Is this true and if so why do we have 4wd or All Wheel Drive?

Recently I made a post that stated "4x4 may give you traction but it does not let you stop any faster." I have always thought this to be the case. Now I am conflicted after being informed of the following by one of our Tundra members:

"The only way to get more traction is to physically change something about your contact with the road with different tires, chains, traction boards, etc."

Please tell me the truth then I can sleep at ease. TIA.

 

Well I got stuck in 2nd today; spin in 4hi and crawled out easily in 4lo. Definitely felt traction with 4lo. Used 4hi many times previously and got me out of jams where 2nd wouldn’t work. That’s good enough for me to say it works

 

It is more traction. In 2wd only half your wheels are spinning to produce drive. In 4wd you are engaging all the wheels to grip and push/pull. It's twice the traction.

 

Yes - the intended purpose of 4wd. Could not agree more.

 

Could not have got out of my neighborhood earlier this week in 2WD. Ice storm. 4WD got us out. Call it traction, power, whatever, 4WD gives you more.

 

Semantics... Sounds like the Tundra member you mentioned was disputing your choice of the term "traction". They are technically correct on that one count but wrong in every other sense of the conversation in play.

Each tire has "X" amount of grip/traction and only by changing something physically does a given tire suddenly have more (or less) traction. What the poster was not taking into account or perhaps being deliberately obtuse about was that that the more tires that are being driven the more total drive/grip/traction is availible to accelerate.

So your statement is correct (minus the semantics issue). 4x4 even with open diffs has more grip/traction to accelerate because more wheels are being driven compared to 2 wheel drive vehicle with an open diff. However neither one has an advantage when it comes to stopping if all other things about them were equal since they both have brakes on all 4 tires.

We've all witnessed the new or careless 4WD owner use the extra grip to accelerate faster and go faster in slick conditions only to find out too late they can't stop any faster than anyone else...

 

4x4 does not help you stop any faster

 

Correct, because you already have brakes at all 4 corners. The drive system isn't using traction to decelerate, the braking system is.

 

I'll quote myself in (since it is about me). @windblown101 you are correct it was a very semantic argument that is taken out of context with that single sentence

I was not trying to even start an argument just wanted to rant about the semantics of a very common phrase that people whip out in the winter

 

And to throw gas on the fire… I would disagree. Simplified version of disagreement reads: static friction is higher than kinetic friction, meaning a rolling tire has more traction than a skidding tire. Weight shifts forward while stopping (on slick roads, it is less than the traditional 70/30 split rule of thumb) so those tires will typically lock first. ABS is supposed to prevent them from locking but in reality on slick roads they will still lock but won’t instantly spin up again before the ABS cycles and pulses again due to the lower coefficient of friction. In 4wd, the front and rear axles are forced to rotate at the same speed, so the rear tires not skidding will keep the front tires rotating, thereby allowing a higher coefficient of friction between all four tires and the road - which is what ABS tries to do but isn’t always effective. Hence better traction while stopping.

 

Old school 4x4 with no ABS and no center differential: All things being equal if both fronts are in a skid the rears will simply be forced into a skid as well as they have a lower traction threshold. The rears will take their queue from what the fronts are doing. Sort of a chicken or the egg thing I suspect...

But what happens if only one front tire is in a skid? What impact if any will the brake proportioning valve have?

In the end no matter what they're driving they'll stop quicker when they plow into the vehicles stopped in front of them. Folks driving in slick conditions should take a page from the boaters handbook - Never approach the dock faster than you want to hit it...

 

Yada yada yada.
Spend the money on quality winter tires if you live where there's snow/ice 3 mo p/yr and don't drive like an idiot.
And actual, bonafide winter tires. Not the A/Ts that you think look cool and have a bullshit snowflake on the side.

 

Traction is being able to apply a force to a surface and creating motion. But it only works within a window of not being too heavy or too light on the surface. Since pickups are front heavy a 2wd pickup can get stuck on flat wet grass. Adding weight to the rear could be enough to create traction. Or adding power to the front wheels will do it too.

4WD won't give you better hydraulic braking. But it could give you better engine braking in low traction. And far better engine braking when it's in low range. But the disc brakes....no.

4WD has a low range gear and direct 4WD transfer case with no slip which is better in working and off road applications. AWD systems don't have a low range gear and allow slip in the transfer case between the front and rear. AWD is better is most on road applications thats why they are found in cars where 4WD is found in work vehicles like trucks. Some vehicles have both like high-end SUVs and trucks like the Sequoia or a Chevy Tahoe.

 

Winter tires makes all the difference.

All Season tires are like the shirts that say, "One size fits all"

 

In 4WD you get perhaps 3-4 times the traction, because most of the truck's weight is situated right above the front axle.

 

Are links allowed?

https://ritzel.siu.edu/courses/302s/vehicle/vehicledynamics.htm

 

I don't think anyone is arguing that you have more traction with AWD or 4wd and can keep going.
The issue IMO is people tend to drive faster with AWD and 4wd on - thus making stopping distances greater.
And this can be dangerous depending on conditions as you cannot stop faster - assuming same tires and everything else same outside of AWD / 4wd option.
As soon as you sense slip - people tend to slow down.

 

It is very easy to figure out traction and how it works. Obviously 4WD helps because you now have more than one wheel trying to move your vehicle so that is traction 101...

"We have come to the conclusion that we can run our car over any road that a man can take a team of horses and a wagon, providing we can get traction." Dr. Horatio Nelson Jackson, 1903

This was the phrase Kevin Patterson (RIP) had in his signature on ih8mud.com and we all lived by it.

 

I thought I read somewhere that to be an all-season tire required just 1/32" of tread depth over a summer tire.....Or was that Mud & Snow.

 

4x4 = more traction in all wheels...so you can "potentially" get unstuck in low traction places. 4-LO = higher torque to the wheels.

If you want to stop that's investing in better brakes/rotors and tires.

 

I heard caster is the key and eliminates the need for 4wd. Pair that with the added weight of 5W-30 and you don't even need brakes.

While none of this is true, I figured I'd use the opportunity to ask what it is just read about.

Traction = good.
More drive wheels with traction = better.
Lubrication (snow, ice, rain) impacts traction = bad.
Heavy vehicles take longer to stop = worse.
People driving heavy vehicles on slippery surfaces thinking they are immune = segment on World's Dumbest Drivers.

 

It depends. Heavier vehicle with narrow tires could stop faster in snow than lighter one with wide tires. There's no universal combo that is better in all cases.

 

Note that I did not include the fat vs skinny debate. We all have our preferences.

But this is all a matter is science. Intro in the link below:

"Some seem to have the notion that driving a four-wheel drive with anti-lock brakes somehow exempts them from Newton’s three laws."

https://www.langleyadvancetimes.com/opinion/editorial-newtons-law-of-winter-driving-2483777

The last post does an even better job at explaining.

https://www.physicsforums.com/threads/newtons-first-law-of-motion-skidding-on-icy-roads.3355/

Overcoming the "from rest" is where AWD/4wd plays a part. Overcoming the "in motion" it offers zero assistance.

 

4x4 does not give more traction. It simply allows all 4 to spin. Traction is only accomplished on the ground by what is touching the ground

 

No, that is friction. Traction is the application of torque that uses the friction to provide momentum. Google "tractive force"