Spring Rates

[riojin]

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?

[Konakid]

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?

[rthy]

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

[riojin]

Tsuchiya runs 15x7 -2 offset all round with the tyres you mentioned.

does chopping springs effect the compression rate?

[roadsailing]

<div class='quotetop'>QUOTE (riojin @ Nov 7 2007, 10:02 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=433145)</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.

[Driftspec]

^^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:

[riojin]

:lol:

sorry.

[rthy]

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

[Driftspec]

<div class='quotetop'>QUOTE (Sam_Q @ Nov 7 2007, 09:40 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=433178)</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 :)

[ghetto ke]

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?

[Konakid]

<div class='quotetop'>QUOTE (driftspec @ Nov 7 2007, 10:00 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=433197)</div>
<div class='quotetop'>QUOTE (Sam_Q @ Nov 7 2007, 09:40 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=433178)
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 :)
[/b][/quote]

Hi josh, i see you thar....

Anyway, Driftspec, stiffening the chassis does not reduce grip as such, but help retain the geometry of the car through keeping the chassis aligned under load. For example, putting a front strut brace on your car doesn't decrease the grip available but keeps the strut towers from flexing allowing the struts to work as they should with out dealing with loads that come from a force on the opposite side of the car. Basically braces help retain standard geometry, allowing the suspension to do its job more precisely.

Stiffer springs = less grip, this is a given. As there is less compression when the the weight transfers onto a corner, the tyres take the brunt of the weight, not the sagging of the stock soft springs. In turn, the tyres break traction more easily.

Drift cars use stiffer rear springs than circuit cars (generally) to make this happen with a flick of the steering wheel. The stiff springs also help to control the weight transfer easily during maneuvers that involve flicking the car. The driver is not left wondering when the tyres are going to break traction because you have to wait for the body to stop rolling before they slip, instead is is instant, the body moves only a tiny bit before the tyres break loose making the rear end predictable when sliding.

Stiffening the chassis is a good thing and does not decrease the cars grip, this is different to stiffening the suspension.

Ill just add that the softer/grippier tyre that you are running, the stiffer suspension settings you can get away with due to the tyres having a lot of grip, i.e semi slicks.

[rthy]

i tottaly agree with you on this one Konakid,

the shitty thing about springs is that what someone loves someone else hates. You really need to get into someones sprinter and take it for a drive and a decent drive, idealy in your area.

If I try to remember I think I have tried 7 different spring combinations on the front and possibly 8 on the rear to get what I want, it was a painfull and expensive process. All because I couldnt test someone elses car with simular specs in my area. So if you have the oppertunity take it, when you drive it check these things:

- is it too firm for my roads?
- is the turn in good?
- does it oversteer on corner exits?
- is it too soft/leans too much?

[Driftspec]

We could be on this one for days :)

I agree with you KonaKid, I think I was a little too general and vague in what I was saying. It does strengthen the chassis/car at that area, but I will say it can also have the affect of 'stiffening' (not an exact term, best I can think of) that area as well. By preventing the flex of the chassis and geometry at that point, there is a side affect of it keeping the weight at that point, which can in turn reduce grip (depending on setup). This is one thing I have experienced first hand with handling setups: In this case, front strut brace = car more prone to understeer. That was matched with (I believe) 8kg front and TRD short-stroke shocks. Of course, that can just come down to having spring/shock combos that are a little too stiff at that point for the rest of the car's setup.

Still important to stiffen the chassis, again handling gains can be made by doing that, to allow the suspension to more accurately do its job. Its all about balance, matching it with the setup of the car, its purpose, and how you feel while driving it.

[riojin]

well all i know is that my ride is too rolly for me at 8kg and 6kg and a 18mm rear swaybar, especially at the back.

ill buy this setup and see what happens. i have a feeling itll be understeery as all hell, but ill try and compensate this by playing with the camber settings to get it just right

[Konakid]

To much roll with 6kg rears? Serious! What speeds are you cornering at? Track car only? damn! 8 and 6 is plenty stiff for street thrashing.

Can i ask what shocks you have? these can make a big difference to the feeling of the cars stiffness and rolling.

[riojin]

i always corner hard....

its my daily driver. but i have monroe gas shocks in the rear. thats whats prolly making it roll too much (well for my liking anyway). i didnt have them put it, its still the previous owners suspension setup.

[rthy]

just remember that roll isnt necessarily a bad thing, it is needed to get the right arc of the suspension and not load the tyres up too much from sideways force or something like that

[anastasios]

i rekon upgrade your shocks 1st

[RobertoX]

TRD blue in the rear FTW

i have stock too

and 6 is hard in the rear


what tyres are you using?

[riojin]

i think im gonna give you a call soon dave and get some stuff from you.

im gonna get some custom springs lowered and with real compression rates of 8 and 6. theyre supposed to be that now but i have a feeling theyre not.

im gonna do the whole suspension in one hit so ill buy more than that

tyres are some nankang garbage atm but im looking into toyos atm

[RobertoX]

no worries mate

ALL of my springs are rate tested BEFORE being sent out so no issues

i keep the majority in stock

also i can send you some bridgestone re001s $27 a tyre to ship if you are keen, ill do you cost on the tyres

they are awesome

email me at sales@ajps.com.au

[mech`s blue]

i also found the 2 of 4 setting on the whiteline front to be spot on. 1 also am using 8kg/6kg with kyb agx shocks.(cheers lawson). the only thing i found with the whiteline sway bar was that tyres rub due to the bar coming over the castor rod where as the trd sway bar goes under the castor rod.

but it's like sam said what works for some won't always work for others

[Konakid]

<div class='quotetop'>QUOTE (Mech`s Blue @ Nov 11 2007, 01:29 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=434954)</div>
i also found the 2 of 4 setting on the whiteline front to be spot on. 1 also am using 8kg/6kg with kyb agx shocks.(cheers lawson). the only thing i found with the whiteline sway bar was that tyres rub due to the bar coming over the castor rod where as the trd sway bar goes under the castor rod.

but it's like sam said what works for some won't always work for others[/b]

Noice, will have to check to see if mines rubbing, cheers.