Johnson Valley, CA - November 1999	Short Cuts
by: Jefe Reynolds [ Main | Results | Trails | WRCC | Perspectives | Galleries | Analysis ]	Navigation Menu OutdoorWire Front Page 4x4 Parts Main Expo Center OutdoorWire Site Index Main Links Index 4x4Wire Front Page 4x4 Tech 4x4 Trails

What You'll Need to Be a Contender...

[ Part I | Part II | Part III ]

Mike Pulskamp

Purpose Built

All but one of the rigs in the dirty dozen were of the trail-only variety. Some of those rigs looked kind of stock, like the Currie TJ, but underneath the sheet metal were some very well thought out, way fine tuned, non-stock drivetrains.The competition's routes this year were geared toward much larger tires than were previous competitions. With few exceptions, competitors with 35" tires did uniformly worse than those with 38" or larger tires. These smaller tires often just fell into the holes and disappeared, leaving frames and pigs beached on the rocks. Yes, great drivers with 35" tires, like Jason Bunch and John Currie did well, but they did well because they are great drivers and over came the handicap of smaller meats with shear driving skill. 38's, 39.5's, 40's, 42's and 44" tires shod the most successful of the dirty dozen. Almost all of them had bead-locked rims. When you get above 36" tires, they're all bias ply with stiffer sidewalls, and consequently must be run at a lower pressure than the smaller radial tires to get the same effect. The tire pressure run by the group seemed to be dialed in for each vehicle. Interco Swamper tires seemed to have replaced the Boggers as the prevalent tire of choice at this event. (Editor's note: few other companies offer tires this big -- c'mon, the rest of you manufacturers, take note!) In addition, many of these were siped or grooved for just a bit more traction.

Drivetrain components do not get much bigger than these Rockwell 2.5-ton military axles (shortened to a practical width). Mike Pulskamp

Big, Bullet-Proof Drivetrain

The drive train bottom line for most of the dirty dozen was their lack of breakage. Ford 9", 35-spline Dana 60, GM 14 bolt, and even narrowed 2-1/2 ton G.I. truck axles backed up those mighty meats. Every finalist drove on solid axles; I don’t even recall an IFS rig even competing. Some had the clearance-robbing bottoms of differentials trimmed just below the clearance for the ring gear and a flat plate welded there instead for clearance. This cut several inches off the clearance robbing GM 14 bolt axle. I didn't see many truly full width axles with the Dozen. Axles were moderately wide. Especially during the preliminaries, full width axles were a handicap, and many jeepers with full width axles and 10-15" wide wheels didn't make the finals as they could not maneuver through the gates without knocking them over. The trend at the moment, at least for the Dozen, seems to be to use wider, almost-but-not-quite full width axles. Many used high-pinion differentials to keep the drive shafts up and out of harm's way.

Scott Wilson

Wheelbases between 94" and 100" seemed to be the norm, with many of the Jeep platform rigs having stretched wheel bases, with axles moved toward the ends of the rig. There is no perfect wheelbase, as the tortuous routes favored a shorter wheel base over some obstacles, and a longer wheel base over many others. Two thirds of the finalists had heavily cooled automatic transmissions; the rest had heavy-duty manual truck 4 or 5 speeds. Well, O.K., Jason Bunch used a disposable AX5, 5 speed installed just for the event. Those that made the finals had low gearing, but I would not consider them ultra low. Even the automatics, assuming a built-in 2:1 gear reduction due to the slippage of the torque converter, had 100:1 gears. In competition, ultra-low gearing -- because of the actual multiplication of torque -- is likelier to break drive train parts and it can also slow you down. Of course, everyone had full lockers on every axle. Most had Detroit Lockers, with the rest using ARB's. Third place finisher Ken Ristau and his chassis/frame Jeep, sported the much-maligned AMC20 rear end with locker by Lincoln., aka: welded spider gears. Some contestants had axle brakes (a separate one for each rear wheel) to lock and pivot on one rear wheel while the other three wheels were used to 'caterpillar' the rig around. Long-splined over-built drive shafts abounded.

Mike Pulskamp

Well-Sprung

The suspensions of the dozen were nicely controlled, with tried and true solutions: leaf springs-over-axles, 3 and 4 links with coils on all corners, 3/4- or quarter-elliptical suspensions. These bullet-proof suspensions were impressive. The finalist's rigs displayed loads of suspension travel, but not so much as to self-destruct. Each of the dirty dozen had a well-integrated suspension with controlled resistance or spring rates at all 4 corners: pliable, but not too soft. No tires rubbed, and there were no quirky motions when rigs got off camber.

Scott Wilson

Power Plants

Eight of the 'thirteen' had dependable, fuel injected, V8 power, with only one high-cube V8. Four had 6-cylinder power, and Jason had the anomaly engine, the 2.5L 4-cylinder, proving again that you don't need high horsepower to be a contender. He did, on further observation, have the rpms up in the power range more than the folks loafing along with their V8s. I'm not sure, but I think every contender that made the final 13 cut had fuel injection. No one stalled. No hiccups, no grinding starters... even when they were way off camber or even laying on their sides, the motors just kept turning regardless of the tilt. Sam Patton was very stylish, with lots of horsepower, and had no fear of using it to 'jump' some ugly holes. During the preliminary rounds, some of the rigs with higher horsepower broke.