kiwi 911

Update - the fault code was 4206 speed sensor, front left (signal implausible).

So issue is to understand how and why we are loosing wheel speed signals?

Rear wheels locked - I have 40m of skid marks as proof.

The max speed I hit is around 160kph on track - I have no idea how much speed I scrubbed - but not enough to not skip over a very long sand trap.

It is amazing how much impact a tire wall takes - if you look at the skid marks beside the car, you can see the car moved quite a bit to be one side of them (i.e. it bounced into that spot). Damage appears to be bumper, pinched guards and radiators x 2 - surprised lights are not damaged and the airbag did not activate.

Dervish

That's pretty scary, glad all is ok and car appears relatively fixable.

spiller

Wow that pic puts it into perspective. Car looks relatively unhurt which is great. Must have wiped off a fair bit of speed before the impact as tyre barriers aren't kind to cars.

LuisGT3

Honkity Hank

I found this post on 6 Speed OnLine

http://www.6speedonline.com/forums/9...06-4201-a.html

see post #3 for some possible causes.

(I have not independently verified this for accuracy)

Gofishracing

I had an ABS sensor failure as well once. You travel a long distance. Looks like you had partial ABS from skip mark in sand. FYI I do not use the ABS as such. I do not lean on the electronics. When it failed it was not activated to my knowledge but effected everything.

Honkity Hank

When this happened did you release and reapply the brakes? I could not tell from the video? Did the pedal remain hard, or go soft?

Thanks,
I have had brake fade from brakes getting too hot on other cars, but never had something like this happen.

Jeff

pete95zhn

So when you installed the suspension, did you disconnect wheel sensor's cable? If yes, did you reconnect it properly? Were the cable, connector and sensor in good shape, they may get brittle because of heat? Is there any play in the bearing?
If all above are 100% in good condition, I'd change both wheel speed sensors. (Maybe I'd first clean the toothed ring.)

Gofishracing

Nope- Pedal went dead feeling- brakes did not respond. I kept my foot in it. No pulsation. Did you see how far I travelled!! Tire was destroyed. I think it was a rear left sensor. I would have thought a front.

spiller

When you say you do not use the ABS as such, what are you meaning? As in you try not to brake in a way that engages ABS? In my experience on track with the 996 GT3 that is nigh on impossible to do.

I wonder if there is a way to disable the ABS system on these cars? As I mentioned earlier, ABS is a big issue with the lotus cars and a lot of guys used to simply unplug the wheel speed sensors and run the cars like this without issue.

kiwi 911

These are for my mechanic to answer.........

I am thinking to just replace the wiring and sensors, for circa $1K USD, I think money well spent......(for a little life insurance).....

kiwi 911

Thank you for posting this.

Gofishracing

don't throw parts at the car. If it's an ABS sensor they are inexpensive.

Honkity Hank

I bought the 996 Essential Companion and just read through the ABS section. According to the book the Mk2 996-GT3's have a four channel system. As noted there are wheel sensors, solenoids, etc that make up the system. The theory of operation is that when a wheel approaches lockup the system will prevent further brake pressure to that wheel (or wheels) it does this with a clever system that re-routes fluid around the caliper, and back to the master cylinder. If the wheel begins to rotate again, the system will allow some additional brake pressure, often resulting in a pulsing feeling through the brake pedal.

So as I understand it, once the system is activated it does not matter how hard you stand on the brake, no additional pressure is seen by the caliper. It stands to reason that if the system activates in a situation where you should have adequate traction, releasing the brake pressure to allow the wheel to return to speed, and then reapplying the brakes, may relieve the effect of hard on the brakes with little braking force to the road, and reset the ABS so that normal braking function is restored.

Not having experienced this myself, this is only conjecture, or at best an educated guess based on my understanding of the system operation. Basically, just like adding more steering input into the car when it is understeering has no effect on the trajectory of the car, changing something that you are doing, may well return control.

That is not to say that a faulty wheel sensor or other component may cause the same thing.

Anyway, thought I would share what I learned. I do recommend the book which you can find on Amazon easy enough. Lots of tech and information on the various models.

Jeff