ABS and 4WD help you stop a Taco in snow/ice?

I am trying to find an answer to the question: Does braking in 4WD help you stop your truck quicker? And, specifically about newer tacomas with ABS.

I have noticed lots of debate about this. I am looking for evidence based on research, physics, technical knowledge.

In my experience it seems 4wd offers a small amount of extra braking ability in snow but not much. Is this from the extra resistance of an axle, two wheels, and drive shaft on the motor in 4wd? But, you still have the same 4 tires and brakes you used in 2wd to do the same work.

Where does ABS on our trucks come in? Doesnt that just cancel any extra braking you had b/c it keeps all wheels going at the same braking speed?

 

whether or not you are in 4wd the trucks tires will still have the same amount of friction with the road so breaking will not be affected by 4wd.

abs should improve stopping distance because a rolling tire has more friction with the road than a sliding tire.

I could be wrong but this is what makes the most sense to me.

 

You are wrong about the ABS. Correct about the 4wd.

OP: 4wd gets you going, it does nothing at all to help you stop faster. Every vehicle ever made has 4 wheel brakes. Effective management of your speed on slippery surfaces requires driving skill - engine braking, gear selection, and not going too damn fast for the conditions in the first place.

Re: ABS: Anti-lock brakes are designed to pulsate the brakes rather than locking the wheel and having it slide. This is to allow the driver to maintain control of the vehicle in an emergency situation. Pulsating brakes provide essentially the same stopping distance as a locked wheel, but the pulsation allows the wheel to continue rolling and thus allows the driver to continue steering. This can help you slam the brake and dodge around an unexpected child/elk/etc. in the road rather than slamming the brake and just sliding into them or fishtailing into a ditch.

 

4wd does not assist when you hit the brakes, it makes no difference. You're still using the same brakes, same tires, etc. It will not do anything more for engine braking power either except give you more traction since the front and rear end are locked together. So on slippery surfaces engine braking may be improved when you're in 4wd vs 2wd.

ABS keeps your wheels turning because if you just lock up a tire, it actually decreases your ability to stop and you lose control of your steering. This has to do with coefficients of friction between the tire and the road. Once the tire locks up and you start to slide, you significantly reduce the tire's ability to grip the road. It's like doing a burn out with the front tires locked, it takes a lot of power to get the rear tires to begin to spin, but once they're spinning, it takes very little power to keep them spinning. Same concept just in reverse if that makes sense. ABS ideally keeps the braking pressure at the sweet spot to get maximum stopping power without locking up the tire. I haven't heard anything about it keeping the tires going at the same speed, it's just meant to keep the tires from locking up (Anti-lock Braking System). Old vehicles that don't have this feature required the driver to pump the brakes to keep the wheels from locking up. Most accidents are avoided by steering away, not stopping. Maintaining control of your steering while heavy on the brakes is why ABS is so effective.

 

theoretically (which is what i know you dont want haha), 4wd should provide SOME extra braking but im not sure if this would even be noticeable. the extra resistance the 4wd would naturally slow the vehicle down more no matter what surface. thats why you get worse gas mileage when in 4wd because it takes more energy to keep all those extra parts moving.

in response to post #2, a rolling tire has much less friction than a sliding tire. the kinetic coefficient of friction of rolling objects is almost nothing compared to a sliding object.

abs works because brake pads sliding on a rotor create much more friction than a tire sliding on a road (in icy conditions). abs ensures it is the brakes that are giving the stopping power and not the road. when the brakes lock, they no longer are providing any retarding force and the vehicle must rely on what little friction the ice provides (which in my physics class was so little we didnt even bother to factor it into equations)

 

my bad, i was thinking static vs dynamic friction for some reason so that proves me wrong about the abs...learn something new every day

What exactly is extra that is moving when you are in 4wd. the front drive shaft still spins weather or not your in 4wd.

 

You just completely contradicted yourself... if the brakes lock the tire, according to your middle sentence, you'll have more stopping power. Back to physics class, a locked up tire is useless, you have no control and your stopping power is significantly longer. The power of the brake pads against the rotor or drum will always be greater than that of the tire against the road. The problem is you don't want the brakes to lock up because it makes your tires slide and you can't stop the vehicle... If you've got a mountain bike, go test your theory with the brakes, coast down a hill and hit the brakes as hard as you can and see how far you skid, then do it again without locking them up but keeping them right on the verge and see what happens.

 

4WD powers the front and rear wheels, meaning that engine braking will slow both sets of wheels because all four are connected, through the diffs and t-case, to the tranny.

In 2WD, engine braking will only slow the rears, as the ADD in the front diff is not engaged.

 

I understand that, I thought this was more about an emergency stop. in which case 4wd shouldn't change anything

 

No...it won't...not sure I understand your question...

 

It won't make a difference in an emergency stop.

 

Not to put too fine a point on it: if you want a research, physics, and technical answer, you're looking in the wrong place. Tacoma World: ultimate storehouse of "happened to me once," "heard it from a friend," "read it somewhere so it must be true" and strong opinion.

I suggest you redirect your search to some of the NHTSA and IIHS sites where I believe what you'll find is that the mandate for ABS was approved because:

1. It improves braking performance and ability to steer to avoid an accident in *DRY* conditions, which are by far and away the most common

despite the documented fact that:

2. ...under some circumstances ABS increases braking distance in some types of *SNOWY and/or ICY* conditions where locking the wheels would be beneficial.

Don't take my word for it. Go look it up, man.

 

+repped.

 

Agreed, that was well said.

 

http://www.4x4abc.com/4WD101/ABS_parttime.html

 

The ABS on my '05 Taco was scarry as hell on wet roads... amazed I didn't hit something... dealer service dept. said what I experienced was normal. The '10 (and my '01) are both fine on wet roads.

The feel of being in 4WD is more comforting... on gravel or wet/ snowy roads... The front tires spin no more than the back when they are connected to the drive train, In 2WD, the front tires are 'free agents'... As I said, it is a 'feeling'... and I am usually one of facts and documentation!

 

Yeah my 08 is that way on snow and ice, it will scare the crap out of you because when it engages it just doesn't reduce braking power but completely removes ALL braking and you will coast too a stop.
You get the same braking effect if you push the clutch in versus the brake pedal.

I have learned that if the ABS engages immediately lift your foot off the brake and then quickly jab the brake pedal, they will then act like normal brakes.

 

I pretty much plan to coast to a stop on icey/snowy roads anyway and drive accordingly with LONG following distances.

 

Thanks, this was the direction I was looking. And, yes most of the answers are what I expected from TW but one person was able to point me in the right direction.

I was looking for answers that related to how our tacomas are designed to handle braking with ABS.

I think my experiences are the same as everyone. In snow and ice, locking your brakes will help you stop quicker but not help you steer. Thats why they used to tell you to pump your brakes.

But ABS does help you steer.

I was looking for evidence to support that 4wd does not help you slow down faster in snow/ice than if you are in 2wd.