Diesel Progress MUST READ

[RVTRKN]

Well, the dually, having more tires on the ground, tends to have more flotation, especially on the rear wheels. On that boat ramp, that can hinder traction if the tire can't cut through the water down to the pavement to get the gear analogy working. So, there are advantages and disadvantages.



Rusty

Well as a boat owner for 16 years now, its not water you worry about under your tires, its the slime line thats dangerous. Before I had a 2X2 gasser and would inspect the surface under the water for this condition or you would have a water logged truck, and out of habit still do.



The 4X4 I have now with the NV5600 will walk out of the water in 4HI and 1st gear with no struggle at all and no slippage, without even touching the throttle, now if you have an automatic and you have to rev the RPM's to lock up the torque converter you will probably slip just a little.



You never spin your tires fast enough to hydroplane when pulling your boat out of water and if you happen to have a 2X2 and you do slip a little you back off on the throttle until you have traction. If you can't get the traction you need then its the slime line and you are in deep doo doo, not hydroplaning. A good rule if you dont have a 4X4 is wait for another to try if possible. Wolfy has it right about the slime, its just like ice and many of boaters have slipped down the ramp and totaled their trucks.

 

[betterthanstock]

The "coefficient of friction" is the percentage of the downforce (weight) on a tire that you can pull with the tire. Most tires are between 0. 7 to 0. 9 (70 to 90%) on dry pavement.



That means that when you have 4 rear tires (DRW), empty, each tire only supports half as much as each tire in a SRW. So the pulling power is identical to a SRW (double the tires times half the weight on each tire=same pulling force).

This neglects the small additional weight of the 2 extra wheels, and the fiberglass fenders. Adding in the extra 300 lb or so, you will get about an extra 200 lb more pulling power with a dually than a single wheel.



When loaded with 5000 lb you gain extra pulling power...



An empty DRW will have much worse traction in the wet than an empty SRW because it takes twice as much force to break thru the water film at high speed (so it hydroplanes at much lower speed). Also, the outside tires ride on wet pavement, the inside ones ride on relatively dry pavement behind the front tires (at speed, if the water is not too deep). Skinny tires are best in the wet.

 

[RustyJC]

The "coefficient of friction" is the percentage of the downforce (weight) on a tire that you can pull with the tire. Most tires are between 0. 7 to 0. 9 (70 to 90%) on dry pavement.



That means that when you have 4 rear tires (DRW), empty, each tire only supports half as much as each tire in a SRW. So the pulling power is identical to a SRW (double the tires times half the weight on each tire=same pulling force).

You're back to classical coefficient of friction evaluation of the tire-to-road interface. Using this logic, pulling power would be identical with bicycle tires on the rear of the truck - smaller surface area x higher unit loading = same pulling power. That, of course, is not the case for the reason I cited earlier.



Rusty

 

[JasonCzerak]

Which is why top fuel, pro stocks and funny cars don't run wide slicks since they don't buy them any advantage.



OK, sarcasm aside, traction doesn't conform to classical Newtonian physics where the force is a function of coefficient of friction between static or sliding bodies. Theoretically, this coefficient of friction can never be greater than 1, which can only generate 1g maximum acceleration (or deceleration).



In actuality, the interface between a tire and pavement is more related to a gear arrangement. The rubber of the tire conforms to the irregularities of the pavement, like meshing gear teeth. The more rubber meeting the road, the more gear teeth are engaged. The force that can be transmitted through this interface depends on the ability of the tire rubber "teeth" to resist deformation or shearing. Since more teeth mean less load is applied to each tooth for a given total force, a larger tire (or more contact area) can generate higher accelerative forces than a smaller one. That's why drag racers can accelerate at much higher accelerations than 1g.



If you don't think this is true, try to run a 1/4 mile drag race with bicycle tires on the rear of that top fueler - in Newtonian terms, it should give the same (or better - less aerodynamic drag) result as those huge drag slicks.



Rusty

I was thinking about this post of yours here lastnight as I was driving down county road 42 here... . Perfectly dry as it can get in the winter time (full month of 25 or colder). You can't see "wet" yet, you know in each little grove or "teeth" in the pavement you know it's full of ice and salt any sand. filling in each tiny hole.



I realize this as I can easly spin the tires in 2WD in 5th gear.

 

[cojhl2]

Actually it's a lot more complicated than any of us have described.



After RustyJC described the Drag Racer I researched further. Of course I did not keep track of where I went so can't immediatly point to it.



There is quite a bit written about the Drag Strip tire issue. It follows a model more akin to adhesive tape where regular tires are more the classical "Columb" rule of Friction.



Net it out: It's a very complicated issue. I still think however, comparing SRW with DRW there is not much advantage so far as traction is concerned.

 

[cojhl2]

I was thinking about this post of yours here lastnight as I was driving down county road 42 here... . Perfectly dry as it can get in the winter time (full month of 25 or colder). You can't see "wet" yet, you know in each little grove or "teeth" in the pavement you know it's full of ice and salt any sand. filling in each tiny hole.



I realize this as I can easly spin the tires in 2WD in 5th gear.

This brings up another interesting point.



The reason Ice is slick undr our tires is because the pressure exerted by the weight transforms the solid ice to liquid. There is then a very thin layer of water between the ice and the tire.



When it is cold enough so that the ice does not turn to liquid it provides quite a good traction surface.



Of course sand ... . etc changes the equation too I suppose.

 

[RustyJC]

Net it out: It's a very complicated issue. I still think however, comparing SRW with DRW there is not much advantage so far as traction is concerned.

Agreed. The primary benefit of dual rear wheels is load carrying capacity.



Rusty

 

[mhenon]

Older dude here too. They're the Honda jockeys with the five inch mufflers on the inch and a half exhaust pipes. :-laf

That's funny! We've all seen those little cars with a big chrome tailpipe hanging out the back end.

The king of all stupid aftermarket products however has got to be the spinning hub caps.

Mike

 

[JasonCzerak]

That's funny! We've all seen those little cars with a big chrome tailpipe hanging out the back end.

The king of all stupid aftermarket products however has got to be the spinning hub caps.

Mike

But don't you wish you thought of the cheap spinny hubcaps? kinda like the pet rock, some retarded kid will buy it!

 

[zippinbye]

My stock 325/600 SWR auto requires powerbraking to spool up the turbo for a decent two-wheel burn out, unloaded. Then it spins a bit and hooks up. A real smoker would require brake and drive train abuse I'm not willing to do. On good black top, these trucks to not smoke-em from a stop as you might imagine.

 

[Mhannink]

Somebody educate me.



Isn't "a standing stop" where most rubber-burning begins? (IMO a rig that can break the wheels loose when already rolling is the more impressive. )



And is it unusual for a presumably empty (no load is mentioned) light-in-the-rear pick-up to be able to break loose from a stop?



Another deduction : If a given 3500, let's say, with SRW is "powerful" enough to burn from a stop, ... then would a similar-but-DRW rig not be launched-and-gone (with twice the driving traction), while the SRW is slippin'-and-burnin'? (Provided nothing snaps)



Admittedly I haven't bought a PU in many years, and am only now contemplating a diesel,... but somehow I'm missing why this statement is thought to be impressive. (?)



Is this somehow related to turbo wind-up or something?

turbo wind up is the key. this fricton stuff has an effect but regardless of that the biggest thing is these trucks are dogs when theres no boost. you have to have boost to get any power. so when your moving along and bog the motor down and let it start to build boost it will break loose when the boost hits. now this new truck has a variable trubo so it spools insanly fast which makes it provide that needed power to spin the tires from a stand still.

 

[Cummins Cowboy]

All regeneration is accomplished by overheating the egts through engine fueling and air. .

don't you just love knowing your truck is set up to run rich ie it is injecting extra diesel into the system that the engine is not burning just to satisfy the AL Gore libs, and the global warming people, next time you hear someone talk about global warming ask them why we had much more pollution in the 70's and we didn't have global warming then?? its nice knowing I am buying all the extra diesel specially treated for low sulfur content sometimes as much as . 60/gal more than gasoline just to satisfy these idiots