Suspension Articulation and Ramp Travel Index - 2015 Ford F-150 Long-Term Road Test
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2015 Ford F-150 Long-Term Road Test

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2015 Ford F-150: Suspension Articulation and Ramp Travel Index

February 25, 2015

2015 Ford F-150

You want a decent amount of suspension articulation if you're going to venture off the pavement very far, especially if you see yourself getting into the kind of frame-twist situations where one tire could hike up off the ground. It turns out this is fairly easy to measure and quantify in terms of Ramp Travel Index (RTI), so named because the frame twist maneuver is artificially created by driving up a ramp.

Last week I drove our 2015 Ford F-150 SuperCrew 4x4 pickup up a 20-degree RTI ramp of our own making to see how much suspension articulation the new Ford has to offer.

2015 Ford F-150

The measurement is simple. Run the driver side front tire up a 20-degree ramp until the moment the corresponding rear tire barely lifts off the ground. Next, measure and record the distance the front tire traveled up the ramp and divide this figure by the truck's wheelbase. Finally, take that number and multiply it by 1,000 to get your RTI score. Why 1,000? It's easier to talk about without decimal places.

Stock vehicles never get to the point where the rear tire touches the ramp, which is why you'll never see a perfect score of 1,000 on anything less than a highly modified Jeep.

So how did our 2015 F-150 SuperCrew 4x4 fare?

2015 Ford F-150

The best small crossover SUV we've ever measured so far (and we have by no means measured them all) is the Mazda CX-5, which scored 334 points. Hot on its heels is the new Jeep Cherokee Trailhawk at 324 points.

Full-sized ladder frame trucks like the 2015 Ford F-150 are supposed to do better, and so it was with our results. Those of you that live in Washington and Colorado will be especially interested to know that it scored exactly 420 points.

It's worth noting that this number applies to the 145.0-in wheelbase. Our truck is a crew cab with the stubby 5.5-foot bed, but the results should be the same for the SuperCab with the 6.5-ft bed because they both ride on the same wheelbase.

For reference, here's how our F-150 lines up against other similarly large crew cab 4x4 pickups that have made the trip up our ramp.

518 ? 2014 Ram Power Wagon, front stabilizer bar disconnected (149.3-in WB)

484 ? 2014 Toyota Tundra TRD Pro (145.7-in WB)

420 ? 2015 Ford F-150 (145.0-in WB)

412 ? 2014 Ram Power Wagon, front stabilizer bar connected (149.3-in WB)

Both of those are pretty serious off-road packages that include targeted factory suspension modifications, so it's no wonder they do better than our Ford, which has more of a broad-spectrum 4x4 suspension.

In fact, the Ram has two results because it comes factory-equipped with a cockpit-controlled front stabilizer bar disconnect mechanism that was specifically engineered  to improve off-road suspension articulation and RTI while maintaining the ability to control body lean when driven on pavement. The improvement amounts to over 100 points.

What's missing is our 2014 Ram 1500 Crew Cab 4x4, a truck that has a matching cab and bed configuration and the same sort of standard 4-wheel drive system. That would be a very interesting result to hold up against the F-150, but it doesn't yet exist.

I'll get right on that. I'm a bit embarrassed I haven't tested that one already. My bad.

Dan Edmunds, Director of Vehicle Testing @ 1,501 miles


2015 Ford F-150

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