running in his TRD gift ae86 with TRD adjustable shocks (which i should also be purchasing). i was just trying to justify why the setup is the way it is.


    could i have your thoughts?

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    Thats right, an easier ratio is that the rears should be 2/3's of the front for a neutral handling car.

    Swaybars don't add to the compression rate of the spring as such, the percentage given is the increase in roll stiffness over the stock sway bar.

    The reason that Tsuchyias car ran such stiff springs at the rear is probably because of running wider rims/tyres at the rear than the front, meaning that he could still have plenty of grip as if running less track and tyre width with a softer spring. He would also be running high grip tyres, probably his usual Potenza RE01R. This is just a guess but from reading the trueno bible, it seems that pretty much everyone goes for a softer rear spring rate when compared to the front usually by the previously stated 2/3's ratio. Thats my thoughts on his setup anyway.

    TRD shocks are almost identical to KYB AGX's (adjustable) that suit 86's so they would be the go id say, around a 1000 a set.

    Ive got a 18mm rear whiteline bar in my car with 8 and 6kg springs and put in a adjustable 24mm whiteline front yesterday and set on 2 of 4 stiffness, it feels really good, i had it on 1 but didnt think it was quite enough so increased it to 2 and now the car feels great, if not a little oversteery which is the effect i was after anyway.

    Personally id just buy whiteline swaybars, as they are good quality and much easier to get than TRD im guessing, at a cheaper price also?
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    I have personally found I prefer just under a 3/2 ratio and closer to 60%, also I am not going to mess with the anti-roll bars

    edit: I am using KYB AGX, great product and TRD re-labels them for their product as KONAkid said
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  • #4
    riojin
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    Tsuchiya runs 15x7 -2 offset all round with the tyres you mentioned.

    does chopping springs effect the compression rate?

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    <div class='quotetop'>QUOTE (riojin @ Nov 7 2007, 10:02 PM) <{POST_SNAPBACK}></div>
    does chopping springs effect the compression rate?[/b]
    way to ruin a "technical" thread!

    yes, chopping coils off a spring will make it stiffer.

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    Site Supporter Driftspec's Avatar
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    ^^Yes, I think there is a calculator floating around the interweb that lets you calculate the spring rate, based on weight, free height, coils etc. Should be easy to find, I think someone was quoting it a little while back.

    Suspension setups have always been something of interest to me, simply because they represent the biggest gain for the (relative) smallest effort to improve the overall handling of any car. The more adjustable it is, the finer you can tune it (and of course, the more you can stuff it up). I would love to be a racing engineer at some stage, putting it all into practise. But for me, learning how it all works is good enough, for the moment

    Enough drivel from me:

    Drift setups typically make the rear softer than the front, simply to induce a slide easier and make holding it easier. The softer a spring/shock combo (without taking rebound/damping rates into account), generally the more weight is transferred to that corner. The harder the combo, the less weight is able to be transferred to that corner. So, with the rears softer, the easier it is to move the weight of the car from one side to the other, while having the front harder means that the weight will stay towards the rear of the car, perfect to get the tail wagging, and keep it that way.

    The disadvantage of such a setup, is that the car then typically becomes an understeering queen when driven normally at higher speeds; the weight of the car cannot be shifted to the front under braking, so there is reduced pressure of the car over the fronts, inducing initial turn-in understeer. This can be reduced by increasing camber slightly (and castor, I thiink, but can't be sure), or by running softer springs all around. I guess it does depend on the driver, messing with the shock rate can also yield some gains, as it will allow the spring to act harder or softer, depending on how you like it.

    Anti-rollbars are slightly different, I found the best explanation was from BillZilla's site (if I remember correctly): The job of an anti-roll bar is literally that, prevent the car rolling. It aims to do this by pulling one side of the car in the same direction of the other. For example, if the left side wanted to arch up while turning left (ie body roll) the bar will pull the other side up as well (essentially preventing one side rolling up, and the other down). So in a way they can refine the overall stiffness of the car, eliminate sudden (nasty) weight transfers, and keeping each end of the car stable and as flat as possible.

    But while that theory is all great, I have no practical experience to back that up, such as knowing what diameter roll bar increases stiffness by what percentage, etc. Would definitely recommend the adjustable version of whatever you buy, because you can modify to a stiffness that you feels suits you and your driving style.


    Well, hope this helps :2thumbs:
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  • #7
    riojin
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    :lol:

    sorry.

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    if the spring rates are made harder on one end then that end is more prone to slide not less, same with anti-rollbar: bigger = less grip at that end
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    <div class='quotetop'>QUOTE (Sam_Q @ Nov 7 2007, 09:40 PM) <{POST_SNAPBACK}></div>
    if the spring rates are made harder on one end then that end is more prone to slide not less, same with anti-rollbar: bigger = less grip at that end[/b]
    QFT


    That is the general rule of thumb, not sure if I really made that point in my previous post. Same deal with putting strut braces on: you stiffen that part of the car, you lose overall grip there.

    I might not have qualified myself as much I though when explaining the drift-style setup, the softness at the rear is more to allow the throwing of the weight around from one side to another. Of course, at speed the forces generated exceed the lateral force the tyres, thus the weight and lack of lateral grip force the tail to go around in that direction.

    There are plenty of factors involved in getting the overall suspension setup right for how you like it. Plenty of people (especially Sam) have been working on it, I hope to get the time to get the kind of practical knowledge you have
    4AGE is here! Cheers 44GTE and Anthony for your help! http://www.ae86drivingclub.com.au/fo...ad.php?t=10384

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  • #10
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    Keiichi Tsuchiya is a professional driver and his suspension setup is specific to his driving techique. I can't think of anyone else that sucsessfully uses such high spring settings in a street AE86 (referring to the TRD Trueno "Touge Monster" as seen in AE86 Club, Hot Version and Best Motoring - Or you mean the N2 Levin? which is quite different) Eitherway his car is prepared for the most part by TRD, and being used to circuit racing he demands a high level of grip and positive chassis feedback. Tsuchiya's car would be a no expense spared toy that would have new tyres on it every time he took it out, he'd even get a new front lip after each track session if he scuffed it! I'd say your car is not likely to be driven and maintained in the same manner?

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