A critical capability that every 4X4 used for more extreme off-roading must have is a wide articulation range.
This flexibility that consists of the range of vertical movement of the wheels and suspension is essential for rock crawling and traveling aggressive trails.
Before you try any extreme obstacles, you'll be one smart off-road driver by learning about the abilities and limitations of your truck or Jeep to avoid getting stuck at the very least or damaging your prized 4X4.
This flexibility is measured by determining your RTI or Ramp Travel Index scores and a better score translates to a more articulate truck or Jeep that is better able to scale larger obstacles.
So to learn what you can expect from your 4X4, you need to understand how RTI is measured and what it means.
What Is RTI?
A Ramp Travel Index score is a measurement of the length of your off-roader’s vertical suspension range which will gauge your success at clearing more advanced obstacles like giant rock piles or high-rated trails.
By testing your Jeep, it’s possible to safely estimate which obstacles you can try and which you should not attempt as scaling it would be a physical impossibility.
A high RTI score is not a guarantee that you’ll make it over large obstacles as there are many other factors that go into whether or not your off-road beast has the ability to clear them; however, it does provide a measurement of the upper limit of what you can expect from your set up.
How Is RTI Measured?
RTI is measured using a ramp, of course!
Usually set at a 20-degree angle, the ramp accommodates only one wheel and provides a chance to see just how wide the articulation range on a 4X4 is without risking getting it stuck on an actual obstacle.
Driving the vehicle onto the ramp with only one front wheel, the goal is to roll it as far forward as possible without the other three wheels coming off the ground.
The highest the vehicle can be driven stretching shocks and suspension in doing so is its top RTI measurement.
The further up the ramp you get and the more your suspension is able to stretch out, the higher the score of your off-road truck.
Ramps set at 23-degrees are sometimes used to measure the RTI for really extreme 4X4 builds.
What Does the RTI Score Mean?
The significance of an RTI score is to determine how long your truck or Jeep can roll forward climbing an obstacle before you can expect one of your other wheels to come off the ground because if any wheel comes off the ground, traction is reduced as is the ability to clear larger obstacles.
The score is calculated by measuring the distance from the edge of the ramp to the center hub of the wheel when the vehicle is on the ramp, then dividing that number by the length of the wheelbase and multiply by 1000.
An ideal score of 1000 means that truck or Jeep can move the entire length of its wheelbase before another tire will lift off the ground which is vital in order to skillfully negotiate obstacles and understand which wheels can be relied on for traction while climbing and which cannot.
Jeeps tend to have the best RTI scores, even before modification and with a modified suspension, longer shocks, and bigger wheels and tires, some Jeeps can get close to that desirable 1000, while other trucks and SUVs usually fall in the 400 to 600 range when unmodified and upwards of that when modified.
Any vehicle’s RTI can be slightly improved by airing down the tires to half-pressure, which is recommended anyway for going off-road and doing things like rock crawling.
Ready to Face The Ramp?
A great way to gauge the capability of your truck or Jeep as well as track how much change your mods gain you over time, you can find ramps at various 4WD events and shows to try it out; if you’re handy with a welder, you can build your own!
In either case, knowing your RTI rating will help you better understand the capabilities of your truck or Jeep in order to know just how far you can push that envelope without getting stuck on the trail or put yourself in danger!