5th Gen Anti-lock Braking Issue on Ice and snow

I can’t emphasize this statement enough. Ever since sliding my 4Runner head first right into my Tundra that was sitting in my driveway, I’ve been going over and over the incident. I keep asking myself “was there a master cylinder malfunction, etc..”. The 4Runner just kept going forward at speed, no braking action at all, and the pedal was firm and wouldn’t depress at all. The only variable was the ice. I’m just glad there is no visible damage and the actual damage was $157.00. That being said, now I’m driving the 4Runner with this overwhelming sensation that my brakes aren’t going to work when I need them.

 

I also had strange experience this winter. I am disappointed, as my old Outback handled similar situations without any issues. Snow tires, was driving in icy conditions very slowly (maybe 15mph) and was slowing down and turning. The truck went into full 4-wheel slide. Traction control and ABS completely checked out. I was able to regain control by pumping brakes, lightly using accelerator, eventually front wheels pulled me out of the skid. A less experienced driver (or one without always-on 4WD) would have ended in a ditch.

 

Its simple, nothing will stop on ice unless you have studded tires etc. ive never had a problem coming ti a controlled stop in snow in my 2007, 2011 or 2022 4rnr. Ice,,, forget it. Stay home and off the roads or sloped driveway.

 

cant compare an outback with less curb weight to 4runner. Heavier objects have more kinetic energy which makes them harder to stop.

 

I do a lot of winter driving and what you are saying is just not true. While studded tires are optimal, good winter tires in most circumstances are sufficient to prevent a slide. This is because it is very rare for you to hit true ice with all 4 wheels at once. Most of the time it is patches of ice with snow or slush around it, so your traction loss is typically 2 wheels at a time. Good traction system, like in Subaru, combined with winter tires is enough to deal with that.

 

My head on collision in my driveway was hard enough to push my 2006 Tundra about a foot. I’m guessing 7-8 mph. I have driven ABS vehicles my whole life and never experienced this sensation. It was just a perfect storm of where the snow had melted and refrozen as ice. I tried to park over and over and came to the conclusion that when there is ice in my driveway to leave the vehicle in 4Hi. It wanted to crab walk on me when leaving it in 2 Hi and enter as slow as possible. Just a weird sensation.

 

ive never had a problem in patches of ice where other tires maintain contact, its when all 4 encounter ice which happens more then you think in certain conditions. Recently in my area it warmed up, fogged up with overnight low temps that refroze things and my entire driveway and street glazed over with black ice.

 

If it makes you feel any better, I’ve gone through 4 winters and brakes/abs have behaved as expected in every other slippery situation. Also, I’m not super freaked out by it because it only seems to happen at very slow speed, so I view it as having low potential for causing grave damage.

Also, I’ve only had the hard-pedal/no-stop condition occur at very very slow speeds (slower than walking speed) on two or three occasions. Maybe it hasnt happened more because I can now anticipate it a little better and just rely on rolling to a stop… without the final bit of touching the brakes at the end.

Those that say it’s normal abs behavior probably never had cars where this “no-braking action” has never been an issue. This is the first vehicle I’ve experienced this with in 30 years of driving with abs.

 

I wouldn't say its "normal" ABS behavior, but its normal Ice behavior. Or normal Ice & ABS behavior at really slow speeds.

 

Then let me clarify what you misunderstood in the statement I wrote. I may have not made my point clearly enough.

I’m not talking about how ice behaves. Ice just sits there, being it’s normal frozen, slippery self, minding it’s own business. For the purpose of my statement, ice is what it is. Some ice more slippery than others.

However, vehicles moving over ice DO behave in certain ways. The behavior of the vehicle can be affected by all sorts of factors, like tire traction, ice condition, weight/balance of vehicle, the driver’s actions, etc.
The vehicle’s behavior is also affected, and *actively* altered, by the ABS/VSC system. That’s what I was referring to in my post.

The ABS/VSC and it’s behavior is designed and programmed by the manufacturer. The 4runner behaves in an odd/unexpected manner on certain types of ice, *compared to* other vehicles I’ve driven in similar types of ice. The behavior is different enough for me to suspect that the ABS/VSC logic programmed into the 4runner is not quite right. Maybe somebody took a coffee break before finishing the line of code for ABS activation decisions below 4mph? Who knows.

So the point I’m trying to express is that the ABS is acting different on the 4runner at walking-pace or slower speeds than any other vehicles I’ve used in the last 30 years of midwest winters.

Since I like the scientific mindset, I’ll admit that it’s possible that my no-brake/no-stop slow speed incidents happened because I’ve never encountered that particular kind of icing condition. But I do think that’s less likely than the possibility that the abs/vsc logic is not quite right (at least for these slow speed conditions,on certain kinds of ice).

I may be wrong, but I think my suspicions are reasonable enough for me to babble on and on about it lol.

 

I think that Toyotas ABS system can be too aggressive. I have had these issues with both my Tacoma and 4Runner. What is happening is the vehicle is sensing tire slippage while braking and then it effectively kills all braking whatsoever to try to stop those wheels from sliding. The result is the vehicle keeps on driving in auto pilot. In these slow speed situations locking up all 4 wheels would stop the vehicle quicker as at least one wheel would eventually find some traction. Some people will disable their ABS in the snow to stop this. I think the best solution is better tires that keep the ABS from activating as much.

 

Where? Location matters a lot in comparing winter driving.

 

Thank you for clarifying. ABS can certainly be quite different between vehicles, like my old 90's Chevy extended van with terrible ABS jerking the darn thing instead of a nice consistent pulse.

It just sounds like normal sliding due to ice to me is why its perplexing. I have had so many instances like this in the NE area where the wheels just lock up after doing there ABS thing and i keep sliding.

 

But did you cry like Nancy Kerrigan?

On my limited with snows or ATs ABS actuation is easy to feel. Any chance you clipped your abs sensor wire or have some sort of brake issue beyond junker tires?

 

In my case it is a brand new truck with brand new Michelin dedicated winter tires. I expected 4Runner to at least handle on-par with much cheaper Subaru, but it is unfortunately offers inferior winter handling characteristics.

 

Its a truck, so it will be different in many ways and noting like a Subaru. But i assure you the 4Runner will get through 2' of snow better than a Subaru and have far better stopping capabilities in 4L.

My Front wheel drive Mazda3 with Vredestein snows was wicked. I always preferred front wheel drive cars with snows over 4WD trucks.

Maxda3 vs Jeep:

 

A Subaru is far superior to any Toyota for snowy travel. Their AWD system is better and they are lighter.

 

In the incidents I’ve had with the 4runner, I actually suspect the front tires aren’t sliding over the ice at all. Rather, it seems all at once the pedal turns rock hard, the hydraulic braking pressure is released by abs, and the tires roll along as if my foot wasn’t even on the pedal. In other words, not sliding, simply rolling. When this happens, the abs is not pulsing. The system seems to simply prevent any clamping pressure between the caliper and rotor. Again, all this is happening at 1 to 4mph, it feels incredibly frustrating to be along for the ride.

It happens at such slow speeds that it’s a bit of a feeling of disbelief. Especially since the feeling of going from a slight deceleration rate to zero deceleration rate feels to the body as if you’ve actually started to accelerate. Very odd feeling.

 

That’s the same thing that has happened to me.

 

I feel like I just went to some therapy group…lol. I will say this. I had a fun drive today in my 4Runner and my confidence in the braking system has returned. Many Thx for all the comments….

 

That one made me giggle MooreKen, you are heard.

I’m not sure if we’re going to have the specific icing conditions again this year, but if we do, then I’m going to play around in the ice to see if I can replicate the issue, so I can more carefully take notes of what’s happening.

 

I doubt I'd be able to do this, but next time someone is in this situation, can you try hitting the parking brake and see if that makes a difference?

That could help support or reject the "ABS isn't working, and locking the wheels would stop faster" argument.

 

It all happens quickly, but I will keep in mind to try this. For science!

Speaking of science, to clarify the hypothesis (I think I know what you meant, so pardon if it seems like I’m being pedantic)…I think the ABS *is* working, because it seems to be actively preventing locking of the wheels.

This thread has me thinking of what really lead to my perception of acceleration at the moment I lost all braking action. Bear with me as I talk out loud…

I mentioned that when I was slowly stopping under braking action, I felt an appropriate/expected slight deceleration (because there was available traction on the road, despite the ice). When the braking action completely and suddenly went to nil, the feeling of acceleration was surprising. It honestly felt like more than the tires simply rolling along. It felt as if I was being driven/pushed. But I chalked it up to “relativity” in the sense that a reduction in deceleration is essentially the same “feeling” as acceleration (from a sensory standpoint). But…maybe I actually was accelerating ever so slightly???

But why would I be accelerating? It occurred to me that this is my first rear wheel drive vehicle in all my years. I was probably in 2wd when it happened (I think this has only happened with a cold vehicle in the neighborhood, so I probably wouldn’t have attempted to shift into 4wd on a cold transfer case). Here’s my train of thought…
-Cold vehicles are in high-idle for a while until warm.
-cold vehicles have cold trans fluid that will transmit more torque through an unlocked torque converter
-The combination of high-idle and more viscous trans fluid will result in significantly more torque transmitted to the wheels, compared to a warm vehicle.
-if there is traction on the road, but the ABS stops transmitting braking pressure to the rotors, then the rear wheels have the traction to literally push/propel the vehicle forward (not simply roll ahead).

(I would expect if the ABS allowed braking pressure and allowed the wheels to lock, it would prevent the rear wheels from accelerating the car forwards)

If these things are the case, then I predict putting the vehicle in Neutral will result in the car immediately decelerating again…even if the wheels are simply rolling along without brakes applied. I also think the parking brake should do the same, but possibly a little quicker, if in fact the tires are rolling with no braking pressure on the rotors.

The trick will be remembering to try these things in the moment!

@MooreKen , do you recall if your engine was cold when this happened? Do you remember if you attempted anything, like putting it in neutral (or using parking brake) when this happened?

I think if anybody else is going to try to science the shit out of this, that they experiment when the vehicle is cold and at high-idle.

 

I agree, I think it's doing it's best, and it thinks there is no available traction to brake. But it may not be the best solution for this particular situation. So "working" can also mean "is effective" in this case.

 

1). My 4Runner had driven approximately a mile and I always allow a good 1-3 mins of warm up, especially on a day like that. (5 degrees F ).
2). I swear it felt as if my 4Runner started to Rev fwd (accelerate), in that split second I remember verifying nothing had gotten wedged under my brake pedal and checked to see if my accelerator was being pushed down by something.
3). It happens so fast, I doubt I’d have reaction time for any of these solutions.
4). I verified over and over that being in 4 Hi allowed me to park and stay in control , so my solution will be: If there is a possibility of snow melt that has turned into ice in my drive, then I’m putting it in 4 Hi when I come in to park. Keep in mind the streets were 95% clear of snow and ice that AM.
5). I thought about neutral and I’m sure it would have worked. Neutral is what we did in the old days (I think wasn’t positrack an issue and putting into neutral would keep your car from continually turning one wheel, etc.. which would keep your from going sideways at stoplights , etc..???). But “yes”. Rolling in in neutral would have most likely of worked.

 

Thank you for the even better clarification. This describes exactly how my 4R brakes in 4 low at slow speeds, but in this case its the low gear ratio within the transfer case multiplying engine power and momentum of it all, kind of pushing it along through the heavy breaking.

 

• Here’s a data point for you. Went on a short trail ride this morning, icy roadways and snow on top of ice forest trail.

Tires are Mickey Thomson Baja Boss AT at 32 PSI and around half tread life remaining. Engine/trans at operating temps. About 200 lbs of permanent gear installed/on-board.

I attempted the following tests in 2WD, 4-Lo and 4-Hi:

Braking tests on level, downhill and uphill (between 1% - 2% grades) from 25 MPH down to <5 MPH. In all circumstances I tried my best to lock up the wheels. Felt the brake pedal (ABS) do its thing, very firm feedback but I could still push down a bit more so I wasn’t locked out. Wheels as best I can tell barely lost traction in fact I can tell that ABS was doing its job very well. I never felt that my braking system locked me out.

What did surprise me was that the throttle response auto-modulated and try as I might (I even floored it to try and slide around a turn) I absolutely could not get any tire to slip more than a milisecond before traction control took over and the throttle backed down to around 1200 or so rpms…just enough to keep the wheels turning.

 

I agree, it kind of feels like braking against the torque of 4lo, then letting go of the brakes all at once.

Thanks for the info! 5F is pretty cold. Even if it was out of high-idle after your warmup, the trans fluid probably did not have enough time to warm up, so it would have had the higher viscosity to drive you forward more than it would if it was warm.

I agree, if someone is interested in avoiding this no-braking problem (not just experimenting), there are two things seem reasonable actions to take if the vehicle is still cold:

1. like you said, leaving it in 4wheel drive will help keep at least one front tire from loosing traction as easily (which prevent the abs from releasing braking pressure and letting the rear tires drive you forward).
2. When approaching marginal/iced over intersections, preemptively slipping the trans into neutral. Or at least having your hand on the shifter ready to do it at the first sign of abs activation.

 

Thanks for the data point! I remember the first time I heard somebody say that 4wd (center locked) actually does help you brake. I couldn’t believe it until watching a few videos and thinking it through carefully. Now I understand how that can be the case.

The VSC system on the 4runner is pretty good. It completely sucks the joy out of doing 2wd donuts in snowy parking lots lol. Until somebody told me how to completly disable it by holding the trac/VSC
button down while stopped lol.

 

Wouldn’t keeping it in gear help slow you down quicker by using engine braking?