[whyzee125]

Square rear wheel setup with 255 or 265 all around

[CptSumTingWong]

So i know it's been a while, i've still be trying to dial out understeer unsucessfully.

I've since changed rear tow to .15 total toe in still 0 toe front

I also added solid whiteline sway bars 27mm front 20mm rear

running 235 front 245 rear RT615K+

I don't think it really made any difference. It rotates a little bit better on the brakes trail braking but still a ton of midcorner understeer. I can't carry the corner speed I want and have to unwind the wheel and track out much earlier.

Just feels like a lot of driving around the car. I'm not chasing lap times since this is just not a fast car but it just doesn't feel good which is then taking away a lot of the fun...

[Tambohamilton]

Put the stock front sway back on, give the rear zero toe.

Also what ride height are you running?

[CptSumTingWong]

Originally Posted by Tambohamilton

Put the stock front sway back on, give the rear zero toe.

Also what ride height are you running?

I'll give it a shot.

Ride height is set to about the middle of the coilover range so about 40mm drop?

[kolopn]

Check telemetry, usage of brake pedal, and speed sensors of wheels. To be honest setup of the car will be last thing to touch. Setup will give you time, but first of all I will focus on tyre pressures and braking style. Maybe you are loading front tyres too much, and they can't provide sufficient lateral grip to turn. Maybe, you're having to high steering input without balancing car with overall brake and throttle usage. Maybe you are holding brake too long, and that causes little lockup. If you don't have telemetry, maybe think about having some kind of easy camera, and pedal camera, or make dynamic log with throttle, brake and steering angle plot. Repeat that with couple of laps, and check how it look.

Overall if you are facing understeer general solution and the quickest will be to increase stiffness of rear arb or decrease front.

Do you have adjustable compression and rebound?

[whyzee125]

255's or 265's up front and lots of camber

[Tambohamilton]

Originally Posted by CptSumTingWong

I'll give it a shot.

Ride height is set to about the middle of the coilover range so about 40mm drop?

The front doesn't respond well to being too low - roll center goes through the floor. I think I'd raise it about 20mm and keep the stock rake. But tbh I wouldn't expect a night/day difference from that alone.

[autoart]

When changed from a 235 to a 245 Michelin pilot sports it made a huge difference.
What are your tire pressure settings? Remember the pressure goes up as you add heat to the tires.
I use chalk on the outside of my tires before I track and check after to see how far my tire has rolled/worn and adj. tire pressure accordingly.
Have you posted in the track section?
good luck on your quest!

[72GMC]

Here's my setup, which I'm really happy with:

Lowered as much as practical, with .75" rake
M3 suspension kit
KW/ST sway bars, 27mm front & 24mm rear
560lb front springs, 672lb rear springs (But 448lb front might be a better choice for daily drivers)
Front -3.5 degree camber, 0 toe
Rear -2.5 degree camber, 0.1 degree toe-in.
265 wide tires, square, on 9" wheels. ET 30, with 3mm spacers (effectively ET27)

Recently replaced rear sway bar, which snapped while powering through a compression corner. (After 50+ track days, which i demonstrates how much it's being stressed) Now running a Whiteline rear sway bar, which was available on short notice.

I rarely any understeer mid-corner, feels perfectly balanced.
If experiencing understeer during initial turn-in, try turn-in sooner with slower hands, or a little trail braking.

[Tambohamilton]

Are you running coilovers on the rear? Because if not, those rear springs are SOFT compared with the front. Interesting.

[72GMC]

Originally Posted by Tambohamilton

Are you running coilovers on the rear? Because if not, those rear springs are SOFT compared with the front. Interesting.

Rear is typcial divorced set-up, not true coilover.
ISC 10kg/12kg
This is an unusual ratio, resulting in wheel rates optimized more for performance and less for comfort.
There's a thread somewhere showing the range of wheel rates from comfort, comfort/performance, track-focused, and aggressive track+aero.

I wouldn't describe the rear as soft, but i would describe the front as quite firm.
On slow bumpy roads, it rides a bit like a garbage truck.
But it's quite composed above 80kph/50mph, even on rough roads.

I run the front at 4/32 clicks (soft) and the rear at 16/32 clicks.
When the front was at 16/32clicks, it was more chirpy in bumpy braking zones.

[Tambohamilton]

Yeah, I've done a fair bit of digging on it myself. I just find it interesting that you've arrived at ~500lb/in front wheel rate but only ~350 at the back. Is the rear of the car stripped out? I guess that would make more sense.

[whyzee125]

Originally Posted by CptSumTingWong

So i know it's been a while, i've still be trying to dial out understeer unsucessfully.

I've since changed rear tow to .15 total toe in still 0 toe front

I also added solid whiteline sway bars 27mm front 20mm rear

running 235 front 245 rear RT615K+

I don't think it really made any difference. It rotates a little bit better on the brakes trail braking but still a ton of midcorner understeer. I can't carry the corner speed I want and have to unwind the wheel and track out much earlier.

Just feels like a lot of driving around the car. I'm not chasing lap times since this is just not a fast car but it just doesn't feel good which is then taking away a lot of the fun...

You need more front camber and 255's up front. You'll be happy.