URGENT! VDC almost made me crash!
 

Hi everyone... well here is my story and now I´m very concern since I can´t find what is going on with my car...

I bought my 2003 6spd touring 350z 6 months ago, and came with all four 235/45/18 new tires... they were TW380 so I went to 5 track days to rip the hell out of them while having fun and then change to new tires...

since car came with 235/45 all around I decided to put the recomended rear tires wich are 245/45/18 like nissan says... with this I will have wider tires on the back and the 235´s on the front wich are not the tiny 225/45 that the book says...

So I bought a set of Toyo for the rear and next week will buy also toyo but 235 for the front...

Everything was fine, car looks nice (better than before) but here is the deal!!

Remember...
Before: 235/45/18 all around
After: 235/45/18 front - 245/45/18 Rear

I was driving home at 50mph and took a long not so tight turn letting the gas off and cruising when suddenly the VDC kicks in creating understeer and almost crashing in to the wall !!!!... there was no water, sand, or anything on the road...

This same effect shows at the Track with old tires but at much higher speeds and tighter turns when pressing the brake in the middle of the turn, But NEVER happend like this! So to be sure I went to a big parking lot and I´m able to recreate this problem over and over again by just cuising, turning tight, and boom kicks in. Even with turning softly but touching the brake does it!

Let me say that the same turn I drove it every day and even at higher speeds, since is my way home!

DAM I REALLY SHT ON MY PANTS :icon43:!! but now I´m really mad!, since I understand that if there is a big difference in wheel size between front and rear, VDC will go crazy, but actually there is very small diference from a 235 to a 245... even bigger difference is between the 225 and the 245 that Manufacturer claims it has to use... And MORE WEIRD is that before I had NO difference since car came with Same tire size all around!! :dunno:

I think my only solution will be to put also 245-45-18 at the front but good bye nice look :(

BTW, No Error Codes at all on the Nissan Scanner.
any ideas?

How much tread is remaining on the fronts?

Out of habit I just turn mine off as soon as I start the car...

The VDC system in the Z is very sensitive, I would recommend running the oem staggered set up. You are going to have more issues if you run a square set up unless you turn off the VDC every time.

where you holding the turn or did you let off at the apex of the turn releasing the gas?

In reality, VDC saved you from crashing, not caused it. Based on your description of when it happened, that should have been the ideal situation for VDC to kick in. The car was not widly upset which might have caused VDC to get confused, i.e. not like you were in a spin.

Letting off the gas going into a turn cause the rear end to want to come around - oversteer.

New tires are greasy, a release agent from the factory that has to be scrubbed off before they grip to their maximum level.

Mixing brands /models of tires on different axles is never a good idea either, especially when one set is new and the other are old and worn. Different grip levels can cause understeer/ovesteer.

False. I have been running square set-up for years now without issue.

+100000000000000000000000000000000.1
Superb input :thumbup:

I even emailed Nitto about mixing front (Invo) and rear tyres (nt555) and replied back to me insisting I should not do that. Also, it takes about 150miles of normal driving before the tyres are safe to push.

I only switch off VDC during trackdays / Autox. For regular driving, it keeps me safe. I sometimes mash the gas a bit too hard during hard turns (specially on very smooth asphalts) and the throttle cut-off keeps me from spinning.

Thank you all for your reply... Here is the deal... I have years driving on race tracks semi and professional. Not to look like a bad ass, but just to get clear that I am aware of what to do and not to do.

Like I said, this turn is very soft, I also have the 100% VDC turn off and on Mod (I will post a full write up on how to do this very clean and plug & play soon)... so I took the same turn Faster with the VDC completely turned off, even forced the car to oversteer and it held perfectly, so actually the VDC wasn't trying to save me before...

Front tires are 1/2 life on front... can 1mm of tread difference cause this weird behaviour? I don't want to spend money on brand new 235's for the front to keep my car looking good and not like a 4x4 and realize that this car will keep doing this!

Also I know I can drive always with the VDC off, but is not nice to have 2 dash lights on all the time. And I only turn it off when at the track were I really need it to let me enjoy... But this VDC behavior so sensitive is just too much!

DAM IT !

I was holding the turn!! The only desceleration was by cars own innertia at 4th gear so nothing heavy or abrupt.

this:thumbup:

^this. if you change the set up it will affect the response. But you might also consider that it was "you" who almost put you into the wall.

you tire sizes are contributing to your problem

ideally, stagger should be about 2.5-2.7% front/back - yours is about half that

with a 235/45/18 up front, the rear should be a 255/45 ideally

what dave posted about tires being greasy when new is absolutely true too - and there are more than a few posts from VDC owners who have described this very issue after installing new tires

for those that posted, pushing VDC off on your dash doesn't really turn it off...it just delays when it will engage

OP does have a 2003 and it appeared as though the early models were more sensitive to square setups than later models. That could explain why it kicked in.

I have had VDC kick in probably a hundred times over the 7+ years I've driven the Z. Never have I had the feeling it was making a situation worse. Never has it kicked in on a situation I couldn't explain and understand - i.e. when it did kick in, I know exactly why it happened.

I have a very similar driving situation to OPs where I can make it kick in almost every day if I wanted to. When I leave my office, I head down a major highway that has a entrance ramp onto the interstate. The radius of the turn onto the interstate is somewhat tight, maybe 300' and it's more open than a 90º turn. It's a blast to go into that turn at 50-60 mph and accelerate out onto the interstate. If I head toward the turn and lift off the gas and immediately make the turn in, VDC will brake one of the front wheels. It's predictable, it's controlled, it doesn't upset the car and it's no longer a surprise to me.

I can see if it does kick in unexpectedly and if you had the natural reaction to let off the gas, touch the brake or make a sudden steering "correction" that you might make the situation worse than it would have been under normal conditions.

As for the tire sizes, another thing to consider in different brands/models is that the actual production dimensions aren't exactly the same as the specification. Tire heights/ODs vary across brands and models. While you may think they are somewhat staggered, in reality they may not be. Not until you get 4 properly sized, matching tires on the car can you honestly evaluate the effectiveness of VDC. The oddball mix is imposing conditions that none of us really know what it is so we're only guessing at what is happening with respect to VDC.

You lift in a corner in a car that has a nearly-50/50 weight distribution, and you'll have the back end start to come around. VDC kicks in to prevent that.

I've got over 20 years of race driving experience in both production and formula cars, and the Z is one of the most lively production cars off the showroom floor that I've driven (not as lively as an unmodified AP1 S2000, but pretty close).

There are a lot of issues right now — the mix of tire brands, tire ages, ratio of tire sizes, plus the unknown condition of the road surface. You say that there was nothing there, but if you're close to the limit it won't take a lot -- even a tiny piece of gravel will negatively affect traction.

for someone with so much racing experience, shouldn't your 'VDC' be your right foot?

Yes, you are right, but I am driving really normal trying to enjoy a ride back home, not racing anyone, not even driving fast or agresively, so on a Daily drive is not nice to have a dash full of lights if I would like to turn completely off the VDC. Race mode for me is only at the track not after work. So this is very frustrating.

Road is very clean. Speed is very low, turn is wide open, not tight, and my driving is very soft, no hard turns, no braking, nothing. Just normal driving. and this happens anytime anywhere, not just once on that turn... Now i´m just expenting VDC to kick in on every turn I make, and I really don´t enjoy my car anymore.

Yes. Maybe brand new rear tires, and used front tires can make some difference. but Why with a square setup of 235´s that I had before, there was no problem if it is supposed that the VDC is programmed for a 225 and 245 tires???..

I read some posts that problem was solved with new front tires, and that is just not nice to change all 4 tires when only 2 are worn.

My fear is that if I go and buy a new set of tires and problem keeps happening I will be really pissed. good tires are not cheap down here :icon14:

I think I will end up shutting VDC completelly off, and getting rid of the dash lights.

This car won´t forgive anything!!! :icon17:

Lets see, new rears , old fronts, let off gas mid corner and VDC thought the front was going into a slide. I don't see a problem here at all.

Yes, yes, No, No...

I did not let off gas mid corner... I entered a WIDE turn with no gas at all since the beggining...
Front never slide, speed was low and turn is very wide. and not only happend once and at same place...

i dont think i ever drove this car without turning vdc off for one and also those tire sizes are weak sauce cant see that being any problem...Learn to drive?