Speedometer Gear Adjustment for big tires on a GenI Montero/Raider

Many of us who enjoy our GenI Montero/Raider offroad have switched to a larger tire size other than stock. A problem with this that you may or may not have noticed is that the larger diameter tire sizes throw the speedometer off. The disparity between actual traveled speed and displayed speed grows in proportion to the larger diameter of the tire.

I first noticed this a few years ago when an officer issued me a ticket for a speed that was 3mph over what I thought I was doing. Even though I knew I was speeding, the speed written on the ticket bothered me as being inaccurate. Fast forward 2.5yrs later to my next speeding ticket and I was in disbelief at the speed the officer said he had clocked me doing. This caused me to take action and look for a possible solution that has plagued most of us larger tire users for some time.

Actually, I made the discovery quite by accident as I was looking for reasons my speedometer needle was bouncing (different tech story). I pulled off the speedometer drive gear assembly to learn how it works. It’s really pretty simple: a nylon gear is turned by a screw on the output shaft.

How I started my 2006 Summer Vacation

Trail Bites: Late May Moab Trek 2006
By Chef Mark

(Portions of this article and photographs are reprinted from Chef Mark’s Jeep Grille Adventures: Camp Kitchen and Cookbook with permission. www.JeepGrilleAdventures.com)

It had been 3 years since my last trip to the Mecca… and since I missed hunting season last fall I deemed it a necessity… a Moab adventure. With some upgrades to the drivetrain; such as a Ford 8.8 in the rear and recently installed Aussie Locker, I felt confident with a newly acquired trailer in tow all thanks to Josh at Crawler Tech 4x4 in Denver. The trailer itself has a unique history, as it had previously hauled rock up the well known Holy Cross Trail just south of Leadville, Colorado in 2000, to fix various spots en route to the “The City”. The trailer has a CJ axle, with locking hubs (great conversation piece obviously not functional), 2.5 inch Rancho Springs, and 32 inch BFG MT’s.

2006:5:21
The intent was to venture down along the Colorado River via Rabbit Valley following the Kokopelli Trail to Cisco and then on to Moab. My plans changed slightly after some confusing map details. Rather than drive onward, not sure of the exact route and not wanting to waste gas, or get lost I backtracked slightly and set up camp on the top of a mesa. I purchased this great one-person camp tent that sets up in a matter of seconds, a Tent Cot if you will, at a local sporting goods store. There is also a two-person version which I hope to acquire in the future.