R33 Gtst Handling Advice

[Littlehorn]

Hey, I have been slowly building up an R33 Gtst track car over the past 5 or so years. I feel that the car is just about where it needs to be in terms of upgraded/strengthened/adjustable parts now but i am having trouble dropping my lap times mostly due to oversteer.

I am hoping there is some knowledge out there that you might be able to share with me.

Here is a video of how the car goes at the moment which also should give you an idea of its handling characteristics.

https://www.youtube.com/watch?v=PeUwsz22pOU

and here is a basic rundown on the car and setup.

It is a 96 S2 Gtst with a steel wheel holset core and about 240kw

Interior

- Stripped interior about 180kgs removed

- 8 point roll cage

Handling

- Bilstein shocks valved for track work

- Springs 350 front 550 rear

- Ikeya formula front upper (front set to 3.2 negative)

- Ikeya formula rear upper (rear set to 1.6 negative)

- Ikeya formula rear toe (pretty sure toe was set to neutral)

- Alloy subframe bushes

- Polly bushes just about everywhere else

- Nismo 2way LSD

- Hicas Lock bar

- Height adjustment set to about stock

- 20mm spacers

- Federal FZ201 semi slicks (about 34psi hot in front and 32psi in rear)

There are other RWD cars running similar setups and power to weight lapping 3-4 seconds faster, now obviously the driver is going to have a big impact here, but looking at there videos they seem to have a lot more corner grip and stability.

[Plattsy]

either im blind or you dont mention sway bars.

these are a must.,

if you do have them, soften the front sway a little, it will correct the oversteer.

just my little 2c on the limited knowledge i have.

[niZmO_Man]

- Springs 350 front 550 rear

Are those 350 pounds front and 550 pounds rear spring rates?

[zebra]

2way diff isn't helping.

Stiffer rear springs isn't helping

neutral rear toe probably isn't helping either.

What width tyres?

[Littlehorn]

Swaybars are whiteline adjustable front and rear

Front is set to the second softest setting out of 4

Rear is set to the softest setting out of 2

Tyres are 17 inch 255 rear and 235 front.

[Littlehorn]

Oh and springs are actually around the other way 350lbs rear and 550lbs front.

I upgraded the diff because the viscous one slipped hopelessly exiting low speed corners.

[hrd-hr30]

I'm tipping it's rear bump steer.

[Littlehorn]

I'm tipping it's rear bump steer.

Can i alter rear bump steer?

Just checked my last alignment settings

Front:

Camber -3.1

Toe 0

Caster 6.5

Rear:

Camber -2.15

Toe +0.6

thrust angle 0

Wonder if there might be a bit too much rear camber.

[ARTZ]

Rear camber about 1-1.5 is good, front is fine

stiffen front sway bar not soften

set rear toe to 0 front to -1 ish

go from.there

[ARTZ]

lol just read height set to standard

Lower that bitch...at least the front...A simple lowering would have set your camber and avoided the need for all those adjustable arms

[Neil]

The initial understeer is what worries me,,,gts-t's don't usually suffer from that. It's certainly not the tyres,,, FZ's are great but your tyre pressures are way different than me,,,I use on a hot day 38 all round and constantly adjust them till I get it. Zebra's on drugs,,,no way is your diff contributing,,,no way. I'm running close to 0 camber on the rears and about 4.5 on the fronts from memory. Artz is right she needs to be lowered,,,big time.

Just do little changes,,,or you will never know what fixed it.

Cheers

Neil.

[Littlehorn]

The initial understeer is what worries me,,,gts-t's don't usually suffer from that.

Yeah hard to recommend changing swaybars when the car is exhibiting both under and over steer.

I found this interesting camber vs tyre pressure info that I will have a go at next track day http://www.turnfast.com/tech_handling/handling_pressure3

I will also lower it a couple of centimetres just a pain for road driving.

I am going to peg rear camber back to about 1 degree if this fixes the rear end grip then maybe i can adjust sway bars to reduce understeer (softer in the front or harder in the back although the links on the whiteline kit seem to only fit in some positions)

[gtr jet]

I bet backing off that rear camber should mack a noticeable distance.

As everyone else has said, lower the boat too.

[White GTS-T]

You stated the tyre size, but size wheels are you running front and rear? If you're running narrower front wheels and tyres, try running the same front and rear. I think you'll find it makes the handling

a lot more neutral. Also, a bit of toe out on the front will help with turn in and that corner entry understeer. Goodluck, and keep us posted.

[Littlehorn]

You stated the tyre size, but size wheels are you running front and rear? If you're running narrower front wheels and tyres, try running the same front and rear. I think you'll find it makes the handling

a lot more neutral. Also, a bit of toe out on the front will help with turn in and that corner entry understeer. Goodluck, and keep us posted.

You are correct on rim size im running 8" on the front and 9" on the rear.

Interesting I need to get some lighter rims current are about 9ks a piece, will take this into account when i upgrade.

What do you reckon 9" front and rear running 255s?

[White GTS-T]

That's what I would be doing. And then, if it still has mid corner understeer, soften the front sway bar one notch.

[Plattsy]

stiffen front sway bar not soften

this counters understeer not oversteer.

[dan.1337]

Your 2-way diff may be making your car oversteer more than what you want

[ARTZ]

this counters understeer not oversteer.

Nope, softening a front sway bar will correct understeer..so I just figured stiffening it will help with oversteer...

ED*

though if you look at the graphs below ther eis no clearcut solution really as softening and stiffening can fix it, depending on situation

I have been reading up on this all week man cause the cressy is understeering mid corner, been looking for a solution

Hey, I have been slowly building up an R33 Gtst track car over the past 5 or so years. I feel that the car is just about where it needs to be in terms of upgraded/strengthened/adjustable parts now but i am having trouble dropping my lap times mostly due to oversteer.

That's what I would be doing. And then, if it still has mid corner understeer, soften the front sway bar one notch.

thats what i read it as.....why are we all talking understeer now?

Also i dont think rim size is going to make alot of difference, mine felt perfectly stable with 8s and 9s..dont get me worng it will help, but i dont think it is something to really be concerned with.....

[ARTZ]

some intereesting graphs i found..