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This past weekend we rolled out a brand new car---our #31 car slated for the new SCCA Pro Racing World Challenger "TC" class. ( www.world-challenge.com ). This was the cars first time on track with the only other effort being dyno pulls to insure the motor and drivetrain worked properly. We used an ABS module from a donor car -- a car that we buy with high miles and no rust before we gut it and put a cage in it, cut metal/weight out, etc., etc....
What some people might see as **** driving is actually an ABS failure. I have experienced this 4 times now and I'm telling you that it is scary as F__K. Especially when we are hoofin' these cars on the edge. The symptoms are a brief sense of security in the brake pedal followed by a wheel (typically one wheel) locking up along with the other 3 wheels loosing a ton of their braking capability. Essentially you have quadrupled your braking zone distance (which you can see in the video above). The way to get out of this is to feather back off the brakes (which has you covering lots of ground at high speed) and look waaaaaaaay in the distance for a clear space to drive to. This is scary fellas. Scary, scary, scary. Typically you just sneak up on this failure until you go deep in the braking zone and all heck breaks loose. Worse case scenario is your hauling the mail, drive deep and the pedal goes to the floor without any advanced notice.
Here is a view from my car. Listen closely and you'll hear the front left lock up (which means you have about about zero steering capability (which means you let off the brakes to allow for steering which means you are not slowing down which means you are still hauling ***** which means you pretty much dont' stop).
What you don't see/hear/experinece is what is going on with my braking foot. Initial brake pedal application gives me an "oh crap" feel which means I let back off and modulate the brake just enough to slow the car down but prevent lockup. Perhaps you might describe this as braking only 30 or 40% of what you would normally brake. This is why you see the car overshoot what would be a location on the track that you'd normally stop----well behind the first car I approach. WELL behind. Did I mention how kick *** these cars brake? Especially when you remove 700 lbs of weight out of them, add $7K of suspension and race tires. These things stop: S T O P.
So------if this ever happens to you may I suggest you check all 4 of your ABS lines/wires to the Wheel speed sensors first.
Here is another example of when the brakes started to go. We put the car on the trailer shortly thereafter because quite frankly I do not enjoy driving at 7/10th's. Boring and you can't expose the cars handling characteristics (which is what our goal was for that track day).
Not fun. This is the kind of thing I have seriously have nightmares about, and I haven't experienced it.
Now to the inevitable question:
If this happens on the street, we pretty much are gonna crash into someone or something. How much of this danger exists on street cars, and what can we do to prevent it and/or detect it ahead of time?
That completely sucks. Thanks for the tip on what to do should I run into it though. It's surprising because I haven't really seen it nor heard of it before, especially from RX8 autocrossers (which they're mashing their brakes all the time) so just surprises me that this seems to be something common. It's also too bad there is no way to test it other than..just go all out at a track and feel the brakes. Sorry to hear it again man.
"Have you ever noticed that anybody driving slower than you is an idiot,
and anyone going faster than you is a maniac?" - George Carlin
If I had to guess I'd say that these failures have to do with taking the system apart and putting it back together. This happened with one race car I drove (not ours). It happened 3X and was traced back to two ABS sensors that were not properly installed. Since then I have been sensitive to "what if this happens?" and am careful to work up to going to heavier brake pressure prior to ABS activation.
The ABS module we used was untested and most likely had a fitting or electronic connection short.
Has anyone ever heard of this issue appearing out of the blue in a street car? I have not.
World Challenge TC #32
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