Odometer Gears TSD Rally


The above video was filmed during our 2013 Oktoberfest during the TSD Rally.

In its purest form, a rally pits competitors against the clock over a prescribed course, starting them at specific intervals.

This was the structure for the London-to-Brighton run in 1896, and it’s been the basis for all-out high-speed stage rallying ever since. The driver who gets from Point A to Point B in the shortest amount of time wins. Rallyists who prefer to employ logic and math skills generally prefer a time-speed-distance rally, or TSD. These rallies may be simple or challenging; some require clue-solving abilities, while others offer straightforward instructions—but all require the basic word-problem math we learned in middle school: If the train leaves at noon averaging sixty miles an hour, what time will it reach the station twenty miles away? (If you think it should arrive at 12:20, then you, too, may be a rallyist!)

A straightforward touring rally is a TSD event in which the rallymaster provides all the information you need in order to calculate the time you should reach any point on the route. If you don’t care for math, then you can enjoy the tour and just try to drive close to the assigned average speeds; you will be surprised to find how well you do compared to others who worked furiously with their iPads and calculators! In fact, rally organizers usually assign classes to rallyists with various types of equipment.

In the BMW CCA, Class C rallyists use simple calculators and the car’s original equipment, including onboard computer and nav system. Class B competitors are allowed laptop computers and auxiliary odometers, usually accurate to a hundredth of a mile, and Class A rallyists enjoy the luxury of full-on rally computers, specifically designed for this sport. The navigator’s job is to dial in the correct average speeds at the proper locations, and the computer continuously tells the driver whether you’re early or late at every point on the route—to a thousandth of a minute!

Just as touring rallies may be simple or challenging, another dimension of TSD rallying is presented by adding additional problem-solving elements. While a proper touring rally may be calculated before you leave the starting area, the rallymaster may omit the mileage at a speed change; that way you have to get there and read your mileage before you can calculate your time. Some rallymasters add even more challenging puzzles or logic problems, making their events into trap rallies. The mildest of trap rallies will keep you on course, but may lead you to calculate an incorrect time; the simplest form of this sort of “gotcha” might set you at an average speed of 20 mph and then instruct you to “divide your speed by ½.” Only those who remember fractions will multiply by the reciprocal to get the correct speed, 40 mph; beginners and the math-challenged will multiply their speed by ½ and get 10—making them rather late.

The most challenging form of TSD rally—challenging in this case may be a euphemism for filthy, rotten, or disgusting, depending on your success with such rallies—is one with puzzles to be solved in order to stay on course. These course-following rallies, which usually rely on a set of prioritized automatic instructions which must be applied at each intersection, can be made even more fiendish—uh, challenging—with the addition of confusing “either-or” instructions or other arcane procedures. It’s like working crossword puzzles: Once you start to figure out the subtleties of the game, you prefer a more challenging puzzle. And TSD rallying is so broad a subject that a few decades ago, writer Clint Goss set about creating the Road Rally Handbook. It may still be for sale here www.goss.com/catrrh.htm, or you may find a copy on Amazon.com or at Alibris.

Whether you stick to fun rallies or take on the challenges of a TSD event, you’ll find rallying to be a great way to have fun with a friend or loved one in your car. And you usually get to keep your clothes on.—Satch Carlson

TSD Rally Meeting

This meeting is designed for both the experienced rally participant and the novice who might be considering doing a TSD Rally for the first time. Organizers will explain the rules, policies, and route to all those interested.


Class A: competitors, regardless of experience level, using a computing device capable of calculating elapsed time based on input from the vehicle’s odometer (i.e., “A-box” rally computers such as TimeWise and Alfa).
Class B: competitors, regardless of experience level, using a computing device which has no direct interface with the vehicle, an auxiliary odometer which cannot compute time based on speed and mileage, and/or an aftermarket GPS device. (“B-box” odometers, laptop and tablet computers, and Curta calculators are found in Class B.)
Class C: all other competitors. Class C teams are restricted to original-equipment odometers, speedometers, on-board computers, factory-supplied navigation systems, and any four-function calculator with single memory.