My friend's 03 track was on the course today. He and the car both did a good job at staying on course and having fun. One of his complaint was the front tires would lock up initially going into the turn. Since I didn't experience the problem personally, I am just curious to see if this is the VDC kicking in again? His VDC was off the whole day, he said he saw the light flashing at one point. Could that be it or what? I honestly have no idea. I dont think it is the EBD as I have it on my enth. model too. Weird

 

Brakes on an ABS equiped car can't "lock up". He may have heard the front brakes pulse (grinding sound that ABS makes).

 

not from what he told me. he said he and the instructor both experienced the lock. He was on stock tires and brakes, so i dont think he is overpowering the system. Weird..

 

I'm inclined to disagree- even with the VDC turned off, I have managed to get the slip/VDC/ABS/Brake light show on the dash due to my Nismo LSD, and this combined with ferocious track pads and big brakes caused my ABS to malfunction and lock up the tires. It was ugly, but it was a reminder that there are things the Z's computer was just not equipped to handle. For the record, it only happened once in the three years I been tracking the car, and I think the aftermarket BBK with over-aggressve pads was the culprit.

 

I've heard that ABS doesn't work at speeds over 40mph. Don't know if it's true though.

 

Car was stock, so I am curious to see what is busted on it.

Yeah 40mph it doesnt work, you might want to try it out...

 

I would have to agree with you that your out-of-spec pads & rotor could have caused brake lockup. If you had R-compound tires that would have made it even more possible.

Since the buddy was running stock brakes and tires I doubt that it would happen in his case. A hard as I've tried in an autocross I've never been able to lock them up, even with non-stock brakes and tires.

 

track is a lot harder on cars than autox. things you never ever think of using will be used at the track

 

This sounds like what many others have experienced: EBD.

I have had one guy at a track come to me and ask about this.
Kolia recently posted about this as well.

Watch it more carefully:
If it is just one tire 'locking' up, the outer one in a turn, I would bet it is the EBD trying to avoid oversteer by forcing understeer.

 

If it is EBD, why doesnt it happen to my car? I dont have VDC, but I do have ABS and EBD. He said it was more than a brief second that it locks up too.

 

As far as I understand on VDC equipped vehicles there is the yaw sensor under the center console which will be used to assess dangerous oversteer.
When detected, EBD is used to selectively brake outside front tire.

Without VDC and the yaw sensor, no such behavior. You may still have EBD, but I am not sure how it will then be used, other than for regular ABS purposes.

Switching off VDC disables the traction control part of VDC, but as the countless threads discuss, not necessarily the braking part of it.

I believe I have run into this on the street, but this is a while back, not sure if I can reproduce it:
With VDC Oem switch ON or OFF, when going very fast into a 90 degree turn (e.g. empty, deserted street crossing without Stop sign , making a right turn) and braking into the turn, you can feel/hear something like ABS coming on selective on one tire.

I have installed the center console switch to cut the power from the yaw sensor, and have not had this happen.

On the track, I have never dared to run without using my center console switch. So I have never run with the yaw sensor functioning (VDC on or off) at the track. And I have never experienced any problems.

this is on a 2005 touring MT

 

Hmmm.. brakes, steering, gas pedal. Yup, used them in both places. Can't think of anything else....

 

It would be better to hear from the driver.

 

Let me know if you hold a steady 1.1G for a period amount of time, I will fly down to drive at that one.

 

I think the EBD only deals with front to rear brake bias.

None the less, and discounting the possible electronic hiccup (a friend has flat spotted a tire on his Z), what your friend is probably experiencing if the Brake Assist braking for him while coming down the brake zone.

If this guy is on (you won't know it's on until you disable the Yaw sensor) the car reactivates the VDC. In that case, any attempt to trail brake (or just quick transition from brake to steering) will trigger the VDC on the front wheels. Messing up corner entry, doing funky things with the brakes.

Nothing is "wrong" with his car. it's simply doing what it's been designed to do. Get to that Yaw sensor ASAP

 

Let's not start an AutoX vs Road Course debate.

Both require slightly different approaches to the exercise. Both have their points.

 

I guess I won't invite you to the autocrosses where I've datalogged a steady 1.2 - 1.3 G, then.

 

Bingo. I had the same problem. It was the result of excessive pad friction on the rear pads. I went to a slightly lower friction pad and it is now gone.

 

He said the car was not locking up under trail brake condition. It just locked during the initial application of the brake pedal. I told him to drive in the rain next time and jab the brakes hard and see how the ABS reacts. I will do the same in my car and see what the difference is. There should be a slight initial lock, and then the thing should pulse. I have to get in and see. I need to spend more time in VDC equipped Zs to know what it is truly doing. I think I have only done 10 laps in cars with them. For some reason, i am always stuck with the base models.

1.2G for 5+ sec? I hope that is a big circle you are running.

 

Correct. The official description:

Electronic Brake Distributor is a function that detects subtle slippages between the front and rear wheels during braking, and it improves handling stability by electronically controlling the Brake Fluid Pressure which results in reduced rear wheel slippage.