sraz786

Folks,

My diff went bad and recently had the Cup Car clutch pack installed on a 2011 RS. I am perceiving much more understeer than before. Normal? Tips on driving through it? If you have done the same, what are you perceptions? Thanks in advance.

Izzone

Learn to re drive car

Adjust sway bar

Ur20v

The extra lock up will cause more push at the front (under steer), more trail braking (change driving style) to load the front and adjust the suspension to increase front end grip. This is a normal side effect of the new stiffer setup of the cup diff pack/ramps or any upgraded mechanical diff, thats why BMW and Ferrari spent so much time on their electronic M/E diffs.

Some adjustments to try and help the front grip...

Softer front sway bar or setting
Harder rear sway bar or setting

Dial in camber and alter tyre pressures as required

Soften front springs and or lower front
Harden rear springs and or raise rear end.

Wider/softer compound front tyres
Narrower/harder compound rear tyres

Welcome to the world or race car set up and compromise!

Jay

Mvez

Drive it in the rain and you'll cure the understeer.

Seriously, just do what they said. The diff allows you to lean on the front end a lot harder.

sraz786

Thank you for your insights.

I must admit, I am an amateur but you gotta start somewhere right?

As far as tire pressure goes, I run 31/34 hot. I'm dialed in almost 2.2 up front with neutral tow, sway bar settings are as you had mentioned. Any recommendations as far as tire pressure goes with this setup?

I'm currently running PSS (mostly street driving) 245/325. Are these better/worse than MPSC and what widths would you guys recommend?

DJN

Don't worry about tires during set up (unless they are very worn, in that case get another set of PSS). Street tires will make it easier to set up.

Later leave the sizes the same (they are perfect) and definately move to MPSC or other R-comp as you progress.

The listing provided by Ur20v is indeed correct but is it best to start simple:

- driving style first as described above by Ur20v
- if you are still not happy, then begin by only changing one thing at a time
- start with something easy

1) tire pressure, HOT (32psi Front/34psi rear for street tires, 30/32 for r-comps) - the GT3/RS loves softer pressures like this, also you can adjust in 1 psi increments to taste using the method: decreasing pressure will increase grip, increasing pressure will decrease - but don't sway more than 2 psi off soft or hard

2) sway bars - easy to adjust yourself, start by stiffening the rear by one hole on both sides - be sure to take note of where you started and what you changed

3) Alignment and ride height set up - this must be done by a Porsche specialist......more camber in the front will reduce understeer (but I think you have plenty for DE), as will a lower ride height up front...............don't mess with shocks and spring, you don't need to.

Cheers!
Doug N

kristob

Better tires for the track would help. That's a street tire. MPSC would be better as it is an 80 rated rubber. Your PSS are probably 300 rated rubber. Also more camber, 2.2 is fairly modest. I run 2.6 and use Hoosier R6. No understeer to speak of.

zanwar

I also had cup car clutches and ramps installed in my 2010 GT3 and I'm experiencing exactly the same problem, understeer coming out of turns under power. I've tried sway bar settings, tire pressures and rear ride height but the problem remains. I'm also running MPSS tires.

Right now I'm having the car aligned and balanced so we can start again with a known set up. I'm also going to try running a set of Pirelli Corsas that I have in storage. If I make progress with the understeer issue I'll post the results here.

TraqGear

What these guys said but make sure it is corner-balanced with proper weight in the car with a shop that knows how much weight bias you can transfer to the front without unsettling the car.

TRAKCAR

Ride height and rake make a huge difference.

sraz786

Please do. Would like to see if that helped among all the other recommendations so far.

10 GT3

Even going full soft front and full hard rear on the sway bars, you won't get rid of it. The suspension geometry needs to be fixed. You need to find someone who knows how to setup these cars. They basically need to remove the lower control arms and re-clock the center bushings to fix the geometry. I did 3 different alignments on mine before having it done. I could not get it to turn in sharp or get rid of the understeer regardless of alignment, sway bar or tire pressure settings. After getting the geometry fixed, car turns in sharp and is dead neutral with both sway bars in center position. I even run .2 less camber in front and .3 less camber out back, yet it laps over 5 seconds faster at the track. The problem is Porsche setup these cars too conservative from the factory.

Protocav

Are you saying that the understeer problem is reduced by adjusting the caster, or does the bushing rotation accomplish something else? Are you running the standard 8 degrees of caster or have you found a different magic number? I confirmed your swaybar comment this weekend. I didn't get any more front grip...just less rear

zanwar

I ran at the track this morning with my new setup. The car is very much improved. The understeer I was fighting has been dramatically reduced. The car feels very controllable with a nice balance between understeer and oversteer. Basically it was a joy to drive. Note that I changed two things at the same time, suspension settings and tires. The work was done at Fall-Line Motorsports. They also installed Tarrett drop links to fix a sway bar preload issue. Here is the alignment and balance data. I hope this helps you out.

Pirelli Corsa 235/305
Cold psi
FL 33 FR 33
RL 33 RR 33

(today I started at 30psi cold all round, ended at 39psi hot all round, ambient temp was 29C)

Front sway : 1 from soft
Rear sway : 1 from hard

Ballast 180lbs

Corner weight
FL 666 FR 607
RL 1075 RR 1014

Ride Height
FL 104.5 FR 105
RL 126 RR 127

Castor
FL 8.0 FR 8.2

Camber
FL -2.4 FR -2.5
RL -2.4 RR -2.4

Toe
FL -0.06 FR -0.06 (out)
RL +0.11 RR +0.08 (int)

85Gold

MPSS have a very soft sidewall and a lot of roll over. You will need more front camber around -2.8 and run higher pressures hot in the 36 to 38 psi range.

Peter