Ramp travel index
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RAMP TRAVEL INDEX / RTI
A vehicles RTI or ramp travel index is a measurement of a vehicles suspension (and frame) flexibility. In many situations off road a vehicles flexibility may be the determining factor of whether or not it can get over an obstacle. If a vehicles suspension is too stiff this may cause a tire or two to be lifted, loosing contact and traction, especially apparent in vehicles with open differentials. While locking differentials will help to maintain forward momentum when a wheel is off the ground, good flexibility will help to keep the wheels on the ground and more able to conform to the terrain.
There are several factors that make up the RTI score. First the ramp. The vehicle attempts to climb the ramp as high as possible without lifting a wheel off the ground. The distance the vehicle can travel up the ramp without losing contact with the ground is measured from the leading edge of the ramp to the center of the hub on the ramp. In most cases the ramp is on a 20 degree angle. Some events measure the extremely flexible vehicles with a ramp of greater angle like the 23 degree ramp.
That number is then divided by the vehicles wheelbase (the distance between the vehicles centerline of the front axle and the centerline of the rear axle) and then multiplied by 1000 to calculate the average. For instance, if a vehicle with a wheelbase of 94 inches travels 62 inches up the 20 degree ramp then the RTI would be calculated as: 62" divided by 94" x 1000 resulting in a score of 659. This method of multiplying by the vehicles wheelbase allows one vehicle to compete with another vehicle on the same ramp test
