Bench racing is a time honored tradition of theoretically figuring out what vehicle is better based on numbers. Sometimes the leads to people actually racing, but usually it is like fisherman getting together after a day on the water. One whopper of a story is followed by a bigger story until everyone is drunk, or their wives make them go home.
The bench racing number of the day today is Corner Travel Index.
What is Corner Travel Index?
CTI measures a vehicle’s maximum travel at each corner of the vehicle. As you can see in the picture above you lift opposing wheels until any tire not on a lift platform leaves the ground. You then measure form the bottom of each tire to the ground. There are two methods Estimated and Certified. Estimated is a two wheel measurement that is calculated to a theoretical movement. Certified is doing one setup and then repeating the process for the other corners. Important note, tire pressure must be at 15PSI to get an accurate CTI score.
Estimated: CTI = (FPT + RDT) x 10 x 2 Example: (19 ½ + 18 ¾) x 10 x 2 = 765 CTI
Certified: CTI = (FPT + RDT + FDT + RPT) x 10 Example: 19 ½ + 18 ¾ + 19 ¼ + 18 ½] x 10 = 760 CTI
Why does this matter?
Frankly it doesn’t. It is like trying to figure out what car is faster based on how much horsepower they make. In theory it tells you how well your vehicles suspension articulates before you would lose traction. It doesn’t take into consideration, tires, vehicle weight, body shift, lockers, limited slip or open differentials etc… It only tells you how far your suspension moves before a tire will leave the ground and allows you to argue with your buddies and measure who has more theoretical travel.
That isn’t to say there is no use to CTI. It is good to see the limits of your suspension in a controlled and safe environment, and yeah bragging rights matter as well.
CTI Versus RTI
Ramp Travel Index or RTI has the same issues as CTI. RTI has more issues in that many outside factors can increase or decrease the RTI value. Driver skill/courage on the ramp, angle of the ground, the ramp angle, weight distribution all change RTI. The RTI calculation is also significantly more complex, and several other factors like tire pressure can alter the RTI number. RTI does account for body shift, and does more accurately show how the vehicle will actually traverse terrain on a side hill versus CTI.
With ramp: r= (d/b)x1000 where b is the wheelbase, d is the distance traveled up the ramp, and r = the ramp calculated index. It leaves a lot of room for variables in measurements.
We don’t think that either measurement on it’s own is conclusive. We also don’t think you should build your rig just to score high on either chart. What we do think is that both are excellent tools for gauging your vehicle and experiencing the full articulation of your suspension before you go off road. Knowing your vehicles limits without damaging it is important and can mean the difference between taking the wrong line off road and the right line over an obstacle.