2WD or 4WD

rhagfo wrote:

RedJeep wrote:
On the beach this weekend in my dually. Got stuck in the sand. Very very very glad I have 4wd. My opinion, get the 4wd. I had contemplated a 2ad because I figured I was a concrete driver only. You never know.

Is that GOT stuck, or ALMOST got stuck?

I was 100% completely stuck.. until I engaged 4wd. ;)

RedJeep wrote:
On the beach this weekend in my dually. Got stuck in the sand. Very very very glad I have 4wd. My opinion, get the 4wd. I had contemplated a 2ad because I figured I was a concrete driver only. You never know.

Is that GOT stuck, or ALMOST got stuck?

One time my Duramax and 5th wheeler got stuck in wet grass leaving the Indy Speedway camp area. I was pulled out by 4wd half ton after the 2wd driver wrecker was stuck, he was pulled out by a 4wd half ton.

otherwise I've never needed it.

On the beach this weekend in my dually. Got stuck in the sand. Very very very glad I have 4wd. My opinion, get the 4wd. I had contemplated a 2ad because I figured I was a concrete driver only. You never know.

Wes Tausend wrote:
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To the OP, the above discussion on "spinning vs slipping" may not mean much, but there is usually a difference in braking, and therefore handling between 4x4 and 2wd. The 2wd will likely handle better and safer in an emergency on dry roads.


Wes
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Wes, going to need to disagree with you on this!
Stock height 4X4 from the factory now days doesn't sit much taller than a stock 4X2, but the 4X4 will have stiffer springs and likely sway bars. I see it as a wash between the 4X2 and a 4X4 on dry pavement, put a little white stuff on the road and the advantage goes to the 4X4 hands down!

Now if you are referring to "Lifted" 4X4 we are in 100% agreement, I have seen a couple that I thought the crown in the road would roll them over.

...

To the OP, the above discussion on "spinning vs slipping" may not mean much, but there is usually a difference in braking, and therefore handling between 4x4 and 2wd. The 2wd will likely handle better and safer in an emergency on dry roads.

The 2wd wins the highway "Tow Award" and here is why:
The center of gravity is normally higher on 4x4 than 2wd because the 4x4 is usually raised for more clearance. This not only makes a difference during cornering where a tall vehicle may tip easier, but also in stopping power. One need only imagine an exaggerated-tall truck might tip forward to stand on the front two wheels just it might lean up on two wheels side-to-side. A 2wd tends to better maintain even tire loading under acceleration stress.

In normal physics, greater weight per square area increases friction in a linear manner. So rotating a multifacet block of iron to slide on a smaller facet area doesn't change the overall coefficient of friction (cf). But rubber tires are different. With weight remaining the same, more rubber (as in a bigger facet) meeting a dry road is better for traction, which accounts for the wide tires on race cars. Wide rubber raises the cf, the traction adhesion.

Rubber tires also have another related peculiarity. As weight is added or removed from a tire, the cf decreases non-linearly. Therefore when a truck is stopping, the "lightened" rear wheels lose a certain amount of traction, and the fronts gain a lesser amount of traction than the rear loses. Some overall four wheel traction is lost because the weight shifted.

A tall 4x4 has a greater weight transfer forward and thereby loses a greater amount of total overall traction compared to it's lower-chassis'd 2wd. I deally the center of gravity would right at ground level, but this is not possible. Still, closer is better than taller.

There were some remarks about a 4x4 losing directional steering control because of the tractive effort of the front wheels pulling. It is true that each tire must share both steering and inline traction. But more of one means exactly less of the other. The commenter had the right idea that acceleration (and deceleration, ie braking) subtract from steering traction, except 4x4 inline forward traction is the same direction as steering traction. So 4x4 do steer better than non-powered front axles in every case "under power" because all traction is directed wherever the front tires are aimed. But, when it comes to braking straight ahead chassis and rig momentum, neither 4x4 nor 2wd have an advantage, and both front tires equally lose some steering traction during hard braking.

All our RV towing unbalances our tow vehicles overall traction to some extent because of uneven tire loading. Normally the rear tires get a greater load percentage-wise when hitched because the rear axle is designed to accomodate the extra weight. There arises a distinct advantage to dual rear tires because they increase the rear rubber to more closely approach the ideal matching weight on every tire that is the special rule in maximum rubber tire traction.

In conclusion, the 2wd is a better, safer vehicle on dry pavement. For a heavier rear axle load, the dually surpasses a heavily loaded single tire in the search for equal traction on all tires. Equal traction means maximum traction possible when it comes to rubber tires.

Wes
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wwest wrote:
The word "spinning" does not connotate slipping even in the context you used

You and I have different ideas about what it means to leave a donut in a school parking lot.

It doesn't mean driving in a circle. You have to have enough HP to break both rear tires loose. Then they go sideways. Todays youth may call it drifting (but in a circle).

Static friction, where the contact patch of the wheel is not moving relative to the surface (a wheel rolling on the road) is always much greater than dynamic friction where the contact patch is moving relative to the surface. Sometimes when the wheels break loose it's best to keep them spinning and let the lesser dynamic friction along with the increased rpms keep you moving. Sometimes it's best to get off the throttle to keep from sliding sideways downhill into a tree or something.

Sport45 wrote:

wwest wrote:

Sport45 wrote:

rhagfo wrote:
Well the fact is when the steering wheels are also driving the vehicle the will go the direction that the wheels are turned, far better direction control.

I wish that was true. If the steer wheels are spinning you actually have little directional control.

If a spinning tire gave directional control we'd of had a lot of trouble burning donuts in the school parking lot, no? The donut is only possible because the spinning rear wheels slide sideways pretty easy.

Spinning vs slipping.

A "spinning" front wheel with traction will "pull" the vehicle in the direction you point it.

A "slipping" front wheel will be USELESS.

Spinning and slipping is the same thing. In my donut example the back tires are spinning, but going sideways instead of forward. And that's on dry pavement (about the best traction you can get.) ;)

The word "spinning" does not connotate slipping even in the context you used

It always amazes me that, in a forum dedicated to an EXTREMELY expensive hobby, people ask whether or not they should try to save a couple grand on a $40-50K truck.

Sure, if you are going to stay on interstates leading to large RV parks in warm climates, you will probably never need 4WD.

Personally, I will never own a 2WD truck because there have been enough times (even while towing) that I have needed it and have been damn glad to have it. I needed it just this past April at a state park of all places. Getting to my spot required navigating a muddy hill.

wwest wrote:

Sport45 wrote:

rhagfo wrote:
Well the fact is when the steering wheels are also driving the vehicle the will go the direction that the wheels are turned, far better direction control.

I wish that was true. If the steer wheels are spinning you actually have little directional control.

If a spinning tire gave directional control we'd of had a lot of trouble burning donuts in the school parking lot, no? The donut is only possible because the spinning rear wheels slide sideways pretty easy.

Spinning vs slipping.

A "spinning" front wheel with traction will "pull" the vehicle in the direction you point it.

A "slipping" front wheel will be USELESS.

Spinning and slipping is the same thing. In my donut example the back tires are spinning, but going sideways instead of forward. And that's on dry pavement (about the best traction you can get.) ;)