Threshold Braking 101: When Rubber Meets Ice

[MOAK]

In central Texas, we get frozen precipitation a few hours every few years. When we do get it, it immediately turns to ice. Even for experienced drivers, it isn't worth going out. Not that you'll get in a wreck but that some knucklehead in a hurry and with no concept of physics will catch you. Best to just sit by the window with a bowl of popcorn and watch the show...it'll only be an hour or two after sunrise when everything melts.

If it is ice, then forget it, don't even go out. The only tire that even has a chance on ice is a tire with studs, or chains, and even then traction is very poor at best. I laugh outloud sometimes when I read folks posts that are debating which tire performs best on ice. No tire performs better on ice than another. There is 0 traction on ice. Don't agree? Try running over a frozen pond with different types of boots.

 

[AKBushDag]

good thing! this what I learned from motorcycling too: you need to focus on the gap. not the object or obstacle.#

to answer davids question: with ABS, hit the brakes as hard as you can, and continue steering. easy as that.

Thank You. I'm able to do that on dry surfaces, but on ice it's different story. The ABS kicks in but fails in that the wheels lock up and the sires slide, hence no steering.

 

[AKBushDag]

Hi David - it is possible to threshold brake while the ABS is active - but as you noted, it can be difficult. That said however, if you were to apply the maximum braking available without activating the ABS, and you continue to modulate to find that limit - you are effectively doing exactly the same thing as when you have no ABS. The difficulty arises due to constantly changing traction availability, which your ABS will more than likely react to faster than you will, thus the likelihood is that you will, unless you have a lot of practice, perform less effectively than what your ABS would do.

Thank you. Looks like I just need to fine tune my braking to find that "sweet spot" where I can achieve threshold with out the ABS taking over.

 

[AKBushDag]

If it is ice, then forget it, don't even go out. The only tire that even has a chance on ice is a tire with studs, or chains, and even then traction is very poor at best. I laugh outloud sometimes when I read folks posts that are debating which tire performs best on ice. No tire performs better on ice than another. There is 0 traction on ice. Don't agree? Try running over a frozen pond with different types of boots.

Good Advice! Right now I'm running on Nokian Hakkapetaliita SUV 8 studded tires. They do offer some advantage, but I'm not aware of any tire that will always work on ice.

 

[AKBushDag]

I thought I would pass this on to anyone who is interested. After reading the various posts on this subject, I looked into finding the ABS fuse on my 07 4Runner. Turns out that was not an option. I dove into the Owner's Manual and learned that the ABS system is part of the Vehicle Stability Control System (VSC). My 4Runner (as well as a number of other 4 buys) has an option to "Lock the Center Differential," when in 4WD. According to the manual, when the Center Differential is locked, all of the systems in the VSC are disabled. So, it sounds like (at least when in 4WD), engaging the Differential Lock will presumably deactivate the ABS system. Going to give this a try!!

 

[Christian]

Thank You. I'm able to do that on dry surfaces, but on ice it's different story. The ABS kicks in but fails in that the wheels lock up and the sires slide, hence no steering.

ABS is made for wet surfaces, snow and ice. It just maintains wheel spin for the tire to provide you with cornering force. When push comes to shove, it's very likely to work more reliable then threshold braking. It's dumb, ok, just knows 0-1-0-1-0-1- .. binary brakes on and off. But it works. Never had any issues.

 

[atIOIYIOI]

I thought I would pass this on to anyone who is interested. After reading the various posts on this subject, I looked into finding the ABS fuse on my 07 4Runner. Turns out that was not an option. I dove into the Owner's Manual and learned that the ABS system is part of the Vehicle Stability Control System (VSC). My 4Runner (as well as a number of other 4 buys) has an option to "Lock the Center Differential," when in 4WD. According to the manual, when the Center Differential is locked, all of the systems in the VSC are disabled. So, it sounds like (at least when in 4WD), engaging the Differential Lock will presumably deactivate the ABS system. Going to give this a try!!

David, any time a diff is truely locked, the computer has no choice but to disable the ABS, or disable the diff lock (not sure any do that) - it can't control wheels individually when they are locked together.

 

[AKBushDag]

David, any time a diff is truely locked, the computer has no choice but to disable the ABS, or disable the diff lock (not sure any do that) - it can't control wheels individually when they are locked together.

Thank you for that info! I appreciate the feedback!!

 

[OkiGoose]

As a driver from the North and a multiple time non-ABS owning driver, these skills came with learning the road. Always good to refresh though.


Meanwhile I'm looking at your wheels and tires for my 80 series... truck looks really good!

 

[drrobinson]

Great demo, thanks for the effort.

 

[Doug2003]

Thank you for taking your time to make the video.

 

[gDanCO]

Tire compound has a lot of influence on braking. summer / all season compounds do not have as much grip as pure snow tires. So go slow when the tmps drops if you don't have a cold weather tire compound. Be Safe.

 

[JCWages]

Quick question regarding cold weather. At what point, if any, will cold begin to impact tire elasticity so much that tire "hardness" might become an issue and impact its "grippiness?" If at all. I'm a Californian, so I don't deal with this much. Just curious if it does.


Sent from my iPad using Overland Bound Talk

I realize this is an old revived thread but since no one has answered the question above I wanted to contribute to the knowledgebase.

The commonly accepted temperature at which "all-season" tires begin to harden and traction levels drop drastically is 45F/7C. However, traction levels actually start to drop off well above 45F. According to America's Tire, traction levels may start dropping at 75F depending on the specific tire and compound. https://www.americastire.com/learn/tires-below-45

This also helps explain why traction boards like Maxtrax become less effective in very cold temperatures. The rubber is just too stiff to mechanically key to the spikes on the boards.


Another good video by Continental