Gtr Understeering Badly

[Pezhead]

OK, I had a bunch of work done on my R33 GTR before xmas - incluing transfer case rebuilt and pan baffle. I'm sure they had to pull a bunch of the front suspension and cross member as they did the pan baffle with the motor in the car.

Now, my problem is really bad understeer. In the wet the car will understeer out of a round about if I accelerate out from normal speed. In fact at speed limit speeds, if I just aggresively turn the wheel the fronts slide and slip.

The car also kicks in the diff lock really agressively as even turning at 5 kph out of my driveway it will lock up the rear diff and make the car surge a bit as it turns.

I've only ever driven the car in 2wd mode as the transfer was stuffed when I bought it. But it never understeered this badly. In fact I think it drove better before becasue at least it oversteered when I put the power on.

I'm thinking I need to bring it in for an alignment check up as the first place to start. If that isn't the prob then I guess back to the shop for more check up (but I'm not really feeling confident as the shop has really taken me for a expensive ride so far).

[nisskid]

useless with out a list of suspension mods, including adjustable arms, sway bars, spring rates, tyres etc etc

also mid corner, entry, exit? is it only when u accelerate, or does it understeer even on coast?

[Pezhead]

Ok, it's got greddy S-Tune all the way around. I lighted up the front adjustment all the way to hope to give it some more grab on the front.

Lowered 1" with whiteline camber bushes and aftermarket sway bars front and rear. The sway bars aren't adjustable so they aren't whitelines, but I don't know which brand.

Adjustable upper camber arms in rear.

Camber at front 1.5-2 negative and rears @ 1 negative degree.

In the wet this is what happens. The understeer happens entry, mid and exit. So entry if I just turn the wheel a bit too much will just slide. Mid if I accelerate will just slide. And exit will slide if I accelerate.

I don't drive that hard in the dry so I cannot comment too much aside from you can still feel the understeer a lot, it just takes a bit more speed and harder acceleration so I'm sure it will be the same as on the wet.

I just feels so wrong and really compromises my confidence.

[some_cs_student]

Have you got a 4WD alignment done recently? Its worth a try and may improve things quite a bit....

I only had serious understeer issues when the transfer case was dying, the GTR does still understeer but not that easily.

The diff does lockup as you described depending on how cold it is.

[_Ryan_]

what tyres and pressures?

[Mr. Keets]

It's a pity you cant soften the front bar that would be a good start after checking tyre pressures, How low is the front end, top of the guard inside to the deck? What are the spring rates? In the end it looks like a few things and I guess the diff isn't helping. I'd talk with the guys in the NSW section to get a referral to a good suspension shop...Heasmans or similar.

This is why I get my tuner to go the mechanical and a specialist suspension shop to do the suspension

[Pezhead]

Tyre pressures are 32 PSI all around. I've got Toyo Transas 275 35 18's all around with plenty of tread so those aren't the prob either.

It could be that the car didn't have the prob before as the diff (and 4wd) wasn't working before so it would spin a back tyre before breaking the fronts loose. I just can't belive how easily the fronts break loose now.

May have to investigate a better front roll bar.

Thanks for the input fellas.

[Lippo]

Get a 4 wheel alignment done first. That way you know the wheels are pointing straight. Secondly, what oil are you using for the diff and transfer case? Maybe wrong type of oil used? The diff should not lock up in the driveway. Just some suggestions.

[Waza_GTR]

Go to 38psi and see if that helps

[scathing]

Kick the clutch.

[bnr#@]

If you have redline light weight shock proof in the rear diff then that can make it lock up at low speeds. Its probably not ideal for a street car if you just want it to be quiet, damn good oil though and makes the diff tighter which is great for track days/spirited driving...

[Dearlove]

Kick the clutch.

LOL

my car does the same, wet + round about = curb

BUT, i know its the tyres are bald, well im hoping, lol

[Gav]

Ok, it's got greddy S-Tune all the way around. I lighted up the front adjustment all the way to hope to give it some more grab on the front.

Lowered 1" with whiteline camber bushes and aftermarket sway bars front and rear. The sway bars aren't adjustable so they aren't whitelines, but I don't know which brand.

Adjustable upper camber arms in rear.

Camber at front 1.5-2 negative and rears @ 1 negative degree.

In the wet this is what happens. The understeer happens entry, mid and exit. So entry if I just turn the wheel a bit too much will just slide. Mid if I accelerate will just slide. And exit will slide if I accelerate.

I don't drive that hard in the dry so I cannot comment too much aside from you can still feel the understeer a lot, it just takes a bit more speed and harder acceleration so I'm sure it will be the same as on the wet.

I just feels so wrong and really compromises my confidence.

Rake angle (or front to rear balance) plays a huge part in how the GT-R corners. Lowering overall by 1" as you say is OK, but you must make sure you keep the front (as measured from the centre of the wheel to the arch) is around 10mm higher than the rear. If you have a neutral (or worse rear elevated) rake the car will understeer like a bitch.

You don't mention if you have a subframe alignment kit (aka "pineapples") installed. If you do, make sure the setting is neutral rather than "traction" or "squat".

Gav

[Pezhead]

Thanks all. Had the 4 wheel alignment done and they said there was a ton of toe in at the front causing my issue. Must have gotten out of alignment with the work that was done.

Driving today in the rain and all seems good so far.

Glad it was just an alignment issue.