I had a flashback to the night a few years ago when I discovered that vtec works in reverse (not sure why I doubted it back then). That got me thinking.

Does anybody know if abs will kick in if you slam on the brakes while going backwards?

The more burning question on my mind is does abs work if you spin out? By "spin out" I mean a situation where all 4 tires can be pointed in one direction relative to the vector of the skidding car at one moment, and then pointed a completely different direction from the skid the very next moment. If you spin off course at the track and "put both feet in," will abs keep the wheels rotating, possibly to your detriment?

 

Yes the abs does modulate the brakes. I know because I wanted to see if it would happen in that type of situation.

 

Good question, I'll try it out sometime! I don't see why it wouldn't work, I don't think the ABS sensors are directional, they're probably working just the same as the forward direction. That lines up with JDM Factor's report.

Here's another doozy:

If you lock up your wheels during a spin while turned sideways, when you continue the spin to the reverse or any other direction, your ABS won't turn back on. It thinks you're stopped?

Maybe.

-Chris

 

If you could gain enough speed, it will trigger.

 

I did not try it on my ITR......but I remember the abs was working when I went backwards on my bimmer (~65 mph).


to answer your second question......I don't think the abs will get trigger if the car is spinning out (going sideway) as the tires are in "standing postion" instead of rotate like going forward or backwards. The very last time when I had my EVO went sideway (both feet in), I didn't feel the abs is being trigger.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Batoutahell &raquo;</TD></TR><TR><TD CLASS="quote">
The more burning question on my mind is does abs work if you spin out? By "spin out" I mean a situation where all 4 tires can be pointed in one direction relative to the vector of the skidding car at one moment, and then pointed a completely different direction from the skid the very next moment. If you spin off course at the track and "put both feet in," will abs keep the wheels rotating, possibly to your detriment?</TD></TR></TABLE>

In my experience going off course last year at the Glen with Ryan as my ballast. Yes. The ABS kicked in just as we went off into the grass and kept pulsating as the car went sideways and almost went all the way around till it righted itself and it came to a halt thankfully in a straight line 5 feet in front of the blue bushes.

We were in a no brakes excersize so the goal was not to use any braking, I fugged a corner (first apex into the bus stop), clipped the gators with the rear passengers tire which threw us the opposite way and immediately shot us off course through the grass. I was able to apply the brakes before we went off course but ABS didn't kick in till we just about started going sideways and didn't stop pulsating till we came to a stop back on the asphalt.

In reverse only I dunno, but I'd make a guess yes it would still work. The sensors on the wheels are not the only thing at work. There is an ABS module that takes motion/G's into consideration, so just like if you're going in a straight line and jam the brakes on and the car won't stop or turn, the ABS takes all this information in and pulses the fluid. If you're going sideways like in my case or in reverse I don't see how much different that action/reaction would be. But I'm totally guessing here and only basing this on my experience and we didn't start in reverse, nor did we ever do a complete 180 or 360 for that matter.

Boy I'll never forget "In a Spin Both Feet In".

Want me to try it again just to make sure?

 

yep.. i've kicked it on in a spin.. never tried it in reverse.. now I think I know what I'll do on saturday in the race car though..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1GreyTeg &raquo;</TD></TR><TR><TD CLASS="quote">Want me to try it again just to make sure? </TD></TR></TABLE>

Sure, just not near anything hard.

Since abs will kick in during a wild spin, doesn't it concern anyone that the front wheels keep turning, when the goal of "both feet in" is to lock them up? I really like the itr's abs on track, but is it worth having if it's going to work against me in the most dire of circumstances? It sounds if I go off and spin, abs could help steer me INTO a wall or shoot me across the track, when my intention with "two feet in" is to ride the skid along the same vector into the tall stuff.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Batoutahell &raquo;</TD></TR><TR><TD CLASS="quote">

Sure, just not near anything hard.

Since abs will kick in during a wild spin, doesn't it concern anyone that the front wheels keep turning, when the goal of "both feet in" is to lock them up? I really like the itr's abs on track, but is it worth having if it's going to work against me in the most dire of circumstances? It sounds if I go off and spin, abs could help steer me INTO a wall or shoot me across the track, when my intention with "two feet in" is to ride the skid along the same vector into the tall stuff.</TD></TR></TABLE>

Yes but if you are all in and keeping the wheel straight then the car is going to do the same thing with or without abs. The wheels will still modulate, but you will still be in an uncontrolled skid.

And yes, abs does work in reverse.

 

Let's assume that the car is spinning because the steering wheel is not pointed straight ahead.

 

I still feel that abs/non-abs car will relatively end up in the same spot when finished spinning

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by walker111 &raquo;</TD></TR><TR><TD CLASS="quote">I still feel that abs/non-abs car will relatively end up in the same spot when finished spinning</TD></TR></TABLE>

That is absolutely incorrect - having ABS in the car makes it very unpredictable in a spin at higher speeds. The ABS will continue to try to modulate the brakes as the car is spinning, when what you want is to lock them up and hold them locked until the car stops spinning. If you start to spin and lock up all 4 tires, the car will keep going in the same direction, not true with ABS.

 

I don't think that's correct. Why would ABS change the direction of the car? That just doesn't make any sense to me.

ABS would release and lock the brakes over and over in a spin, very quickly, just like it would in a straight line. And, just like in a straight line, this would have the effect of shortening the stopping distance, compared to tires that are totally locked up and sliding.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">
I don't think that's correct. Why would ABS change the direction of the car? That just doesn't make any sense to me.</TD></TR></TABLE>

It doesnt change the direction of the car, it prevents it from locking up and going in a straight line.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">And, just like in a straight line, this would have the effect of shortening the stopping distance, compared to tires that are totally locked up and sliding.</TD></TR></TABLE>

A locked tire sliding across the pavement will stop faster than ABS - at the expense of your rubber of course (flat spots, square tires, etc).

 

If you took a car with abs and one without and went 50mph, the wheel locked straight, slammed on the brakes, both vehicles would more than likely stay straight.

I understand that a vehicle without abs will stop slightly sooner than a vehicle with abs. If the vehicles were spining uncontrollably imo it would have the same effect.

If you could reenact the same spin twice I feel that the results would be the same +/- a few feet.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by walker111 &raquo;</TD></TR><TR><TD CLASS="quote">If you took a car with abs and one without and went 50mph, the wheel locked straight, slammed on the brakes, both vehicles would more than likely stay straight.</TD></TR></TABLE>

Right, I wasnt talking about a car travelling in a straight line.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by walker111 &raquo;</TD></TR><TR><TD CLASS="quote">If you could reenact the same spin twice I feel that the results would be the same +/- a few feet.</TD></TR></TABLE>

Think about how abs works - it senses the wheels locked and continually releases/reapplys pressure on the brakes in order to regain traction and in a spin, the car will become somewhat unpredictable - in a spin this is not what you want, you want to lock them down and skid. I've experienced it on track and autox and it sucks, for a track/race car toss the ABS in the trashcan.

 

I guess my point is ABS can change the direction of the car during a spin. .RJ sees where I'm coming from.

During a spin, at any given moment the car is traveling along a particular vector. During my theoretical spin, let's assume the front wheels are pointed in a direction different than the vector along which the car is sliding. If you can lock up the brakes, the front wheels will not be able to rotate, thus, the car will continue to slide along the same vector. If abs keeps you from locking up the front brakes, and the front wheels are allowed to rotate freely (despite "two feet in"), then I would imagine as the front wheels gain traction the car will change its path from the original vector of the skid. Depending on how much traction the freely rotating front tires have, and the velocity of the car, I would think the car could end up a very long way away from where it would have come to rest if all 4 brakes had locked up!

If I'm wrong about this, someone please explain why.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">
Think about how abs works - it senses the wheels locked and continually releases/reapplys pressure on the brakes in order to regain traction and in a spin, the car will become somewhat unpredictable - in a spin this is not what you want, you want to lock them down and skid. I've experienced it on track and autox and it sucks, for a track/race car toss the ABS in the trashcan.</TD></TR></TABLE>

I don't know which ABS you're talking about but in the ITR the ABS did not kick in for me when I was in a spin, nor traveling backwards after a spin during an autocross.

Same thing with the 350Z.

In a spin, you're outside of the traction circle of (some or all) tires, the ABS is not going to change that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">In a spin, you're outside of the traction circle of (some or all) tires, the ABS is not going to change that.</TD></TR></TABLE>

If the abs doesnt engage, then its a moot point

 

and you're saying that the ABS engaged for you in a spin?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Batoutahell &raquo;</TD></TR><TR><TD CLASS="quote">
If I'm wrong about this, someone please explain why.</TD></TR></TABLE>

No, I think I agree with both you and RJ on this.

My instance was total driver error but the more I think about it, the more I can see how the ABS activating and the quick change of surfaces and grips as I slid combined to slingshot me around.

I need to go home and look at my hands and steering inputs another time. There was a time where I was overcorrecting and as the car went sideways while I was trying to steer into the slide and apply more throttle that I felt it just go and knew there was no way to save it so I did my best to just get the wheels straight as possible & both feet went in instinctively.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">and you're saying that the ABS engaged for you in a spin?</TD></TR></TABLE>

Yes but only because the brakes were applied before the car went sideways or an actual spin.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1GreyTeg &raquo;</TD></TR><TR><TD CLASS="quote">
My instance was total driver error but the more I think about it, the more I can see how the ABS activating and the quick change of surfaces and grips as I slid combined to slingshot me around.
</TD></TR></TABLE>

The change of grip would have spun you around, with or without abs, if anything the ABS should have made the spin less severe at that point.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1GreyTeg &raquo;</TD></TR><TR><TD CLASS="quote">

Yes but only because the brakes were applied before the car went sideways or an actual spin.</TD></TR></TABLE>

same here..

but yeah, I can't speak to how it could or could not effect severity, I was just answering that question..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">A locked tire sliding across the pavement will stop faster than ABS - at the expense of your rubber of course (flat spots, square tires, etc).</TD></TR></TABLE>

No, it won't. If the tire is locked and the car is moving, the tire is sliding and has no grip, and stops are longer.

I think you're confusing the common notion that it's possible to have shorter stopping distances without ABS than with ABS. That's not the case when the tires are locked. That's the case when you use threshold braking, where you brake so that the tires are at the threshold of locking, without actually locking. Threshold braking enables you to stop quicker than ABS braking. But ABS braking enables you to stop quicker than locked wheels.