Turbocharged
Posts: 365
Joined: Mon Jun 25, 2012 5:26 pm
Cars: 13 Nissan Pathfinder
99 Nissan Frontier
84 Jeep CJ7 (rock crawler)
Off Road
Which is mostly rock crawling and general trail riding with a smattering of sand and mud. While I don't claim to know everything, and there are several types of
off-roading each with either a slightly different, to completely different setup I am fairly experienced.
The main things for off roading are ground clearance and traction. Ground clearance is mostly gained by larger tires. I have been stuck often due to hanging up
on a rock because my tires are pretty small.
While traction is gained through a combination of keeping all the tires spinning and keeping all of the tires on the ground.
Keeping the tires spinning is the job of the locking differential. There are many types of lockers
so here is a link to a brief explanation of some of the basic types.
http://www.offroaders.com/tech/locking-differential.htm
My preference is for selectable lockers because I can turn them off to turn without any weird stuff happening.
Keeping the tires on the ground is best done with a flexible suspension.
Ladder vs Unibody Frame: I have seen no difference in capability as far as unibody and ladder frame. Unibodies do tend to pop windows out shortly before the frame
starts to crack. And I have also had issues with cracking with box frames so its probably more of an issue with quality and the fact that we tend to push our rigs to the
limits. As far as cracks go a ladder frame is at least easier to fix.
Independent vs solid axle: There are some types of off-roading where independent suspension is best, but largely a solid axle will work out best. This is because when
one wheel goes up something like for instance a rock the spring or bump stop (usually in line with the spring) will act like a fulcrum and the axle acts like a lever pushing
the other tire down keeping it in contact with the ground longer. In rock crawling bump stops are often moved in towards the middle to give the tire going up more
leverage and forcing the other side down more.
Coil vs leaf springs: Even among off roaders there is no agreement, personally I feel that leaf springs can get better flex out of leaf springs, due to better down travel
(if only slightly). Coil springs often become unseated and can fall out of place when flexed to the limits where as leaf springs hold together. The advantage to coil
springs is they do definitely give a smoother ride. There is another suspension type which is a 4 link on a solid axle, I have only really seen those on dedicated off road
rigs, they can flex very well but take up a lot of room are complicated as far as getting all of the angles right (to keep it from binding) and can get pricy . There is a
link at the end that goes pretty in depth as far as coil-over shocks
Fat vs skinny tires: There are a few theories I have heard, skinny tires sink down to the bottom to get traction, provided they are tall enough, which I have seen work
with heavier rigs with mud and snow. On the other side light rigs tend to fair better with fatter tires which enable them to float on the surface which works best with
sand, and very deep mud and snow.
Power: Except for sand, mud and racing power is of little use. I can navigate most obstacles with only 5-10 horsepower, and have seen rigs with 4 cylinder engines
putting along at idle climbing nearly straight up. I have also seen many high powered rigs trying to climb a hill do nothing but break traction as soon as the climbing
gets difficult and do nothing but dig holes in the side of the hill, or simply shatter parts. I have had great luck with a wide low rpm torque curve often going down to
500 rpm without stalling.
Size: Small narrow rigs are easier to squeeze through tight places. It is not uncommon to see a small rig go between obstacles where a large rig has to climb over
them or perform multiple maneuvers to get through.
http://www.pirate4x4.com/tech/billavist ... rs/Part_1/