Threshold Braking 101: When Rubber Meets Ice

[Corrie]

Corrie submitted an Article on the main site!

Threshold Braking 101: When Rubber Meets Ice on the Trail

This article is a starting point to learn more about threshold braking. We hope it helps keep you rubber side down on the trails!

As many of you know, Michael...
Continue reading the Original Blog Post.

 

[vicali]

Good day eh Bruce.
Great video, great demo, great cruiser..
Subscribed from BC eh?
Good day.

 

[AKBushDag]

This is a great tip and I thank the author for posting it. I have one question for clarification, and that is with regard to vehicles with ABS. My understanding is that it is very difficult (or even not possible) on ABS systems to use/apply threshold braking, as that is what the ABS is trying to do? Just asking if anyone can offer any insight on this

 

[The other Sean]

This is a great tip and I thank the author for posting it. I have one question for clarification, and that is with regard to vehicles with ABS. My understanding is that it is very difficult (or even not possible) on ABS systems to use/apply threshold braking, as that is what the ABS is trying to do? Just asking if anyone can offer any insight on this

First off, this is a wonderful topic. Even here in MN where we can have snow and ice on the roads what seems like half of the year, many drivers don't fully understand the whole topic of traction.

In theory, you are threshold braking all day every day by not standing on the gas pedal or brake pedal and not violently whipping the steering wheel left or right. The ABS only comes in to account when you exceed your traction limits.

The ABS is not 100% fool proof.

In theory, you are to rely on the ABS system. However... there are certain specific times where even the ABS will not work properly. For instance, Ice. solid sheet of ice. when you hit the brakes, all 4 wheels lock up instantly and the computer thinks you are stopped and offers no brake modulation. I've seen it, I've done it. Scary. In this instance, you would need to let off the brakes and either steer only or figure out how much steer and how much brake to apply. Remember, the ABS will only activate when it senses one or more wheels braking at a different speed than the others. But, 99% of the time, you should rely on the ABS, but, you should be aware there are certain times where it is not the best.

The easiest way to wrap your head around this topic (and any topic of tire traction) is to understand you only have a set amount of traction and this traction is responsible for ALL stop, go and turn actions. if you are using 90% of the available traction your tires offer to turn, you only have 10% left to brake. So... if you go in to a turn too fast and start to slide, if you hit the brake pedal, you are almost guaranteed to slide more. If you Google how road racers negotiate a curve, it is explained quite well.

 

[Lassen]

This is a great demo, for sure! But, for me being from the Bay Area in California, if I get in to questionable conditions, that's it. I either stop and wait for better conditions - like overnight not wait until spring! - or call it a day and head back. When it comes to icy conditions, I'm a coward. And I find it to be best for me[emoji3]

 

[Jeepney]

With glaring ice, the best you can do is scream loud, that's negative propulsion. I've had my car on winter tires slide uncontrollably on ice -- and i know not to touch the brakes.

On most snow conditions, locking it up is a proper technique for getting those tires to dig thru snow/slush. This is where ABS can bite you. It will detect lockup and will let the tires roll and prevent it from digging. This is when you can differentiate a properly tuned ABS (i.e. overly aggressive ones are bad). On the positive side, majority of folks in panic condition will benefit from ABS since most are not trained to deal with these conditions.

I always recommend my friends to do some autocross or driving school, it really helps understand the traction circle.

 

[vicali]

This is a great demo, for sure! But, for me being from the Bay Area in California

Haha, This is a great Demo! But, for me being in the interior of BC, we've been driving like this since October..

Winter tires go a long long way

 

[Anders0nic]

I think its safe to say that most people here in the US get a low grade of car control theory before they are sent out onto the roads and taught basic skills. If you grew up in the northern half of the country, you probably learned how to drive on the ice and snow from a family member. Here in California, the amount of skill needed to pass the exam can be found in the small brain cells of a common household fly. I learned adverse condition driving by frequenting the family cabin in Soda Springs from the moment I got my license. I can remember sliding around in the parking lot of True Value in Truckee or doing donuts in the parking lot of Soda Springs Ski Lodge. It was there I learned throttle and brake modulation. I can only hope that by sharing this article more on social media we can teach the citizens of the roadways proper winter driving techniques. I cannot count how many times I have seen the "brodozer" bounce off the snowbanks/siderails of the freeway because they don't know how to drive in the snow/ice ,but think because they have 35's and 4WD that they are invincible.

 

[Billy "Poserlander" Badly]

I cannot count how many times I have seen the "brodozer" bounce off the snowbanks/siderails of the freeway because they don't know how to drive in the snow/ice ,but think because they have 35's and 4WD that they are invincible.

Exactly right. If there's one thing I wish everyone understood, it's simply that you have to change how you drive in icy/snowy conditions. It seems so basic, and yet it's clear plenty of people just don't get it. Dudes w/ jacked up rigs are often the worst offenders, and they have a much greater capacity for causing collateral damage, but it applies to everyone.

 

[BobG]

Great advice... Thank you!

 

[AKBushDag]

First off, this is a wonderful topic. Even here in MN where we can have snow and ice on the roads what seems like half of the year, many drivers don't fully understand the whole topic of traction.

In theory, you are threshold braking all day every day by not standing on the gas pedal or brake pedal and not violently whipping the steering wheel left or right. The ABS only comes in to account when you exceed your traction limits.

The ABS is not 100% fool proof.

In theory, you are to rely on the ABS system. However... there are certain specific times where even the ABS will not work properly. For instance, Ice. solid sheet of ice. when you hit the brakes, all 4 wheels lock up instantly and the computer thinks you are stopped and offers no brake modulation. I've seen it, I've done it. Scary. In this instance, you would need to let off the brakes and either steer only or figure out how much steer and how much brake to apply. Remember, the ABS will only activate when it senses one or more wheels braking at a different speed than the others. But, 99% of the time, you should rely on the ABS, but, you should be aware there are certain times where it is not the best.

The easiest way to wrap your head around this topic (and any topic of tire traction) is to understand you only have a set amount of traction and this traction is responsible for ALL stop, go and turn actions. if you are using 90% of the available traction your tires offer to turn, you only have 10% left to brake. So... if you go in to a turn too fast and start to slide, if you hit the brake pedal, you are almost guaranteed to slide more. If you Google how road racers negotiate a curve, it is explained quite well.

Shizzy - Thank you for taking the time to provide a very clear and detailed answer to my question. I was taught Threshold braking in the early 1980's, and used it on countless occasions. I became quite proficient in it and it saved my butt many times. I had always preferred this over ABS. Then I bought 2007 4Runner and naturally it came with ABS. This really wasn't a problem when I lived in Calif. But, ever since I moved to Alaska, whenever I've tried to Threshold brake, the ABS kicks in and overrides me. Might you know of any to selectively deactivate ones ABS system?

 

[MOAK]

Nice article. After a lifetime of winter driving and 25 years of shoving an 18 wheeler through all kinds of weather, including those nasty winters in NB, NS, QC and ON, I'll have to agree 100% that good driving skills and the mastering of "threshold braking" can be better than ABS. I pulled the 15 amp ABS fuse from my Landcruiser long ago. I was in too many situations in my Landcruiser where the ABS just would not stop me. I much prefer gliding into and out of a controlled 3 point slide while navigating to a safe stop. During my 25 years of driving truck I only broke traction 3 times. Fortunately 0 accidents as I was always able to regain control. However, an ABS equipped truck scared me bad one day when a truck passed me then wiped out about 200 yards in front of me on a downhill run. With ABS, the truck would not slow down, the only control I had was steering. That was a poopy pants day, as I literally had about 6 inches to spare between him and the guardrail as I flew by at about 50 mph. ( I had actually gained 5 mph, even with jake brakes roaring and downshifting one gear. I am convinced that without the ABS, I could have slowed down a lot more, and passed through at a much lower speed.

 

[The other Sean]

Another thing to touch on is many people have no idea how their vehicle (or any vehicle) responds in loss of traction situations. As a few of us who grew up in snowy parts of the country have said, we have many times been and are now familiar/comfortable when a wheel slips and know how to handle it (in theory). Many people would benefit greatly by taking some kind of driving course where they purposely have you put the vehicle in to a slide or spin and show you how to recover.

 

[AKBushDag]

Nice article. After a lifetime of winter driving and 25 years of shoving an 18 wheeler through all kinds of weather, including those nasty winters in NB, NS, QC and ON, I'll have to agree 100% that good driving skills and the mastering of "threshold braking" can be better than ABS. I pulled the 15 amp ABS fuse from my Landcruiser long ago. I was in too many situations in my Landcruiser where the ABS just would not stop me. I much prefer gliding into and out of a controlled 3 point slide while navigating to a safe stop. During my 25 years of driving truck I only broke traction 3 times. Fortunately 0 accidents as I was always able to regain control. However, an ABS equipped truck scared me bad one day when a truck passed me then wiped out about 200 yards in front of me on a downhill run. With ABS, the truck would not slow down, the only control I had was steering. That was a poopy pants day, as I literally had about 6 inches to spare between him and the guardrail as I flew by at about 50 mph. ( I had actually gained 5 mph, even with jake brakes roaring and downshifting one gear. I am convinced that without the ABS, I could have slowed down a lot more, and passed through at a much lower speed.

Thank you for that info. I never thought it could be as easy as pulling a fuse. I'm going to try that on my 4Runner.

 

[atIOIYIOI]

This is a great tip and I thank the author for posting it. I have one question for clarification, and that is with regard to vehicles with ABS. My understanding is that it is very difficult (or even not possible) on ABS systems to use/apply threshold braking, as that is what the ABS is trying to do? Just asking if anyone can offer any insight on this

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.

 

[Christian]

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.

 

[Lassen]

"Here in California, the amount of skill needed to pass the exam can be found in the small brain cells of a common household fly."

LOL! So true! I remember back in 1983 taking drivers ed/training in high school -- back when it was still offered. You'd be taken out in the car, get a few miles in, city, getting on/off a highway then you had to get in miles at home with parents before coming back to take a final driving test saying you were good to go to DMV to get permit. The miles and experience you needed at home was 20 miles - 10 city, 10 highway.

Well, it just happened that spring break came up and we went to Death Valley. In one week I put in 1,500 miles! Dirt trails, gravel trails, some 4-wheel trails that didn't even require putting the Suburban in 4-wheel, and a lot of two-lane highway driving and even a few miles, about 50, towing a 23' long house trailer! Covered that valley from north to south, down a road with a 14% grade, up to Telescope Peak, the kilns, down to Badwater, The Race Track, Ubehebe and Little Hebe, Scotty's Castle, Beatty Nevada, everywhere. Even picked up a nail or something in the back right tire. I kept saying it feels like we were getting hit by wind - car was dragging to one side, tire issue never occurred to me - and then on one of the two-lane roads, at about 60 MPH, back tire blew out. Shredded it. Great experience for a novice!




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[Lassen]

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.


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[Longshot270]

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.

 

[atIOIYIOI]

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

Hi Lassen - I'm not sure on the temperature/grip scale, but I can tell you it's fairly common to get "square" tires after a cold night, at say -25C (-13F) or so. By "square" tires, I mean the flat on the bottom from being parked stays there when you start to roll. Can usually feel it for the first few hundred feet - then it goes away. I suspect at this point, the rubber is likely affected by the cold, but since the heat begins to build once you start driving I don't suspect it has a lasting effect. (Note - no facts in there! - just my observations and thoughts!)