Metal Cloaks CTI Trailer

Money Pit Editorial Staff

Metal Cloak CTI Trailer

What is a CTI (Corner Travel Index) trailer? It’s a trailer specifically designed and built to measure the suspension articulation of any vehicle that will fit on the trailer.

In 2014 Doug Powell, Metal Cloak's chief engineer and co-founder noticed that accurate results from typical RTI (Ramp Travel Index) ramp tests were difficult to obtain because hard-to-control conditions like uneven ground influenced the measurements. Also, an RTI ramp causes weight transfer that can give false readings. This lead Doug to design the patent-pending CTI trailer which picks up the opposing tires of the vehicle, keeping the vehicle relatively level during the test. Doug sent the initial design to the fabrication shop at Metal Cloak in early 2014 where the team built the original trailer.


In February of 2014 the trailer made its debut at the King of the Hammers off road race held each year in Johnson Valley, California. The trailer was used to demonstrate the flexibility of the latest Metal Cloak suspension installed on a Jeep JKU. The first actual CTI's were conducted at Tierra Del Sol Desert Safari in March, 2014, where the trailer was an instant hit. Now, whenever we see the trailer in action, there is always a line at least 10 vehicles deep, with drivers anxious to test their design and fabrication skills. In 2014 Metal Cloak sent the trailer on a cross country tour, hitting 12 events in 11 states in only 3 weeks.

The idea of the trailer evolved through trying different methods for testing a vehicle’s flex. One way that has been used by off road shops and fabricators for years is to have 2 fork lifts pick up opposing tires. The problem with this method is that since there is so much variation between fork lifts, fork spacing, and tire pressures, results were hard to replicate. So, for greater reliability and accuracy of articulation measurement, Metal Cloak built two air-bag lift platforms which worked well. But to take the platforms to the next level, they fired up Solidworks and built the first CTI trailer. The design incorporates a hydraulic lift table on each corner of the trailer, allowing testing to be done on opposing corners.



Metal Cloak offers two different tests: the Certified CTI and the Estimated CTI. The Certified CTI score is done under controlled circumstances. For example, tires must be at 15 PSI and all four platforms are used - first Passenger Front and Driver Rear, then Driver Front and Passenger Rear. Certified CTI's are used for making specific comparisons between different suspension systems on the market. The Estimated CTI, though, is what is done for fun at most events. With Estimated CTI, only the two opposing platforms (Passenger Front and Driver Rear) are lifted and tire pressure is not considered.

Calculating the score is quite simple. The operator raises opposing corners of the vehicle just until the other tire on the same axle is about to lift off the trailer. Next, he measures the height of each platform and adds the 2 numbers together. Then you take that number and times it by 20. That is the CTI score for your vehicle. Metal Cloak has set up a web site to record your score.



Besides learning a rig’s score, there are other elements to testing vehicles at events. The first is that people really love to see how far their vehicle will flex, oftentimes comparing to their buddy’s vehicle. Another is that when the vehicle’s flex is maxed out the owner, his buddies, and the CTI trailer operator have a chance to inspect for any conflicts in design like tires rubbing on the frame, body, or suspension parts; drive line interference; suspension components limiting flexibility; and even suspension components binding on one another and causing stress on the vehicle.

All you have to do to ride one of the two CTI trailers that Metal Cloak has traveling around the country, is show up at an event and fill out their form. The information you provide about your rig is stored in a database and used to better understand the dynamics between tires, shocks, and various suspension kits. They’ve already measured and recorded over 4,000 vehicles, with no end in sight.


Last year Money Pit Classifieds had a chance to put Rocksanne on the CTI trailer, and she did not disappoint! With the trailer maxed out, the car still had about 3” of travel left front and rear and had an estimated score of 1480. This was great for us because it gave a chance to inspect the car for potential problems. And with all we could see from the CTI trailer vantage point, we are happy to report no apparent design flaws.

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