I am frustrated with the amount of understeer my 350Z has when navigating around the tighter cones. I dropped my front tire pressures low to (what I think) is the lowest I can go without rubbing my sidewall. The fronts get 40 psi when hot and rears are about the same when hot, but they are very far from rubbing the sidewall.

Is there anything else I can do with tire pressures to reduce undesteer and improve the turn-in throughout the tight sections?

I'm on stock Potenza's and I have 2006 350Z Touring.

Thanks in advance for any tips.

 

a. Brake in a straight line. Brake early. Brake hard.
b. Accelerate through the turn. Transfer the weight from the front tires to the rear.

 

Swaybars will help

 

IMO, the best, fastest, and easiest way to eliminate understeer is to get all 4 of your tires the same size.

 

X10,000

That is the key.

 

That is a start. It will help a lot.

The number one way to to eliminate understeer is simply to not overdrive the corner entry.

 

you could try a different alignment. A little bit of toe-out in the front will definitely help your turn in, and maybe a little bit of more camber if you can squeeze it on the front tires. That and maybe a bigger front sway bar will help keep more of your front tires in contact with the road.

 

Alignment and driving style.

That will increase understeer by unweighting the front tires, not decrease it as desired.

 

In theory that is true. I've got all four the same size and still the Z understeers. Maybe it's at a higher speed than before but it's still bad.

 

Your front tire pressure should be higher than the back if you want to decrease understeer.

If your fronts are running 40psi when hot drop your rear 2-3lbs. Get some adjustable sways and make the front stiffer.

 

You also have an LSD set pretty tight right? That certainly won't help slow speed corners.

 

non-staggered tire sizes and sway bars will help dramatically.

 

Like I said before, QUIT OVERDRIVING CORNER ENTRY.

It's "slow in, fast out" -- not "fast in, fast out."

 

I don't know if you were looking for this type of responce, but here's the setup that a well known 350Z owner used, don't think anyone place higher then he did in nationals or went to as many events. He no longer drives a Z in events.

Side note: The Cusco front bar is also solid at 1 3/8" or 35mm in diameter. Since the above was posted, H&R has come out with a 36mm solid front bar as well.

 

That's true, except when you want your front tire pressure to be the same as the rear tire pressure. Or when you want your front pressure to be lower. In other words, that's not really true.

There's an optimal tire pressure which varies by tire brand, size, course conditions, the car's setup, and other factors. Given that, "your front tire pressure should be higher than the back" is too general -- the right approach is to determine the optimal tire pressures, then, if you want to reduce rear grip to fix the car's balance, increase or decrease the rear pressures from optimal.

Having said that, I wouldn't try to fix the problem by reducing rear grip with tire pressures. Besides alignment, are you sure you're driving the car correctly? To elaborate on my reply and PDX_Racer's: make sure you're not carrying too much speed into the corner. Try getting all of your braking done in a straight line before you turn in, and see if that helps. Alternately, try trail braking (starting your braking before the corner, but carrying some brake into the corner as well) and see if that helps. Play with the throttle in mid-corner; light throttle can induce understeer, but heavy throttle can bring the tail out.

Last but not least, have someone experience drive your car and give their perspective -- that will be a quick sanity check on whether it's your car or you.

 

This will make the car push more.

I run a 275R and 255F and +2 psi in the fronts gets me very close to neutral.

Start with driving. Have an instructor or other good driver ride with you (or better yet drive your car) to see if it is the car or your technique.

If it's the car's fault. Try finding a tire pressure that uses all the front tread without rolling over on the sidewall of the tire. Then adjust the rear for balance.

If thats not enough. A tighter rear swaybar will be the next-cheapest fix. (get an adjustable one to dial it in)


Good luck.

 

Definately learn to drive better from someone more experienced (we all have room to improve).
As far as car setup, you can't argue with results... if you want to stay in stock class this is the setup:

The above was a 2nd place BS finish in 2006 SCCA Solo Nationals (just .100 second behind an RX-8).

 

A common problem with drivers -- they drive too fast in the slow corners, and too slow in the fast corners. Most get the "too slow in the fast corners" figured out, but the drivers who get the "too fast in the slow corners" solved are the ones that end up doing well.

Guess what the symptom of "too fast in the slow corners" is? Yup. Understeer.

(BTW, Who do you think jumped on the opportunity to get those shocks when they were for sale... )

 

I have to admit - that's my #1 problem. Time to work on the driver some more.

 

It was close.

#1 like PDX said, slow in. 100% of the time understeer is caused by the driver. Yes you can tune/adjust the car to make it happen later or you can go so far the other way you end up with a drift car. The only way to really fix it is slow down on corner entry.