geometry and spring setup

[Trip]

What do you guys suggest for hill climb geometry setup ?

I have lots of understeer both going into corners and exiting under power. I would like a more balanced setup more biased to oversteer both on entering and exiting.

My current setup:
Tein HA coilovers with front adjustable top mounts
Whiteline anti roll bars and adjustable rear
Spherical bumpsteer kit
Spherical drop links all round
Whiteline anti-dive kit
5mm spacers at the back
Rear camber bolts
Front Modena LSD
Car is fully lightened front and rear (too much to mention)

I might invest in some other coilovers cause the HA are too hard or at least change the front spring for a softer set. My rear ARB is on middle setting and will move to the inner one. Also considering the castor mod but will i loose some negative camber by doing so? the car height is set at 330mm front and 340mm back


Thanks

 

[gtiroz]

try to find a (used) nismo 2-way mech rear lsd (38420-RS420),
cusco still make their rs and mz options for the gti-r (but they're only 1-way so won't have much effect under brakes)

strut braces (front and rear) and 4-point underbody brace will also help...

have you replaced all the suspension-related bushes with poly items?

what are your existing alignment settings?

 

[Trip]

try to find a (used) nismo 2-way mech rear lsd (38420-RS420),
cusco still make their rs and mz options for the gti-r (but they're only 1-way so won't have much effect under brakes)

strut braces (front and rear) and 4-point underbody brace will also help...

have you replaced all the suspension-related bushes with poly items?

what are your existing alignment settings?

Forgot to add that i have an upper and lower front brace. the rear does not need since the turrents are being held with a rollcage . All bushes have been replaced too.

My wheels are 225/45 R16 R888 and fitted with 30 offset making tracking wider.


I don't know what my geometry is at present.

 

[PobodY]

Based purely on information from the Whiteline website, I'd say you need to soften the front suspension. - The logic is that understeer and oversteer occur when the wheels loose contact (and therefore traction) with the ground. A bit more body roll at the front should allow the tyres to bite a bit more and shift the understeer to oversteer.
That's the logic of their adjustable rear ARB; the tightest setting allows for very little roll at the rear, thus dialling-out the understeer. They also suggest that the cheapest way to do this in a road car is just to polybush the rear (so the front remains squishy). I think it's also why their front ARB is actually smaller than the standard one.

I'm sure that someone who knows how to do this properly will post shortly. It will probably come down to "use 5 clicks on your rear shocks, but only 3 clicks on the front ones". - As I said, I'm just parroting what's in the technical articles from Whiteline.

 

[olliecast]

have you done the castor mod?

start with basics, what camber are you running and also what suspension heights, centre to wheel arch, front and rear?

 

[Trip]

have you done the castor mod?

start with basics, what camber are you running and also what suspension heights, centre to wheel arch, front and rear?

What is the max camber you can get with the castor mod ? I am running on Tein adjustable top mounts

Suspension height is written on first post

 

[stumo]

What is the max camber you can get with the castor mod ? I am running on Tein adjustable top mounts

Suspension height is written on first post

You re-set the camber after doing the castor mod. You can set the camber to anything you like.

what are your spring rates?



If it's just for sprinting and for tight corners i'd set it up something like this...

Do the caster mod

disconnect the ARB's (both of them)

set ride heights to what you want but have the rear a minimum 10mm more than the front. 15mm will give you a more lively rear end. start at 330mm front 340mm rear between the wheel center and the wheelarch.

reconnect ARB's...make sure that the rear bar is level between the body mounting and the point where the link attaches to the ARB. also make sure that when you connect the links they don't "pull" on the ARB.

set the front and rear cambers (and obviously reset the front and rear toe). Keep the rear camber around 0.5 to .75 deg less than what the front is.

I would set the front to anywhere between -1.5 to -2.2deg depending on tyres, available grip etc etc

Set the toe to parallel all round to start with.
Toe out will make that end turn more than before.
That means if you set the rear toe to out 0.5deg then it will give less understeer than if it was set at parallel.

Be careful, toe WILL scrub your tyres out very quickly.

That's a basic setup guide, have fun experimenting....

 

[Trip]

great in detail. Thanks

 

[gtiroz]

save for a mech rear diff - sounds like you have all the right bits then for understeer reduction

the whiteline antilift(dive?) kit (offset lower control arm bushes) already add caster - so not sure how much more you will get from the castor mod?

removing the front arb completely will increase intitial turn-in (although you will lose some mid-corner stability)
but since you already have the (smaller-than-stock) whiteline item the effect will be less dramatic

do you know the rates of the springs in the ha's? are they different fron the ss's? (f:4kg/r:3kg)

what tyre pressures do you use?

but as stumo suggests - alignment settings are probably going to see the greatest gains,
if you're currently still getting "lots of understeer" with all your bits then it's quite possible something isn't right in that department...

 

[stumo]

save for a mech rear diff - sounds like you have all the right bits then for understeer reduction

the whiteline antilift(dive?) kit (offset lower control arm bushes) already add caster - so not sure how much more you will get from the castor mod?

removing the front arb completely will increase intitial turn-in (although you will lose some mid-corner stability)
but since you already have the (smaller-than-stock) whiteline item the effect will be less dramatic

do you know the rates of the springs in the ha's? are they different fron the ss's? (f:4kg/r:3kg)

what tyre pressures do you use?

but as stumo suggests - alignment settings are probably going to see the greatest gains,
if you're currently still getting "lots of understeer" with all your bits then it's quite possible something isn't right in that department...

Doing the castor mod, either with or without the Whiteline bushes, will make a dramatic difference.

If you set the car up well you get very little (or no) understeer.

 

[Trip]

save for a mech rear diff - sounds like you have all the right bits then for understeer reduction

the whiteline antilift(dive?) kit (offset lower control arm bushes) already add caster - so not sure how much more you will get from the castor mod?

removing the front arb completely will increase intitial turn-in (although you will lose some mid-corner stability)
but since you already have the (smaller-than-stock) whiteline item the effect will be less dramatic

do you know the rates of the springs in the ha's? are they different fron the ss's? (f:4kg/r:3kg)

what tyre pressures do you use?

but as stumo suggests - alignment settings are probably going to see the greatest gains,
if you're currently still getting "lots of understeer" with all your bits then it's quite possible something isn't right in that department...

My Teins HA fronts are 8kg and rears are 7kg, pretty much hard for the kind of roads we race on. But that will be delt with in the future. Either change the springs are go for a totally different Coilover.

Tyres are 25psi all round cold.

 

[Trip]

If you set the car up well you get very little (or no) understeer.

I do hope so

 

[DanDud]

As has already been said, do the castor mod, makes a massive difference! You can still set the camber to what you want.

Iv played about with a few setups, and found having the rear 15mm higher than the front made a huge difference to when it was set at 10mm higher. Rear end is a lot looser.

Iv found toe parallel all round suits me, but you can have a play with this a bit. If you toe the rear out a bit it should be more willing to oversteer on initial turn in, but will also be a bit less stable under braking.

Iv managed to minimise a lot of the understeer, initial turn in is sorted, but it still pushes wide on corner exit if i keep the power on. If im aggressive with the wheel and the throttle i can get the back end to step out.

At the moment my setup is this:

Front 325mm, Rear 340mm.
Castor mod
Front camber: -1.5, Rear -1.0
Toe set to 0 all round
Whiteline front and rear antiroll bars (Rear on middle hole)

Could be a starting point if you dont know what your current setup is?

 

[keastygtir]

up your tyre pressure to 37psi

 

[Trip]

I just finished off doing the castor mod this eve. It was a very straight forward job to do.

Next will be getting my height in order which i'll go for the aggressive 15mm difference front/back. If everything goes to plan early next week i'll take it for a laser alignment and off for more testing

but it still pushes wide on corner exit if i keep the power on. If im aggressive with the wheel and the throttle i can get the back end to step out.

That is exactly what i am suffering. On power while going round a roundabout, Its like the car is RWD and the rear wheels are pushing the car straight forward ignoring front wheel direction. Its like the front wheels are hovering in air .

With my other car which is RWD, in a similar situation where i suffer from understeer while on power in a long sweep turn, i just tap the throttle (release and press again) to unbalance the rear and off it goes to oversteer :lol: . The Pulsar stayed put and kept on understeering .:doh:

 

[Trip]

up your tyre pressure to 37psi

Is that at cold temperature or hot ?

 

[keastygtir]

thats cold mate

 

[keastygtir]

light feeling front (like on ice) is usually tracking, I would get it set neutral

 

[Trip]

I just need to play and test with different setups.. I won't go for 37psi of pressure though. Toyo recommends to go for between 25 and 28 psi cold for my car's weight.

 

[keastygtir]

37psi is the recommended pressure on the original 14" wheels, you should have this at least in a lower profile tyre